Summer hits and it is time to start keeping an eye out for the symptoms of spider mites. I say symptoms of spider mites because it can be really hard to spot the actual insect. This minute pest can go after a variety of plants including evergreen and deciduous alike. They have multiple generations in a season and so take a true IPM (integrated pest management) approach to control them.
The presence of webbing along with a stippling of brown to yellow dots can be a sure tip off that you have spider mites. As the dots become more numerous they coalesce to show a discolored appearance that also ranges from reddish brown to brown to yellow depending on the type of plant. One of the reasons they can be so harmful is that they thrive in conditions that stress their host plants, namely drought or the removal of predatory insects. Primary host plants in the southeastern Idaho area include alberta spruce, spruce, juniper, honey locust and mountain ash.
There are many varieties of spider mites, each attacking a different range of hosts. Some will overwinter as eggs while others as adults. They all have the same overall 5 stage lifecycle however: egg, larvae, protonymph, deutonymph and adult. With the whole cycle taking less than a week from egg laying to adult they’re worse than rabbits! This accelerated reproductive rate allows them to quickly build up a resistance to any pesticide if the same one is used over a long period of time.
What is needed for good control is harnessing the power of IPM. This means to first see if the flare up of spider mites is a “secondary infection” aka is the result of your plants being stressed by any abiotic factors(drought, heat, wind) then biotic factors(a drop in predatory insects, fungi, bacteria). If it is a secondary infection we take steps to solve the first problem, whether it be by increasing watering or adjusting spray timing. Then we try to use any natural methods such as washing plants down with water or horticultural oils and finally treating with insecticides that use different modes action at the appropriate times.
If you have any questions about what you’re seeing in your landscape or would like an estimate on getting your plants taken care of, please give our office a call at (208) 523-5296