Exploitation micromus igorotus Banks and micromus timidus Hagen (Hemerobliidae: Neuroptera) in the management of aphids in cotton and tobacco
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Date
2009
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UAS Dharwad
Abstract
Micromus timidus accepted nine aphid species and a psyllid as host. Leaves, open
bolls and cotton thread served as oviposition substrates. Full grown larva pupated in double
layered cocoon in counseled places. Aphis gossypii and Melanaphis sacchari found to be
most suitable hosts as growth, development reproductive traits and feeding potential were in
favour. Egg to adult and egg to egg duration was shortest on A. craccivora followed by M.
sacchari. Both larva and adult of M. timidus consumed higher number of A. gossypii and M.
sacchari as most palatable food sources. Morphometry of mouth and body parts were also
recorded. Rearing of Micromus igorotus on A. gossypii and C. lanigera for five generations
did lower fecundity slightly but not other traits. Reduction in survivability of egg, larva and
adult was evident.
Micromus igorotus @ 1,000 adults/ha outperformed in reducing cotton aphid
population. Five pairs of M. timidus adults/plant reduced the cotton aphid population. Five
pairs of M. timidus adults/plant reduced the cotton aphid population effectively with higher
predatory recovery. On tobacco, 20,000 to 25,000 M. igorotus adults/ha reduced aphid
population and increased yield by 46.6 and 56.8 per cent. Release of five pairs of M. timidus
adults/plant was also effective.
Emamectin benzoate was highly toxic to all stages of M. igorotus and M. timidus and
thiodicarb was least toxic to eggs and larva. Profenophos at recommended field concentration
persisted at greater level to inflect above 90 per cent mortality to grubs up to 7 days and
retained toxicity for 30 days. The order of persistent toxicity was profenophos>thiomethoxam
>methomyl>imidacloprid>novaluron>thiodicarb>emamectinbenzoate>spinosad> indoxacarb.
Micromus igorotus eggs were devoured by C. carnea grubs, C. sexmaculata grubs and adults
and syrphid maggots under free choice in the presence of aphid. While, M. igorotus did not
feed on any stage of these predators.
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Keywords
micromus, cotton, tobacco