I received a question this week about spraying for spider mites and protecting honey bees.
First and foremost, spider mite problems are frequently a result of repeated application of broad-spectrum insecticides. Don’t apply these products without a specific need. That said, spider mites have become a more consistent problem in the past decade and are usually of greatest concern when we experience hot, dry weather. This can occur early in the season, but is usually later when crops are blooming and bees are visiting flowers. Protection of bees has become a greater concern for most growers, and rightfully so. While there are several things that can be done to help protect bees (avoid drift, spray late in the day, etc.), close communication with your beekeeper is paramount. A critical decision is which pesticide to spray. Which products will provide good control with minimal potential impact on the bees?
We have several excellent acaricides in vegetable crops that can control spider mites. Generally, our most consistent control is obtained with Agri-mek (because it is translaminar and will provide control on the bottom of leaves even with less-than-perfect coverage), but this product is highly toxic to honey bees. Keep in mind, that for mite control, all of our other products are primarily contact pesticides and good coverage is essential for good control.
Of the acaricides most widely labeled on vegetables, Agri-mek, Acramite, and Torac all indicate that they are toxic or highly toxic to honey bees and should not be sprayed when bees are foraging. Kanemite, Zeal (Zeal only controls immature stages of mites), and Oberon (Oberon has a very slow mode-of-action and is not ideal for a rescue type treatment) do not specify toxicity level to bees on their labels. This generally indicates they are relatively safe for bees. The label for Portal indicates it has minimum honey bee toxicity (practically non-toxic). Even with these safer options, I suggest avoiding direct contact with bees (avoid drift, spray late in the day, move the bees if necessary).