How to Manage Pests

UC Pest Management Guidelines

DESCRIPTION OF THE PESTS

Leafhoppers are small, light green, wedge-shaped insects that measure a little more than 0.12 inch (3 mm) in length. The western potato leafhopper is a pest throughout California whereas the southern garden leafhopper occurs mostly in the southern California desert areas. Adult females insert kidney-shaped eggs singly in the plant just below the surface. Eggs hatch and the nymphs pass through five instars. Nymphs are whitish to pale green and move rapidly (often sideways) when disturbed. They are found mainly on the underside of leaves.

DAMAGE

The leafhopper has sucking mouthparts and can cause severe white stippling and yellowing of the leaves, green spotting of the fruit, and premature leaf drop. Large populations can reduce quality as well as yield.

MANAGEMENT

Generally good field sanitation and crop growing practices are adequate for preventing damage by these pests.

Cultural Control
Melons and other cucurbits can tolerate fairly heavy feeding provided they are not stressed for moisture and possess six to eight healthy noninfested terminal leaves. After harvest, destroy crop residue as soon as possible to eliminate breeding areas.

In desert production areas, exclude leafhoppers by applying row covers (plastic and spun-bonded materials) at planting and gradually removing them at first bloom or earlier if needed. Row covers are not recommended for the San Joaquin Valley.

• Do not remove the entire plastic row cover at one time because a drastic reduction in humidity will shock plants and can lead to collapse. Instead vent the covers and remove them gradually. Covers made of spun-bonded materials do not need venting because hot air is able to escape.
• Remove row covers if the air temperature underneath reaches 104° F before bloom.
• Remove row covers before plants grow high enough to touch hot plastic.

Organically Acceptable Methods
Cultural controls are acceptable to use in an organically certified crop.

Monitoring and Treatment Decisions
Treatment thresholds have not been established, but pesticide sprays are not usually required. If leafburn occurs, or if leafhoppers are moving into an immature field from nearby harvested sugarbeet, potato, or other crops, a treatment may be needed.

Common name		Amount/Acre	R.E.I.+	P.H.I+
(trade name)			(hours)	(days)
The following materials are listed in order of usefulness in an IPM program, taking into account efficacy, pesticide registrations, information related to natural enemies and honey bees, and environmental impact. Not all registered pesticides are listed. Always read the label of the product being used.
A.	DINOTEFURAN
	(Venom 70W)	See comments	12	see comments
	MODE OF ACTION GROUP NUMBER1: 4A
	COMMENTS: Rates vary depending upon whether a soil or foliar application. Soil application preferred because it has less impact on beneficials.
B.	THIAMETHOXAM
	(Platinum)	5–8 fl oz	12	30
	MODE OF ACTION GROUP NUMBER1: 4A
	COMMENTS: At seeding or transplanting, apply in sufficient water to ensure uniform application and incorporation into the soil. Provides about 40 days of protection. Use where field has history of these pests.
C.	IMIDACLOPRID
	(Admire Pro)	7–10.5 fl oz	12	21
	MODE OF ACTION GROUP NUMBER1: 4A
	COMMENTS: At seeding or transplanting, apply in sufficient water to ensure uniform application and incorporation into the soil. Use where field has history of these pests.
D.	ESFENVALERATE*
	(Asana XL)	5.8–9.6 oz	12	3
	MODE OF ACTION GROUP NUMBER1: 3
	COMMENTS: Repeat as necessary to maintain control. Do not exceed 0.25 lb a.i./acre/season. Highly toxic to honey bees.
E.	ACETAMIPRID
	(Assail 30SG)	2.5–5.3 oz	12	0
	(Assail 70 WP)	1.1–2.3 oz	12	0
	MODE OF ACTION GROUP NUMBER1: 4A
F.	METHOMYL*
	(Lannate LV)	1.5–3 pt	48	see comments
	MODE OF ACTION GROUP NUMBER1: 1A
	COMMENTS: Labeled for use on cucumbers, melons and summer squash only. Use sufficient water for thorough coverage. Highly toxic to honey bees. PHI is 1 day if 1.5 pt or less is used/acre; if over 1.5 pt, PHI is 3 days.
G.	DIMETHOATE	Label rates	48	3
	MODE OF ACTION GROUP NUMBER1: 1B
	COMMENTS: Labeled for use on melons and watermelons only. Highly toxic to honey bees.
H.	DIAZINON*	Label rates	see label	see label
	MODE OF ACTION GROUP NUMBER1: 1B
	COMMENTS: Not labeled for pumpkins and squash. Highly toxic to honey bees.
I.	OXYDEMETON METHYL*
	(MSR Spray Concentrate)	2 pt	14 days	14
	MODE OF ACTION GROUP NUMBER1: 1B
	COMMENTS: Apply in sufficient water for complete coverage, but not less than 1 gal/acre. No more than 1 application/season. Repeated use of this material is very disruptive to beneficials. Moderately toxic to honey bees.
+	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 REI exceeds the PHI. The longer of two intervals is the minimum time that must elapse before harvest.
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.

PUBLICATION

UC IPM Pest Management Guidelines: Cucurbits
UC ANR Publication 3445
Insects and Mites
E. T. Natwick, UC Cooperative Extension, Imperial County
J. J. Stapleton, UC IPM Program, Kearney Agricultultural Center, Parlier
C. S. Stoddard, UC Cooperative Extension, Merced & Madera counties
Acknowledgment for contributions to Insects and Mites:
R. L. Coviello, UC Cooperative Extension, Fresno County
L. D. Godfrey, Entomology, UC Davis
C. B. Fouche, UC Cooperative Extension, San Joaquin County
C. G. Summers, Entomology, UC Davis/Kearney Agricultural Center, Parlier
J. B. LeBoeuf, AgriData Sensing, Inc., Fresno
M. Murray, UC Cooperative Extension, Colusa/Glenn counties

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