How to Manage Pests
UC Pest Management Guidelines
Of the two species of katydids found in California stone fruit orchards, the forktailed katydid occurs most frequently. Angularwinged katydid nymphs and adults have a distinct humpbacked appearance. The forktailed bush katydidis smaller and is not humpbacked. Nymphs of both species have very long antennae that are banded black and white.
Katydids lay disc-shaped eggs in fall. The eggs of the angularwinged katydid are 0.125 to 0.15 inch long (3–6 mm), gray, and laid in two overlapping rows that form a long "tent" on the surface of twigs and branches.
Forktailed bush katydid eggs are about 0.125 inch long (3 mm) and are inserted into the edges of leaves. Eggs of both species hatch in late March and April. Adult katydids appear in midsummer and lay eggs through late summer and fall.
The angularwinged katydid emerges in May and has only one generation a year. Forktailed bush katydids emerge earlier than the angularwinged species. Eggs are laid in June and July. Some of these eggs will hatch in July and August (about 15%), whereas the rest will overwinter.
Katydids occasionally become damaging pests in orchards that have not been treated with broad-spectrum pesticides. High populations of these pests also occur in cycles, and they may cause damage one year and not the next.
Nymphs feed on leaves or fruit. Katydid nymphs tend to take one bite out of a fruit before moving on to another feeding site. Hence, a few katydids may damage a large number of fruit in a short time. Feeding wounds heal over and enlarge into corky patches as the fruit expands. The most serious damage occurs when katydids feed on young fruit, which become severely distorted as they develop. Nymphs and adults also chew holes in foliage. Smaller nymphs feed in the middle of the leaf, creating small holes, whereas larger nymphs and adults feed on the leaf edge.
Look for katydid damage when monitoring for leafrollers in spring. From April to May, examine shoots in the center of the tree for feeding damage. Early in the season when katydids are small, they create small holes in the center of the leaf, whereas cutworms and other leaf feeders will be feeding on the leaf edge. Fruit damage will also be seen in May. If you find feeding damage, look for nymphs. Shaking foliage onto large beating sheets may be helpful; nymphs can be difficult to see on the tree because they jump readily when disturbed. Treatments are most effective when applied to nymphs; best results have been achieved with late April and early May sprays.
Take a fruit damage sample at harvest to assess the effectiveness of the current year's IPM program and to determine the needs of next year's program (see FRUIT SAMPLING AT HARVEST). Record results (sample form— ).
UC IPM Pest Management Guidelines: Apricot
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