Winston Churchill wasn’t talking about spider mites, but he could have been. These pesky little insects feed on the underside of leaf tissue, causing a yellow/green mottled appearance. Weakened plants appear unhealthy, are more susceptible to other insect and disease damage, and often prematurely lose their leaves.
More closely related to tics and true spiders than insects, the most common Two-Spotted Mite (tetranychus urticae) does just as much damage. If they didn’t do so much damage, they would be very interesting little creatures. They winter over in the egg state and in the spring the hatchlings disperse into open foliage and flower buds where they penetrate the plant tissue using sharp mouth-parts.
There could be multiple generations doing damage in a growing season. Motionless while feeding, they are easily disturbed and move quickly in the loose webbing they create as shelter. The webbing is very fine, but backlighting the leaves will make it easier to see on infected plants.
Check for mites by shaking the infected foliage over a sheet of white paper. They may be temporarily stunned by the fall, but will shortly begin to run around in circles looking for “their leaf.” Look for tiny spots no larger than the period at the end of a sentence.
Persistence is your best friend when trying to get rid of spider mites. You can kill/remove a lot of mites with a strong jet of water, but take care not to strip the plant of foliage. Use Neem Oil (Fertilome Triple Action Spray) or Permethrin (Fertilome Fruit Tree Spray) as a liquid spray on edible plants. Imidacloprid (Fertilome Tree and Shrub Insect Drench) is stronger on ornamental plants, but may not be used on edibles. Adult spider mites are comparatively easy to kill, but the eggs are not affected by the sprays. Therefore, treat at least three times in a row, at exactly seven-day intervals. The goal is to kill the hatchlings before a new generation of eggs is deposited.
Remember to follow current label instructions on any pesticide you might use. The label is always the most current.
If you have any questions about eradicating spider mites in your yard, stop by any Western Garden Center in Utah and one of our expert gardeners will be happy to help. Be sure and mention that you read the blog and follow us on Facebook.