Description: Spider mites are not insects but are more closely related to spiders. They have four pairs of legs, no antennae and a single, oval body. Most spider mites have the ability to produce a fine silk webbings. They are very tiny, less than 1/50 of an inch when adults. To the naked eye, they look like tiny moving dots. The twospotted spider mite is the most common species. This pest has been found on over 180 hosts, including field crops, oranmental plants, house plants and weeds.
Symptoms: Spider mites use their tiny mouth parts to pierce individual plant cells and remove the contents. This results in tiny yellow or white speckles on the leaves. When a large number of feeding spots are close together the foliage takes on a yellow or bronzed cast and may drop prematurely. Heavy infestations can stunt or kill a plant.
Another sign of spider mite damage is the presence of fine silk webs on the foliage, which collects dust and looks dirty. One way to see these tiny creatures is to hold a white piece of paper under the leaves of an infected plant. Shake the leaves and you will be able to see mites walking slowly on the paper.
Adult females usually lay eggs on the host plant. The eggs hatch the larvae from a few days to a few weeks later. Larvae are round bodied and have three pairs of legs. They feed for a few days and then molt. Now they have 4 pairs of legs. These nymphs feed for a few days, rest and then molt into the adults.
Most spider mites spend winter in the egg stage but the twospotted spider mite overwinters as an orange to orange-red adult female, hiding in protected places such as ground litter or under the bark of trees and shrubs. Twospotted spider mites may be brown or orange-red but a green, greenishyellow or an almost translucent color is the most common.
Action: Mites prefer hot, dry weather and often do not reach damaging populations in cool, rainy periods. Early detection is important for control before damage occurs. Forcefully spraying with the hose can remove small populations. Horticultural oils are also effective. Chemical controls are more limited for spider mites, as they are not insects and most insecticides will not kill them. An actual miticide must be sprayed to control a severe infestation of mites.
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