Jul 22, 2011 – Spider Mighty Mites
QUESTION:
I'm having difficulty controlling spider mites. What do you recommend for treating these pests? I have tried Bifen IT and Sevin. I have not used a systemic yet.
ANSWER:
Spider mites can be challenging, and from back when I worked in horticultural pest management I was taught that carbaryl (Sevin) may not be a good choice for plant mites. This product is a weak miticide but very good at killing all other arthropods, including those that prey on spider mites. In fact, it is possible that using the wrong insecticide could even encourage the production of the mites by removing these other natural controls that were keeping their population down a bit.
Bifenthrin (Talstar, Bifen, MasterLine Bifenthrin) is supposed to be an excellent mite control material, so I would suspect that it is less the active ingredient that is causing you problems and more other factors. One is that these mites breed quickly, and repeat applications are necessary every week or so until the problem is resolved. The mite eggs are not likely to be killed by pesticides, other than horticultural oils that would smother the eggs if the application is very thorough, and even molting nymphs may be protected from typical insecticides within their old exoskeleton.
Another important factor is that spider mites will normally live and feed on the undersides of the leaves, making it much more difficult to contact them with standard contact insecticides such as bifenthrin. The spray application must be made so that the lower surfaces of all foliage are contacted evenly. This may be the advantage of systemics such as acephate (Orthene) where the active ingredient gets into the foliage and can be ingested by the feeding mites. Spider mites do feed in a similar manner as do aphids, by inserting their needle-like mouths into the cells of the plants to remove fluids, so a systemic material that is within these plant cells should be ingested. Even with systemics a thorough coverage is essential, and again, bifenthrin should be an effective material if the entire leaf surface is covered and repeat applications made as needed.
Spider mites also create a lot of fine webbing over the leaves, and this could become a physical barrier to your sprays. The use of a surfactant wetting agent will really help in breaking this barrier down and getting penetration to the leaf surface where it is needed. Also keep in mind the possible "soft" pesticides such as horticultural oils and soaps. These materials will be a greener, more natural approach to the problem if the customer prefers this, but they require very thorough coverage and would not be expected to leave any residual behind. They affect only what they land on during the application.
If the problem you are dealing with is on trees or larger shrubs you also can consider dormant oil applications during the late winter, treating the bark of the trunk and branches with the oil. Many horticultural pests overwinter in crevices on the bark or deposit eggs on the bark to overwinter, and the oil on top of them smothers them to prevent that new generation from coming out in such force the next spring.
View past Ask Mr. Pest Control questions.
I'm having difficulty controlling spider mites. What do you recommend for treating these pests? I have tried Bifen IT and Sevin. I have not used a systemic yet.
ANSWER:
Spider mites can be challenging, and from back when I worked in horticultural pest management I was taught that carbaryl (Sevin) may not be a good choice for plant mites. This product is a weak miticide but very good at killing all other arthropods, including those that prey on spider mites. In fact, it is possible that using the wrong insecticide could even encourage the production of the mites by removing these other natural controls that were keeping their population down a bit.
Bifenthrin (Talstar, Bifen, MasterLine Bifenthrin) is supposed to be an excellent mite control material, so I would suspect that it is less the active ingredient that is causing you problems and more other factors. One is that these mites breed quickly, and repeat applications are necessary every week or so until the problem is resolved. The mite eggs are not likely to be killed by pesticides, other than horticultural oils that would smother the eggs if the application is very thorough, and even molting nymphs may be protected from typical insecticides within their old exoskeleton.
Another important factor is that spider mites will normally live and feed on the undersides of the leaves, making it much more difficult to contact them with standard contact insecticides such as bifenthrin. The spray application must be made so that the lower surfaces of all foliage are contacted evenly. This may be the advantage of systemics such as acephate (Orthene) where the active ingredient gets into the foliage and can be ingested by the feeding mites. Spider mites do feed in a similar manner as do aphids, by inserting their needle-like mouths into the cells of the plants to remove fluids, so a systemic material that is within these plant cells should be ingested. Even with systemics a thorough coverage is essential, and again, bifenthrin should be an effective material if the entire leaf surface is covered and repeat applications made as needed.
Spider mites also create a lot of fine webbing over the leaves, and this could become a physical barrier to your sprays. The use of a surfactant wetting agent will really help in breaking this barrier down and getting penetration to the leaf surface where it is needed. Also keep in mind the possible "soft" pesticides such as horticultural oils and soaps. These materials will be a greener, more natural approach to the problem if the customer prefers this, but they require very thorough coverage and would not be expected to leave any residual behind. They affect only what they land on during the application.
If the problem you are dealing with is on trees or larger shrubs you also can consider dormant oil applications during the late winter, treating the bark of the trunk and branches with the oil. Many horticultural pests overwinter in crevices on the bark or deposit eggs on the bark to overwinter, and the oil on top of them smothers them to prevent that new generation from coming out in such force the next spring.
View past Ask Mr. Pest Control questions.
