Strawberries are a high demand/high value crop, so growing a healthy crop means successfully managing pests, especially mites.
A recent and ongoing study from the Michigan State Department of Entomology, conducted by Lauren Goldstein, Joshua Striegle, Caz Schwennesen, Mia Bianchi and Rufus Isaacs, evaluated several different miticides for controlling mite pests in strawberries. They shared their results at the most recent Great Lakes Expo.
The research team found there is a need to determine the most effective controls for mite pests on strawberries to support updated recommendations to strawberry growers. Specifically, they looked at the two-spotted spider mite (TSSM), which can weaken plants, reduce return bloom and decrease marketable yields by feeding on and damaging the leaves of strawberry plants. This damage also causes plants to become more vulnerable to pathogens and other pests.
They tested and compared six different miticides for use in strawberry to determine their efficacy against TSSM and guide future recommendations. The miticides tested were Magister® SC, Spear-T®, Kanemite® 15SC, Agri-Mek® SC, Portal® and Envidor®.
In this laboratory experiment, potted ‘Jewel’ strawberries were infested with TSSM one week before a miticide treatment. Each treatment was applied using a handheld spray bottle at the label recommended rate. Spray solutions were evenly applied to the tops and the undersides of leaves to achieve good coverage.
After the treatment, mite assessments were done weekly by randomly sampling one leaf per plant to count the number of TSSM eggs, adults and predators.
What the team found was that seven days after treatment, plants sprayed with Magister and Agri-Mek had the fewest TSSM eggs. Additionally, 28 days after treatment, plants treated with Magister and Agri-Mek had the healthiest leaves.
Magister, Kanemite, Agri-Mek and Portal provided the longest-lasting protection against TSSM adults. Meanwhile, Spear-T and Envidor posed the lowest risk to predatory insects.
“Through this study, we determined that Magister and Agri-Mek miticides provide the greatest level of control against multiple life stages of TSSM in potted strawberry plants. Kanemite and Portal were of similar efficacy,” the MSU team concluded.
Their next step is to measure the efficacy of these miticides in a field trial at the MSU Horticulture Farm in 2025. This experiment will include a comparison of a standard insect and mite program to a threshold-based program.
They added that future research should determine the effects of these – and additional – miticides on natural enemy populations and explore ways in which biological and chemical control may work together for the management of TSSM in strawberry.
by Courtney Llewellyn
