Chinch Bug Control in St. Augustine Grasses

The Southern chinch bug is currently the most difficult-to-control and damaging insect of St. Augustine grass in Florida.  Nymphs and adults feed on plant fluids within leaf sheaths, down in the thatch, and this feeding kills the grass plants and contributes to weed invasion.

The chinch bug belongs to a group of insects we call “true bugs” along with plant bugs and stink bugs they have that characteristic “buggy” order if crushed.  Chinch bugs start the size of a pinhead when first hatched (reddish in color with white strip) and grow to 1/5 inch adult (black with white or silvery wings).  They feed on the grass by sucking juices, which leads to a yellow and then brown color as grass dies.  Most rapid loss occurs when temperatures are high and grass is dry.  Areas near the edges of walks and drives are often the first to be affected.

Southern chinch bug activity occurs from March through November in north-central Florida and is year-round in southern Florida. It is estimated that 3 to 4 generations with overlapping life stages develop each year in northern Florida and 7 to 10 generations develop in southern Florida. New damage may appear by May or June, depending on spring temperatures, and any damage that existed in late fall will become apparent in the spring. Part of the difficulty in dealing with this pest is that one generation may develop in 4-6 weeks during the summer. Any insecticides used to treat turfgrass will likely kill most nymphs and adults, but the eggs will survive, nymphs will hatch, and the infestation will continue. Thus, damage may become visible again within 2 -3 months of treatment. Encroachment from neighboring lawns is also a possibility.

Chinch bugs can be seen with the unaided eye.  To spot them part the grasses at the edge of a yellowing spot and watch a few minutes.  Repeat this several times.  If there, they will be seen scurrying about.  Another technique is to cut the two ends from a coffee can, push it into the soil, and then slowly fill it with water.  If present, chinch bugs will swim to the surface.  An easier method is to mix two tablespoons of any dishwashing soap to two gallons of water (without making suds) and pouring this over a two-foot square area that is yellowing.  Wait a few minutes and if chinch bugs are present they’ll come up. Always check at the edge of where yellow turns to green.  Checking in dead areas will give poor results.

Studies have revealed that the frequent application of liquid or quick release fertilizers encourage chinch bugs.  Going to two fertilizer applications per year (March and August) and using a 16-4-8, 15-0-15 or 10-10-10 fertilizer has shown to reduce the incidence of chinch bugs.  Many homeowners, using low fertilizer levels, report going years without having chinch bugs.

It has also been shown that prolonged periods of moisture stress encourage chinch bugs.  Keeping the lawn watered (not overwatered) makes a difference in their activity.  Remember that mowing high with a sharp blade conserves water and helps to prevent drought stress as well. 

When it is determined chinch bugs are present and causing damage, a pesticide should be applied.  Products containing Malathion, Sevin, Orthene, Permethrin and Talstar are suggested for homeowner use.

To apply a product properly, read the pesticide label.  If liquids are used they can be applied with a hose-end attachment. To make sure that the proper amount is used, do a test run with only water in the jar and see how far that amount covers at the walking speed you will be using.  That will determine how fast or slow you walk will need to put out a certain amount of gallons for a particular square foot area.  It’s easiest to divide the lawn into 1,000 sq. foot areas and treat one section at time, but unnecessary to treat the whole lawn.  Only treat those sections that are infested. 

As an alternative, granular formulations may be used and put on with a spreader.  They should be watered in lightly with about 1/8 inch of water right after application.  Keep monitoring to make sure control has been achieved.

For more information on chinch bug control please contact your local Cooperative Extension Office or visit our website @ http://www.gulf.ifas.ufl.edu.