How to Manage Pests

UC Pest Management Guidelines

DESCRIPTION OF THE PEST

Western boxelder bug may be more damaging in North Coast districts near riparian vegetation. Adults are slender and gray brown to black, with conspicuous red lines on the thorax and wing coverings. The body beneath the wings is orange red and very noticeable in flight. Immature bugs are bright orange-red until they are half grown. Eggs are laid in groups and resemble miniature red kidney beans. The adult bug overwinters on boxelder, maples, and cottonwoods in a riparian corridor. There is one generation a year.

The adults aggregate in the winter months in riparian vegetation where they overwinter. On warm March days, adults are active; they mate and move to the edge of the orchard. Egg laying begins in late March and continues through April. Eggs are laid on riparian vegetation (blackberry, cottonwood, maples leaves) and on leaves and fruit of pear trees close to the riparian corridor. Nymphs develop from April through July. Adults begin to emerge in mid-July.

DAMAGE

Adults and nymphs feed on fruit, causing dimples very similar to stink bug damage. A small dark depression is formed where they feed, producing a hard pithy area under the skin. In orchards, the highest boxelder bug damage is seen in the first 10 to 30 rows adjacent to riparian vegetation. Damage incidence decreases as you move away from the river and can be seen throughout the orchard but in low incidence. Fruit damage incidence increases starting in mid-June when nymphs are larger and as fruit softens.

MANAGEMENT

Western boxelder bugs may become more important pests in orchards where mating disruption is used for codling moth control. Monitor weeds in spring and trees in early summer to determine need for treatment.

Monitoring and Treatment Decisions

In orchards next to riparian corridors with a history of boxelder bug, monitor pear trees at the edge of the orchard. Monitor during April by inspecting leaves in flower clusters for eggs. (For more information, see SAMPLING AT BLOOM.) Also examine nearby maples, cottonwoods, boxelder, and blackberries near rivers for adults. Beginning in April, continue monitoring fruit clusters and shoots for the presence of eggs and nymphs in the first 20 to 40 rows adjacent to the riparian corridor. Monitor fruit damage beginning in May. (See SAMPLING DURING FRUIT DEVELOPMENT for more details.)

No treatment thresholds have been developed for boxelder bug. In an orchard with a history of damage, treating the first 20 to 40 rows adjacent to the riparian corridor may be warranted. Control is most effective when the nymphs are small in May.

Harvest fruit sample

At harvest, assess your IPM program by monitoring fruit in the bins for western boxelder bug damage. Sample 200 fruit per bin from 5 bins per orchard (or 20-acre block in large orchards). (For more information, see HARVEST FRUIT SAMPLE.)

Common name		Amount to use**		R.E.I.+	P.H.I.+
(trade name)		(conc.)	(dilute)
				(hours)	(days)
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 the label of the product being used.
MAY/JUNE to PREHARVEST
A.	FENPROPATHRIN*
	(Danitol 2.4EC)	16–21.33 fl oz	4–5.3325 fl oz	24	14
	MODE OF ACTION GROUP NUMBER1: 3A
	COMMENTS: Harmful to beneficial insects and mites; will suppress spider mites. Take care to avoid spray runoff or drift when spraying adjacent to riparian corridors because of water quality concerns. Do not apply to blooming plants, including fruit trees and broadleaf weeds.
B.	LAMBDA-CYHALOTHRIN*
	(Warrior with Zeon)	2.56–5.12 fl oz	—	24	21
	MODE OF ACTION GROUP NUMBER1: 3A
	COMMENTS: Harmful to beneficial insects and mites; will suppress spider mites. May cause outbreaks of pear rust mite. Take care to avoid spray runoff or drift when spraying adjacent to riparian corridors because of water quality concerns. Do not apply to blooming plants, including fruit trees and broadleaf weeds.
C.	CLOTHIANIDIN
	(Clutch 50WDG)	2–6 oz	—	12	7
	MODE OF ACTION GROUP NUMBER1: 4A
	COMMENTS: Do not apply to blooming plants, including fruit trees and broadleaf weeds.
D.	ACETAMIPRID
	(Assail 70WP)	1.1–3.4 oz	—	12	7
	MODE OF ACTION GROUP NUMBER1: 4A
	COMMENTS: Do not apply to blooming plants, including fruit trees and broadleaf weeds.
E.	THIAMETHOXAM*
	(Actara)	4.5–5.5 oz	1.125–1.375 oz	12	see comments
	MODE OF ACTION GROUP NUMBER1: 4A
	COMMENTS: Allow a minimum of 10 days between applications; do not exceed 8 oz/acre per season. Preharvest interval is 14 days when 2.75 oz/acre or less is used and 35 day when more than 2.75 oz/acre is used. Do not apply to blooming plants, including fruit trees and broadleaf weeds.
F.	IMIDACLOPRID
	(Provado 1.6F)	10 fl oz	2.5 fl. oz	12	7
	MODE OF ACTION GROUP NUMBER1: 4A
	COMMENTS: Effective against boxelder and lygus bugs, but not stink bugs. Do not apply to blooming plants, including fruit trees and broadleaf weeds.
G.	DIMETHOATE	Label rates		see label	28
	MODE OF ACTION GROUP NUMBER1: 1B
	COMMENTS: May kill beneficial mites and pear psylla predators. Do not apply to blooming plants, including fruit trees and broadleaf weeds. Not allowable by some processors.
**	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 (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.
*	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 are assigned by IRAC (Insecticide Resistance Action Committee). For additional information, see their Web site at www.irac-online.org.
—	Not recommended or not on label.

PUBLICATION

UC IPM Pest Management Guidelines: Pear
UC ANR Publication 3455

Insects and Mites

L. G. Varela, UC IPM Program, UC Cooperative Extension, Sonoma County
R. B. Elkins, UC Cooperative Extension, Lake County
R. A. Van Steenwyk, Insect Biology, UC Berkeley
C. Ingels, UC Cooperative Extension, Sacramento County
Acknowledgment for contributions to Insects and Mites:
C. Pickel, UC IPM Program, UC Cooperative Extension, Sutter/Yuba counties
P. W. Weddle, Weddle, Hansen & Associates
R. Hansen, Weddle, Hansen & Associates
P. Chevalier, United Ag Products, Ukiah
M. Hooper, Ag Unlimited, Lakeport
B. Knispel, Pest Control Adviser, Upper Lake
T. Lidyoff, Purity Products, Healdsburg
G. McCosker, Harvey Lyman Agservices, Walnut Grove
B. Oldham, Ag Unlimited, Ukiah
J. Sisevich, AgroTech, Kelseyville (retired)
D. Smith, Western Farm Service, Walnut Grove
B. Zoller, The Pear Doctor, Inc., Kelseyville

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