Description of the Pest
Several kinds of stink bugs feed in nectarine orchards including consperse stink bug, green stink bug, redshouldered stink bug, Say’s stink bug, and Uhler’s stink bug, but they are not pests in every orchard every year. Outbreaks appear to be cyclical.
The different species of stink bugs all have similar life histories. They overwinter as adults under leaves and trash, in the crowns of plants, and in clumps of grass on the orchard floor. They also may be found outside the orchard in the crowns of plants such as blackberry or in other protected places such as box piles and buildings. After mating, if suitable host plants are not present in the orchard, adults move out of the orchard to suitable host plants. Most of the species remain on weeds and ground cover plants at this time, but the green stink bug may move into the trees.
Adults have shield-shaped bodies that are about 0.5 inch long and either brown or green with red, pink, or yellow markings. Barrel-shaped eggs are laid in clusters of about 14 on leaves of broadleaf plants. Eggs are pearly white when first laid, later turning cream colored or pinkish just before hatching. For consperse stink bugs, a row of spines encircle the top of the eggs; the other species have concentric black rings on top of the eggs. Early nymphal stages have various markings and patterns and no wings but resemble adults in shape. Nymphs develop prominent wing pads in the fourth and fifth instars.
In early June, adults may migrate to trees where they deposit eggs on the foliage. Adults from this generation also feed on developing fruit. Second generation adults begin appearing in late July-August and can cause severe damage to unharvested fruit. Second generation adults feed until the onset of cool weather when they migrate back to protected sites or overwintering hosts.
The rough shield bug, Brochymena sulcata, is a beneficial insect and should not be confused with harmful stink bug species. This stink bug is common in Central Valley orchards; adults are 0.5 to 0.66 inches long, brownish or gray, with a very rough and angular shape. Both nymphs and adults feed on caterpillars and other insects.
Stink bugs insert their needlelike mouthparts into fruit and feed on plant juices. Initially the feeding sites are small, translucent, blue-green spots. Damaged flesh under the skin later turns into gray or whitish pithy areas. Gum may exude from feeding areas on green nectarines. Because frost damage can also cause the nectarine to exude gum, examine the flesh of the fruit for needlelike stains caused by stink bug feeding. Damaged areas will fail to grow, and fruit attacked early in the season develops irregular, depressed areas or dimples. On nearly ripe fruit, exterior symptoms resemble a bruise and if the fruit is peeled, white corky or pithy areas will be found. One bug may feed on many fruit, thus a rather low population can cause severe damage. On nectarines, the damage resembles that caused by rust; look for the presence of stink bugs to confirm the cause of the damage.
Focus your stink bug management program on keeping damaging populations from moving into the fruit trees. Monitor the orchard in spring to detect their presence.
Monitoring and Treatment Decisions
Using a sweep net, begin monitoring after the weather has warmed up in March and look for overwintering bugs feeding on curly dock, common mullein, Russian thistle (especially the base of the plant), or other broad-leaved plants. Sample the orchard and adjacent weedy areas. If bugs are found, apply spot treatments to kill adults before they can move to other locations. Orchards with ground covers are likely to harbor stink bug populations. If stink bugs are present, cultivate or mow closely before green fruit appear.
Monitor fruit beginning in early June every other week. Adult bugs often hide on the opposite side of the limb as they are approached, making them difficult to see. Look for sappy exudate on fruit, blue-green spots, or gum that may exude from feeding sites. Some fruit should also be peeled to detect the presence of white pithy or corky areas, or the trees can be sampled with a beating tray.
Double cone traps that are baited with an aggregation pheromone are also available for monitoring the consperse stink bug but will not attract other species of stink bugs. Place these traps in tree crotches near the orchard's border to detect the presence of adult consperse stink bugs.
Consider treating if damaged fruit is common or if adult bugs are seen. Apply a full coverage spray to trees in affected areas of the orchard. Clean cultivation of orchards in fall will discourage overwintering bugs.
Examine fruit on trees every week after color break (see PREHARVEST FRUIT SAMPLES) to detect any developing problems in the orchard, and take a fruit damage sample at harvest to assess the effectiveness of the current year's IPM program and to determine the needs of next year's program, see FRUIT EVALUATION AT HARVEST. Record results for harvest sample.
|Common name||Amount per acre**||REI‡||PHI‡|
|(Example trade name)||(conc.)||(dilute)||(hours)||(days)|
|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 and 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.|
|MODE-OF-ACTION GROUP NUMBER1: 22A|
|COMMENTS: Also controls katydids and Oriental fruit moth. Do not apply in more than 200 gal/acre. Highly toxic to bees; do not spray directly or allow to drift onto blooming crops or weeds where bees are foraging.|
|(Sevin XLR Plus)||3–4 qt/acre||12||1|
|MODE OF ACTION GROUP NUMBER1: 1A|
|COMMENTS: May cause increased spider mite problems; best used late in the season. Do not apply more than 14 qt/acre per season. Highly toxic to bees; do not spray directly or allow to drift onto blooming crops or weeds where bees are foraging.|
|(Asana XL)||4.8–14.5 fl oz||2–5.8 fl oz||12||14|
|MODE-OF-ACTION GROUP NUMBER1: 3A|
|COMMENTS: Based on research in California pistachio orchards, this material effectively controls stink bugs. For dilute applications, do not apply in more than 200 gal water/acre at the 5.8 oz rate. Highly toxic to bees; do not spray directly or allow to drift onto blooming crops or weeds where bees are foraging.|
|**||For dilute applications, rate is per 100 gal water to be applied in 300-500 gal water/acre, according to label; for concentrate applications, use 80-100 gal water/acre, or lower if label allows.|
|*||Permit required from county agricultural commissioner for purchase or use.|
|‡||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.|
|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).|