Key Features
- Bronzing of leaves
- Webbing on leaves or flowers
- Activity on underside of leaf
Symptoms
Spider mites feed on plant leaves by piercing leaf tissues and sucking the green liquid that oozes out. Leaves appear bronzed after the green color is lost from many tiny feeding spots. Heavy infestations are often associated with lots of fine webbing. The best way to confirm a spider mite infestation is to hold a sheet of white paper under a leaf and then tap the leaf sharply. If present, they will fall off and be seen as tiny specks crawling over the paper. The ability to crawl clearly distinguishes mites from the grit that can be knocked off a plant. Leaves infested with spider mites will usually have fine webbing and eggs on the leaf undersides. Although spider mite injury is superficially similar to that of lacebugs, spider mite injury can be distinguished by the presence of webs, egg shells on the mid-vein, and lack of tar spots on the leaf surface.
Biology
Spider mites are tiny, 8-legged animals that are closely related to spiders. Under favorable conditions, spider mite populations can grow rapidly and threaten plant health. Multiple generations occur in one season and all life stages can be observed simultaneously.
Management Recommendations
Spider mites thrive on the leaves of flowering plants that are lacking adequate water or those that are receiving excessive fertilization. Be sure to keep flowers well watered and give them adequate light. Do not over fertilize or under fertilize. Dry weather favors spider mite outbreaks because rain can knock them from leaves and promote fungal infection. Many insects, like lacewings and minute pirate bugs also keep spider mites from becoming pests. If spider mite injury is starting to damage plants you may be able to manage the problem by spraying the foliage with a hard stream of water twice, weekly. If the water stream does not control the spider mites, try insecticidal soap, horticultural oil, or neem oil. Professionals can use products that kill mites (eg bifenazate, spiromesefin, and hexythiazox) but spare predators.
Effective Pesticides
Active Ingredients include: Azadirachtin, Horticultural oil (Paraffinic or superior oil) , Insecticidal soap (Potassium salt of fatty acid)
