Farm Focus: New Approach to Spider Mites


Last week you read about how we use an approach to manage pests called Integrated Pest Management, or IPM. IPM is an ecosystem-based strategy that focuses on long-term prevention of pests or their damage through a combination of controls. A key component of IPM is monitoring pest populations, also known as pest pressure, throughout the farm so that we know when something is out of balance and can react before it turns into a bigger problem.

Many gardeners will know the dreaded two Spotted mite, more commonly known as Spider Mite, a small arachnid that is a summer foe in our orchard. If you have ever seen an unhealthy looking plant covered in white cobweb-like strings then you too know the spider mite.  In our orchard these little creatures overwinter in cover crop growing between trees and as it dries out during the summer migrate up into the tree for fresh food. They create colonies here they lay eggs and produce a protective webbing (it looks like white cobweb) and start sucking on the leaves of our beloved trees. They can actually defoliate (remove all the leaves) from a whole tree which means it can't produce weather energy from the sun. 

So, what is an organic farm to do? From an IPM perspective, our first control option is using a cultural control like weed whacking the cover crop at the base of trees which we did a few months ago. Since the spider mites are still present and are starting to make their way up the trees our next option is using a biological control which uses living organisms to reduce pest pressure.

We are fighting fire with fire, or in this case, fighting mite with mite! There happens to be another mite, called the Western Predatory Mite, or  Galendromus occidentalis which actually preys on both the adult spider mites and their eggs.  The goal is to reduce the current spider mite population in the short term while also establishing a healthy population of the predatory mites to keep spider mite pressure down in the future.


Last Wednesday our crew went out with Greg to learn out to apply 20,000 mites to 3 acres of trees. That's about mites per tree! The Predatory mites arrive live in a bottle from the insectory and are mixed with organic oat bran which serves as the perfect medium for the predatory mites to hang on to. Then that mix is put in a backpack sprayer. Greg vigorously walks by the trees spraying them with the oat/mite mixture. The oat bran, with mite passengers, will land on the leaves and branches allowing the predatory mites to do their work. If all goes according to plan will begin to integrate this practice into our orchard maintenances program. We will keep you posted!

Click here to see a video of Greg explaining the process and spraying some trees!