Very often twospotted spider mites can collect at the edges of your fields, especially if the fields are bordered by weeds. Although the mites don’t have wings, the insects can travel with the wind and a mite problem that began at the periphery can eventually spread and create an infestation that spans your fields.
Here’s how to know if you’ve got an infestation of twospotted spider mites.
Signs of an infestation
To determine whether or not twospotted spider mites have infested your fields first inspect the edge rows for the mites. As we explained in a previous post about these bugs you should examine the leaves of your crops for a stippled appearance. As the mites feed and remove the contents of leaf cells, heavily-infected foliage will eventually turn pale, dry up, and fall away. Large infestations can defoliate or kill your crops.
Look to find mites on the undersides of leaves, and on stems. You’ll need to use a magnifying glass because their green/greenish-yellow—sometimes brown/orangey-red—oval-shaped bodies are only 1/50th of an inch long. The abdomens of the insects have two distinct dark spots. If you notice webbing on the edges and undersides of leaves it’s an indication that there has been prolonged colony feeding, since the mites use the webs to lay and store eggs.
Twospotted spider mites can move from dying plants to areas with healthy plants by way of the wind. So if you spot mites while scouting the edge rows of a field, it’s important to also examine areas that are downwind from the infected sections. You can estimate mite populations throughout an infected field by walking in a Z or W pattern.
Many factors can influence the severity of a twospotted spider mite infestation, including the time of year, the duration of feeding, crop load, and weather conditions.
