It’s the time of year again when strawberry growers should scout for chilli thrips and chilli thrips damage on young strawberry plants. Conditions for chilli thrips population growth were favorable throughout the planting period, and while cooler days may slow population growth, significant chili thrips mortality does not seem to occur with nighttime temperatures around 50 °F.
What to look for:
Scout fields for chilli thrips damage. Look for darkening/reddening of the leaf veins near the base of the leaves. Look for more heavily damaged plants that have dark streaks on the entire surface of leaves. Severe damage will cause extensive darkening, crinkling and deformation of the leaves.
Remove lightly or moderately damaged leaves and hold into the sun to look for active chilli thrips. Chilli thrips are yellowish, small and slender and will move when disturbed.
How to scout fields:
Focus scouting on field edges, particularly on edges bordered by oaks and other large trees. However, high chilli thrips infestations have been found in some fields next to grassy areas or ditches, and field centers are not necessarily free of infestation.
Walk down an aisle and briefly look at each plant. Keep track of the number of plants showing damage symptoms versus total number of plants observed. When a damaged plant is noticed, remove a damaged trifoliate and look for chilli thrips on the upper and underside of the leaves. Examine a newly emerged leaf on the same plant with little or no observable damage to determine if chilli thrips have moved to new foliage – this will be particularly important when evaluating efficacy of an insecticide application.
Currently, there are no thresholds for number of chilli thrips per plant or numbers of damaged plants per row or field on which to base a management decision. Research is ongoing, but we suspect that plants can recover from minor damage and low chilli thrips populations can be tolerated. However, when damage is moderate to severe in late October and November, application of a control product is recommended.
Trials at UF-GCREC have shown that of the registered products, Radiant SC (spinetoram) at 10 oz/A is the most effective against chilli thrips. However, Radiant SC is also effective against flower thrips, and it is recommended that growers use Radiant SC for chilli thrips only if infestation levels are high and damage is severe.
Other products with efficacy against chilli thrips are Assail 30 SG (acetamiprid), Sivanto Prime (flupyradifurone), and Entrust (spinosad).
VoliamFlexi (thiamethoxam + chlorantraniliprole) is not registered for thrips in strawberry but has shown moderate efficacy against chilli thrips in trials at UF-GCREC.
The label for Exirel (cyantraniliprole) is expected in strawberry, and it has shown chilli thrips efficacy comparable to Radiant SC in trials at UF-GCREC.
Contact: Justin Renkema, 813 419 6585, firstname.lastname@example.org