Abstract

 Effect of climatic factors on population build-up of aphid complex of rapeseed-mustard viz. mustard aphid, Lipaphis erysimi (Kaltenbach), cabbage aphid, Brevicoryne brassicae (Linnaeus), and green peach aphid, Myzus persicae (Sulzer) and associated natural enemies (coccinellids, syrphids and a parasitoid, Diaeretiella rapae M’Intosh) was studied at Experimental Farm of CSK HPKV Palampur over a period of three years. Correlation coefficients indicated that the temperature favoured build-up of aphid population and their natural enemies while rainfall exerted negative impact. The population of coccinellids was negatively correlated with the population of L. erysimi and M. persicae while, positive correlation with B. brassicae was observed. On the other hand, population of syrphids was found to be positively correlated with aphid population. Predictive model using stepup regression analysis revealed that a weak relation in aphid population was attributed by weather parameters particularly minimum, maximum temperature and bright sunshine hours. Regression analysis revealed that 89 per cent variation in parasitization by D. rapae was attributed by minimum and maximum temperature, rainfall, relative humidity and bright sunshine hours.
Highlights
The rapeseed-mustard group broadly includes, Indian mustard
Keeping in view the importance of the crop and the damage caused by these species of aphids, the present investigations were initiated to study the population buildup of aphid complex i.e. L. erysimi, B. brassicae and M. persicae on rapeseed-mustard, and the population dynamics of associated natural enemies (Coccinellids, syrphids and a parasitoid, Diaeretiella rapae McIntosh) in relation to climatic factors under natural field conditions
The perusal of pooled data revealed that among the three aphid species, L. erysimi was the first to appear on the crop in the month of December (49th SMW) and remained active for a longer duration followed by B. brassicae and M. persicae (Table 1, Fig. 1)
Summary
The rapeseed-mustard group broadly includes, Indian mustard Aphid complex comprising mustard aphid, Lipaphis erysimi (Kaltenbach), cabbage aphid, Brevicoryne brassicae (Linnaeus), and green peach aphid, Myzus persicae (Sulzer) are serious pests and one of the important limiting factors in the production of rapeseedmustard. Relative humidity, sunshine hours and rainfall play vital role in multiplication and distribution of insect-pests. Keeping in view the importance of the crop and the damage caused by these species of aphids, the present investigations were initiated to study the population buildup of aphid complex i.e. L_erysimi, B. brassicae and M. persicae on rapeseed-mustard, and the population dynamics of associated natural enemies (Coccinellids, syrphids and a parasitoid, Diaeretiella rapae McIntosh) in relation to climatic factors under natural field conditions
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