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Kaolin and Limonene as Repellents for Whitefly Management In Vegetables

Dr. Xavier Martini
Department of Entomology
UF/IFAS North Florida REC

Due to the development of insecticide resistance and difficulties in whitefly management with conventional insecticides, significant agricultural research has been aimed at identifying alternative strategies. Dr. Martini is investigating the utilization of Kaolin clay (Surround®) and limonene (an essential oil from citrus peels) to keep whiteflies out of susceptible crops. Kaolin acts as a contact repellent, whereas limonene repels whiteflies from a distance.

Figure 1. Kaolin and limonene applied to (A) tomato plant at the vegetative stage, and (B) tomato plant at the flowering stage.

Initial trials were conducted at the North Florida Research and Education Center in fall of 2019. Kaolin and limonene each slightly reduced whitefly populations on tomato. More significantly, results demonstrated an additive effect when applying both Kaolin and limonene (Figure 2). The efficacity of Kaolin + limonene was particularly high during dry condition, whereas it was reduced after rainfall.

Figure 2. Number of whiteflies per tomato leaflet (± SE) in a 2019 field trial at NFREC. Kaolin and limonene combined showed additive effects in reducing whitefly counts.

An on-farm trial was conducted in fall 2021. Treatments included the grower’s weekly insecticide program, a treatment alternating the grower’s weekly insecticide program and weekly applications of Kaolin + limonene, and a third treatment with only weekly Kaolin + limonene applications. (See below for information on the grower’s standard practice). Results demonstrated reduced whitefly counts with Kaolin + limonene. The greatest reduction was observed with alternating the grower’s weekly insecticide program and weekly applications of Kaolin + limonene (Figure 3).

Figure 3. Number of whiteflies per tomato leaflet (± SE) in a 2021 trial conducted in collaboration with a North Florida tomato farmer. Whitefly counts with Kaolin and limonene were similar to counts with the farmer’s insecticide program.

While Kaolin and limonene will not replace the use of insecticides, this data suggests that this treatment can be used as an alternative for growers. Use of Kaolin and limonene may therefore be an important part of an integrated whitefly management program.

The grower’s standard practices included cyantraniliprole (Verimark), esfenvalerate (Asana), bifenthrin (Bifenture and Bifen 2ec), beta-cyfluthrin (Sultrus), fenpropathrin (Danitol), and pyrifluquinazon (PQZ).

In this study, Surround was used at half the industrial rate (¼ lbs. per gallon of water or 113g/gal), and limonene was used at 0.5% (19 mL per gallon of water). Kaolin and limonene were mixed directly in the sprayer tank. To avoid clogging of spraying material with Kaolin, it is important to use a sprayer machine with high horsepower equipped with an agitator.

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