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
- What is the secret to getting carrots to germinate?
- Why do my tomatoes have brown spots on the bottom?
- The last few years, I have had persistent grass growth in my vegetable garden. I till the area each fall and spring, and pull out and discard all the vegetable plants. For the first couple of months, its easy to control the weeds and grass, then about 2/3 of the way through the summer, the grass starts to take over. By the time I pull out the plants in the fall, I practically have a lawn underneath them. Now that everything is pulled up, should I spray Round-up or another grass killer on the entire garden area? Or is there a better way to control the grass?
- I understand that Ace 55 tomatoes are low in acid. Is it unwise to use them for canning even if Lemon Juice is added?
- How can I store my fresh garden fruits and vegetables?
- We just moved to Davis County and want to plant our first garden. What things will grow well? What should we avoid? When should we plant? Any other basic tips about our area would be appreciated.
- How do I get rid of squash bug?
- I planted my tomatoes last Thursday, May 22. It was just before all this rain and colder air came in. Now all the plants leaves are turning yellow/cream color, except for the veins are staying green. Some neighbors said they might have had too much water, I have never had tomatoes do this before.