No abstract

Responses of male and female Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae) to colors of various hues and brightness levels were compared between swarming and non‐swarming behavior periods. Relative rankings of color preference were similar between males and females and between swarming and non‐swarming behavior periods. Numbers of thrips were higher on blues, violets, white and somewhat less on some yellows, while lower numbers were found on greens, reds, some yellows and highly UV reflective white. The effect of UV reflection on thrips response to color depended upon the amount of UV reflectance. Highly UV reflective white (78% reflectance at 365 nm) captured very few thrips compared with low UV white (14% reflectance at 365 nm), but colors with less than 35% UV reflectance had no negative effect on numbers of thrips captured compared with their lower UV counterparts. Correlations of average preference rank of colors across all tests with relative rank of brightness of the colors (based on the area under the reflectance curve in different spectral ranges) indicated highly significant correlations of preference with the brightness in the blue‐violet range (R = 0.69 for females; R = 0.86 for males, P < 0.0021), but no significant correlation with brightness in the visible, green‐yellow, or UV range. This contrasts with previous physiological research which indicates that spectral response efficiency of this species peaks in the UV and at 540 nm (green‐yellow range). Several possible physiological, behavioral and color brightness explanations for this discrepancy are discussed. Significantly higher numbers of male thrips were trapped during swarming (4.5–6.3 ×) compared with non‐swarming behavior periods. Significantly higher numbers of males were trapped than females during swarming behavior periods, but more females were trapped than males during non‐swarming behavior periods. Sex ratios during non‐swarming periods approximated sex ratios found in populations in plants. Based on the density change relative to sex ratio change between behavior periods, there was an indication of a greater change in male behavior than in female behavior. Since males and females responded similarly to color during both behavior periods and attractive colors were similar to flower colors, this suggests that male thrips use resource‐based areas for aggregation sites.

Test plots were established at the UI Research and Extension Center, Aberdeen, ID. Potatoes were planted 20 May and irrigation was by fixed sprinkler sets. There were seven chemical treatments and one untreated check replicated four times in a randomized complete block design. Individual plots were 2 rows (36 inch spacing) by 25 ft. Rows were not closed at planting to facilitate hand application of the granular NTN. After insecticide application, the rows were mechanically closed. On 10 Jun foliar applications were made of NTN 240 FS and Furadan 4 F in a 4-5 inch band (20 gal/acre) over the center of the row as a broadcast spray using a CO2 pressurized backpack sprayer. On 9 Jul a second foliar broadcast application (20 gal/acre) of NTN was made on treatment 5 approximately 50 d after planting. On 25 Jun, a single application of Ambush 2 E was applied as a broadcast foliar spray (20 gal/acre) using the previously mentioned system. On a weekly basis, all stages of CPB were counted and percent defoliation estimations were made using whole plant inspections of the center five plants within the two plot rows. Larval stages were separated into small (1-3 instar) and large (4-5 instar). Data were analyzed using ANOVA and significant means separated using Newman-Keuls studentized range test.

Experimental plots were established on the UI Research and Extension Center, Kimberly, Idaho. Potatoes were planted on 28 Apr and irrigated by solid set sprinkler. The soil type was Portneuf silt loam. Seven treatments and one untreated check plot were replicated four times in a randomized complete block design. Individual treatment plots were 4 rows (36-inch row spacing) wide by 25 ft long with 5-ft alleyways separating the plots. Green peach aphids were mass reared on greenhouse mustard plants (Brassica juncea L. ‘Florida Broadleaf’) for release into individual plots. Aphid releases were made into test plots on 14 Jun. A total of four heavily infested leaves were used to inoculate each plot. Treatment sprays were broadcast applied using a CO2-pressurized backpack sprayer (30 psi) and delivering 20 gal finished S per acre (four, 10X hollow-cone nozzles). Aphid counts were made by non-destructively sampling leaves at random from the top, middle, and bottom sections of plants in the center two rows of each plot. The data collected and presented is the total no. of aphids per 20 leaves. On 25 Jun a pre-treatment count was made and all treatments were applied later that d. Data was analyzed using ANOVA and Newman-Keuls multiple means comparison (Significance Level P = 0.05).