THE ATTRACTANCY OF CERTAIN GENOTYPES AND THE EFFECTS OF PLOT SIZE ON THE DENSITY OF SOME INSECT POPULATIONS IN COTTON.

摘要

Studies were conducted at the New Mexico State University Plant Science Farm in Las Cruces, New Mexico to evaluate the attractancy of eight cotton genotypes and the effects of two plot sizes on the densities of pest and beneficial insect populations.; The cotton genotypes evaluated were Stoneville 825 (nectariless); Stoneville 817 (frego bract); La. 15177-392 Sm (smooth leaf); Gumbo, Stoneville 7A and 213 background (okra leaf); HGVNB 1977 O.P. (high gossypol); Stoneville 483 (glandless); G. 1821 (nectariless-glandless) and the check, Stoneville 7A (glanded).; Samples were taken with an International High Clearance tractor equipped with a vacuum sampler (a 2400 CFM vane axial fan powered by a 36 hp Rockwell 2 stroke engine).; The pest insects studied included: Cotton bollworms, Heliothis zea (Boddie), lygus bugs, Lygus spp., green stink bugs, Chlorochroa sayi Stal and C. ligata (Say).; The beneficial insects studied included both predators and parasites. The predaceous species included: Lacewings, Chrysopa spp., minute pirate bugs, Orius spp., big eyed bugs, Geocoris spp., lady beetles, Hippodamia convergens Guerin-Meneville, collops beetles, Collops spp., and the nabid bugs, Nabis spp. The parasitic species studied were all from the Order Hymenoptera and included 5 super=families and 21 families of which 38 were identified to the genus and 14 to the species level.; An illustrated key, using line drawings, was prepared for the identification of the most common hymenopterous parasites of economic importance for cotton in this area.; The data indicates that most insect populations, both pest and beneficial species, were either significantly attracted or repelled by the characteristics of the different cotton genotypes.; Plot sizes were significantly different at the individual species or group level, with more insects as a whole being collected from the larger eight-row plots than from the one-row plots. However, a nonsignificant interaction between plots and genotypes indicates that the order of attractancy of the genotypes was statistically the same for both plot sizes.