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Back To Pest & Disease Control :
Back To Spider Mites
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| Item Description: |
You'll first suspect spider mites when your plants start showing up with little yellow speckle marks, right on the leaf surface. (Also see thrips.) When you turn the leaf over, tiny, oval shaped mites are seen scurrying around, about pin-head in size. Their eggs, best seen with a magnifier, will be scattered around at random (perfectly round, all the same size, color ranging from clear to tan). With larger infestations, a fine webbing can be seen covering the plant tops (crawling with mites), and leaves will be browning and dying. Spider mites seem about the most common pest to show up in a greenhouse or indoors. They're best controlled with spider mite predators (see right), similar sized mites that eat them. A few gardeners report success with pirate bugs or ladybugs.
Spider mites take about 2 weeks per generation at 70 F. (from egg to adult). At low temperatures below about 50'F. they become dormant, and at higher temperatures above 86 F., their life cycle is sped up to about double. They prefer lower humidity levels, so raising the humidity helps control them.
The most common mite species by far is the "two-spot" spider mite. They're usually yellow/tan/greenish in color, and have two dark spots on their shoulders, one on each side. How large these spots get depends on the age of the mite; they get larger as the mite gets older. These two spots are also varied according to how much chlorophyll is in. the plant being reared; some crops produce mites colored much darker than others.
Strangely, spider mites have the ability to go dormant in winter, and then return when it warms up again. Triggered mostly by the daylight getting shorter in the fall, some or most of the mites turn red in color, stop feeding and egg laying, and then crawl off to protected nooks and crannies to hide through the winter. A warm, heated greenhouse can counteract these impulses to hibernate, but some probably will anyway, so it's easy to 'see why spider mites tend to keep coming back - season after season. Spider mites can also float along with wind currents, or be carried by pets or clothing. The common two-spot spider mite is found throughout the world, it's so widespread.
Feeding only on spider mites (and their eggs), spider mite predators also breed twice as fast, making them our most popular mite control. Actually carnivorous mites, each predator feeds on about 5 spider mites a day, or 20 of their eggs. Used as directed, predators should gain control within 4 weeks, and then continue until the spider mites are nearly or completely wiped out later. Predators disappear when the mites are gone.
Surprisingly, spider mite predators are this effective even through they're no larger than the spider mites, and sometimes smaller. Shaped a little more streamlined, they have longer legs which let them run faster, too. Attacking from the side, they suck the juices out of their spider mite prey.
For best results, start with at least 1 predator for every 25 spider mites. (1 to 15 for ornamentals, where appearance is important.) No, you don't have to count every mite! Count the mites on just a leaf or two, on perhaps every 10th plant, average them out, estimate the garden population, and divide this by 25 for the number of predators to use. If this sounds too complicated, start with 2 predators per leaf, or perhaps 30-50 per plant. Using more predators gives faster control.
We have 3 kinds of predator mites, that can all be used together or separately. Their different temperature and humidity preferences are listed on the chart. They all like higher humidities (70-90%); you'11 note that tolerance for lower humidity varies. Cool temperatures in the low 50's tend to make them go dormant, but they'11 actually survive short periods down almost to freezing. Upper temperature limits vary according to species. They're all priced the same, and you can order any combination at no extra cost. If you don't specify, we'11 send a mix of all 3 kinds.It is highly recommended that you be there when they arrive. If it is too cold, (below freezing) or too hot (above 90F), they could die.
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