Katydids

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.

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.

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

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

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

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.

• Photos of damage to fruit