Questions and answers on chinch bugs



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Question: How do chinch bugs damage grass?
Answer: We don’t know. Other similar insects seem to damage plants from their saliva, which causes major physiological changes, sometimes first cutting off the translocation stream. Chinch bugs do not kill grass by “sucking it’s juice,” because there is too little material involved.

Question: How do grasses resist chinch bugs?
Answer: We don’t know. There is no known chemical antibiosis of St. Augustinegrass to chinch bugs. Resistance of St. Augustinegrass varieties is a feeding resistance. The bug stops feeding on the resistant plant, and feeds normally when it is returned to a suitable host.

Question: Where should we look for chinch bug damage?
Answer: Chinch bugs are first noticed in the drier, sunnier parts of a lawn. A source of radiant heat, such as a driveway, or a well-drained area such as a hill, favors chinch bug outbreaks, that is, overpopulation to lawn-killing numbers. Like lemmings, they start their piercing, sucking march across the landscape. Accurate detection is also critical, because chinch bugs get blamed for things they don’t do, such injury from drought and disease, even nutritional problems.

Question: How do chinch bugs invade?
Answer: Mostly, by walking. But chinch bugs also fly, which I have seen rarely. Kuitert explained, “Just this week I was on the second floor of a building downtown. I am sure it must have been blocks away from a St. Augustine lawn–but what did I find on the second floor of that building, on the inside–a chinch bug!” I have had the same experiences as Kuitert, in a lumber yard and in a barren field which we had treated with methyl bromide.

Question: Does fertilization bring on chinch bugs infestation?
Answer: Yes, depending on how it’s done. High rates of water-soluble nitrogen fertilization are associated with subsequent chinch bug outbreaks. Once an outbreak has occurred, the gregarious chinch bugs move as a frontal mass to kill lawn sized areas, sometimes within 2 weeks, but more commonly over 3-5 weeks. This research was published with Dr. George Snyder, and it confirmed what lawn applicators such as Mr. Vic Woodbrey had been saying for years, as well as data that Dr. Horn and Dr. W. L. Pritchett had reported in the Florida Turf-Grass Association Bulletin in 1963.

Question: Is it true that Floratam was never really resistant to chinch bugs?
Answer: No. The Floratam-type of resistance to chinch bugs was and is a strong resistance, but it is specific only to certain populations of chinch bugs. When this strong type of resistance occurs, chinch bugs are no economic problem. When this strong resistance is overcome, chinch bugs can cause severe damage. The planting of hundreds of thousands of acres of one variety, Floratam, increases the opportunity for superbugs to spread.

Question: What about other varieties?
Answer: Among varieties of St. Augustinegrass, there are measurable degrees of resistance. For example, in long-term plots at Fort Lauderdale, Seville suffered only 18% incidence of chinch bug outbreak per year. In the same study, Florida Common was damaged by chinch bug outbreaks in 90% of the plot-year combinations.

Question: When do chinch bugs damage St. Augustinegrass?
Answer: Chinch bugs attack St. Augustinegrass in Florida during 12 months, but the vast majority of their attacks, even in south Florida, is May through October. This was based on three years of observation of chinch bug damage, and subsequent treatment, in 160 plots representing 20 varieties of St. Augustinegrass. I treated each plot chemically whenever it showed damage.

Question: How often should one spray for chinch bugs?
Answer: A single curative insecticides treatment, done thoroughly to cover the chinch bug infested area, usually protects against reinfestation for the season. Your client may expect you to treat year-round, but it is unnecessary if you can scout for damage.