| [Image: Spider mite damage in field] |
| [Image: Two-spotted spider mites] |
| [Image: spider mites] |
Two-spotted spider mites are a season-long pest of strawberries in Louisiana. The most critical component for mite control is development of a plan to manage mites. Use of the wrong pesticide at the wrong time can result in a season-long infestation of mites, which will be difficult to control with miticides.
One of the commonly used pesticides to control spider mites in Louisiana is the product Brigade. After doing some research, I’ve concluded that Brigade should be avoided at all cost. Although the label does include spider mites, it is a pyrethroid. Because it is a pyrethroid it will be highly toxic to all beneficial insects such as predatory mites, big-eyed bugs and other insects that would normally prey on the spider mites. What is likely to happen following a Brigade application is that some of the spider mites will be killed and most or all of the predators also will be killed. Very quickly, the spider mites that were not killed by the application will begin to produce eggs, and when those eggs hatch there will not be any predators present to kills the mites. Then you will be forced to spray again to control the mites. If you use a more selective miticide that will not kill the predators, they may be able to consume the mites that were over following the spray or may invade from surrounding fields. Also, Brigade should never be applied multiple times in one season because the spider mites will quickly develop resistance to this product.
I recommend the following miticide rotation to control two-spotted spider mites in your strawberries. Be sure to read the labels before using these products. Follow all label recommendations, being sure to pay careful attention to the pre-harvest interval.
1) Acramite – limit to 1 application per season. This is a contact miticide, meaning that it kills mites that come into contact with the miticide. But it also has long residual activity, so that larvae that hatch out of eggs will also be killed from the first application.
2) Agri-mek – If mites are still present, apply this product 21 days after the Acramite application. This is best when applied in a paired application -- two applications spaced 7-10 days apart. This product moves in the leaf -- from the top to the bottom -- and will remain in the leaf for a period of time. It is less effective when used in cold weather because it does not move in the leaf as well as in warm weather. Combine Agri-mek with a horticultural oil to help movement in the leaf. Don’t do this in extremely hot weather, because the oil may burn the leaf. Do not exceed 16 fluid oz. per application or 64 fluid oz (4 applications) per acre in a growing season. Do not apply in less than 100 gal water per acre (200 gal/acre is optimal). Do not repeat treatment within 21 days of second application.
3) The third product you should rotate with is Savey. This is a growth regulator that kills eggs, young nymphs (immature mites) and sterilized females. This should also be limited to 1 application per season.
In general, be sure to include enough water to adequately cover your strawberry plants since most of these are contact miticides. It is important to make sure there is good spray coverage on your plants.
Other products that can cause mites to become a serious problem include Sevin and Carbaryl. These products should be avoided in your spray rotation if you typically have a problem with mites.
I encourage you to scout for mites before you spray. Just because I am presenting you with three miticides does not mean you should use these products without scouting. It may be possible that predators can keep your mites in check, but only if you don’t kill them by using a broad-spectrum product that will kill the predators. In general, mites can become a huge problem if they are sprayed on a schedule. A balance of natural control (predatory mites and other insects that eat the mites) and miticides is the best way to control mites. If you use the wrong product at the beginning of the season (e.g. Brigade), then the entire season could be worse because all the natural enemies were killed by that first spray.
Scout for mites using a 10X hand lens and treat when you see more than 5 mites per leaflet on young plants.