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It’s the year of the two spotted mites. A mite is a species of spider. The two spot might and the European red mite can cause devastating damage to peaches and nectarines. Luckily, they ignore everything else in our orchard but this season they are going wild for our peaches and nectarines, which as you know, make up a significant portion of our summer harvest.
The mites look like tiny red dots on the leaves of the trees with the naked eye. The mites pierce the leaf cell walls and suck out all of the cells contents, yellowing the leaf and rendering the leaf incapable of providing proper nutrition to ripen the fruit or to manufacture buds for next year’s crop.
Mites love hot weather and they like dust. We have plenty of both during the summer months at Frog Hollow. The mites overwinter in the soil. When the weather warms up, they can migrate out of the ground and onto the leaves.
Historically, in years where we’ve noticed mite populations surging, we’ve sprayed our trees with stylet oil, which is an organic mineral oil. Since pest pressure this year has been high we’ve sprayed the trees three times but this treatment has not proved effective. We have slowed their damage but their populations are still high enough that they causing more damage than we’d like.
We are in the process of experimenting with a new control strategy using vermicompost tea. Compost tea derived from vermicompost is rich in phenolics that are produced by the microorganisms that are present in the vermicompost piles. Phenolic compounds have been shown to play a key defensive role in plants when they are under stress such as high or low temperatures, excessive light, or pathogenic stress. Phenols have been shown to make plants less attractive to pests and to interfere with their reproduction. Experiments with vegetables, tomato and tea plants have shown that vermicompost teas have dramatic effects on infestation by spider mites: the plants were less attractive to new infestations, the rates of reproduction of the pests decreased and with time the pests left the plants or died.
To trial this method we are spraying the entire tree with the tea after all the fruit has been harvested from it. We will also put the compost tea into our irrigation lines in order to allow the tea to enter the soil in hopes of reducing the populations of mites in the soil and encouraging uptake of the phenols into the tree from the roots. If we are able to reduce mite populations in the soil using our compost tea this season, we should have less pest pressure in the farm ecology when things heat up during the dusty summer months.
As long as the infestation lasts this season, we will drench the soil and spray the leaves about once a week, since we don’t know how fast the phenolics will be taken up from the trees roots to the leaves. We are hopeful this strategy will be effective. We’ll keep you posted.
