Ask a Question
Notify Me On Question Update
Email this Question
What causes plants to look dirty and lose their green color during the heat of the summer? One culprit is spider mites.
Rate This FAQ
Another droughty year with intense heat - another bad year for spider mites. Or a good year for mites, depending on your point of view. Spider mites are prolific arthropods, related to ticks and spiders, that attack most types of plants and suck the water and life out of them. Spider mites are small (1/60 inch) and make the leaves appear dirty due to their copious webbing and adhering dust. They feed primarily on leaves, but can also feed on fruits. Symptoms are at first white stippling, turning to bronzing or silvering as mite feeding increases, and finally resulting in complete browning or necrosis of foliage when damage is severe. Shake suspected mite infested leaves over a white sheet of paper and if the small dots that fall to the paper walk around, they are spider mites. So what do you do when the weather is hot and dry and mites are increasing in the late summer?
Good plant care that includes adequate water, fertilization and reduction of stress. Water stressed plants attract mites. Water adequately and if possible, sprinkler-irrigate to occasionally to wet the leaves, unless this may cause other problems. A stiff spray down with a hose can wash off some mites and the moist environment deters their population growth. Some plants are more likely to attract mites, including some weeds. Field bindweed, morning glory, mallow, and knotweed are attractive weed hosts. Avoid ornamental plants that have chronic problems with spider mites. Utah is a haven for spider mites, and they will flourish in hot years.
Predatory mites that prey on spider mites occur naturally. They are more prevalent on perennial plants, such as fruit trees, caneberries and some ornamentals where they can over winter and find spider mite prey year after year. Predaceous mites can be purchased and released, but generally the native species perform better in home yards and gardens. Avoid insecticides that are nonselective to help preserve the predators. Examples of insecticides that can kill predaceous mites include carbaryl (Sevin), malathion, pyrethroid insecticides, such as Asana, Pounce, Tempo and Talstar, and miticides, such as Kelthane and Vendex.
Soap and oil can help control spider mites by disrupting their cuticle (skeleton on the outside) and suffocation. Insecticidal soap and horticultural oil (1 to 1.5%) should be applied at dusk for best effects. If applied in the heat of the day, the products will dry too quickly giving reduced effect and can burn plant leaves. Soap and oil applications should be made two or three times, 5-7 days apart for better kill of mites. Chemicals that specifically target mites, such as Kelthane and Vendex, should only be used in cases where mite populations are high and severe plant damage is likely. They are effective in killing spider mites and most beneficial arthropods. Following use of a miticide, resurgence of spider mite populations is common, requiring additional treatments. And beneficial arthropods may be diminished for several years.
Submit Your Suggestion
Other Questions In This Topic
- I have heard that black walnut sawdust should not be used in composting. People have told me it is poisonous to other plants. Is that true. I have several bushels of sawdust and would hate to send it to the land fill, but don't want to poison my garden either.
- I'm wondering if there is a variety of Almond tree that grows well in Davis county. And, are they self-fertile? Can they be grown near nectarines? (I've read that they shouldn't be grown near peaches as they can develop a bitter taste.)
- I left my carrots in the ground over winter this year without mulching them. Now it is May and they have resumed growing. We pulled a few out and, other than a little bit of woodiness they seem to be okay. Is it safe to eat carrots that have been left so long in the ground with no mulch?
- How can I store my fresh garden fruits and vegetables?
- What is the shelf life of fertilizer? I have some bags that have been stored in an outside shed and wondered whether they can be used or should be discarded.
- How can I stay on top of yard and garden problems?
- This is my first year planting carrots. Should I try to germinate them indoors before planting outside? Also, is it too soon to plant them outside?
- I purchased several pepper plants from a local nursery this spring one of them I do not know if the fruit is a pepper. They are black fruit about the size of a grape, full of seeds, and they do not smell hot, all the others are jalapeno.