|Posted on February 20, 2015 at 3:40 PM|
There are hundreds of species of spider mites in the Family Tetranychidae. These 8-legged mites damage plants by inserting their piercing-sucking mouthparts into the leaves and suck out the juices. If unnoticed they reproduce in astounding numbers. Research shows that one mite can produce around 12 eggs per day per season. There can be 4 to 8 overlapping generations in a season. Mites are parthenogenetic, meaning they lay eggs without fertilization. They are also asexual. You see what a pest they can become.
The warmer the weather the faster they reproduce. Each mite grows in this progression: egg, larva, 2 nymph stages then adult. They hatch within 2-5 days as larvae, grow, molt and become adults in 7 to 21 days depending on the weather conditions. In September the adult over-winters in the soil, plant debris, canes or stems emerging in May or June. They start feeding on the older or mid-shoot leaves and disperse to the upper canopy in July and August.
How do you know they are there?
You will see white speckling on plant leaves and/or yellowish very small spots on upper leaves. There can be a silk webbing on the underside of the leaves. As populations grow, leaf margins (the outer edges of the leaf) appear dried and leaves turn silver or bronze, followed by turning yellowish brown then dry up and fall off. We use a 10X or 20X hand lens to see eggs which are tiny, clear marbles 1/150th of an inch and the adults who are 1/60th of an inch. Little creatures potentially causing major damage.
How do we find them?
Scouting (looking for signs and mites) starts in late May to early June. Leaf samples are taken from lower and higher branches. If with our lens we find more than one or two adults per leaf, we know that management is needed. A simple home owners test can be taking a piece of white paper, putting it under a suspect leaf and giving the leaf a few good whacks. Then you would need a high powered magnifying glass to see if the dark spots are moving. If they are, you have mites.
How do we treat them Organically?
Treatment decisions are based on good practices. They include spider mite density, abundance of predators, population trends, damage to foliage and weather conditions. We need to consider that mites do not fly but are spread by the wind. A few mites are usually controlled by predatory mites and insects, some lady beetles are good but they prefer aphids. Cool and rainy weather will reduce populations. These soft body mites are susceptible to water so a powerful spray of water hitting the underside of the leaves as well as the top can often fix a moderate infestation. A full blown infestation may require the adding of an organic wash such as Mighty Wash or a soil drench such as Azamax. Neem oil can be used but often customers do not like the light odor it creates.
All in all you may want us to come and check it out for you. Our garden experts will give you advise or will fix the problem. Remember, when you first notice them, you waited too long to contact us.