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. Both angularwinged nymphs and adults have a distinct humpbacked appearance. The forktailed bush katydid is smaller and 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 April and May. Adult katydids appear in midsummer and lay eggs from summer to fall.
The angularwinged katydid emerges in May and has only one generation a year. Forktailed bush katydids emerge about a month earlier than the angularwinged species. Eggs are laid in June and July. Some of these eggs will hatch in July and August, whereas the rest will overwinter.
Katydids often become damaging pests in orchards that have not been treated with broad-spectrum pesticides or where tillage is not used. 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 feed on a small section of a fruit (about 0.5 inch wide and 0.25 inch deep) 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. Damage to a young fruit can cause it to become severely distorted as it develops. 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. Damage to fruit and foliage can resemble that of green fruitworms.
Look for katydid damage when monitoring for leafrollers in spring, see EARLY SEASON MONITORING. Also, use a sweep net to detect populations in the orchard cover crop. It is important to treat populations early in the season if they have been a problem in the past and are detected in the orchard. Adult katydids migrate readily from adjacent orchards, and late season fruit is particulary susceptible to feeding.
From April to May, examine leaves on 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. Look at 50 trees throughout the orchard and examine each tree for 30 seconds. If you find feeding damage, look for nymphs by shaking foliage onto large beating sheets; nymphs can be difficult to see on the tree. Generally, treatment may be necessary if any of the foliage examined has feeding damage.
Examine fruit on trees every week after color break, see PREHARVEST FRUIT SAMPLES, to detect any developing problems in the orchard. 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 EVALUATION AT HARVEST. Record results for harvest sample.
UC IPM Pest Management Guidelines: Nectarine
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