Efficacy of selected insecticides against flower thrips infesting southern highbush blueberry, 2023

This study aimed to evaluate the effectiveness of selected insecticides against flower thrips infesting southern highbush blueberries in a commercial blueberry field located in Bacon County, Georgia (31.655371, −82.586161). A total of 7 treatments, including an untreated check, were applied using a boom sprayer (Bennett’s Tractor Service, Waycross, Georgia) at an output of 40 gallons per acre. The insecticides used were Assail 30SG, Movento 240 SC, Sivanto Prime 200 SL, Delegate WG, Entrust SC Naturalyte, and Spear T. The experimental design employed a randomized complete block design with 4 replications. Each plot consisted of 2 adjacent rows of 18 bushes per row, with an approximate size of 1,045 sq. ft. (36 bushes per plot). To minimize drift, each block was separated by 1 untreated buffer row.

For sampling, 10 flower clusters (1 cluster equals 7–8 individual flowers) from each plot were collected, placed in ziplock bags marked with the sampling date and treatment plot, and transported to the Fruit Entomology Lab in Athens, Georgia, for processing. The samples were placed in a one-quart plastic cup with 70% ethanol for 30 min to dislodge the life stages of thrips. The samples were then removed, leaving the thrips in the alcohol. The contents in the alcohol were sieved using a 25-µm grating USA Standard Testing Sieve (W. S. Tyler, Inc.), and the residue in the sieve was washed off with 75% alcohol into a Petri dish. The number of flower thrips adults, and larvae were then counted using a stereo microscope. The data obtained were analyzed using JMP Pro software, and analysis of variance (ANOVA) was used to test the effects of the treatments on the number of flower thrips adults and larvae. Means were separated using Tukey’s HSD test.

The efficacy of the treatments was assessed based on the mean count of flower thrips adults, and larvae. No significant differences were observed in the count of adults and larvae in the pre-spray samples (Tables 1 and 2). However, the adult population was significantly affected by the treatments at 1 DAT, 4 DAT, and 7 DAT, while the larval count was significantly suppressed by the treatments in all sampling dates from 1 DAT to 10 DAT (Tables 1 and 2).

Regarding adult control, all insecticide treatments, including Assail, Movento, Delegate, Entrust, and Spear T, resulted in significantly higher suppression of the adults at 1 DAT and 4 DAT (Table 1). However, Assail was found to be more effective in controlling adults than the other treatments (Table 1). At 7 DAT, Assail was significantly more effective than Sivanto in controlling adults (Table 1).

As for larval control, Movento treatment resulted in significantly higher suppression of the larvae at 1 DAT compared to the untreated check (Table 2). At 4 DAT, 7 DAT, and 10 DAT, the larval counts were significantly lower in all the insecticide treatments in comparison to the untreated check (Table 2). However, Delegate, Movento, and Assail were found to be more effective in controlling the larvae than Sivanto and Spear T (Table 2).

Funding

This research is supported in parts by industry gifts of products.