Applied IPM for Two-Spotted Spider Mite

As a crop, strawberries occupy a niche market which many find attractive due to their relatively high marketability and breadth of established knowledge available to the farmer. Like every other crop, however, strawberries pose their own challenges to the farmer seeking to supplement or dominate their farm income with this high value crop. Among these challenges is selecting an appropriate pest management practice.

If you happen to come across a magnifying glass lying in your field or handily sitting in your pocket, pick it up and take a look at the underside of your strawberry plant leaves. You might spot some spider mites, among other critters.

Spider mites can be difficult to identify to the untrained eye, and are quite small, so to see them and their eggs it’s much easier to use a hand lens. In the Sacramento area, it’s usually the two-spotted spider mite on strawberries (right).

Nai Saechao is one of many growers in the Mien community who has chosen to specialize in the production and direct marketing of strawberries. Last year Nai noticed a high population of

unknown species on his strawberry plants. Rex Dufour of NCAT and Margaret Gullette Lloyd of University of California Cooperative Extension visited Nai’s farm and noticed high populations of spider mites on his strawberry plants and determined that they were the primary pest challenging healthy growth in his plants.

With the help of funding from the Risk Management Agency, Rex and NCAT colleague Thea Rittenhouse purchased some Ambylesius fallacis, a predatory species,  and persuaded Nai to try these for controlling his spider mites. Nai was worried about his strawberry plants, so he sprayed Acramite (miticide), one week prior to application of the predatory mites. Acramite’s label notes that it is compatible with the use of predatory mites.

The idea here was to use the A. fallacis species which tolerates cooler weather better and is more of a general predator, able to feed on thrips and even pollen. Other predatory species like Phytoseulis persimilmilis feed exclusively on spider mites. 

For this distribution, NCAT ordered A. Fallacis in 5 bottles of 5,000 mites each ($59/bottle if you order 5 or more). Predatory species can be ordered straight to your door! The recommended rate of application is 10,000 mites/acre. The bottles of mites, about the same size as spice bottles, have 5 large holes in the plastic cap. We taped over all but one part of one hole to ensure that the vermiculite-like substance used as the “mite carrier” did not flow out too quickly. The bottles were duct-taped to sticks and then gently (and briefly!) shaken over each strawberry plant. See the video with this story to observe how it’s done. It’s our hope that these predatory mites will become established and help keep the spider mite populations under control, and reduce the use of chemical miticides.

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