Description of the Pest
Two species of katydids are present in the North Coast pear district: forktailed bush and Mediterranean katydids. The forktailed bush katydid is about 1.5 inches long from head to wing tip while the Mediterranean katydid is 1.25 inches long. Several characteristics can be used to differentiate these two species. The hind wings in the Mediterranean katydid are about 0.1875 inch (7.5 mm) longer than the front wing while in forktailed bush katydid they are only 0.3125 inch (4.5 mm). The body and legs of the Mediterranean katydid are marked with dark red dots both in the adult and nymphal stages. The forktailed bush katydid has red line markings. The male forktailed bush katydid has a dorsal genitalia plate protruding as a conspicuous forked up-turned process. The nymphs' body of both species is cylindrical, strongly arched, green in color, with long antennae that are banded black and white.
Eggs are white, kidney-shaped, and about 0.125 inch long (3 mm). In fall, Mediterranean katydid females insert their eggs singly lengthwise into the outer bark layer of grapevines, and forktailed bush katydids insert their eggs into leaf edges of evergreen shrubs and trees. Eggs of both species hatch in May.
Small nymphs are most easily seen when feeding in weeds such as little mallow. Mediterranean katydids overwinter in vineyards and migrate to pear orchards starting when they are third instars in early June. In June and July, nymphs can be seen feeding on fully-grown tender leaves on new shoots. Adult katydids appear in mid-summer. Male song is heard at dusk and in the evening as a series of three or four "zeek" sounds a few seconds apart. Females respond after a little over a second with ticking, which attracts the males. There is only one generation a year in the North Coast.
Katydids may occasionally cause damage by feeding on pears shortly before harvest, especially in orchards that have not been treated with broad-spectrum pesticides. High populations of this pest occur in cycles, and they may cause damage one year but not in the next. Damage has been observed in orchards next to riparian vegetation or vineyards.
Young nymphs feed on leaves; as the nymphs become 4th and 5th instars and adults, they may feed on the fruit as it softens. Pear damage is first seen 3 to 4 weeks before harvest. Katydid nymphs tend to feed on a small portion 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. Nymphs and adults also chew holes in foliage. Small nymphs feed in the middle of the leaf, creating small holes, whereas larger nymphs and adults feed on the leaf edge.
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.
Organically Acceptable Methods
Treatments with azadirachtin (Neemix) and the Entrust formulation of spinosad are acceptable in an organically certified orchard.
Monitoring and Treatment Decisions
Look for small nymphs on weeds such as little mallow and lambsquarters beginning in mid-May. Also, use a sweep net to detect populations in the cover crop. In late May and early June examine the 3rd or 5th leaf from the tip of growing shoots for feeding damage and for katydids sitting on top of the leaf. 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 at 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, because other leaf feeders can cause similar damage. Nymphs can be difficult to see on the tree. Treatment may be necessary if you find both nymphs on the tree and damage.
Monitor fruit once a week starting in mid-July to detect any feeding damage. Take a fruit sample at harvest to assess the effectiveness of the current year's IPM program and to determine the needs of next year's program. Sample 200 fruit per bin from 5 bins per orchard (or per 20-acre block in large orchards) for a total of 1,000 fruit. For more information on sampling at harvest, see HARVEST FRUIT 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: 5|
|COMMENTS: Apply to young nymphs (1st to 2nd instars). Not as effective on adults. Apply with oil. Residual efficacy is affected by pH but initial efficacy is not; verify that water pH is greater than 6 and less than 8.|
|(Dimilin 2L)||12–16 fl oz||12||14|
|MODE OF ACTION GROUP NUMBER1: 15|
|COMMENTS: Apply to young nymphs (1st to 2nd instars). Not as effective on adults.|
|(Intrepid 2F)||6–16 fl oz||4||14|
|MODE OF ACTION GROUP NUMBER1: 18|
|(Delegate WG)||4.5–7 oz||4||7|
|MODE OF ACTION GROUP NUMBER1: 5|
|COMMENTS: Residual efficacy is affected by pH but initial efficacy is not; verify that water pH is greater than 6 and less than 8.|
|(Neemix 4.5)||0.25–1 pt||4||0|
|MODE OF ACTION GROUP NUMBER1: un|
|COMMENTS: Moderately effective on immature katydids, which must be contacted by spray so good coverage is essential.|
|**||Dilute rate is the rate per 100 gal water; use 400 gal solution/acre. Apply concentrate in 80–100 gal water/acre, or less if the 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 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 are assigned by IRAC (Insecticide Resistance Action Committee).|
|*||Permit required from county agricultural commissioner for purchase or use.|