As part of an IPM project for resistance to early season pests, the US Asiatic Cotton Germplasm is being screened for resistance to thrips. Twelve accessions of Gossypium arboreum were evaluated in a field test for resistance to natural infestations of thrips. Two commercial cultivars, 'Tamcot CAB/CAS' and 'Stoneville 506', were included as checks. The experimental design was a split plot: main plot treatments received insecticide (Temik) or no insecticide; subplot treatments were cotton accessions. Plant damage due to thrips was rated 28 days after planting (DAP) using a 0-5 scale. Thirty-six DAP, nine plants per plot were harvested and fresh weights obtained. A ratio of untreated to treated plant weight was used to estimate plant growth reductions due to thrips. One Asiatic accession, A2 154, was significantly different from the commercial checks (P=.05) in ranked damage ratings. Fresh weight of whole plants were correlated with damage ratings.

No-choice growth chamber experiments were begun to determine if anti-biosis contributed to the reductions in damage found in the field test. In the first experiment, six Asiatic accessions were selected from the field test: five showed some resistance and one was comparable to the commercial varieties. Eight seedlings per accession were infested with two adult Frankliniella fusca per seedling. Two noninfested seedlings per accession were placed in a separate chamber. Plants were grown for 21 days, with one accession per chamber except for the noninfested controls. Data were taken on damage and total number of thrips per accession. Due to low damage ratings, infestation rate was increased and 'Stoneville 506' was substituted for one of the Asiatic accessions in the second experiment. Although damage ratings in the both growth chamber experiments were lower, the accessions responses were consistent with those in the field. These preliminary tests indicate reproduction may be inhibited on accessions which show resistance.