With such high reproductive capabilities, spider mites would overwhelm all Christmas trees if there weren't factors keeping them in check. The egg state is particularly difficult to control.įactors Affecting the Spruce Spider Mite Skip to Factors Affecting the Spruce Spider Mite This affects pesticide performance as not all miticides control all stages. In addition, at any given time during the growing season, all stages of the mite may be found. Therefore, many generations occur each growing season, especially in the mountains where the mites can be active from early spring to late fall. It can take as little as two weeks from egg to adult. What makes the SMM such a dynamic pest is the speed with which this lifecycle can be completed. At maturity, females mate with males, lay eggs, and the cycle begins again. During molting, the mites go through a resting stage where they don't move and may appear to be dead. Both males and females are produced, females being larger than the males. The larva molts to the nymph with has eight legs like the adult, but is slightly larger than the larva. The immature mite, or larva, is similar to the adult, only smaller, and has three pairs of legs instead of four. When temperatures are warm enough, the eggs hatch. The mite overwinters as eggs on tree shoots. Spruce Spider Mite Lifecycle Skip to Spruce Spider Mite Lifecycle In the winter, only eggs are present unless the weather is mild. If the damage occurred earlier in the year, the mites may have died out because of changes in the weather or natural predators. Remember that mites cannot always be found on damaged foliage. Mites are usually more common on the lower half of the tree, and first appear on the smaller, interior shoots found partway into the canopy of the tree. The best time to look is on sunny days when the foliage is dry. Look for both mites and eggs on the most current growth of Fraser fir. The SSM egg is small and brilliant red with a single hair in the center. These mites range in color from green to red, though in western North Carolina they appear dark red to almost black with lighter-colored heads and legs. Spruce spider mites, like all mites of the tetranychid or spider mite group, have small, soft bodies with eight legs at maturity. Many growers have treated trees damaged by spider mites when no mites were left to control, wasting pesticide application without preventing damage.
If a field of trees isn't visited for a month or more, spider mites can easily build-up, cause damage, and then die out. Spider mite numbers can build rapidly and crash just as rapidly. It is important to be able to distinguish both spider mite damage and the mites themselves. That is because trees vary in their susceptibility to spider mites.įinding the Spruce Spider Mite Skip to Finding the Spruce Spider Mite Trees with heavy damage may be right next to trees with almost no damage at all. Spider mite damage is never uniform across a field. That may take one or two growing seasons, depending on the density of the tree and bud set. They can only be hidden from view by new, green, undamaged growth. In some cases, trees tagged for market have had to be left to grow another year or more after the SSM has caused so much damage that the plant is unsaleable. Spider mite damage can cause serious economic loss, especially if the trees are nearing harvest. Occasionally there may be webbing present among the needles when the mites are actively feeding, similar to spider webs, hence the name, spider mite. Mite-damaged needles are more likely to fall off the tree, especially after the tree is cut. As mite numbers increase, the entire needle becomes spotted.
When damage is light, spots are found at the base of the needles. From several feet away needles may appear generally yellow but when viewed close-up it can be seen that there are tiny yellow spots on the foliage. Their feeding causes yellow spots on needles. Spider mites have piercing and sucking mouthparts. Spruce Spider Mite Damage Skip to Spruce Spider Mite Damage
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