When you pull row covers off plasticulture strawberries, it is time to scout for two-spotted spider mites.
Tim Elkner, Extension horticulture educator, explains overwintering two-spotted spider mites are females ready to lay eggs, so populations can increase quickly. Mites and eggs are mainly found on the leaf undersides. Unless you are young or have really good eyes, you will probably need a magnifying glass or hand lens to see them.
Two-spotted spider mites are normally light yellow-green but take on an orange color in winter. They get their name because they have two black spots, one on each side of their midsections. This is from an accumulation of frass (waste) in their bodies. They go through a few molts as they grow, and the spots may be missing if the mite has recently molted.
Frass dropped onto the leaf looks like tiny black spheres. While scouting for the mites you also look for their eggs, as they are an indication of whether populations might be on the verge of exploding. Eggs are tiny, clear, and light yellow.
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