Fruit Crops

Fungus for Control of Tarnished Plant Bug on Strawberry

The fungus Beauveria bassiana shows promise in controlling tarnished plant bug in strawberry fields as long as no fungicides are used. Fungicide use on strawberry can be reduced through the use of specific cultural practices and the fungal antagonist Trichoderma harzianum for Botrytis fruit rot control.

B. bassiana acts as a contact insecticide, growing directly through the insect cuticle to kill the insect in 3-7 days. Certain strains of the fungus have proved to be effective against other pests, such as whiteflies and aphids.

The effectiveness of Mycotrol WP, a formulation of B. bassiana produced by Mycotech Corporation (Butte, MT), was tested against tarnished plant bug on a 5-year-old strawberry planting in New York. Sprays were applied either prophylactically (on two dates during mid to late bloom) or when tarnished plant bug populations reached a threshold of 0.25 nymphs per cluster. All sprays were applied at a rate of 1 pound per acre with a wetting agent (0.02% Silwet L-77).

Although the fungal sprays didn't reduce the numbers of bugs present, both treatments were effective in reducing tarnished plant bug injury to the berries. In the first picking over 25% of the berries showed plant bug damage in the control, while the two Beauveria treatments had only 3-6% damage. In the second picking, plant bug injury was probably overestimated (small fruits due to lack of water made it difficult to differentiate between the apical seediness of plant bug injury and drought stress) and the difference between the control and treatments was not as large (28% vs. 16-17%).

Although additional testing is needed, it appears that Mycotrol WP in combination with a wetting agent, applied either as two prophylactic sprays or as one spray at threshold, can reduce tarnished plant bug injury in strawberry to commercially acceptable levels.

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