Pest complex of groundnut: Thirty six species of insect pests belonging to 10 orders and 19 families were found to infest the groundnut crop at BARI farm, Joydebpur, Gazipur. Of these, only five namely, hairy caterpillar, Spilarctia obliqua ( Walker); common cutworm, Spodoptera litura F.; jassid, Empoasca terminalis Distant; leaf miner, Stomopteryx nerteria M.and leaf roller, Anersia ephippias (Meyr.) were considered as the major pests, while the rests were of minor importance on the basis of their population densities per plant, nature and extent of damage and yield reductions. The population density per plant of major insects namely, S. obliqua, S. litura, E. terminalis, S. nerteria and A. ephippias ranged from 0.25 to 0.30, 0.30 to 0.35, 12 to 14, 1.00 to 1.20 and 1.00 to 1.20, respectively in 2008 while the population density per plant of the above insects ranged from 0.32 to 0.36, 0.35 to 0.40, 15 to 18, 1.20 to 1.25, 1.20 to 1.25 and 1.20 to 1.25, respectively in 2009. Most of the major and minor pests of groundnut were found in higher number per plant in 2010 than in Among the minor insects, pod borer, H. armigera; hairy caterpillar, S., nydia; hairy caterpillar, P. ricini; semilooper, P. orichalcea; green grasshopper, A. crenulata; aphid, A. craccivora; green stink bug, N. viridula; thrips, S. dorsalis; termite, M .obesus; white grab, O. versicolor; and leaf miner, S. emissaria become occasionally important and cause serious damage to the groundnut crop. Lygaeid bug, E. sordidus is mainly post harvest pest. On the basis of feeding behaviour, 12 insects species were grouped as leaf eater, nine as sap sucker, five as root and stem cutter, four as leaf roller and eater, two as flower eater, two as stem borer, another two as leaf miner and remaining one as pod borer
Nature of damage of the important pests: After sowing, ants damage the seeds of groundnut in the soil by boring and eating the kernel and taken away from the original sowing place. The termite damages the seeds by boring the underground nuts and cutting the roots and eating the germinating roots and shoots. The larvae of S. obliqua fed on the older leaves, stems, shoots and flowers causing serious damage to the plant. Spodoptera larvae feed on leaves, tender shoots and flowers voraciously. They completely defoliated the plant in a short time. Jassids (E. terminalis) suck the sap from the leaflets causing yellowing of leaflets, leaf curling, necrosis and finally stunted the growth and gradually die. It also acts as a vector of a leaf curled, tomato spotted and other viruses. The larvae of leaf roller (A. ephippias) feed on shoots and web the top leaves. They make short holes in the leaves and web of the growing points. The larvae of shoot miner ( S. nerteria) web together leaves and feed on them remaining within folds.
Succession of the pests: In 2009 and 2010 groundnut crop was first attacked by ant, Camponotus sp.; and termite, O. redemani; and earwig, U. stali during seed germination stage. Then leaf beetle, Monolepta signata; black weevil, Cyrtozemia cognata; black cutworm, Agrotis ipsilon; leafhopper, Cofana spectra; lygaeid bug, Elamolemus sordidus; jassids, Empoasca terminais; at the seedling stage and their infestation continued up to pod formation stage of the crop during January to May of 2009 and 2010. After 2-3 weeks, aphids, A. craccivora; leaf roller, A. ephippias; common cutworm, S. litura F. ; pod borer, H. armigera; shoot miner, S. nerteria; green grasshoppers, A. crenulata; green stink bug, N. viridula; thrips, S. dorsalis; flower thrips, F. schultzei and M. usitatus; groundnut moth, S. emisaria and other pentatomid bugs, were frequently observed from flowering to maturity of the crop and recorded on February to May of both the years. Lygaeid bug, E. sordidus, attacked the crop during pod prematurity stage till harvest and also in the threshing floor in the heap. Most of the major and minor pests appeared in the crop during the vegetative and flowering stages (35-55 DAS) and the maximum infestation occurred during pod formation and pod filling stages (50-80 DAS) of the crop in both the years.