Description of the Pest
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.
Damage
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.
Management
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.
Monitoring and Treatment Decisions
Starting in April monitor weekly through nut development.
- 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.
- Also sweep for redshouldered and green stink bugs in surrounding cover crops and vegetation.
- Sample the trees with a beating tray for green stink bugs while also sampling for leaffooted bug and small plant bugs.
- Hold the tray under nut clusters while striking the limb sharply three times with a lightweight club.
- Examine bugs that drop onto the tray.
- The best time to take beat samples is in the morning when bugs are less active and easier to examine.
- 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.
Pesticides and Natural Enemy Releases
Not all registered pesticides are listed. The following are ranked by their IPM value, with the most effective and least harmful to natural enemies, honey bees, and the environment listed at the top of the table. When choosing a pesticide, consider information related to water and air quality, resistance management, and the pesticide's properties and application timing. Use PestManage to compare summarized management options for different pests in the same crop. Always carefully read the label of the product being used and take all necessary precautions when handling pesticides.
| Rank | Active ingredient | Example trade name | Group | Group Order | MoA 1 | Amount per acre | REI (hours) ‡ | PHI (days) ‡ | Comments | Selectivity 2 | Bees 3 | Predatory mites 4 | Predators 5 | Parasitoids 5 | Residue duration 6 | Leaching(fish) 7 | Adsorbed runoff(fish) 8 | Solution runoff(human) 9 | Leaching(human) 10 | Solution runoff(human) 11 | Last updated 12 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
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Brigade WSB | Application Timing Varies (See UC IPM Pest Management Guidelines and Label) | 8 |
3A |
8–32 oz | 12 | 7 | Do not apply near aquatic areas. Brigade... | broad | high | high | high | long | intermediate | low | extra high | very low | intermediate | 10/2014 | ||
|
|
Baythroid XL | Application Timing Varies (See UC IPM Pest Management Guidelines and Label) | 8 |
3A |
2–2.4 fl oz | 12 | 14 | Do not apply near aquatic areas. Baythro... | broad | high | high | high | moderate | intermediate | intermediate | extra high | very low | very low | 10/2014 | ||
|
|
Warrior II | Application Timing Varies (See UC IPM Pest Management Guidelines and Label) | 8 |
3A |
1.28–2.56 fl oz | 24 | 14 | Do not apply near aquatic areas. Warrior... | broad | high | high | high | moderate | intermediate | low | extra high | low | high | 10/2014 | ||
|
|
Pounce 25 WP | Application Timing Varies (See UC IPM Pest Management Guidelines and Label) | 8 |
3A |
8–16 oz | 12 | 0 | Highly toxic to honey bees. Do not apply... | broad | low | high | high | long | intermediate | low | extra high | very low | intermediate | 10/2014 |
Legend
- ‡ a b Restricted entry interval (REI) is the number of hours (unless otherwise noted) from treatment until the treated area can be safely entered without personal protective equipment. Preharvest interval (PHI) is the number of days from treatment to harvest. In some cases, the REI exceeds the PHI. The longer of the two intervals is the minimum time that must elapse before harvest.
- 1 ↩ Group numbers for insecticides and miticides are assigned by the Insecticide Resistance Action Committee (IRAC). Insecticides with unknown modes of action are assigned mode-of-action group numbers (MoAs) that begin with UN. Rotate pesticides 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; insecticides with a 1B group number should be alternated with insecticides that have a group number other than 1B.
- 2 ↩ Range of insect and mite groups affected by a pesticide. Broad means the pesticide affects most groups of insects and mites; narrow means the pesticide affects only a few specific groups.
- 3 ↩ Risk of harm to honey bees. For more information, see Bee Precaution Pesticide Ratings.
- 4 ↩ Risk of harm to predatory mites. Toxicities are generally to western predatory mite, Galendromus occidentalis. Where differences have been measured in toxicity of the pesticide-resistant strain versus the native strain, these are listed as pesticide-resistant strain or native strain.
- 5 a b Risk of harm to parasitoids and general predators. Toxicities are averages of reported effects and should be used only as a general guide. Actual toxicity of a specific insecticide depends on factors including the application rate, environmental conditions, and the life stage and species of a parasitoid or predator.
- 6 ↩ Length of time residue affects natural enemies. Short means hours to days; moderate means days to 2 weeks; and long means many weeks or months.
- 7 ↩ Risk of harm to fish from leaching, based on USDA Natural Resources Conservation Service Windows Pesticide Screening Tool (WIN-PST).
- 8 ↩ Risk of harm to fish from adsorbed runoff, based on USDA Natural Resources Conservation Service Windows Pesticide Screening Tool (WIN-PST).
- 9 ↩ Risk of harm to fish from solution runoff, based on USDA Natural Resources Conservation Service Windows Pesticide Screening Tool (WIN-PST).
- 10 ↩ Risk of harm to humans from leaching, based on USDA Natural Resources Conservation Service Windows Pesticide Screening Tool (WIN-PST).
- 11 ↩ Risk of harm to humans from solution runoff, based on USDA Natural Resources Conservation Service Windows Pesticide Screening Tool (WIN-PST).
- 12 ↩ Date information was last updated in the UC IPM Pest Management Guidelines.
UC IPM Pest Management Guidelines: Pistachio
UC ANR Publication 3461
R.H. Beede (emeritus), UC Cooperative Extension Kings County
W.J. Bentley (emeritus), UC IPM and Kearney Agricultural Research and Extension Center, Parlier
K.M. Daane, Kearney Agricultural Research and Extension Center, Parlier
D.R. Haviland, UC IPM and UC Cooperative Extension Kern County
Acknowledgement for Contributions to Invertebrates
R.E. Rice, Kearney Agricultural Research and Extension Center, Parlier
