Stink Bugs

The redshouldered stink bug (Thyanta pallidovirens) is somewhat triangular in shape and about 1/3 inch (8.3 mm) in length. It is predominantly green with a narrow red band across the shoulder; sometimes the band is absent. There is also a brown-colored phase, usually found in overwintering bugs. The green stink bug (Chinavia hilaris) which was previously called Acrosternum hilare is dull to bright green and slightly larger (2/5–3/5 inch) and less common than the redshouldered stink bug. Adult green stink bugs are bright green with the entire lateral margin lined in yellow or orange. Two other species are similar to the green stink bug, these are the Uhler's stink bug (Chlorochroa uhleri), and the Say's stink bug (Chlorochroa sayi). Green stink bug nymphs are a mixture of green, black, and orange.

Stink bugs often develop in weeds or field crops and move to pistachio, but they have also been found overwintering in orchards, especially the green plant bug. Eggs of these stink bugs are laid in clusters, are barrel shaped, and have concentric dark rings at the top. Immature stages of these species range widely in coloration, often marked brightly with red, yellow, green and black or brown, different from the adult stage and changing as the nymphs develop.

Do not confuse pest stink bugs with the rough stink bug, Brochymena quadripustulata, a predator that is speckled white and gray and quite common in pistachio orchards throughout the year. Nymphs of Brochymena are colored red, white, and blue.

Before shell hardening, stink bugs cause damage similar to their smaller relatives (small plant bugs) by causing epicarp lesions associated with a white netting inside the nut. Often these damaged nuts drop along with a large number of other naturally aborted nuts. Due to the relatively low number of stink bugs typically found early in the season, coupled with the ability of the tree to compensate for aborted nuts, stink bug damage prior to shell hardening rarely causes an economic loss of crop.

After shell hardening in July, stink bugs may cause kernel necrosis, which is identical to damage caused by leaffooted plant bugs, and contributes to offgrade nuts at harvest. Kernel necrosis is not obvious externally, but inside the nut, the nutmeat is darkened, often develops a sunken necrotic area, and has an off-flavor. In July and August, feeding damage is indicated by an external, brown pinpoint mark; no white netting is visible.

Stink bugs are capable of transmitting some pistachio diseases, such as Stigmatomycosis and Botryosphaeria panicle and shoot blight, making control of these pests important.

Stink bugs are primarily late season pests. When stink bug density is high in July and August, a treatment may be required to reduce the incidence of kernel necrosis.

Starting in April monitor weekly through nut development.

1. Spend about 30 minutes looking for adult stink bugs migrating into the orchard from overwintering sites. Start from the edge of the orchard and work your way inward.
2. Also sweep for redshouldered and green stink bugs in surrounding cover crops and vegetation.
3. Sample the trees with a beating tray for green stink bugs while also sampling for leaffooted bug and small plant bugs.
   1. Hold the tray under nut clusters while striking the limb sharply three times with a lightweight club.
   2. Examine bugs that drop onto the tray.
   3. The best time to take beat samples is in the morning when bugs are less active and easier to examine.
4. It is also helpful to look for small damaged or blackened nuts. Cut them open to confirm bug damage (black lesions inside the hull).

Time insecticide applications after the majority of eggs have hatched and nymphs are easily found. In many cases broad-spectrum treatments already being used for small bugs, leaffooted bug, or navel orangeworm provide adequate control of stink bugs.

	Common name	Amount per acre**	REI‡	PHI‡
	(Example trade name)		(hours)	(days)
Pesticide precautions Protect water Calculate VOCs Protect bees
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.
A.	PERMETHRIN
	(Pounce 25WP*)	8–16 oz	12	0
	(Ambush 25W*)	12.8–25.6 oz	12	0
	MODE-OF-ACTION GROUP NUMBER1: 3
	COMMENTS: Highly toxic to honey bees. Do not apply near aquatic areas; Pounce 25WP and Ambush 25W are restricted-use pesticides because they are highly toxic to fish and aquatic organisms.
B.	BIFENTHRIN
	(Brigade WSB*)	8–32 oz	12	7
	MODE-OF-ACTION GROUP NUMBER1: 3
	COMMENTS: Do not apply near aquatic areas. Brigade WSB is a restricted-use pesticide because it is highly toxic to fish and aquatic organisms.
C.	LAMBDA-CYHALOTHRIN
	(Warrior II with Zeon*)	1.28–2.56 fl oz	24	14
	MODE-OF-ACTION GROUP NUMBER1: 3
	COMMENTS: Do not apply near aquatic areas. Warrior II is a restricted-use pesticide because it is highly toxic to fish and aquatic organisms.
D.	CYFLUTHRIN
	(Baythroid XL*)	2–2.4 fl oz	12	14
	MODE-OF-ACTION GROUP NUMBER1: 3
	COMMENTS: Do not apply near aquatic areas. Baythroid XL is a restricted-use pesticide because it is highly toxic to fish and aquatic organisms.

**	Unless otherwise noted, apply with enough water to ensure adequate coverage.
‡	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.
*	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 http://www.irac-online.org/.