Katydids

Of the two species of katydids found in California stone fruit orchards, the forktailed katydid occurs most frequently. It is smaller than the angularwinged katydid nymphs and adults and also does not have the distinct humpbacked appearance of the angular winged katydid. Nymphs of both species have very long antennae that are banded black and white.

Katydids lay disk-shaped eggs throughout summer. If the eggs do not hatch before the end of August, they will overwinter. The eggs of the angularwinged katydid are 0.125 to 0.15 inch (3.2–3.8 mm) long, gray, and laid in two overlapping rows that form a long "tent" on the surface of twigs and branches. In contrast, eggs of the forktailed bush katydid are about 0.125 inch (3 mm) long, and inserted into the edges of leaves. Eggs of the forktailed bush katydid hatch in late March and April. Adult katydids appear in midsummer and continue to lay eggs during June and July. Some of these eggs will hatch in July and August (about 15%), whereas the rest will overwinter. The angularwinged species, however, emerges in late May and has only one generation a year, laying overwintering eggs during the summer.

Katydids occasionally become damaging pests in orchards where broad-spectrum pesticides were not applied or are under minimum tillage programs. High numbers of these pests may occur near raisin and wine grape vineyards, where the do no damage to the fruit.

Nymphs feed on leaves or fruit early in the spring as they climb from the ground to the tree. 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 the characteristic 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 (example form—PDF).

• Harvest fruit damage evaluation form (PDF)