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UC Pest Management Guidelines


Adult lygus bug, Lygus hesperus.

Eggplant

Lygus Bugs

Scientific Name: Lygus hesperus and others

(Reviewed 4/10, updated 12/11)

In this Guideline:


DESCRIPTION OF THE PESTS

Adults are yellowish, brownish, or greenish bugs, about 0.3 inch (7–8 mm) in length, with a conspicuous triangle in the center of the back that is tinged brown, red, or yellow. Nymphs resemble adults, but are uniformly pale green with red-tipped antennae and have no wings. Lygusfeed on the fruit or seeds of many crops, including alfalfa, beans, sugarbeets and safflower, as well as a wide range of weed hosts. They can move to eggplant when their primary hosts dry or are disturbed, such as when alfalfa is cut, crops are harvested, or weedy fields dry down or are removed.

For additional information on identifying lygus bugs, see A Field Key to the Most Common Lygus Species Found in Agronomic Crops of the Central San Joaquin Valley of California, UC ANR Publication 8104(PDF).

DAMAGE

Lygus bugs feed by injecting phytotoxins into floral structures such as flower buds or small fruit. This feeding causes the floral structure to abort within days of feeding, and the structure is shed from the plant. Damage symptoms appear as dropped buds on the ground, and while there are several causes of fruit abscission (shed), lygus bugs are a primary culprit. Losses of floral structures relate directly to loss in yield as each bud or flower represents a potential fruit.

MANAGEMENT

Because eggplant is maintained in a reproductive state for a long period of time through an extended harvest period, new fruiting structures can be vulnerable throughout the season. This makes management difficult because lygus bugs can migrate into a field at anytime, depending on the crops or weeds that surround the field. After the first floral buds appear, the plant remains susceptible to damage for the remainder of the season.

Monitoring and Treatment Decisions
There is no published sampling method for lygus bugs. Sweep nets can be employed to locate populations and to determine the relative population levels, but the numbers are not related to damage. Walking through the fields during periods of warm temperatures causes the insects to fly off, so briskly walking and sweeping gives a better estimate of their numbers. The IPM guidelines for cotton and the sweep net techniques described may be somewhat useful with eggplant lygus populations (see http://www.ipm.ucdavis.edu/PMG/r114301611.html).

Observations of flower and bud abscission coupled with presence of the pest on plants has been used by field personnel to make treatment decisions, but no reliable data are available to confirm these decision processes. Confirm that lygus is in the field because fruit drop may also be caused by heat. The use of sweep net samples to detect the presence of immature lygus bugs is a good indication of a resident population.

Common name Amount/Acre** R.E.I.+ P.H.I.+
(trade name)   (hours) (days)

  Calculate impact of pesticide on air quality
The following materials are listed in order of usefulness in an IPM program, taking into account efficacy and impact on natural enemies and honey bees. When choosing a pesticide, also consider information relating to environmental impact. Not all registered pesticides are listed. Always read label of product being used.
 
A. FLONICAMID
  (Beleaf) 50SG 2–2.8 oz 12 0
  MODE OF ACTION GROUP NUMBER1: 9C
  COMMENTS: Research is lacking on the effectiveness of this insecticide in eggplants, but it has proven to be effective against lygus and aphids in other crops such as cotton and not as detrimental to beneficials as the other products registered.
 
B. PERMETHRIN*
  (Pounce) 25WP 6.4–9.6 oz 12 3
  MODE OF ACTION GROUP NUMBER1: 3
 
C. METHOMYL*^
  (Lannate) 90WSP 0.5–1 lb 48 5
  (Lannate LV) 1.5–3 pt 48 5
  MODE OF ACTION GROUP NUMBER1: 1A
  COMMENTS: This material will also control armyworm. More effective against a resident population than a migrating one.
 
D. MALATHION Label rates 12 3
  MODE OF ACTION GROUP NUMBER1: 1B
 
E. FENPROPATHRIN*
  (Danitol) 2.4 EC 10.66 fl oz 24 3
  MODE OF ACTION GROUP NUMBER1: 3
  COMMENTS: Do not exceed 2.66 pt/acre/season.
 
** See label for dilution rates.
+ 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 until harvest can take place. In some cases the R.E.I. exceeds the P.H.I. The longer of these two intervals is the minimum time that must elapse before harvest may take place.
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). For additional information, see their Web site at http://www.irac-online.org/.
* Permit required from county agricultural commissioner for purchase or use.
^ Do not apply when bees are present.

[Precautions]

PUBLICATION

[UC Peer Reviewed]

UC IPM Pest Management Guidelines: Eggplant
UC ANR Publication 3475
Insects and Mites
R. H. Molinar, UC Cooperative Extension Fresno County
J. L. Aguiar, UC Cooperative Extension Riverside County
M. J. Jimenez, UC Cooperative Extension Tulare County
P. B. Goodell, UC IPM, Kearney Agricultural Center, Parlier

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