Epilachna beetle complex in vegetables

Abstract

Studies on the epilachna beetle complex occuring on selected vegetable crops were carried out at the College of Horticulture, Kerala Agricultural University, Vellanikkara, Thrissur, Kerala during 1995-1997 to establish their taxonomic identities. The morphology, biology and the natural enemy association of these beetles were also studied. Based on the male and female genitalial characters, the epilachna beetles feeding on brinjal, bittergourd and cowpea were identified as Henosepilachna vigintioctopunctata (Fabricius), Henosepilachna septima (Dieke) and Afidenta misera (W eise) respectively. The salient features to distinguish between these three species are the curvature of the apex of sipho which is a part of the male genitalia and the shape of the female genital plates. The apex of sipho is curved outwards with a bluntly rounded tip in both H. vigintioctopunctata and A. misera, while it is curved inwards with a sharply pointed tip in H. septima. A semicircular notch is present on the female genital plates of H. vigintioctopunctata, while there is a slit like notch in H. septima. The notch on female genital plate is absent in A. misera. It was confirmed that the beetles are highly host specific. Henosepilachna vigintioctopunctata showed a strict host restriction to solanaceous plants, while H. septima and A. misera are restricted to a few cucurbitaceous and leguminous plants respectively. There was not much gross morphological variations between the species except for their body size, H. septima being the largest and A. misera the smallest. The different spot variants met within the species by the variations in elytral maculation was found to be a morphological character only. Though the grubs of the three species are similar in external appearance, they can be easily distinguished by the structure and sclerotisation of the scoli on body surface and the details have been discussed. The three species showed similar biological attributes with a life cycle period of 25.25, 2l. 59 and 24.76 days for H. vigintioctopunctata, H. septima and A. misera respectively at 27.6°C and 89.5 per cent relative humidity. Under . field conditions, the grubs and pupae of the three species were parasited by Pediobius foveolatus (Crawford) (Eulophidae:Hymenoptera) and the egg masses were parasitised by Tetrastichus ovu/orum Ferriere (Eulophidae:Hymenoptera).