BIO-ECOLOGY OF HELOPELTIS ANTONII SIGN. INFESTING CASHEW TREES

The bio-ecology, morphometrics and the nature of damage have been studied in the Cashew Research Station, Kerala Agricultural University, Vellanikkara and in the laboratories of the Department of Entomology from August 1977 to September 1978.

For biological studies, adults reared out from field collected nymphs confined on apical shoots of cashew seedlings of 6 – 8 months growth were used. For oviposition, pairs were confined on shoots and these were kept at 25 ± 1 °C in an air conditioned insectary. The embryonic and post embryonic developmental stages were studied at 28 ± 1 °C in the B.O.D. incubator.

In the adult field populations, females always predominated and during October 1977 – January 1978, the ratio of females to males ranged from 1:0.49 to 1:0.62. The pre-oviposition and oviposition periods last for 4 and 6 days respectively. The mean longevity of females is 6.5 days, while the male life-span lasts for 5.2 days only. The mean fecundity per female at 25 ± 1 °C is 31.15. The life-cycle from egg to adult emergence occupies 22.2 days at 28 ± 1 °C, the duration of the different stages being 7.3, 2.1 3.5, 3.2, 3.3 and 2.8 days for the egg and the nymphal instars I, II, III, IV and V respectively.

The adults and nymphs feed on tender shoots, tender foliage, floral branches, tender apples and nuts. On the lamina, nearly triangular, water soaked non-coalesing necrotic lesions develop around the veins as a result of feeding and the tissues eventually dry up leaving brownish patches. The symptoms on other plant parts are different, being characterised by necrosis of affected tissues followed by the exudation of a gummy substance around feeding punctures. The symptoms are more pronounced at higher temperature levels of 31 ± 0.5 °C. Periodical sampling of field populations of adults and nymphs did not reveal any associated parasitoids and pathogenic micro-organism.

Download Adobe Acrobat Reader (free software to read PDF files)