Eggplants are a popular vegetable crop susceptible to various pests, including two-spotted spider mites (Tetranychus urticae). These tiny arachnids can quickly become a problem for eggplant growers, particularly after using broad-spectrum insecticides. Spider mites are known for piercing, sucking mouthparts, which they use to extract the plant’s sap, causing damage to the leaves. In hot, dry weather, their populations can increase rapidly, leading to yellow stippling on the foliage and the production of webbing.
Spider Mite Management in Eggplant
The Life Cycle of Spider Mite
- Egg stage: Spider mites lay their eggs on the undersides of leaves, often under the webbing. The eggs are tiny, spherical, and pale white. They can only be seen with a magnifying lens. Eggs hatch in 4 or 5 days.
- Larva stage: After hatching, spider mite larvae emerge. They are light green or pinkish, slightly larger than the eggs, and have six legs. Larvae feed on plant sap, which is when they cause the most damage to the plant.
- Nymph stage: The next spider mite life cycle stage is the nymph stage. Nymphs look similar to adults but are smaller. They are green or red and have eight legs. They continue to feed on plant sap during this stage.
- Adult stage: Adults are oval-shaped and have eight legs. They are tiny, usually not exceeding 0.5 mm, and can resemble tiny moving dots to the naked eye. The male is usually smaller than the female and has a more pointed abdomen. Spider mites are variable in color depending on the species, with many species being bright red, sometimes referred to as red spider mites. Others are yellowish, greenish, pinkish, orange, or reddish. The two-spotted spider mite has a large dark blotch on each side of the body. Adult spider mites continue to feed on plant sap and reproduce, starting the life cycle again.
Identification of Spider Mite in Eggplant
To identify spider mites in eggplant, look closely at the undersides of the leaves for tiny, spherical, pale-white eggs. The eggs are often found under the webbings on the leaves. After 4 or 5 days, the eggs hatch into nymphs that look similar to adults but are smaller and have only six legs. The nymphs molt three times before becoming an adult.
Depending on the species, adult spider mites are very tiny and may be yellowish, greenish, pinkish, or reddish. They have an oval body with eight legs and two red eyespots near the head. Males are smaller than females and have more pointed abdomens. A female spider mite usually has a large, dark blotch on each side with numerous bristles covering her legs and body.
Damage Symptoms of Spider Mite in Eggplant
- Spider mites can cause a range of damage symptoms on eggplant plants. The initial symptom is usually the appearance of tiny yellow spots on the leaves, which later turn into a yellow or bronze discoloration of the leaves.
- As the infestation progresses, the leaves may become stippled, as if they have been speckled with salt or pepper.
- Severe infestations can cause defoliation, leaving the plant with few or no leaves. This reduces the plant’s ability to photosynthesize and produce energy, leading to stunted growth and reduced yield.
- The plant may sometimes die if the infestation is not controlled in time.