Chilli Thrips Control in Strawberry: Comparison of Conventional and Organic Treatment Efficacy

1 F.V. Sances, 2 B. Aglave, 2 K. Williams, 2 C. Brown, 3 S. Lahiri (Collaboration)​;  
1 Ag Metrics Group, 2 Florida Ag Research, 3 UF-GCREC

Contact: 
Frank Sances: [email protected]
Balaji Aglave: [email protected]
Florida Ag Research
3001 Kingsway Rd.
Thonotosassa, FL. 33592

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Justification: Chilli thrips are increasing in severity and distribution in Florida’s strawberry industry every year, and reports of severe crop injury are commonplace in all strawberry production districts statewide. In warm fall years, Chilli thrips can become established in strawberry plantings during plant setting periods of overhead irrigations when foliar insecticide spray applications are not possible. Within the first trimester of the crop, most strawberry plantings are infested with rapidly increasing populations of these pests, with injury to foliage, blossoms and fruit evident by mid-season.

​This occurs despite repeated insecticide sprays or inundative releases of hundreds of thousands of predatory mites and/or beneficial insects. One strategy proposed is to apply insecticides (conventional or organically approved) as early as possible before plant canopies are established and spray coverage limits control. If insecticide materials could be used during the first month of crop establishment, thrips populations could be delayed, and plant damage minimized later in the season. This project seeks to test insecticide application methodologies during the critical crop establishment period under actual field conditions at the Dover lab.

​Photo 1. Close up of Chilli Thrips (Scirtothrips dorsalis) on strawberry leaf (left) and the feeding damage on infested strawberries rated a 5 on a 0-5 scale (right)

Methodology: Three experiments were carried out on naturally infested Brilliance strawberries transplanted in October 2024 at the Dover research station. All three experiments include untreated check plots and a grower standard foliar insecticide rotation. ​

1. Pre-Plant Conventional + Organic – Transplant dips and at plant into planting hole​
2. Post-Plant Conventional – Drip applied (minimal water), overhead sprinkler, night spray​
3. Post-Plant Organic – Drip applied, overhead sprinkler, night spray​

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​Treatments: ​
Conventional systemic insecticides​

1. Abamectin (plant dip, starter, drip, overhead, night spray)​
2. Cyantranilprole (plant dip, starter, drip, overhead, spray)​
3. Imidacloprid (plant dip, starter, drip, overhead, night spray)​
4. Acetamiprid (plant dip, starter, drip, overhead, night spray)​

Organic products (1-2 applications)​

1. Azadirachtin (plant dip, starter, drip, overhead, spray)​
2. Entomophagous nematodes  (overhead, night spray)​
3. Capsicum oleoresin (overhead, night spray)​
4. Beauveria bassiana (overhead, night spray)​
5. Pyrethrum/Azadirachtin (overhead, night spray)​

​Data Collection: Thrips counts on ten blossoms per plot were reported weekly. Feeding damage on fruit was rated on a 0-5 scale, where 5 is severely damaged (see photo 1).​

Early Season Chilli Thrips Counts* on Flowers

Pre-Plant dips for Cyantranilprole and Imidacloprid had the fewest thrips on flowers in the pre-plant conventional program.

Post-plant Conventional treated strawberries saw the fewest Chilli thrips on standard tank mix program.

Strawberry blossoms treated with experimental organic programs saw higher average Chilli Thrips than the standard and untreated plants.

*Time weighted average count, six week total pressure. Larvae, adult and combined counts analyzed separately

Average Fruit Damage % Control

Pre-Plant: Imidacloprid as a Preplant Dip controls fruit damage better than standard, statistically (p<0.05)

Post-Plant: Night sprays were significantly less effective than sprinkler or drip applications for experimental treatments (p<0.05)

Organic: No significant differences for standard rotation or experimentals

Results: The abnormally cool temps in November and December delayed Chilli thrips establishment until mid-January at Dover. As a result, foliar populations remained very low for the first 5 weeks of the season and comparison of insecticide efficacy during crop establishment was not possible on leaves alone. However, beginning weekly in December, blooms were sampled along with foliage and Chilli thrips were recovered in low but quantifiable densities to compare treatments after plants had set and irrigations stopped.

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Conclusions: Chilli Thrips populations were low in 2024, limiting the conclusiveness of insecticide efficacy data. However, evaluations based on Chilli thrips presence in blooms and fruit damage indicated that the systemic insecticides Imidacloprid and Cyantraniliprole demonstrated efficacy against both nymphs and adults. Although efficacy was demonstrated rates used for dip and drench treatments negatively impacted plant growth and delayed crop development. The use of insecticide plant dips and drip chemigation methods is not recommended currently due to potential phytotoxicity effects. None of the organic insecticides tested provided observable control under the conditions of this study. Further research is planned for Fall 2025 to determine safe and effective rates for soil-applied insecticides and to reassess efficacy under higher pest pressure.

We are grateful for the support of the Florida Strawberry Growers Foundation for this research project. Thanks to Dr. Sriyanka Lahiri for assisting with technician training and collaborating on this project.

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