Citrus thrips insecticide efficacy trial of organic insecticides, 2025

A field trial was conducted in a 42-year-old ‘Washington’ navel orange orchard at the Lindcove Research and Extension Center, Exeter, California, to compare efficacies of organic insecticides to reduce rind scarring caused by citrus thrips. Beleaf, followed by Minecto Pro, was included as a conventional grower standard for comparison. The first application was made on 1 May, and the second application was made on 15 May. Treatments were diluted in 125 GPA and were applied using a 100-gal high-pressure D30 diaphragm pump sprayer with mechanical agitation at 200 psi. For the 2 lime sulfur products, water pH was adjusted to 9.5 by adding Manni-Plex K before the products were mixed. All treatments included 1% 415 Supreme Spray Oil as an adjuvant, except for Gargoil, which contained Xena Spreader Sticker, and lime sulfur, which did not include any adjuvant. The experimental design was an RCB. Each block consisted of 7-tree plots and was replicated 3 times. Posttreatment evaluations of fruit scarring damage were done in the last week of August. All outside fruits within reach on each tree were evaluated and rated as 0 (no scar), 1 to 2 (slight scar), and 3 to 4 (severe scar) level of thrips scarring. The mean percentages of scarred and severely scarred fruit were calculated. Within each plot, we also inspected 20 fruits for the presence of thrips and counted the number of predatory mites present on 20 inner canopy leaves at 1 wk after the first and second treatments (1WAT1 and 1WAT2) and 2 wk after the second treatment (2WAT2). Treatment means were compared using ANOVA, and means were separated using Fisher’s protected LSD (P < 0.05) after logarithmic (log10 (x + 1)) transformation of count data and arcsine (square root (x)) transformation of the proportions, respectively. The mean number of fruits examined for rind scarring ranged from 91.9 to 150.4 per tree. In the untreated check, 53.5% of fruit was scarred, with 33.9% severely scarred (Table 1). Three treatments, Venerate, Lime Sulfur Ultra, and Beleaf followed by Minecto Pro, significantly reduced the percentage of severely scarred fruits compared to the untreated check. Grandevo had overall fewer scarred fruit compared to the untreated check, but did not significantly reduce the percentage of severely scarred fruits. Beleaf followed by Minecto Pro, a conventional grower standard, was the only treatment that reduced the incidence of severe scarring below 5%. Means within each column followed by a different letter are significantly different (P < 0.05). Proportions were transformed to arcsine (square root (x)) before analysis. Untransformed means are reported. Gargoil is a combination of 15% cinnamon oil and 20% garlic oil. Lime sulfur solution contains 29% calcium polysulfide. Lime sulfur ultra contains 27% calcium polysulfide. Among treatments, with a few exceptions, all organic treatments had an overall high percentage of fruit infested with thrips compared to Beleaf followed by Minecto Pro, which had less than 5% fruit infested with thrips after the second application (Table 2). Among organic insecticides, Grandevo and Venerate at 1WAT1 had significantly fewer fruit infested with thrips compared to the untreated check (Table 2). At 2WAT2, 3 treatments, Lime Sulfur Solution, Grandevo, and Venerate, had lower thrips infestation compared to the untreated check. Means within each column followed by a different letter are significantly different (P < 0.05). Proportions and numbers were transformed to arcsine (square root (x)) and logarithm [log10(x + 1)] before analysis. Untransformed means are reported. Gargoil is a combination of 15% cinnamon oil and 20% garlic oil. Lime sulfur solution contains 29% calcium polysulfide. Lime sulfur ultra contains 27% calcium polysulfide. Overall, the number of predatory mites was low across treatments. Notably, all organic treatments had significantly fewer numbers of predatory mites throughout the assessment period compared to untreated check and conventional treatment (Table 2). This research was supported in part by the Citrus Research Board with additional industry gifts of pesticides and funding. None declared.