Problem type: Insect
Name of problem: Chinch bug
Plant name(s): All grasses
Symptoms / Characteristics:
The overall damage appears as round patches of brown or dead grass that may rapidly expand outward depending on the severity of the infestation. Eventually these expanding patches may converge, yielding large, irregularly shaped areas of dead turf. An examination of individual leaves may reveal spotting or bleaching. Chinch bug damage is often mistaken for drought-injury or fertilizer burn.
Chinch bugs use their piercing mouthpieces to extract sap from the crowns and stems of grasses while injecting a phytotoxic substance into the plant tissue. Feeding damage can be attributed to both adults and nymphs. Adult chinch bugs are dark brown to black with white wings that fold in such a way that an "X" is visible on the back. Adults are very small, reaching a mature length of approximately 4-6 mm. Chinch bug nymphs are significantly smaller (1 mm) but more harmful than adults. They are initially bright red in colour and darken to black with maturity. A conspicuous whitish stripe can be seen running across the back.
Chinch bugs overwinter in the adult stage beneath shrubbery, within leaves, in garden beds etc. When spring temperatures begin to increase (May or June depending on the year) the females deposit eggs into the grass. Immature nymphs emerge within a few weeks and undergo five molts before reaching adulthood. Seasons that are characterized by high temperatures and little rainfall yield the largest populations and the most severe damage. Symptoms may appear as early as mid-July but become most obvious in August when conditions are especially hot and dry. In the past, chinch bugs have not been a serious pest on the prairies due to extreme winter temperatures. They have become significantly more important in recent years.
Control / Preventions:
Begin monitoring for the insects early in the summer. Remove the top and bottom of a large coffee tin and push the cylinder partway into the grass adjacent to a dead patch or suspect area. Fill the tin with water and within ten or fifteen minutes the chinch bugs will float to the surface for easy identification. Refill the tin as necessary within that time frame. Repeat the test in different areas in the garden. An average exceeding three chinch bugs per tin may warrant a suitable control.
Another method involves spraying a mixture of soap and water over damaged or suspect regions and then placing a white flannel cloth over the area. The soapy water drench will force the chinch bugs up and out of the grass where they will proceed to cling to the cloth for easy collection and disposal.
Chemical controls are available but should be used sparingly in order to prevent the eradication of natural chinch bug predators and other beneficial insects. Always follow the manufacturer's directions and recommendations regarding application rates, timing, equipment and safety. Diatomaceous earth has also been recommended for chinch bug control. It is an abrasive substance that cuts the insect's protective outer covering, causing desiccation and subsequent death.
A properly maintained lawn will not be susceptible to chinch bugs. This includes a regimented watering plan, a balanced fertilizer program, proper mowing techniques and overall good sanitation. Leaves and other plant debris should be removed in the fall in order to reduce potential overwintering sites. Excess thatch should be removed or broken down via top-dressing. Heavily damaged areas will need to be reseeded. When laying new grass seed, choose a fescue or ryegrass variety (or mixture) that is labelled "endophytic". Endophytic grasses contain nonpathogenic fungi that deter chinch bugs, white grubs and other insects. They also have an increased tolerance for dry, infertile soils.