Two-spotted spider mites are rearing their ugly heads and reproducing like mad in this hot weather.
A couple of weeks ago, I was checking out my Baptisia and noticed that it was showing symptoms of two-spotted spider mite damage. Unfortunately, I was hitting the road for a conference for a week and couldn’t do anything about it.
While I was gone, the population of two-spotted spider mites on this plant not only exploded but spread to my eight other plants in the bed.
I shouldn’t really be surprised because these mites love it hot and dry. This type of weather leads to massive populations; these mites can complete a life cycle in five to seven days.
In addition, the lack of rain also has been a positive factor for their development. One of the recommended management techniques is to use a good spray of water to knock some of them off.
I haven’t had any significant rain in my gardens for the entire summer, so the rain hasn’t helped in washing them off.
The symptoms of two-spotted spider mite damage include stippling of the leaves. Stippling simply means tiny yellowish spots on the leaf surface.
In this case, they insert their piercing-sucking mouthparts into the leaf and feed. This results in the stippling symptom.
In addition to the stippling, the leaf turns a bit off-color and in the case of heaving feeding, you may notice a bronze coloration of the leaf surface.
Underneath the leaf you may find webbing (in heavy populations) and you will find the nymphs and adults feeding. They move rather quickly but you can see them with a hand lens.
The adult is about 1/60” long and ranges from pale yellow in color to orange, green and brown. There are two distinct black spots on what appears to be the back; these dark spots are actually the contents of the gut showing through the body wall.
When populations are high and damage is significant, leaf drop eventually occurs. Most of the time, people don’t notice two-spotted spider mite damage until leaves fall.
The back of the leaf surface also feels sort of gritty.
Control in the early stages in necessary. As mentioned, a hard spray of water will knock a good many from the plant.
In addition, sprays of horticultural summer oils and insectidical soaps work great. You need to make sure you contact the lower leaf surface to kill the mites. You may also have to repeat.
Traditional miticides have a tendency to send their reproduction ability into overdrive. These are not recommended.
I tend to leave them alone and let the natural predatory mites do their work. At this point, my leaves are too damaged to warrant spraying.
I have heard from others that they are on numerous species of perennials and annuals, so I would suggest that you take a look at the underside leaves of these plants.