Agriculture: Citrus Pest Management Guidelines

Katydids

  • Angularwinged katydid: Microcentrum retinerve
  • Forktailed bush katydid: Scudderia furcata
  • Description of the Pest

    Katydids resemble grasshoppers but have long antennae. Nymphs are wingless and have black and white-banded antennae. Females of the forktailed katydid chew the edge of the leaf and insert gray, oval, flat eggs inside the edge of the leaf. Nymphs appear in April and May and take 2 to 3 months to mature through 6 to 8 instars. Angularwinged katydids also appear in citrus orchards, but are larger than forktailed katydids, have broader wings, and have a humpback appearance both as nymphs and as adults. Angularwinged females lay their gray, oval eggs in two overlapping rows on twigs and leaves. Both species of katydids have only one generation a year.

    Damage

    Of the two species feeding on citrus, only the forktailed katydid causes economic damage. Nymphs of this species feed on leaves during bloom and young fruit at petal fall. Forktailed katydids take a single bite from a fruit and then move to another feeding site on the same or nearby fruit. In this way, a few katydids can damage a large quantity of young fruit in a short time. Fruit damage causes a subsequent buildup of scar tissue, often in a round or oval shape, and distortion of expanding fruit. This fruit damage sometimes resembles damage caused by citrus cutworm or earwigs.

    The angularwinged katydid is less abundant than the forktailed katydid and feeds only on leaves.

    Special Considerations for Mandarins and Clementines

    Forktailed katydids have the potential to create varying levels of damage in different citrus species. Katydidsare not considered economic pests in ‘Tango' and ‘W. Murcott Afourer' (Citrus reticulata) mandarins. Katydid nymphs may be present in the groves of these cultivars, but do not feed on the fruit. They may taste the fruit, causing small, superficial scratches, but these do not develop into perceptible scars at harvest. More substantial feeding on the fruitlets of these cultivars is exceedingly rare, and any damaged fruit tend to quickly abscise. This natural resistance to katydid feeding has not been formally evaluated in all cultivars but may include other Citrus reticulata relatives.

                                                                                                                                                    

    Forktailed katydids can be highly damaging to clementine mandarins, including the cultivars ‘Clemenules' (‘Nules'), ‘Fina', ‘Fina Sodea', and ‘Corsica #1'. Forktailed katydids chew deep holes into young clementine fruit, causing irregular, webbed scars that appear similar to the scars caused by orangeworms in navel oranges. Developing clementine fruit with katydid scars will often split along the scar late in the season. Satsumas, tangelos, and tangors have not been surveyed for this type of damage.

    Management

    With the reduced use of organophosphate and carbamate insecticides, katydids have become more numerous. Larger instars are not well controlled by cryolite or spinosad.

    Biological Control

    A number of parasitic wasps will attack katydid eggs; however, they are generally not effective enough to prevent damaging levels from developing.

    Organically Acceptable Methods

    Use biological control and the Entrust formulation of spinosad in an organically certified citrus crop.

    Monitoring and Treatment Decisions

    Monitor for katydids starting in April. Before petal fall, they will be feeding on the newly expanding leaf flush. A timed search (3 minutes per tree) of 20 trees can be used to estimate their numbers. Approach the tree slowly, because katydids have excellent eyesight and will hide behind leaves if they see you coming. Look for damaged leaves and search the foliage around the damaged area for katydids. There is no treatment threshold for katydids; however, if you detect leaf or fruit feeding damage and can find one or more per tree in a timed search, then for most citrus varieties it is time to apply an insecticide. It is not necessary to control katydids in Citrus reticulata cv. ‘Tango' and ‘W. Murcott Afourer', and possibly other related cultivars of mandarins, because while katydids may be present, they do not like to feed on the fruit of these varieties.

    If applications of diflubenzuron (Micromite) or cryolite are planned, apply them before petal fall because they are slow acting. Micromite does not kill the katydid until it tries to molt (10&–14 days) and cryolite is a stomach poison that slowly kills the katydid over several days.

    After petal fall, katydids can cause a lot of damage in a short amount of time, so killing them quickly is important. If they are found at this time, many growers add a low rate of an organophosphate or a low rate of a pyrethroid insecticide to the citrus thrips petal fall application. The reduced rate of the organophosphate or pyrethroid helps to preserve natural enemies needed for other pests but is still very effective against katydids.

    Common name Amount to use REI‡ PHI‡
    (Example trade name) (type of coverage)** (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.
    SELECTIVE
    A. CRYOLITE
    (Prokil Cryolite 96) 8–20 lb/acre (OC) 12 15
    RANGE OF ACTIVITY: Pests: intermediate (foliage feeders such as worms, katydids, and Fuller rose beetle); Natural enemies: few, if any
    PERSISTENCE: Pests: long, unless washed off by rain; Natural enemies: none to short
    MODE-OF-ACTION GROUP NUMBER1: 8C
    COMMENTS: Check label for variety. Use higher rate for larger trees. Slow-acting stomach poison that may take several days of warm weather to kill katydids. Use of Prokil Cryolite 96 allowed under a supplemental label.
    B. DIFLUBENZURON
    (Micromite 80WGS) 6.25 oz/acre (OC) 12 7
    RANGE OF ACTIVITY: Pests: intermediate (katydids, peelminer, leafminer, grasshoppers); Natural enemies: predatory beetles
    PERSISTENCE: Pests: intermediate; Natural enemies: intermediate
    MODE-OF-ACTION GROUP NUMBER1: 15
    COMMENTS: Can be used during bloom. Requires 1 to 2 weeks to kill immature stages of katydids as they molt. Apply by ground application using 50 to 200 gallons of water per acre. Do not apply within 25 feet of bodies of water.
    . . . PLUS . . .
    415 NARROW RANGE OIL
    (various products) 0.25-1% See label See label
    RANGE OF ACTIVITY: Pests: broad (unprotected stages of insects and mites); Natural enemies: most
    PERSISTENCE: Pests: short; Natural enemies: short
    MODE OF ACTION: Contact including smothering and barrier effects; also improves insecticide spread and persistence.
    C. SPINOSAD
      (Entrust SC)# 4–10 fl oz/acre (OC) 4 1
      RANGE OF ACTIVITY: Pests: narrow (thrips, orangeworms, katydids); Natural enemies: predatory thrips
      PERSISTENCE: Pests: intermediate; Natural enemies: intermediate
    RESISTANCE: Some citrus thrips populations in Kern County.
      MODE-OF-ACTION GROUP NUMBER1: 5
      . . . PLUS . . .
      415 NARROW RANGE OIL
      (various products) 0.25-1% See label See label
      RANGE OF ACTIVITY: Pests: broad (unprotected stages of insects and mites); Natural enemies: most
      PERSISTENCE: Pests: short; Natural enemies: short
      MODE OF ACTION: Improves translaminar movement and insecticide persistence.
      COMMENTS: To avoid potential phytotoxicity of oil to the fruit, do not apply 30 days before or after a sulfur application, and do not apply to small fruit (less than 1 inch in diameter) on a day when the ambient temperature has or is expected to exceed 95°F or when the relative humidity has or is expected to drop below 20%. Use a ground application at 3 mph with reduced wind velocity to achieve outside coverage
    BROAD-SPECTRUM
    A. NALED
    (Dibrom 8 Emulsive)* 1–2 pt/acre (OC) 48 7
    RANGE OF ACTIVITY: Pests: broad (many insects); Natural enemies: most
    PERSISTENCE: Pests: short; Natural enemies: intermediate
    MODE-OF-ACTION GROUP NUMBER1: 1B
    COMMENTS: For use on oranges, grapefruit, lemons, and tangerines. Apply at petal fall.
    B. DIMETHOATE
    (Dimethoate 400) 0.5–2 pt/acre (OC) See comments 15
    RANGE OF ACTIVITY: Pests: broad (many insects); Natural enemies: most
    PERSISTENCE: Pests: intermediate; Natural enemies: intermediate
    MODE-OF-ACTION GROUP NUMBER1: 1B
    COMMENTS: For use on oranges, grapefruit, lemons, and tangerines. Reentry interval is 14 days in areas that receive less than 25 inches of annual rainfall and 10 days otherwise.
    C. BETA-CYFLUTHRIN
    (Baythroid XL) 6.4 fl oz/acre (OC) 12 0
    RANGE OF ACTIVITY: Pests: broad (many insects); Natural enemies: most
    PERSISTENCE: Pests: intermediate; Natural enemies: intermediate (low rates), long (high rates)
    RESISTANCE: Some citrus thrips populations in the San Joaquin Valley
    MODE-OF-ACTION GROUP NUMBER1: 3A
    COMMENTS: To reduce the potential for resistance, make a total of only one pyrethroid application (for all pest species) per year. Do not apply in the vicinity of aquatic areas.
    D. FENPROPATHRIN
    (Danitol 2.4EC) 16–21.33 fl oz/acre (OC) 24 1
    RANGE OF ACTIVITY: Pests: broad (many insects and mites); Natural enemies: most
    PERSISTENCE: Pests: intermediate; Natural enemies: long
    MODE-OF-ACTION GROUP NUMBER1: 3A
    COMMENTS: To reduce the potential for resistance, make a total of only one pyrethroid application (for all pest species) per year. Do not apply in the vicinity of aquatic areas.
    E. ZETA-CYPERMETHRIN
    (Mustang) 4.3 oz/acre (OC) 12 1
    RANGE OF ACTIVITY: Pests: broad (many insects and mites); Natural enemies: most
    PERSISTENCE: Pests: intermediate; Natural enemies: intermediate
    MODE-OF-ACTION GROUP NUMBER1: 3A
    COMMENTS: To reduce the potential for resistance, make a total of only one pyrethroid application (for all pest species) per year. Do not apply in the vicinity of aquatic areas.
    ** A - Aircraft applications 5 to 20 gal water/acre.
    OC - Outside coverage uses 100 to 250 gal water/acre.
    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.
    * Permit required from county agricultural commissioner for purchase or use.
    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).

    Important Links

    Text Updated: 07/20
    Treatment Table Updated: 07/20