Description of the Pest
Of the two species of katydids found in California stone fruit orchards, the forktailed katydid occurs most frequently. The nymphs and adults of the angularwinged katydid have a distinct humpbacked appearance. The forktailed bush katydid is 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 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 may 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 resembles 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 particularly susceptible to feeding.
In early spring, shred leaves on the orchard floor to destroy forktailed bush katydid eggs.
Monitoring and Treatment Decisions
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 other week after color break (see PREHARVEST FRUIT SAMPLES) to detect any developing problems in the orchard and 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.
|Common name||Amount to use**||REI‡||PHI‡|
|(Example trade name)||(conc.)||(dilute)||(hours)||(days)|
|Not all registered pesticides are listed. The following are ranked with the pesticides having the greatest IPM value listed first—the most effective and least harmful to natural enemies, honey bees, and the environment are at the top of the table. When choosing a pesticide, consider information relating to air and water quality, resistance management, and the pesticide's properties and application timing. Always read the label of the product being used.|
|MODE-OF-ACTION GROUP NUMBER1: 28|
|COMMENTS: For best results, apply in 100 to 150 gal water/acre.|
|(Imidan 70-W)||2 1/8–4 1/4 lb||7 days||14|
|MODE-OF-ACTION GROUP NUMBER1: 1B|
|COMMENTS: Effective against nymphs and adults. Highly toxic to bees; do not spray directly or allow to drift onto blooming crops or weeds where bees are foraging.|
|(Delegate WG)||4.5–7 oz||4||1|
|MODE-OF-ACTION GROUP NUMBER1: 5|
|COMMENTS: Toxic to bees; do not spray directly or allow to drift onto blooming crops or weeds where bees are foraging.|
|MODE-OF-ACTION GROUP NUMBER1: 22A|
|COMMENTS: Apply in no more than 200 gal/acre. Highly toxic to bees; do not spray directly or allow to drift onto blooming crops or weeds where bees are foraging.|
|(Entrust)#||1.25–2.5 oz||0.42–0.83 oz||4||1|
|(Success)||4–8 fl oz||1.3–2.7 fl oz||4||1|
|MODE-OF-ACTION GROUP NUMBER1: 5|
|COMMENTS: Apply to young nymphs (1st and 2nd instars). Not as effective on adults. Toxic to bees; do not spray directly or allow to drift onto blooming crops or weeds where bees are foraging.|
|(Neemix 4.5)||0.25–1 pt||0.0625–0.25 pt||4||0|
|MODE-OF-ACTION GROUP NUMBER1: un|
|COMMENTS: Moderately effective on immature katydids. Must be contacted by spray so good coverage is essential.|
|**||For dilute applications, rate is per 100 gal water to be applied in 300-500 gal water/acre, according to label; for concentrate applications, use 80-100 gal water/acre, or lower if label allows.|
|‡||Restricted entry interval (REI) is the number of hours (unless otherwise noted) from treatment until the treated area can be safely entered without protective clothing. Preharvest interval (PHI) is the number of days from treatment to harvest. In some cases the REI exceeds the PHI. The longer of two intervals is the minimum time that must elapse before harvest.|
|#||Acceptable for use on organically grown produce.|
|1||Rotate chemicals with a different mode-of-action Group number, and do not use products with the same mode-of-action Group number more than twice per season to help prevent the development of resistance. For example, the organophosphates have a Group number of 1B; chemicals with a 1B Group number should be alternated with chemicals that have a Group number other than 1B. Mode of action Group numbers ("un" = unknown or uncertain mode of action) are assigned by IRAC (Insecticide Resistance Action Committee). For additional information, see their Web site at http://www.irac-online.org/.|