How to Manage Pests

UC Pest Management Guidelines

Blueberry

Katydids

Scientific names:
Forktailed bush katydid: Scudderia furcata
Angularwinged katydid: Microcentrum retinerve

(Reviewed 4/14, updated 4/14)

In this Guideline:


DESCRIPTION OF THE PESTS

Katydids are an occasional pest of blueberry in the San Joaquin Valley. There are two species of katydids found in California blueberries, the angularwinged katydid and forktailed bush katydid. The forktailed bush katydid occurs most frequently in blueberries.

Forktailed bush katydid Angularwinged katydid
Smaller and not humpbacked Distinct humpbacked appearance
Long, banded black and white antennae Long, uniformly green antennae
Flat bean-shaped eggs 0.125 inch long (3 mm) inserted into the edges of leaves in fall Flat elliptical eggs 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 in fall
Nymphs emerge late March through May; adult katydids appear 2 to 3 months later Nymphs emerge in May; adult katydids appear 2 to 3 months later
Oviposition begins in June and July, and continues through summer and fall Oviposition begins midsummer, and continues through the fall
Some eggs hatch in July and August, the rest overwinter Eggs overwinter
1 or 2 generations per year 1 generation per year

DAMAGE

Katydids occasionally become damaging pests in fields that have not been treated with broad-spectrum pesticides or where tillage is not used. High numbers of these pests occur sporadically and they may cause damage one year and not the next.

Both nymphs and adults feed on leaves or fruit, but the adults are the most damaging. Katydids tend to feed on a small section 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. Katydids will feed on any size fruit. Feeding wounds heal over and enlarge into corky patches as the fruit expands. Damage to a young fruit can cause it to become 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.

MANAGEMENT

In most years katydid management in blueberries is only needed in a few fields in the San Joaquin Valley. These sites are often near alternate hosts such as stone fruits or citrus. In these areas, monitor for katydid migrations from April through May using sweep nets or beat sheets on cover crops and weeds near the perimeter of the fields. Monitor blueberries by looking for feeding holes on leaves and feeding scars on fruit. If significant amounts of fruit are damaged, consider a treatment; damage to foliage is not of economic importance.

Biological and Cultural Control

To date very little is known about cultural controls for katydids in blueberries. Egg parasites can reduce katydid numbers throughout the year, but provide minimal to no control of katydids that mature in overwintering hosts and then migrate to blueberries as adults.

Common name Amount per acre R.E.I.‡ P.H.I.‡
(example trade name)   (hours) (days)

Calculate impact of pesticide on air quality
Bee precaution pesticide ratings
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. Not all registered pesticides are listed. Always read the label of the product being used.
 
A. SPINETORAM
  (Delegate WG) 3–6 oz 4 3
  MODE-OF-ACTION GROUP NUMBER1: 5
  COMMENTS: Do not spray directly or allow to drift onto blooming crops or weeds where bees are foraging.
 
B. AZADIRACHTIN
  (Aza-Direct)# 1–2 pts 4 0
  MODE-OF-ACTION GROUP NUMBER1: un
  COMMENTS: Moderately effective on immature katydids. Must be contacted by spray so good coverage is essential.
 
C. PYRETHRIN
  (Pyganic EC1.4II)# 16–64 oz 12 Until dry
  (Evergreen EC60-6) 2–16 oz 12 Until dry
  MODE-OF-ACTION GROUP NUMBER1: 3A
  COMMENTS: Do not spray directly or allow to drift onto blooming crops or weeds where bees are foraging.
 
Restricted entry interval (R.E.I.) is the number of hours (unless otherwise noted) from treatment until the treated area can be safely entered without protective clothing. Preharvest interval (P.H.I.) is the number of days from treatment to harvest. In some cases the R.E.I. exceeds the P.H.I. The longer of the 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/.

[Precautions]

PUBLICATION

[UC Peer Reviewed]

UC IPM Pest Management Guidelines: Blueberry
UC ANR Publication 3542

Insects

D. R. Haviland, UC Cooperative Extension, Kern County

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Statewide IPM Program, Agriculture and Natural Resources, University of California
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