BIOMETEOROLOGY FOR LIVESTOCK HEALTH & PRODUCTION
G SINGH AND D C SHUKLA
Centre of Advanced Studies in Veterinary Physiology
Division of Physiology & Climatology
Indian Veterinary Research Institute
Izatnagar- 243 122 (U.P.) India

Bioclimate generally refers to the physical or meteorological and biological environment surroundings an animal, whereas biometeorology refers to study the biological effects of weather and climate on living organism, plant, animal and man and their direct physico- chemical environment.Domestic animals, depending on the species and level of productivity, have an optimal environmental zone and they must maintain within this zone for optimal growth, lactation and reproductive functions. In the zone of thermoneutrality, livestock can maintain, by physiological and metabolic mechanisms, a fairly constant body temperature and efficient level of growth, lactation and reproduction. Reduced performance under heat or cold stress is due to associated effects on thermal regulation, energy balance, water balance and endocrine changes among other factors.

Many factors combine to create a specific climatic zone or microclimate. Climate determines the ecological niche inhabited by specific plants and animals. The organism’s environment (humid and cold, hot and dry etc.) determines the type and magnitude of environmental factors that affects its behaviour. Certain environmental conditions may exert little or no stress on a particular organism, whereas different environmental conditions may be so severs that survival of the animals is dependent on its ability to acclimatize. More than 70 countries lying in the warm climate belt (falls between latitude 30° North and 30° South) and this region contains a substantial parts of world’s livestock. Climate in this region is not uniform and varies with latitude, altitude, distribution of land and water, soil and topography and variable factors such as winds, rainfall and vegetation. Interaction of all these factors result in specific microclimate at specific localities.

In a thermal environment in which the animal’s heat production exceeds heat loss, an increasing amount of heat is stored in the animals body, resulting in increased body temperature. When the body temperature is significantly elevated, a myriad of homeothermic events are initiated. These events include increase in evaporative heat loss by respiration and skin , and increases in urinary excretion which may aid in conductive and convective cooling. However, when high temperatures and radiation lessen the ability of the animals to radiate heat, feed intake, metabolism, body weight and milk yield decrease to help in maintaining the heat balance. Even though tissue substrate are mobilize, energy metabolism, growth, lactation and egg production declines. A growing or lactating animal is influenced by the environment via its neuroendocrine system which may alter energy, thermal, water, and mineral balance. It is believed that deviation of any of these systems or functions beyond a certain threshold or critical temperature level by the environment may modify the growth lactation or reproduction processes.

A number of mechanisms exist to maintain the temperature balance, within a range of ambient temperature refered to as thermoneutral zone. The upper and lower boundry of the thermoneutral zone, often called the upper critical temperature and lower critical temperature, is of great practical importance. Above or below these temperatures thermolysis or thermogenesis mechanisms have to come into play to compensate for heat gain or heat loss. The thermoneutral zone may vary with age, body condition, breed, season, dietary DE intake and, production status. For exaple, under moderate heat stress the onset of decrease heat production begins at 21°C in lactating Brown Swiss, 24°C in lactating Holstein Friesian, 35°C in lactating Brahman (Indian), 35°C in Brown Swiss heifers and 38°C in Brahaman heifer (Hefez, 1968).

When animal kept outside theses zones of productivity and the necessary acclimatization due to severe climate does not cause excessive reduction in growth or milk yield, then animals are regarded as ‘more adaptable for the climatic region’. To avoid this excessive acclimatization or adjustment in an adverse environment, animal management, shelter provisions and the many factors associated with modern animal husbandry are used to alter the severe climatic influences of a temperate, arctic or tropical environment. Since most of the tropical and subtropical countries including India, are having burden of higher temperature rather than cold temperature stress, therefore, it is rather relevant to discuss the various physiological responses of animals related to production, in warm climate.

Feed intake

One of the most noticeable responses of most livestock to thermal stress is decrease in feed intake. The extent of depression appears to be directly related to the level of stress. Similar obsesrvations have been made with laying hens. Birds decrease their intake by about 1.5% for each 1°C rise in environmental temperature above 25°C Lactating cows producing 30 kg or more milk per day exhibit some depression in appetite at 25°C, show a marked decline above 30°C and virtually stop eating at 40°C. In one experiment, the digestible energy consumed by lactating Holstein cows declined 14% from the level at 21°C after one week of exposure to 32°C and there was further decline of 4% during the second week.Our indegenous livestock are able to withstand higher ambient teperature and usually do not show any significant change in their feed intake up to 37°C (Mc Dowell, 1972).

The level of feeding prior to the time of thermal stress is a factor in determining both the ambient temperature at which appetite will decline and the rate of decline as well (High fed animals show more decline under stress than low fed ones). In general young cattle have a higher threshold to higher temperatures for decreased appetite than lactating cows, although it is not clearly established. There are at least three factors involve: 1. direct regulation by the heat regulation centers, 2. interference with feeding by high respiration rate, and 3. changes in behaviour directed towards decreased heat production.The evidence from experiments conducted under constant temperature conditions in laboratories and in some cases field experiments suggest that the prevailing temperatures in much of the N-S 30° latitudes have a direct effect on appetite and level of feed intake; but apparently the direct influence of temperature does not seriously impair feed intake under good management regimens. For example cattle and sheep may seek shade during the hottest part of the day and avoid eating, but if adequate feed is available they will normally consume their full requirement in the cooler part of the day (Mc Dowell, 1972).

West (1999) suggested that Lower DMI during hot weather reduces nutrient availability for absorption, and absorbed nutrients are used less efficiently. An excess of degradable dietary protein is undesirable because of energy cost to metabolize and excrete excess N as urea.

In our country diets of cattle and buffaloes are largely mature forage from tropical pastures or crop residues, which are generally low in protein and of low digestibility. Lang and Kunju (1990) suggested that supplementation with rumen bypass protein to supply the animal directly with additional amino acids improves efficiency of feed utilization by reducing the heat increment of feeding and under hot environment this reduces heat stress and allows feed intake to be maintained.

Practical management considerations such as frequent feeding and ready water availability are logical. Provisions of fresh feeds through multiple feedings encourages frequent feeding bouts by cows, and making the feeding area comfortable through shading and (or) cooling enhance feeding frequency and total intake. Animal behavior during hot weather indicates that the animal will consume more feed during cooler parts of the day and feeding quantities and schedule should be adjusted to accomodate changes in behavior because of season of feeding (West, 1999).

Efficiency of feed utilization

Most of the reports dealing with feed utilization in relation to temperature levels are expressed as gross efficiency i.e. the amount of feed consumed per unit of yield measured as milk or body weight gain. The research has shown depression in gross efficiency, decreased intake of food, and lowering of total heat production with rising temperatures, upto about 30°C (Mc Dowell, 1972). However, above 30°C there is a rise in heat production because of the added heat from increased activation of the heat loss mechanisms. With the lowered intake and resulting lowered total heat production, a greater proportion of the energy consumed goes for maintenance, resulting in a decline in gross efficiency.

In lactating Holstein cows it was found that the efficiency of utilization of digestible energy for milk was 60% at 21°C, but only 40% after 7 days at 32°C and 31% after 14 days. The average daily consumption of digestible energy declined about 16% at 32°C, but the daily output of milk energy (Solids corrected milk) declined more than 22%; hence, the cows continued to consume more energy than they needed for body maintenance and production under the stress conditions but gave poorer returns. These findings clearly show that thermal stress would have the same wasteful effect in the energetic of production as shivering in the cold. Experimental evidence suggests that cattle too, may have to make increased energy expenditure to combat thermal stress. The observed decreased energy intake by the cows probably resulted from a combination of the effect of the 32°C on the appetite center and the interference with feeding by high respiratory rate. These findings indicted that in hot climates the cost of producing a unit of energy, measured on an input-output basis, will be higher than in cool climate because thermal stress increases the animal's maintenance requirements. From existing evidence it can be concluded that the direct influence of high temperatures brings about a reduction in efficiency in the utilization of feed energy for productive processes. Not only do animal eat less, but also they return less per unit of intake.

Growth

Many experiments under controlled temperature conditions have demonstrated retardation in growth rate at higher temperatures, the degree of retardation depending upon the age and size of the animals and the level of ambient temperature. For example, the optimum temperature range for swine of 45 kg or larger is in the range of 21-24°C, while that for a baby pigs is 27-29°C. The rate of gain for 45-90 kg pigs will be depressed by 40-50% at 4-5°C, 25% at 27°C and 40% at 32°C. An environmental temperature of 38°C will decrease gain by 80% or even bring about loss in weight, depending on the size of the animals. Level of humidity is also a critical factor in the growth rate of swine, particularly at 27°C or above (Mc Dowell, 1972). High temperature probably also have same influence on growth rate of cattle. What is probably more important than the influence of environmental temperature on weight gain is its apparent influence on body confirmation? For instance our cattle are shorter in body length and hight at withers than the temperate zone cattle. A decreased growth rate and smaller adult size provides the animal a large surface area in relation to mass. This might be regarded as a form of acclimation to a higher environmental temperature. In other words, animals whose growth rates are not reduced at high environmental temperature are apparently more fit than animals whose growth rates are reduced.

Although it is accepted that small Cattle (e.g. Red Sindhi) are better adapted to high temperatures than large once (e.g. Brown Swiss), it does not necessarily follow that an environmentally reduced growth in weight is an adaptive response to thermal stress. On contrary, even though animals reared at high temperature conditions show less response in heat tolerance tests than animals reared under cool conditions, the capacity to acclimatize appears best in the animals whose growth is least reduced.

Milk production

The effects of temperature on milk production are probably the most widely publicized. All are in agreement that elevated ambient temperatures may seriously reduce the feed intake of lactating cows, resulting in lowered milk yield. Although the best temperature for lactating cows is 10-18°C, no significant decline in milk yield is usually evident under cold conditions until the temperature drops to about -12°C. On the other hand, the level of milk yield is very sensitive to elevated temperatures, with measurable declines occurring in high producing cows at 24°C. The level of temperature at which significant depressions will occur is dependent upon the level of production and the animal’s size, stage of lactation, and genetic potential for milk yield. Humidity may play a vital role in it. For Karan Fries and Karan Swiss cows the comfort zone for maximum milk yield was 7°C and 25°C (Shinde and Taneja, 1986); and the milk yield per day decreased with an increase in temperature and humidity (Shinde et al, 1990). The Jersey crossbreds were less affected by climate than Holstein crossbreds for average milk yield per day (Thomas and Acharya, 1981).

There is some degree of variation within breed groups in depression of milk yield in response to rising ambient temperatures, but there is no effective way of identifying those showing minimum decline due to the confounding factors of level of production, stage of lactation, age and size. From all these observation at least it may be suggested that useless heat increment should be reduced to prevent a decrease in milk production under high temperatures and much more attention should be given to feeding management to alleviate the impact of hot environment on lactating cows.

Reproduction

High environmental temperatures can cause a decline in the reproductive efficiency of both male and females through decreased gametogenesis, libido, estrus, ovulation, fertilization, implantation, embryo survival, gestation length, and mothering ability of the female, as well as increased problems at parturition. Numerous reports concerning the influence of thermal stress on the reproductive efficiency of males agree that high temperatures can interfere with the process of spermatogenesis in all the species of livestock. Ambient temperatures above 29°C are severe enough to impair spermatogenesis and the quality of semen. There also seems to be a positive relationship between the number of abnormal and dead sperm and the level of environmental temperature. When the relative humidity exceeds 70% at 27°C and above, humidity becomes an additional inhibitor. Dutt et al (1991) observed that in crossbred cows (Haryana X Bos taurus) the conception rate increased from October to May and declined thereafter, the maximum and minimum number of conception were observed in March and September. Shinde et al (1990) reported that in Karan Fries and Karan Swiss cows the correlation for number of services per conception was significant with Temperature-Humidity-Index (THI) and Temperature-Humidity-Sunshine-Index (THSI).

In buffaloes the length of the estrous cycle and the degree of expression of estrus are affected by climate, photoperiod, temperature and nutrition. Reddy et al (1999) reported that in Murrah buffaloes the maximum percentage of estrus (11.44) were observed in November and the minimum (5.97) in June. Maximum (31.79%) estrus were detected during the coolest part of the day (0-4h) followed by 24.20% during the period 4-8h and the lowest (3.39%) during 16-20h period. However, the conception rates were more or less similar for heats detected during different period of the day. Tailor et al (1990) found that the lowest number of services per conception (2.26) and the highest percentage of conceptions (39.3) were observed in buffaloes when both temperature and humidity were moderate (31.3°C and 72.6%); reproductive performance was poorest at high temperature (38.1°C) and low humidity (53.4%).

Research in temperature controlled laboratories has shown that thermal stress does not seriously impair libido in cattle, buffaloes, goat and swine, but does impede libido in rams with wool covering. Severe thermal stress will cause a cessation of oestrus and even ovulation in cattle and sheep (Mc Dowell, 1972). High temperatures also cause a shortening of the duration of visible expression of oestrus and decreased embryo survival. Body temperature of the cow at the time of insemination may be important in conception. It was found that if the rectal temperature of a dairy cows exceeds 39°C at the time of breeding, conception rate was near to zero. The offspring in hot climates are usually somewhat lighter at birth than similar offspring in cool climates. Involution of the reproductive tract may be delayed indirectly as a result of thermal stress principally through hormonal imbalance.

Milk composition

The yield of milk fat of cows exposed to thermal stress declines with decreasing milk yield. Under hot-room conditions at the university of Missouri, the milk fat yield of Holstein cows declined at temperatures above 27°C. Singh (1979) reported that in Haryana cows contents of milk like milk fat, SNF, protein, ash and calcium were highest in winter than summer and rainy season. Studies of the fatty acid composition of milk fat under controlled high temperatures showed that any external heat load that raised rectal temperature by one degree or more caused changes in the characteristics of milk fat. In particular, the content of lower chain fatty acids decreased whereas, that of palmitic and stearic acids increased. The reason for the shift in the ratios of fatty acids is unknown. Nevertheless, these shifts can be of practical significance as they influence the quality of the milk for cheese making. High ambient temperatures appear to have a more marked influence on the solid-not-fat (SNF) content of milk than on milk fat. Thermal stress also appears to bring about some decrease in percentage of lactose and acidity in the milk, lowers its level of pantothenic acid and lowers its freezing point. It increases the pH and levels of ascorbic acid and riboflavin. But it has little effect on salt balance or the carotenoid and vitamin-A levels in milk fat.

Disease Occurrence & its forecasting

Though the information available on the effect of climate on the health of livestock are not much, it is now globally proclaimed that the climatic stress can lead to substantial losses in the productivity and health of animals and poultry both. Climate plays an important role in vector borne diseases, which are major cause of illness and death in tropical countries for example, Singh et al (2000) reported that temperature and rainfall had high influence on the tick dynamics, while relative humidity had a lower bearing on the tick population (Boophillus microplus). Many infectious agents are transmitted from animal to animal over relatively short distances by air route. Singh et al (1996) observed that the incidence of mastitis was found to be higher in July to October (Hot-Humid) than March to June and November to February, mainly attributed to comparatively more calving, a greater fly population and heat stress. Wind may be responsible for the spread of such infections to over long distance. Foot and mouth disease may be an example of such transmission.

Based on above observation, a new concept of disease forecasting has emerged which may play on important role to forewarn and forecast of the devastating disease problems and to take appropriate preventive health measures so that the health of livestock may be protected and production be maintained.

Conclusions

Currently, the general conclusion is that the decline in the milk yield of cows exposed to thermal stress is predominantly the result of heat-induced depression in feed intake i.e. an indirect effect of climate. This leads a series of physiological changes in the body leading to adaptive mechanism unto its threshold and thereafter breakdown of the physiological mechanism. The change includes all the aspects of health and production of livestock including the epidemiology of these diseases. From all these observation at least it may be suggested that useless heat increment should be reduced to prevent a decrease in milk production under high temperatures and much more attention should be given to feeding management to alleviate the impact of hot environment on lactating cows

With global changes in the climate its effect on livestock health and production also can not be ignored and the required capacity building to face these climatic challenges will be essential for sustainability of economic as well as eco-friendly livestock production and health.

References

Dutt, T.; Singh, A. and Taneja, V. K. (1991) Effect of tropical climate on monthly distribution of successful conception rate in crossbred cows. Ind. J. Anim. Sci. 61:11, 1193-1194.

Hafez, E. S. E. (1968) Adaptation in domestic animals. Lea & Febiger, Philadelphia.

Leng, R. A. and Kunju, P. J. G. (1990) Feeding strategies for improving milk production from milch animals owned by small farmers in India. Domestic buffalo production in Asia. Proceedings of the final research co-ordination meeting on the use of nuclear techniques to improve domestic buffalo production in Asia – phase II, 20-24 February, 1989, Rockhampton, Australia, organized by the joint FAO – IAEA Division of nuclear techniques in food and agriculture, 1990, 3-19.

Mc Dowell, R. E. (1972) Improvement of livestock production in warm climates. W. H. Freeman and Company. San Fransisco.

Reddy, A. O.; Ramesha, K. P. and Rao, M. K. (1999) Effect of climate on the incidence of oestrus, conception and cycle length in Murrah buffaloes. Ind. J. Anim. Sci. 69: 7, 485-489.

Reddy, A. O.; Tripathi, V. N. and Raina, V. S. (1987) Effect of climate on the incidence of oestrus and conception rate in Murrah buffaloes. Ind. J. Anim. Sci. 57: 3, 204-207.

Shinde, S. and Taneja, V. K. (1986) Effect of physical environment on daily milk yield in crossbreds. 3rd world congress on genetics applied to livestock production, Lincoln, Nebraska, USA, July 16-22, 1986. XI. Genetics of reproduction, lactation, growth, adaptation, diseases and parasitic resistance, 505-509.

Shinde, S.; Taneja, V. K. and Singh, A. (1990) Association of climatic variables and production and reproduction traits in crossbreds. Ind. J. Anim. Sci. 60: 1, 81-85.

Singh, A. P.; Singla, L. D.; Avtar Singh and Singh, A. (2000) A study on the effects of macroclimatic factors on the seasonal population dynamics of Boophilus microplus infesting the crossbred cattle of Ludhiana district. Ind. J. Anim. Sci. 15: 1, 29-31.

Singh, B. B. (1979) Effect of seasons on chemical composition of milk. Ind. Vet. J. 56: 9, 768-771.

Singh, K. B.; Nauriyal, D. C.; Oberoi, M. S. and Baxi, K. K. (1996) Studies on occurrence of clinical mastitis in relation to climatic factors. Ind. J. Dairy Sci. 49: 8, 534-536.

Tailor, S. P.; Jain, L. S.; Gupta, H. K.; Bhatia, J. S. and Tiwari, B. K. (1990) Effect of climatological factors on reproduction of Surti and Mehsana buffaloes. Ind. J. Anim. Sci. 60: 8, 956-957.

Thomas, C. K. and Acharya, R. M. (1981) Note on the effects of physical environment on milk production in Bos indicus X Bos taurus crosses. Ind. J. Anim. Sci. 1: 3, 351-356.

West, J. W. (1999) Nutritional strategies for managing heat-stressed dairy cows. J. Anim. Sci. 82 (suppl. 2): 21-35.

WEATHER BASED FORECASTING MODELS ON PESTS OF RICE AND THEIR OPERATIONAL USE
R P SAMUI, N CHATTOPADHYAY, J P SABALE and *P V BALCHANDRAN
Agrimet Division, India Meteorological Department, Pune-411005
*Regional Agricultural Research Station, Kerala Agricultural University, Pattambi-679306

Early attempts to develop the forewarning models with qualitative data in the form of percentage of damaged or intensity of attack by the pests and the corresponding mean meteorological parameter of the fortnight have been found not satisfactory. The major problems in developing such forewarning models are non-availability of a long series of qualitative data and also getting real time meteorological and pest data from the field for operational crop protection. The simple and multiple regression techniques have been used for developing models using pest and meteorological data for the corresponding standard week. The standard weeks having highest correlation coefficient (cc) values significant at 5% levels were selected. As the weather requirements of pest at their different developmental stages are quite different, attempts have also been made to work out the relationships between the intensity of attack or population and meteorological parameters not only for the corresponding week bur also for previous weeks as the favorable weather conditions at egg, larva and pupa stages would have considerable bearing on the development of the adult.

Under favorable weather condition rice is mainly infested by gall midge, stem borer, leaf folder, green jassid and rice bug. These pests become the dreaded one and causes considerable damaged to the crop. Thus light trap catches for each for each of pest have been correlated with meteorological data for the corresponding, 1st week, 2nd week, 3rd week and 4th previous weeks for working out correlation coefficients. The stepwise multiple regression technique has been used to determined the most predominant parameter 3 to 4 multiple regression equations were developed for each of the pest for operational use. The forewarning models for each of the rice pest accounted for only 68% to 85% variation e.g., for gall midge – 68%, stem borer – 67%, rice bug –84%, leaf folder – 85% and green jassid – 77%. This may be due to the fact that there are several other factors such as natural enemies, parasites etc. which equally played important role in reducing the development of the pests. As operational crop protection is an interagency collaborative work and is required to be taken up on real time basis, all concerned agencies such as meteorological, entomological and extension departments are required to act quickly based on past, present and future weather condition and field observation on pest.

EFFECT OF WEATHER VARIABLES ON OUTBREAK AND SPREAD OF POWDERY MILDEW DISEASE IN BER
V PANDEY, D S PATEL, B M PATEL and S I PATEL
C P College of Agriculture, Gujarat Agricultural University,
Sardar Krishinagar 385 506

Ber is an important fruit crop of arid and semi-arid region of India. The fruits of ber are infested by powdery mildew disease, the outbreak and severity of which is largely determined by the environmental factors particularly temperature, humidity and sunshine etc. The knowledge of interaction between weather parameters and disease can help in development of control strategies.

Field experiment was conducted at Sardar Krushinagar for 11 years (1989-90 to 1999-2000) on epidemiological study of ber powdery mildew (Oidium erysiphoides f. sp. zizyphi). The disease was observed in 7 years out of 11 years of the study period. Disease initiation took place in the first week of October in most of the years. It was observed that whenever the weekly morning relative humidity was less than 85% during September, disease did not occur. Higher humidity (85-90%) and moderate temperature (maximum temperature 33-34°C; minimum temperature 23-25°C) provided favorable condition for the initiation of disease infestation. The percent disease index (PDI) was calculated on weekly basis. Mean weekly PDI increased linearly and reached to its maximum value during 52nd week (last week of December) and thereafter it decreased. The correlations were worked out between weekly PDI and the corresponding weekly weather parameters. The results revealed that PDI was negatively correlated with temperature, but positively correlated with relative humidity and wind speed. Low temperatures (Max. temp. < 27°C and Min. temp. < 10°C) were found to have retarding effect on the spread of disease. Multiple regression equations have been developed to predict the PDI at any stage of disease development.

Helicoverpa armigera - WEATHER RELATIONSHIP STUDIES IN COTTON AT HISAR
V U M RAO, RAJ SINGH, DIWAN SINGH, P D SHARMA* and S C BHAN**
Department of Agricultural Meteorology, CCS HAU, Hisar
*Dept of Entomology, CCS HAU, Hisar
**IMD, Chandigarh

Besides weather, pests and diseases may cause significant reduction in crop yields. Timely application of remedial measures to control these may reduce the yield losses. However, for application of these remedial measures one must know of the time and severity of outbreak of pests and diseases. In turn, both these aspects of pests and diseases are influenced by interactions of number of factors like weather, crop stage/condition, presence of natural enemies/predators etc. For proper and effective management of pests and diseases in crops both the outbreak and spread need to be correlated with the weather. Minimum weather data set required could consist of temperature and humidity and other weather variable or their derived parameters such as accumulated heat or degree days. In an exercise similar to this, population of Helicoverpa armigera in cotton crop for growing seasons from 1990 to 2001 were correlated with the weather parameters of the pertaining period. Simple and multiple correlation equations were developed. The results showed that role of weather parameters varied with the crop growth and crop season/month. The study revealed that the weather parameters viz., rainfall, cloudiness, temperature, relative humidity and wind direction played significant role in population development during the month of August. Likewise, wind speed and direction during September and wind speed and temperature during October were important for multiplication of H. armigera. The pest population build up occurred over wide range of weather parameters viz., maximum temperature (30-40°C), morning and evening RH (70-96 and 40-85%, respectively) and evening actual vapour pressure (17-27 mb). In case of minimum temperature, the value of around 25°C was found critical for development of the population of H. armigera in Hisar region.

STUDIES ON Heliothes armigera POPULATION DYNAMICS AND WEATHER RELATIONSHIP IN COTTON AT AKOLA
S A NIMBALKAR, S M PATIL, S S NARKHADE and S P UKEY
Panjabrao Deshmukh Krishi Vidyapeeth, Akola (Maharashtra)

Heliothes armigera population dynamics and weather relationship was studied from the database generated in surveillance scheme and AICRP on Cotton at Dr. Panjabrao Deshmukh Krishi Vidyapeeth, Akola (MS) during 1983 to 2002. The data were rigorously screened before analysis. The technique used was multi-collinear regression with step down analysis. It was observed that the weather parameters found to significantly influence the population dynamics of Heliothes armigera were maximum as well as minimum temperature, and mean relative humidity prevailed during previous week, minimum temperature prevailed at two weeks log period i.e. between 7 to 14 days of observation and current week’s rainfall. The contribution of maximum temperature of previous week was 81.5 per cent. Whereas, the weather parameters viz., Minimum temperature at 2 week’s log period, mean relative humidity of previous week and current weeks rainfall was 42.7, 24.3 and 5.7 per cent, respectively. Minimum temperature during previous week had 54.1 per cent contribution with a negative significantly. The regression equation realized was as under.

Y= 243.42 – 5.132 T.max.1 + 2.242 T.min.1 – 1.617 T min.2 – 0.844 Mean RH + 0.141 RF current.

Where the suffix 1 and 2 of the weather parameters indicate the weather prevailed during previous week and weather prevailed at the log of 2 weeks. The value of R2 was 0.82. The F value of R2 was significant. All the values of regression coefficient were significant. Standard error of intercept was 41.98.The favorable ranges of weather parameters for increasing the Heliothes armigera population were as under.T max.1 25 to 29 °C T.min.1 6 to 11 C, Tmin2 9.5 to 16.5 C and Mean relative humidity: 50 to 62 per cent.It may be mentioned that the population of Heliothes armigera is based on abiotic factors i.e. weather but it is highly lightly influenced by biotic factors like presence of bioagents and their population, built up as weeks availability of alternate host plants.

PREDICTION AND VALIDATION OF Helicoverpa INCIDENCE ON COTTON IN PUNJAB
BEANT SINGH, BALJINDER SINGH, AMIT SETHI and V K DILAWARI
Department of Entomology, Punjab Agricultural University, Ludhiana-141001

Information on likely timing of Helicoverpa armigera incidence can be useful for growers planning to cultivate cotton. A simple population dynamics model was developed to predict the incidence of Helicoverpa on cotton using Dymex (Software for modelling insects). Dymex makes use of different growth constants such as development threshold (Temperature, humidity and photoperiod etc), stress factors (heat and cold stress, rainfall etc) and weather data to predict the probable adult population of H. armigera. The prevailing weather conditions during Rabi 2002-2003 were found to be similar to Rabi 1993-94. Therefore, Dymex was run for 1993-94 and 2002-03 Rabi season. The observed peaks of Helicoverpa incidence coincided with peaks simulated using Dymex in 1993-94. The expected population peaks for Helicoverpa incidence were obtained during mid Feb. to mid Mar. in both the years. The validity of the model was checked by comparing the expected and observed moth population during Rabi 2002-03 season. The results show that expected number of adult counts was statistically non-significant (P=<0.01) with the observed ones. Assuming that the weather conditions during 2003 might follow similar trends as in 1994 for rest of year, the predictions have been made for Khraif 2003 season using weather file of 1994. The model predicts that season will experience peaks of Helicoverpa population during July and Sept.-Oct.

WEATHER EFFECT ON WHITE-FLY ACTIVITIES AND LEAF CURL VIRUS OF TOMATO
M K NANDA, S ALI, SAON BANERJEE and B K DE
Bidhan Chandra Krishi Viswavidyalaya, Mohanpur, Nadia, West Bengal: 741252

Tomato leaf curl is an important viral disease being spread by insect vector known as white fly (Bemisia tabaci), which has been shown to develop high degree of pesticide resistance. Earlier works suggest that the population dynamic of white flies is largely influenced by meteorological parameters, especially temperature and relative humidity. The present study was carried out at a district seed farm, BCKV, Kalyani (22o 57’ N Latitude, 88o 20’ E Longitude and 7.8 m above MSL) during rabi season, 1998-99 with some determinate and indeterminate types of tomato varieties. The study aims at finding out the meteorological relation of white fly population under field condition and its effect on leaf curl virus. Periodic observations on white fly count (during early morning) and percentage of viral infection from 15 randomly selected plants were recorded at 15 days interval till 90 days after planting. The data were analyzed with ambient and average meteorological parameters pertaining to the period of observation.

The results revealed that white fly population at 30 to 45 days after planting is the most critical viral infection point of view. But the same at later stages did not have that significant impact. A through analysis of meteorological parameters pertaining to the period of study implied that high air temperature and relative humidity favoured increased white fly population in the field where as, increased bright sunshine hour showed negative correlation with white fly population

POPULATION DYNAMICS OF SPOTTED POD BORER (Maruca testualis (Geyer)) AS AFFECTED BY WEATHER PARAMETERS IN COWPEA (Vigna unguiculata (L.) Walpers) AT ANAND IN GUJARAT
USHA G PATEL, R C JHALA and A M SHEKH
B.A. College of Agriculture, Gujarat Agricultural University, Anand-388 110

Studies were carried out in cowpea (var. Pusa Phalguni) crops sown in different months starting from July 1997 to June 1999 to know the impact of different weather parameters on population fluctuation of spotted pod borer, M. testulalis Syn.M. vitrata (Lepidoptera: Pyralidae).

It was indicative from the week-wise data on percent pod damage averaged over crops and years that pest incidence started from forth week, increased gradually and reached to peak (15.07%) in the 11th week of sowing. It decreased gradually in the later period of the crop. The August sown crop had maximum (42.52%) pod borer infestation, followed by crop sown in July (29.17%), June (19.73%) September (19.38) and October (1.77%). The crops sown in rest of the months were free from pod borer attack.

The pod borer incidence on cowpea crops was highest as well as throughout the kharif season with peak activity (>30% damage) during September and October. In winter season, the incidence was at low level (<10% damage) and it was only during early months (November and December). The crops were free from pod damage during summer season.

It was indicative from the stepwise regression analysis that there was a significant positive effect of morning vapour pressure (X8) and mean vapour pressure (X10) in winter season, and significant positive effect of bright sunshine hours (X1) and negative effect of morning vapour pressure deficit (X11) in Kharif season on percent damage (Y) by the larvae of M. testulalis. The stepwise regression analysis carried out on overall basis indicated that there was significant positive effect of morning relative humidity (X5) and negative effect of evening vapour Pressure deficit (X12) on pod damage (Y). The regression equations developed are:1. For winter season : Y= - 7.4419 + 3.0335 X8 + 1.8979 X10 , (R2 = 0.63) 2. For Kharif season : Y = 27.4064 + 4.1609 X1 – 11.5325 X11 (R2 = 0.59) 3. On over all basis: Y = - 2.2804 + 2.1968 X5 – 2.2796 X12 (R2 = -0.52). By plotting the data on pod damage against weather parameters, It was indicative that morning relative humidity more than 80 percent and evening vapour pressure deficit less than 20 mm were found to be favorable conditions for an increase in infestation by M. testulalis in Cowpea crops.

POPULATION DYNAMICS OF LEAF MINER (Acrocercops caerulea (Meyrick)) AS AFFECTED BY WEATHER PARAMETERS IN COWPEA (Vigna unguiculata (L.) Walpers) AT ANAND IN GUJARAT
USHA G PATEL, R C JHALA and A M SHEKH
B.A. College of Agriculture, Gujarat Agricultural University, Anand-388 110

Studies were carried out in cowpea (var. Pusa Phalguni) crops sown in different months starting from July 1997 to June 1999 to know the impact of different weather parameters on population fluctuation of leaf miner, A. caerulea (Lepidoptera: Gracillaridae).

It was indicative from the week-wise data on larval population averaged over crops and years that pest appeared in the 3rd week of sowing, increased gradually and reached to highest level (1.34 per plant) in the 6th week of sowing. And then declined gradually in the later period of the crop. The July and October sown crops harbored maximum (1.85 per plant) and minimum (0.11 per plant) larval population, respectively. The population remained throughout the three seasons but it was comparatively at higher level during kharif season than in winter and summer seasons.

It was further indicative from the stepwise regression analysis carried out to find out specific impact of different weather paramerters (X) on pest population (Y) than there was a significant positive effect of bright sunshine hours (X1) and evening vapour presure deficit (X12) in winter season, and significant negative effect of bright sunshine hours (X1) and positive effect of minimum temperture (X3) in summer season and and significant positive effect of mean vapour pressure (X10) in Kharif season on larval population. The stepwise regression analysis carried out on overall basis indicated that there was significant positive effect of evening relative humidity (X6) and rainfall (X15) on larval population. The regression equations developed are:

1. For winter season: Y= - 1.0943 + 0.0833 X1 + 0.0535 X12     R2 = 0.78

2. For summer season: Y = 0.9418 – 0.0559 X1 + 0.1540 X13     R2 = 0.63

3. For Kharif season: Y = - 0.7536 + 0.0849 X10     R2 = 0.28

4. On over all basis: Y = 0.0506 + 0.0169 X6 + 0.0038 X12     R2 = 0.29

The data on larval population plotted against weather parameters, clearly indicated that evening relative humidity above 60 percent during rainy days was found to be favorable conditions for an multiplication of leaf miner population in Cowpea.

EFFECT OF WEATHER PARAMETERS ON CHILLI DISEASE COMPLEX
R JAGADEESHWAR, K M DAKSHINA MURTHY, G UMA DEVI and E RAMAKRISHNA GOUD
Regional Agricultural Research Station, Jagtial, AP, 505327

The influence of weather parameters in development and spread of major diseases of chilli was studied during 2nd fortnight of August to 1st fortnight of January 2003. A mean temperature range of 16.88 to 30.95°C, relative humidity (96.16%) and total rainfall of a magnitude of 35.4-39.83 mm with 4.04 mm rainy days per weak during the crop growth favoured high incidence of chilli mosaic (32.50%). Similarly powdery mildew incidence increased from October onwards due to decrease in minimum temperature (< 20oC). The incidence of die back (2.85-12.00%) was observed right from transplanting to final picking due to prevailing maximum temperature (28.8-32.8°C) coupled with high relative humidity (>95%).When linear regression equation were subjected to the meteorological data of standard weeks to find out the stability of simulations model it was observed that the observed values of the disease severity were quite close to the calculated values

EFFECT OF WEATHER PARAMETERS ON POPULATION FLUCTUATION OF Aphis gossypii Glover AND ITS PREDATORS ON ISABGOL
H M PATEL, P K BORAD and P R VAISHNAV
Department of Entomology, B A College of Agriculture, GAU Anand Campus, Anand – 388 110

An attempt has been made in this study to workout the role of meteorological parameters on the population fluctuation of Aphis gossypii Glover and it’s predatory fauna on medicinal crop isabgol at medicinal and aromatic farm, Gujarat Agricultural University, Anand during 1999-2000 and 2000-2001. The mean temperature was found to have positive and significant association with A. gossypii and it’s predatory fauna during both the years. Increase in temperature from 20 to 28 °C induced the multiplication and growth of the pest accompanied by increase the population of it’s defenders (Coccinellid, Chrysopid and Syrphid) in nature. The association of relative humidity and bright hours of sunshine with aphid population and it’s natural predators were significantly negative and positive respectively during 1999-2000. The vapour pressure (VP) had significantly positive influence on predators (Coccinellid and Chrysopid) of A. gossypii during 2000-2001 while association with pests (aphid) was not established during both the years.

INFLUENCE OF ANTECEDENT WEATHER VARIABLES ON BACTERIAL LEAF SPOT OF GRAPES IN NORTHERN KARNATAKA
M R RAVIKUMAR, H VENKATESH, SHAMARAO JAHAGIRDAR, M A BELLAKKI and K N PAWAR
University of Agricultural Sciences, Dharwad-580005.
College of Agricultural and Regional Agricultural Research Station. Bijapur-586101

In Northern Karnataka increasing area under grape cultivation has led to multifold dynamism in the horticultural system. Bacterial leaf blight caused by Xanthomonas campestris Pv. Viticola has become a stumbling block in the production system in recent years. Studies on influence of weather parameters on incidence of bacterial leaf spot was undertaken for three years with regular fortnightly recording of the severity levels at disease development, peak and decline stages. Correlation analysis with present week’s and cross correlation with previous week’s meteorological data was performed. It is noticed that in the present and previous week analysis both hygric and thermal factors have influenced the diseased at all stages. The evening time relative humidity (RH2) in present (r= -0.50) and previous (r= -0.49) week at disease initiation stage had negative influence. The diurnal range of relative humidity in present (r= -0.59) and previous (r= -0.56) week at disease initiation stage had shown significant negative association. At one–week lead-time in peak stage the maximum temperature (r= -0.54) and minimum temperature (r= -0.43) had significant negative relation with the disease. However, maximum (0.79) and minimum temperature (r=0.68) at decline stage at one-week lead-time had significant positive association with the disease. Different types of statistical models were tested and the polynomial model gave the best fit for development and declining stages of the disease.

Development Stage:

D1= 0.0014 X5 – 0.055X4 + 0.739 X3 – 3.331 X2 – 0.646 X + 66.07 R2 = 0.68

Decline Stage:

D1= 0.0152 X5 + 0.499X4 – 5.80 X3 +30.7 X2 – 65.80 X + 53.9 R2 = 0.71

Where X = Maximum temperature at one week lead-time

Thus, it is noticed that meteorological factors namely maximum and minimum temperature have got greater negative influence in initiation of the disease, while , at decline stage these two factors have got significant positive association at one week lead time. The rainfall at initiation stage in present week had significant negative association with the disease. The models developed can be used in development of in development of Agro advisory bulletins through routine monitoring of weather and disease.

ROLE OF WEATHER FACTORS IN THE DISEASE DEVELOPMENT AND SPREAD OF ANTHRACNOSE OF GRAPE
B PAMPANAGOUDA, V I BENAGI and V B NARAUND
Krishi Vigyan Kendra, Regional Agricultural Research Station-Bijapur-586106

Field trial was carried out to know the unravel effect of environment on anthracnose of grape on two successive seasons of 1999 and 2000. Among the epidemiological factors Viz., temperature, rainfall and relative humidity were studied on disease development. Further the percent disease index was correlated with previous weeks average of weather parameters. The present study reveal that, the disease development was observed from 2nd week of August to 2nd week of September and this period was characterized by decrease in maximum and minimum temperature and increase in maximum and minimum relative humidity followed by increase in rainfall. Further it indicated highly significant positive correlation between the disease index and rainfall (r= 0.602), maximum and minimum relative humidity (r=0.801 and 0.936). Where as it showed negative correlation with maximum and minimum temperature (r= -0.902 and –0.240).

IN VITRO EVALUATION OF PLANT EXTRACTS AGAINST ANTHRACNOSE OF GRAPE
B PAMPANAGOUDA, V I BENAGI and M K NAIK
Krishi Vigyan Kendra, Regional Agricultural Research Station-Bijapur-586101

The evaluation of plant extracts against anthracnose of grape was carried out during 1999 in plant pathology laboratory, College of Agriculture, Raichur. The plant extracts tried were onion bulb extract, neem leaf extract and Castor leaf extract but complete inhibition of the fungus was not observed with any of the plant extract tried. Considerable amount of inhibition was noticed in onion bulb extract (46.21%) followed by Neem leaf extract (38.83%) and Castor leaf extract (33.30%).

DEVELOPMENT OF WEATHER BASED PREDICTION MODELS FOR WHITE RUST DISEASE IN MUSTARD UNDER A SEMI ARID ENVIRONMENT
SANJEEV KUMAR, ASHOK KUMAR, *RANJNA AGGRWAL and N V K CHAKRAVARTY
Division of Agricultural Physics, Indian Agricultural Research Institute, New Delhi-110012
*Indian Agricultural Statistics Research Institute, New Delhi-110012

Field experiments were conducted during rabi season of 2001-2002 and 2002-2003 to study the relationship between different weather parameters and the development of white rust disease in two mustard varieties viz., Varuna and pusa Jaikisan. The crops were sown at ten different dates at weekly interval, starting from 1st October till 3rd December. Weather data were recorded in the conventional meteorological observatory as well as automatic weather station installed in the experimental field. Data on disease initiation and progress were recorded twice a week till the crop harvest. Utilizing the weather and disease data different predication models were developed for each week starting from pre-sowing week onward and validated on the disease progress data independent data set. Highly significant correlation between percent disease severity and Temperature (min., max. & mean) (p=0.01), Relative humidity (evening) (p=0.05) and growing degree-day accumulation (p=0.05) were observed during pre-sowing and first three weeks of sowing. During fifth, sixth and seventh week of sowing a significant correlation was observed between percent disease severity and temperature (maximum and mean) (p=0.01), relative humidity (morning, evening and mean) (p=0.01) and sunshine hours (p=0.01).

The model equations developed showed a highly significant coefficient (R2) of above 0.90 up to fifth week after sowing. The mustard crop is vulnerable to attack of white rust right from germination till harvest, infection at flowering stage results in most damaging from the disease. Therefore further modification and validation of these models over the season may provide a suitable prediction system that will help in scheduling the plant protection measures to minimize the damages and having a healthy harvest.

EFFECT OF WEATHER FACTORS ON POPULATION OF ALATE MUSTARD APHID IN MUSTARD CROP
ASHOK KUMAR, SANJEEV KUMAR, N V K CHAKRAVARTY, S K PRASAD* and R D GAUTAM*
Division of Agricultural Physics, Indian Agricultural Research Institute, New Delhi-110012
*Division of Entomology, Indian Agricultural Research Institute, New Delhi-110012

Field experiments were conducted during rabi season of 2001-2002 and 2002-2003 to study the pattern of appearance and dispersal of alate aphid in mustard crop. Two mustard varieties viz., Varuna and pusa Jaikisan were sown and the surrounding fields were also having mustard crop. Sticky traps installed in the field at a height of five feet above ground were used for the study. Traps were replaced at weekly intervals and number of aphids was counted. Data on weather variables were recorded using an automatic weather station installed in the field. The data were analyzed to find out the effect of different weather factors on appearance and dispersal of alate aphids.

The first alate aphids appeared on 25th October when the first sown crop was at four-leaf stage. Average number of alate was 85, which showed an increase in the first two weeks of appearance and then a declining trend was observed through December and January. This was followed by an increase in alate formation during the month February and reached the peak population during second to third week of March i.e. the time of crop harvest. The intermittent rise and fall in alate formation was found to be affected primarily by rise or fall in the mean daily temperature and to some extent by mean relative humidity. Temperature showed a positive whereas relative humidity a negative correlation with the alate aphid population. The study holds relevance in studying the degree of aphid infestation in mustard crop. The increase or decrease in alate formation has been observed to give some account of corresponding aphid infestation in mustard crop.

DEVELOPMENT OF Helicoverpa armigera FOREWARNING SYSTEM FOR PULSE BASED CROPPING SYSTEM AT KANPUR
A DHANDAPANI, VISHWADHAR*, D K DAS, T P TRIVEDI, NAVEEN CHONA, PINKI BHANDARI and S K SINGH*
National Centre for Integrated Pest Management,Pusa, New Delhi-110 012.
*Indian Institute of Pulses Research, Kalyanpur, Kanpur-208 024,Uttar Pradesh

Helicoverpa armigera is the most important insect pest of chickpea and pigeonpea. It causes considerable damage to the total pulse crop production in India. The data on pheromone trap catches of male moth of H. armigera from 1983 to 2001 were recorded at Indian Institute of Pulses Research, Kanpur and analyzed along with regular weather parameters. Three criteria have been developed for predicting the initiation and peak activity of H. armigera during 10-14 standard meteorological weeks (March). At first, there should be sudden rise (>4°C) in minimum temperature around 5-9 standard meteorological weeks. Secondly, considerable (>15 male moth/ trap/week) base population of the pest must be present during 1-9 standard meteorological weeks. Lastly, there should be some rainfall during 1-9 standard meteorological weeks.If all the three factors are satisfied in a year, the expected population of H. armigera in the month of March would be on the higher side. On the other hand, if no or only one parameter is satisfied, the expected population would be on the lower side. Agreement with two parameters indicates moderate pest population levels. Thus, using the weather parameters along with pheromone trap counts during 1-9th meteorological standard weeks, the H. armigera population level can be predicted one month in advance. The pest population of 10 years out of 14 years was predicted satisfactorily using these three criteria and all the years with higher populations are predicted accurately.The validation was done at field conditions during 2001-02 and 2002-03 and the prediction found to be accurate during these two seasons.

CONSTRUCTION OF WEATHER INDICES USING PRINCIPAL COMPONENT TECHNIQUE FOR POPULATION DYNAMICS STUDY
H M BHATT, B K BHATT* and M G PATEL**
Dept.of Agricultural Statistics, *Deptt.of Agricultural Meteorology, ** Deptt. of Entomology
B A College of Agriculture,Gujarat Agricultural University, Anand Campus, ANAND-388 110 (Gujarat)

Average population of mango hopper recorded fortnightly in an entomological experiment during 1999 to 2001 were used to assess the role of weather parameters on hopper population dynamics. Statistical techniques viz, correlation, multiple regression and weather indices constructed using Principal Component Technique were used for data analysis.

Among the sixteen weather parameters used, eight-showed significant positive association while only one showed significant negative association with hopper population. The full model regression using original weather parameters accounted about 89 per cent of the total variation in hopper population. However, none of the regression coefficient was found to be statistically significant. Hence the data were subjected to principal component technique (Anderson, 1972). Total 94 per cent of the variations among weather parameters were accounted by first two principal component scores were utilized for fitting the regression equation. The fitted equation explained about 68 percent of the total variation in hopper population along with significant regression coefficients of both the principal component. The fitted model is as under

Y=47.94+6.39 PCI -15.84 PC2 (R2 =0.681)

Thus weather indices constructed on the basis of principal component analysis technique can be effectively used in regression analysis for the prediction of hopper population as compared to the regression technique using original parameters.

FOREWARNING OF CHICKPEA POD BORER IN NORTHERN KARNATAKA
H VENKATESH, A P BIRADAR and M A BELLAKKI
Regional Agricultural Research Station, Bijapur-586 101

The paper presents results of an experiment on incidence of pod borer, Helicoverpa armigera (Hubner), on chickpea grown under varying meteorological conditions. The sowing time varied from September 15 to October 31 at fortnightly interval during 1999-2000 to 2002-03 under depleting soil moisture situation. The larval load was collected four times in the crop-growing period, at weekly interval commencing from four weeks after sowing. The crop was sown within the rainy period in case of first two dates of sowing (early sown) conditions, but the sowing was performed after cessation of rains in case of the last two dates of sowing (late sown conditions). Thus the pest initiation period varied from humid warm conditions in case of early sown crop, to drier conditions for the later sown crop. The pest load was generally higher for the crop sown in intermediate situation, i.e., D2 and D3.

Sunshine duration during the week of sowing had an important role in determining the larval load four weeks later, in all sowing conditions. However, the thermal and hygric factors had differing roles for influencing the pest incidence in case of early and late sown conditions. The thermal variables, namely, maximum, minimum and mean temperatures were generally negatively associated with the larval load, with the best correlation of r=0.67*,at three weeks lead time; Whereas the humidity variables, viz. morning and afternoon relative humidity indicated positive association in the sowing week (r=0.48). Completely contrasting thermal relations were noticed for late sown conditions; therein minimum and mean temperature were significantly and positively correlated at all lead weeks, with particular importance at two weeks lead-time (r=0.63). The temperature range was negatively associated with same significance at 2 WLT.

These results have been utilised in development of multiple regression models, which can be used in advising the farmers through Agromet Advisory Bulletins for appropriate pest management in chickpea.

FOREWARNING SYSTEMS FOR THE MANAGEMENT OF DISEASES IN GRAPE: AN OVER VIEW
SHAMARAO JAHAGIRDAR, H VENKASTESH, M R RAVIKUMAR and K N PAWAR
Regional Agricultural Research Station, Bijapur- 586101

Grape (Vitis vinifera L.) is an important commercial horticultural crop of the sub continent. It is grown mainly in warm humid climate of the country. Generally, pest and diseases pose major threat for successful rising of the crop. The major diseases observed in all production areas are powdery mildew, downy mildew, anthracnose, alternaria fruit Rot caused by Botrytis (fungal diseases); bacterial spot disease. In Northern Karnataka increasing area under grape cultivation has lead to multifold dynamism in horticultural system. The fore warning systems developed for mildews and anthracnose has not only helped in issue of accurate advisory but also helped in test verifying the models developed. The models developed for different systems are as follows:

a) For Powdery mildew

Early pruned cases:

DI = 64.85 - 1.83RHR (1) R2 = 0.97

Late pruned case:

DI = 86.69 + 6.41 Max T (2) + 0.30RF (4) R2 = 0.97.

b) Downy mildew:

Early pruned:

DI = 321.15 + 3.82 TR (1) 1.25 RHR (4) (R2 = 0.67)

and Late pruned

DI = 325.59 + 11.25 Max T (3) (R2 = 0.67)

c) Anthracnose:

Early pruned cases:

DI = 188.36 - 9.98 TN (5) 1.53 RH (3) (R2=0.91)

Even though there has been increase in area under grapes in the Northern Dry Zone of Karnataka in recent years due to prevalence of moderate temperature and low humidity, the crop has been affected by diseases. The models developed were test verified by installation of automatic weather station in the farmer’s field for two years. The models developed found most suitable taking into the cognizance of the local abberatic weather situation.

INFLUENCE OF ANTECEDENT EDAPHIC FACTORS AS GOVERNED BY THE PHYSIOLOGICAL TRAITS OF RABI SORGHUM GENOTYPES AGAINST STALK ROT RESISTANCE AND DROUGHT TOLERANCE.
K N PAWAR, SHAMARAO JAHAGIRDAR, B D BIRADAR and M R RAVIKIMAR
Regional Agricultural Research Station, Bijapur- 586101

Fourteen genotypes comprising of released varieties, hybrids and parental lines were screened. For drought tolerance and charcoal rot resistance under sick plot screening methodology during 2000 and 2001 at Regional Agril, Research Station, Bijapur. The entries RS-29,E-36,DSV-4,296 B and RSLG-262 were found promising in medium soil. The periodical soil moisture and soki temperature were receded in the experimental period- indicated positive influence with soil temperature and significant negative association with soil moisture (r=0.72). The important physiological traits identified, which governed their drought tolerance i.e. reduced soil moisture status, are relative water content (RWC), photosynthetic rate at 50% flowering, Transpiration rate and harvest index. The unique traits such as stay green type and delayed senescence were identified as key components in governing tolerance to terminal drought/ stress and charcoal rot resistance in rabi tract of Northern Karnataka. The entries that showed better promise for physiological traits such as RWC, photosynthetic rate, transpiration rate and harvest index are M 35-1, RSLG 262, RSP-3 and DSV-4. Thus, the studies clearly demonstrated that selection of genotype for geographical adaptation is depended on not quality governing genotype but also soil moisture regimes in given situation. The entries RSLG 262, DSV-4, E-36-1 and 296 B showed stay green nature and delayed senescence