Damage resembles the response of the plant to drought stress or nutrient deficiencies. Leafhoppers feed on the underside of leaves. Injury usually starts with chlorotic areas developing around the feeding points and a slight rolling of the leave edges. Generally, the symptoms are known as “hopperburn”. Later on, the chlorotic areas expand to the rest of the leaf blade. Leaves may curl downwards and finally fall off. This leads to stunted plant growth and may reduce fruit yield.
The damage is caused by several species of Amrasca leaf hoppers. They are mostly a greenhouse pest and even low numbers can cause damage. The adult leafhoppers are green, about 3-4 mm large, and overwinter on evergreen plants. The females lay their eggs within the leaf vein tissue, mostly on the downside of leaves. The larvae hatch after one to four weeks. Nymphs and adults damage their hosts by sucking at plant tissues. While sucking, the insects inject toxic compounds which may lead to blocked plant vessels, which is why the symptoms resemble water or nutrient deficiencies.
Spinosad and bioinsecticides containing parasitic fungi species such as Metarhizium anisopliae, Beauveria bassiana, Paecilomyces fumosoroseus and Verticillium lecanii can be applied to control acute infestation. Insecticidal soaps can also be used against infestations. There are parasitic insect species such as Anagrus atomus which can provide some control method. Beneficial insects such as ladybugs and lacewing are voracious predators of both the egg and larval stage.
Always consider an integrated approach with preventive measures together with biological treatments if available. Seeds treatments with specific insecticides based on chlorpyrifos, fipronil or flonicamid show positive results in controlling leafhopper populations. Applied to the soil, they kill the insects living there, preventing them from attacking the roots, and also provide protection to the plant itself. Fixed treatment include spraying applications to plants 30, 45, 60 days after sowing. Chlorantraniliprole + Lambda-Cyhalothrin (0.5ml/l), Lambda-Cyhalothrin (1ml/l) or Cypermethrin (1ml/l) can also be applied 1 or 2 times in later stages of the crop.