Spider mites are a pest in many crops. Their great reproductive capacity enables them to cause enormous damage in a short period of time. In many protected crops the two spotted spider mite Tetranychus urticae is the most important pest. In field crops, other Tetranychus species can also cause damage.
The spider mite goes through five stages, namely egg, larva, first nymphal stage (protonymph), second nymphal stage (deutonymph) and adult. All stages can be observed in the crop.
- Spider mite larvae, nymphs and adults feed on the underside of the leaves and cause yellow spots, later even yellow leaves. This results in decreased plant growth and production. Finally the crop may die from the infestation.
- Nymphs and adults produce webbing that can cause cosmetic damage to the crop. If large numbers of spider mites are present, plants may be completely covered with webs.