Frankliniella occidentalis (Pergande) obtained from native (N), laboratory (L), or greenhouse (G) environments in California (CA), Nevada (NV), Texas (TX), Illinois (IL), or Massachusetts (MA) were evaluated for feeding aggressiveness on Impatiens wallerana Hook.f. and for spinosad resistance on Gerbera jamesonii Bol. ex. Adlam. In one experiment, insects from seven populations, CA-L1, CA-N2, TX-L1, IL-G1, CA-N3, IL-L1, and CA-G1, were used to assess feeding aggressiveness or to initiate a laboratory colony. Feeding aggressiveness was assessed 0, 7, 14, and 21 weeks after collection (WAC) using a digital image analysis system to determine the percent leaf area damaged by feeding. Damage varied the most at 0 WAC and variation decreased until 21 WAC. Declining damage was attributed to the standardization of fitness in the laboratory colonies or possibly to limited genetic diversity within the colonies reducing insect fitness over time. In a second experiment, nine populations, NV-N1, NV-N2, CA-N1, CA-G1, IL-G1, IL-L1, TX-G1, TX-L1, and MA-L1, reared for 4 months in the laboratory varied in percent survival when flowers inoculated with 25 F. occidentalis were sprayed with spinosad at label (0.81 ml·L-1), half label (0.41 ml·L-1), deionized water, or no spray. At the 0.41 ml·L-1rate, IL-G1 and CA-G1 populations had the highest survival at 8.8 and 5.0%, respectively. At the 0.81 ml·L-1 rate, 8.8% of applied insects from IL-G1 survived which was significantly more than any other colony. Feeding aggressiveness of F. occidentalis populations on I. wallerana leaves varies. Some resistance to spinosad exists in greenhouse populations of F. occidentalis.
Species 1: Thysanoptera Thripidae Frankliniella occidentalis (western flower thrips)
Keywords: Impatiens wallerana, image analysis
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