CHINCH BUGS Which is the best way of chemically controlling chinch bugs, regular prevention or treatment after damage? Broward County

ANSWER: Curative pesticide treatments are effective and environmentally the more appropriate, provided chinch bug infestation is diagnosed promptly. I have noticed that it takes 3 to 8 weeks or longer for chinch bugs to kill a lawn-sized area, once damage is first noticed. Therefore,

monitoring should be performed every week during hot, dry weather when chinch bugs are most destructive. Be on the lookout for yellowing grass, particularly near heat sources (sidewalks, sun-exposed walls, etc.) and dry, elevated areas.  When you see questionable areas, "coffee-can flotation" is an effective monitoring technique. Alternatively, if you are confident of the appearance of the bugs, use your hands to part the thatch at several locations, revealing the furtive insects. With either technique, look for slate-black adults, only 1/8 to 1/6 inch long, with silvery wings. Younger chinch bugs, which are smaller and reddish, are slower walkers, so you might notice them more easily than the adults.

Chinch bugs kill grass progressively in a blotchy, frontal advance, thus they are more numerous along the edge of damage. Along the edge of usually totally dead, brown grass, the yellowing, dying St. Augustinegrass will often show an orange hue. During two years of monitoring at UF-Fort Lauderdale research plots, three-quarters of all chinch bug infestations occurred from June through November. The most susceptible St. Augustinegrass varieties showed damage at an average frequency of every year to every two or three years. This is an indication of the many unnecessary months of preventative pesticide use that may be avoided by treating after damage is first noticed. Pesticide use can be reduced further by treating on a spot basis, and extending about 10 feet outside the affected area. While chlorpyrifos (Dursban) is a frequently used "knock-down" pesticide against chinch bugs, I have found at Fort Lauderdale that significant residual toxicity is present on the grass 15 days after treatment. Considering that the average generation time of chinch bugs is around 45 days, this means that even in situations where a "knock-down" pesticide is used preventively, it probably won't have to be reapplied against chinch bugs for at least two months.

The southern chinch bug is the most widespread pest of St. Augustinegrass, Florida's most widely used lawn grass. Other lawn grasses in Florida are rarely affected. Although the resistant St. Augustinegrass variety 'Floratam' held up for years, chinch bugs are now adapted to it, so pesticides are required occasionally. A preventative approach which is environmental appropriate is to avoid high rates of nitrogen application, which are associated with earlier and higher levels of chinch bug damage.