Seasonal abundance of chrysopids (Neuroptera: Chrysopidae) preying on Helicoverpa armigera (Hubner) (Lepidoptera: Noctuidae) and Aphis gossypii (Glover) (Homoptera: Aphididae) on cotton in eastern Tanzania
1996
Kabissa, J.C.B. | Kayumbo, H.Y. | Yarro, J.G.
The occurrence of chrysopids on cotton in relation to Helicoverpa armigera and Aphis gossypii was studied between 1988 and 1991. By the 8th week after germination predators and their prey were already established on the crop. Among the chrysopid species observed on cotton, only Mallada desjardinsi (Naves) and Chrysoperla sp. occurred on cotton when both H. armigera and A. gossypii were present. Chrysopids and A. gossypii were most abundant on cotton between the 12th and 15th weeks after germination. However, peak abundance of eggs and larvae of H. armigera on cotton occurred earlier between the 8th and 13th weeks. Parasitism in populations of field collected larval, pupal and imaginal chrysopids was noted. Activity of adult H. armigera and chrysopids monitored by light traps showed two peaks of abundance coinciding with short and long rains. Prospects of manipulating chrysopids for biological control of H. armigera and A. gossypii are discussed.
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