Spider Mites: The Summer Garden Pest


While summer is in full swing and produce is coming in by the bushel, there is one summer pest that can wipe a smile from my face.  It’s spider mites!

spider mite damage on basil

spider mite damage on basil

They are a very tiny arachnid in the Tetranychidae family.  This family also also includes spiders, ticks, and daddy-longlegs.    Their coloration can range from  brownish to red to green and even yellow.

I find it helpful to know what spider mite damage looks like since they can be difficult to see with the naked eye.  In this photo, they have feasted on a basil leaf.  (Mites suck the contents from cells.)  The damage on this leaf appears as pin pricks (stippling) that are light yellow.  If the attack is severe enough, the affected area becomes a bronze color and can even cause the leaf to curl around the edges.  In a lighter infestation, the general appearance of leaf is dull compared to healthy ones. One other sign signalling an infestation is webbing on the underside of a leaf or between leaves.

For the the two-spotted spider mites typically seen in a garden setting, damage usually occurs during the summer months.   Late June through mid-September  for most parts of the country mean hot, dry weather and spider mites thrive under these conditions.  One of the reasons why they thrive during this time is that some of their natural predators require more humid conditions and their numbers my dwindle during this time.

To help control spider mites in your garden beds you can do the following:

1) Water plants well during periods of drought.  A plant that is not stressed will fare better against infestations.

2) Use a garden hose with a strong stream of water to knock mites off of the plants.  Remember to spray the underside of the leaves where the majority of mites are located.

3) Repeat water sprayings to help control future infestations. (Mites like dry conditions.)

4) Remove severely infected foliage or if the plants is at the point where it is dropping leaves due to the infestation, remove the entire plant (useful for annual crops, not trees or bushes).  For example, if a basil plant is severely infested, I will pull up that plant rather than treat it,  However,  I would not pull up a raspberry bush if infected, but would treat with either insecticidal soap or miticide.

5)  The use of miticides and insecticides such as Neem.  For best results, follow manufacturer’s directions.

6) The use of insecticidal soaps, such as Safer.  Insecticidal soaps are most effective with frequent applications.

By following these steps, you too, can control spider mites in your fruit, herb, and vegetable crops.  Happy gardening!


5 responses »

    • Spider mites infestations can occur on, but no limited to: tomato, eggplant, beans, fruit trees such as pear, raspberry, gooseberry, currents, melon, squash, watermelon, peas, cucumber, potato, citrus, and herbs such as basil.

      • Yes, spider mites like to suck cell contents from quite a few different types of plants. However, the infestation tends to be quite localized. For instance, if I have spider mites on a basil plant, it tends to be on just one plant. So if it is a heavy infestation, I tend to pull up the entire plant. This year, I have had very few plants with spider mites. Our unusual rainfalls of July and now August are helping keep things cool as well as keeping the plants hydrated so they aren’t stressed compared to our typical hot summers.

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