How to Manage Pests
UC Pest Management Guidelines
Several kinds of stink bugs feed in nectarine orchards, 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
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.
UC IPM Pest Management Guidelines: Nectarine
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