| What Pest Is That? SPIDER MITES |
Spider mites belong to the Family Tetranychidae, Order Acari, & are not insects. They are closely related to spiders, the Daddy Longlegs (harvestmen), and Ticks in particular. Unlike insects which have six legs and three body parts, spider mites have eight legs and a one-piece body , they also lack wings, antennae, and compound eyes (I guess this makes them easier to sneak up on!). The adults and young are barely distinguishable to the naked eye, the females are only about half a mm long and the male is even smaller, but they may be noticed at times when they move the about in sunlight. Both adults and young may be red or greenish-red. The two-spotted mite overwinters as an adult in the soil, but most other common species on trees and shrubs (Red Mites included) overwinter as tiny round eggs on leaves or bark, but in greenhouses, overwintering survival is no problem at all for these little beasties. These eggs hatch in August or September & first- stage larvae emerge, having only six legs at this stage of their lives, but after a good feed session they start molting, & become eight-legged nymphs, they will then feed up again before another molting & resting period at which point they become adults. Both larvae and nymphs resemble the adults. Development time from egg to adult varies from 5 to 21 days depending on the species of mite and the weather. Red Mites and Two-Spotted Spider mites thrives whenever conditions are favorable for plant growth & under optimal conditions, populations can build up very rapidly, with many generations occurring each year. The Two-Spotted Mite & his cousin the Red Mite are usually found on the underside of leaves, but general infestations feed on all parts of the plant. The damage they cause to foliage is similar on all host plants which is first noticeable as a fine stippling on the leaves which , if left unchecked, progresses to an overall bronzing of the leaves. Even though mites are almost microscopic, when they occur in large numbers, they can cause serious damage to your plants. Damage Spider mites lack chewing or piercing-sucking mouth parts. Instead they have a pair of needle-like structures called stylets which are used to rupture leaf cells. A feeding spider mite pushes its mouth into the torn tissue and draws up cell sap. Small patches of cells are killed, resulting in a stippling or fine flecking on the upper surface of leaves, giving the leaves a "sandblasted" appearance. On heavily infested plants, the foliage will become bronzed, bleached, yellow, or grey. Untreated, such plants lose vigor, become progressively thinner, and may eventually die. Recognition When mites are numerous, fine webbing is often visible where the leaves join the stems & if you have a hand lens or magnifying glass, egg shells and cast skins are usually visible on the underside of damaged leaves. Mites can be observed by shaking infested leaves over a white piece of paper, you’ll see some little red full stops zipping around at speed, this is a sure sign of an infestation. Control Treat any areas as soon as possible, where and when mites are found, it is quite possible that repeat applications may be necessary at weekly to ten daily intervals. Most insecticides are not effective on mites, but there are several excellent MITECIDES available at our local Garden Centres. Another effective way of keeping the little beasties at bay is keep the humidity levels up as these guys don’t appreciate muggy conditions, but if the humidity is high you should also ensure that there is good ventilation so as not to encourage rots to set into your plants. |