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Key words: Population, stem borer and natural enemiesIn India maize crop is being attacked by about 139 species of insect pests with varying degree of damage. However, only about a dozen are quite serious (Sarup et al. 1987, Siddiqui andMarwaha 1993). Among them some important lepidopteran stem borers seriously limit potentially attainable maize yields by infesting the crop throughout its growth, from seedling stage to maturity. Seventeen species in two families (Pyralidae and Noctuidae) have been found to attack maize in various parts of Africa. However, Chilo partellus (Swinhoe), Chilo orichalcociliellus Strand, Busseola fusca Fuller, Sesamia calamistis Hampson, and Eldana saccharina Walker are of great importance. The yield losses caused by stem borers to maize vary widely in different regions and range from 25-40% according to the pest population density and phenological stage of the crop at infestation (Khan et al. 1997).Among them maize stem borer, C. partellus is most dominant contributing 90-95 per cent of the total damage in kharif season (Jalali and Singh 2002). Despite of, intensive work done in India on C. partellus yet, the work in Jammu region is lacking. As this pest is becoming a major problem in sub mountainous region of Jammu, yet distribution and intensity of infestation of this pest has not been studied therefore; it is imperative to study population patterns and natural enemies associated to this pest. To achieve this objective, a multi directional light trap was operated from 1800 to 0600 hours daily. The collections were made weekly throughout the crop seasons of 2006 and 2007. Infestation of stem borer was determined by counting the total number of dead hearts and the leaf damage in each selected plot at weekly interval. Total number of healthy and infested plants was counted in each plot during each week and means of three selected locations were calculated.It was evident that stem borer appeared in the light trap in 21 st week (6 adults), when the mean maximum and minimum temperature (25.70 and 14.95ºC) with relative humidity (63.50 %) (Table 1). Maximum traps (47 adults / trap) were observed in 29 th week, when average maximum and minimum temperature (29.25 and 16.45ºC) with relative humidity 82.6%. After 35 th standard week, number of adults decreased gradually to 3 moths/ trap in 41 th standard week when the maximum and minimum temperature (23.34 and 12.54ºC) with relative humidity of 67.61%. Thereafter no catch was observed. The adult population was positively correlated with weather parameters viz. relative humidity (r=0.908, P<0.01) maximum (r=0.501, P<0.05)and minimum (r=0.484, P<0.05) temperatures.Results clearly indicate that initially adult population tends to increase in summer months and decreases further till onset of winter season. Such results might be attributed due to hibernation of larvae into the stubbles and maize stalks. These findings are supported by Kumar (1984), Singh et al. (1985) and Kfir (1988) who found that overwintering larvae causing infestation hibernate...

Larvae that survived sublethal infection of Spodoptera litura granulovirus (SlGV) as 4th and 5th instars led to an increase in the larval period of treated larvae when compared with control. While pupal period and pupal weight remained unaffected, a significant alteration in sex ratio was observed. Although survivor moths could mate successfully, there was a significant reduction in the proportion of ovipositing females in treated larvae as compared with control. A significant reduction in fecundity of moths emerging from treated larvae was also noticed, but the egg viability was never influenced by the treatment. However, there was a significant increase in progeny mortality in treated larvae over control. The offspring mortality in survivors increased up to three subsequent generations but not thereafter. Hence, repeated field applications of inoculum are required. The implication of the present findings in terms of reduced fecundity coupled with increased larval development indicates that vertical transmission can lead to increased virus dispersal, both of which would reduce the host's innate capacity for population increase. This is particularly important in S. litura, which is a migratory species and occurs sporadically in a particular agro-ecosystem.

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