How to Manage Pests
Pests in Gardens and Landscapes
Figure 3. Adult bigeyed bug, a similar-looking predatory insect that can be confused with chinch bugs.
The false chinch bug, Nysius raphanus (Hemiptera: Lygaeidae), is a small insect commonly found within grassy or weedy fields, pastures, and foothills. Each spring, once the plants in these areas dry up, the false chinch bug migrates to find new places to feed. This becomes a nuisance for homeowners when these bugs migrate into their landscapes and homes and can cause problems for gardeners and farmers.
False chinch bug problems often are most serious in years with wet, cool springs. Above average rainfall encourages abundant growth of weeds and grasses in areas with natural vegetation. Relatively cool spring and early summer weather prolongs the survival of these plants, resulting in greater increases in false chinch bug populations, which reproduce on this vegetation.
Adults are grayish-brown, slender, and about 1/8 to 1/6 inch long. Like many other insects in the order Hemiptera, their forewings are partly thickened and partly membranous so when folded, the tips of the wings overlap, forming a fairly well-defined X on the back of the body (Figure 1). Immature stages (nymphs) lack wings and, from a distance, look like individual coffee grounds in size and color. Nymphs are a mottled gray brown often with reddish or orangish markings on the abdomen (Figure 2).
Both immature and adult false chinch bugs feed on plants through a proboscis, a hypodermic-needlelike structure they use to probe into plant tissue and drink up plant fluids. This type of feeding can cause severe damage to plants that are unable to compensate for lost leaf tissue and sap.
Don’t confuse false chinch bugs with other similar-looking bugs in the same family, the seed bug family Lygaeidae. Bigeyed bugs, which are wider and have larger eyes, are beneficials that feed on pest insects and mites (Figure 3). These never occur in abundance as do false chinch bugs. Another Lygaeid, the southern chinch bug, Blissus insularis, sometimes feeds on turfgrass, but rarely does it significantly damage lawns in California, except for St. Augustine grass. Adults of this species are black with whitish wings.
False chinch bugs spend the winter as nymphs and adults, usually in uncultivated areas beneath debris or in plants, often feeding on mustards or other winter annual plants. As new spring plant growth increases, so do populations of false chinch bugs. Adults lay eggs in soil cracks or loose soil around plants. After hatching, nymphs feed on weeds, especially mustards, molt three times, and develop into adults in about three weeks. There can be several generations a year.
As weedy mustards and other cruciferous plants dry out and die, false chinch bugs move into irrigated crops or landscapes. Adults are good flyers and can move significant distances. False chinch bugs tend to aggregate in large groups on plants or on walls of houses.
In normal years, false chinch bugs are considered a pest only of seedlings. Plants might wilt but only rarely die. Larger annual plants and established perennials have sufficient size to be relatively unaffected by attacks against them. However, when populations are high in wet years, the sheer numbers of these pests can cause alarm for farmers and homeowners alike. Homeowners have been particularly hard hit, as waves of these insects completely envelop garden and landscape plants. Some homeowners have stated that it appears as if the ground is moving. Also, small false chinch bugs often are able to get underneath sliding screen patio doors and enter into homes, where they become a nuisance.
In rare situations, aggregations of false chinch bugs can result in plant and tree decline, and there have been reports of these bugs killing young almond, pistachio, pomegranate, and citrus trees. This level of damage typically is reported only from the lower San Joaquin Valley. Initial symptoms include wilting and a scorched appearance to the leaves, followed by total plant death; the constant probing and feeding from this pest essentially can suck young trees dry. The decline of young trees often is so rapid many entomologists have hypothesized the false chinch bug injects a toxin into the plant as part of the feeding process.
There are few management options for the false chinch bug in gardens and landscapes. Low numbers do not need to be managed, because most garden plants can tolerate some feeding. Keep plants well irrigated to compensate for loss of sap due to chinch bug feeding. If your garden is near an uncultivated area with a lot of mustard, you might want to consider using row covers or caps to protect vegetable seedlings until migration had ended.
Usually the mass migration lasts only one week at most. These insects move predominantly in the cooler mornings or late evenings, so water sprinkling can help reduce movement during these two periods. Creating a water moat around gardens also can reduce insect infestation.
Prevent entry into houses by making sure screens on windows and patio doors are intact and sealing up other entryways. Some pest control companies or homeowners will apply a pesticide around the perimeter of the house to keep the bugs out. However, these products have very short residual, meaning they can save you from insects in your yard today but have little effect on those that arrive tomorrow. A better approach is to seal up entryways. If bugs get into houses, vacuum them up.
Authors: D. R. Haviland, UC Cooperative Extension, Kern Co.; and W.
J. Bentley, UC Statewide IPM Program, Kearney Agricultural Center, Parlier.
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