Biology of whitegrubs in relation to physico chemical properties of soil

Abstract

In Himachal Pradesh, Brahmina coriacea, Holotrichia longipennis, Anomala dimidiata and Melolontha indica were found to be the important species endemic to Shimla, Kangra, Una and Mandi districts, respectively. The soil pH in the state ranged from 4.7 7.4, and organic carbon varied from 0.75 2.94 per cent. The observations on biology of B. coriacea, H. longipennis and A. dimidiata were recorded in soils collected from whitegrub endemic pockets. The incubation period was not affected by the soil type in any of the species, however, egg hatching was significantly affected ranging from 41.5 94.8 per cent in different species in different soils. The duration of first instar in B. coriacea and A. dimidiata, second instar in B. coriacea, H. longipennis and A. dimidiata and third instar in B. coriacea and H. longipennis was not affected in different soils. The duration of first instar in H. longipennis and third instar of A. dimidiata was significantly affected in different soils. Shortest duration of first instar of H. longipennis (11.7 days) and third instar of A. dimidiata (207.3 days) was recorded in Janjehli and Nauni soils, respectively. The larval survival differed significantly in most of the instars in different species. Overall value of larval growth index (0.22) was calculated to be maximum for B. coriacea in Seobagh soil. The pupal period in H. longipennis and A. dimidiata was not affected in different soils, but pupal survival in B. coriacea (16.7 81.0 %) and A. dimidiata (27.8 73.8 %), and pupal period in B. coriacea were significantly affected in different soils. The fecundity of B. coriacea was found to be maximum in Una soil. The females of H. longipennis and A. dimidiata deposited maximum eggs in Seobagh and Bharmour soils, respectively. Soil moisture conditions severely affected oviposition in different scarab species, and there was no egg laying at moisture percentage of and#8805;30 per cent. At 15 per cent soil moisture, significantly higher fecundity was recorded in all the species. Soil moisture