St. Augustinegrass lawn damaged by the southern chinch bug, Broward County.

Old plague:  The cavortin' chinch bug

Philip Busey
(also see Q & A)

During the second UF Turf Conference Louis C. Kuitert spoke about the cavortin chinch bug, causing damage in "considerably greater intensity than in prior years . . . tremendous increase in the population."  This build up of turf damaging insect, he explained in 1954, was probably due to hot, dry weather.

Much of Dr. Kuitert's presentation concerned the biology of the chinch bug, and how little was known.  Today the chinch bug still remains an elusive creature.  From a practical viewpoint, you know you have chinch bugs when your lawn is destroyed.  Or you would like to think you know.  In 1954, Kuitert estimated that 40% of the chinch bug diagnoses were mistaken.  While the southern chinch bug, which attacks St. Augustinegrass, causes massive damage, many people have never seen a chinch bug.  Therefore, the first thing to do when you see rapidly yellowing patches in St. Augustinegrass is to get on your hands and knees, and quickly, gently part the grass to look for bugs.

The adults have slate black bodies, 1/8 to 1/6 inch long, with silvery wings covering most of the back (the dorsal abdomen).  The pattern of the wings, and their overlap across the back, gives them an hourglass or crossed-arms pattern.  Juvenile chinch bugs ("instars") progress from red to brown before finally becoming winged adults.  The easiest way to picture the first instars, 1 millimeter long, is to think of spider mites.  The instars also walk slowly, so they're not as hard to find as the adults.  Other verification methods exist.

	Chinch bugs feeding on St. Augustinegrass in the laboratory. The one with silvery wings is an adult, and the other six bugs are 5th instars.

The Mississippi State University Extension Service says, "you can readily find any chinch bugs by slowly sliding your foot through the sod and watching for the bugs to crawl across your shoe." That sounds easy enough! I have also noticed the distinctive, pungent odor of chinch bugs when I mow.  The scent of a bug is not as reliable as other detection methods, but it has alerted me to part the grass.  Some argue more strongly the need for early detection.  Integrated turf management workers have advised that 10 to 15 adult chinch bugs per square foot are a treatment threshold.  I have never seen such a high count except when chinch bugs were already damaging the turf.  Use scouting and prompt diagnosis, but early detection is unproven.

When chinch bugs damage St. Augustinegrass, the only choices are to treat with insecticides or to watch the lawn die.  Numerous insecticides have been used for killing chinch bugs, but the insect has managed to adapt.  Chinch bug populations evolved resistance to DDT, the insecticide recommended in 1954.  Despite occasional reports of resistant chinch bugs, chlorpyrifos (e.g., Dursban®) remains the commonest insecticide used against the southern chinch bug.  Chlorpyrifos is a contact insecticide with surprisingly lengthy protection (3 weeks) against chinch bugs, based on my field research.  This is not to imply that you would use it preventatively, but it shows that when control fails, it's probably not reinvasion, but rather misapplication or resistant bugs.

Residual control of the southern chinch bug on St.Augustinegrass with chlorpyrifos (e.g., Dursban®), imidacloprid (e.g, Merit®), and isofenphos (e.g., Oftanol ®). Chinch bugs were confined in the laboratory on St. Augustinegrass plugs removed from insecticide-treated field plots at timed intervals. Chinch bug mortality was determined by flotation counts, 12 days after confinement.

Floratam, the dominant variety of St. Augustinegrass, was released in 1973 because it had resistance to chinch bugs.  To the investigators of the 1970s, laboratory tests proved that Floratam had antibiosis.  The bug died when it was confined on Floratam, therefore the grass had antibiosis.  They were wrong for the right reasons, as I showed in later research.  But sod growers and lawn maintenance professionals realized that Floratam was not damaged in the field.  Regardless of the mechanism of grass resistance, they didn't have to spray, and hundreds of thousands of acres of Floratam were planted.  Billions of dollars have been exchanged over Floratam, developed by G.  C.  Horn.  It would be nice if all stories had such a nice ending.

But that wasn't the ending.  In 1985 sod growers asked me to solve a new problem.  Chinch bugs were killing their Floratam fields.  They hadn't sprayed chinch bugs for years.  They had forgotten so much about chinch bugs that some lost entire blocks of sod before they realized what was attacking.  Their first question, "Has resistance broken down?" was easy to answer.  Floratam hadn't changed, because when I confined the old garden variety of chinch bugs in the lab, they were still incapable of living on Floratam.  The grass had stayed the same, but the bugs had changed.  So I described and researched a new race of chinch bugs, and showed that its adaptation to Floratam is genetically inherited.  Organisms often adapt to new hosts, and plant breeders seek new defenses.  Coincidentally, when I did my sabbatical research in 1992 at the University of Nebraska, I had the opportunity to be work on another host-jumping chinch bug, which had adapted to buffalograss.  No grass is completely safe.

	Southern chinch bug, second instar nymph.

During 10 years of research on the host relationship of St. Augustinegrass to southern chinch bug, I developed a variety, FX-10, resistant to the virulent superbugs that had troubled Floratam.  Although FX-10 had production problems, it represented the first Plant Patent by the University of Florida, helping shape future release policies within the University.  You won't find much FX-10 around today, but it caused the creation of the Florida Sod Growers Cooperative, which remains healthy today.  Another byproduct of the work on chinch bugs was that I refocused more work on other aspects of plant resistance.  Working with Dr. Robin Giblin-Davis, I learned that some of the same sources for genetic resistance to chinch bugs were also resistant to the sting nematode, our main turf parasitic nematode.

Thanks to other support by sod producers, I did other extensive research on chinch bug biology, and the easiest way of summarizing it is to list some findings in the context of questions I have received over the years.

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.

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:  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.

Selected chinch bug information

Busey, P.  1990a.   Inheritance of host adaptation in the southern chinch bug (Heteroptera: Lygaeidae).  Ann. Entomol. Soc. Amer. 83:563-567.

Busey, P.  1990b. Polyploid Stenotaphrum germplasm:  resistance to the polyploid damaging population southern chinch bug.  Crop Sci. 30:588-593.

Busey, P.  1993.   Registration of 'FX-10' St. Augustinegrass.  Crop Sci. 33:214-215.

Busey, P.  1995a.  Field and laboratory resistance of St. Augustinegrass germplasm to the southern chinch bug.  HortScience 30:1253-1255.

Busey, P.  1995b.   Genetic diversity and vulnerability of St. Augustinegrass.  Crop Sci. 35:322-327.

Busey, P. and B. J. Center.   1987.  Southern chinch bug (Hemiptera: Heteroptera: Lygaeidae) overcomes resistance in St. Augustinegrass.  J. Econ. Entomol. 80:608-611.

Busey, P. and B. L. Coy.  1988.  Vulnerability of St. Augustinegrass to the southern chinch bug.  Florida State Hort. Soc. Proc. 101:132-135.

Busey, P.  and G.  H.  Snyder.  1993.  Population outbreak of the southern chinch bug is regulated by fertilization.  International Turfgrass Society Research Journal 7:353-357.

Busey, P. and E. I. Zaenker.   1992.  Resistance bioassay from southern chinch bug (Heteroptera: Lygaeidae) excreta.  J. Econ. Entomol. 85:2032-2038.

Davis, M. G. K. and D. R. Smitley.  1990a.  Association of thatch with populations of hairy chinch bug (Hemiptera: Lygaeidae) in turf.  J. Econ. Entomol. 83:2370-2374.

Davis, M. G. K. and D. R. Smitley.  1990b.  Relationship of hairy chinch bug (Hemiptera: Lygaeidae) presence and abundance to parameters of the turf environment.  J. Econ. Entomol.  83:2375-2379.

Horn, G. C., A. E. Dudeck, and R. W. Toler.  1973.  'Floratam' St. Augustinegrass:  A fast growing new variety for ornamental turf resistant to St. Augustine decline and chinch bugs.  Fla. Agr. Expt. Sta. Cir. S-224.

Horn, G. C. and W. L. Pritchett.  1963.  Chinch bug damage and fertilizer:  Is there a relationship?  Florida Turf-Grass Assoc. Bull. 9:3,6-7.

Kuitert, L. C.  1954.  Insect problems in turf.  Part I - Cavortin' chinch bugs.  pp. 97-100. in:  Proc. 2nd Annual University Florida Turf Conference.

Reinert, J. A. and K. W. Portier.  1983.  Distribution and characterization of organophosphate-resistant southern chinch bugs (Heteroptera: Lygaeidae) in Florida.  J. Econ. Entomol. 76:1187-1190.

Reinert, J. A.  1978.  Natural enemy complex of the southern chinch bug in Florida.  Ann. Entomol. Soc. Amer. 71:728-731.

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