Chinch Bugs In the Lawn
SEMINOLE COUNTY URBAN HORTICULTURIST
The Southern chinch bug is one of the most important insect problems in St. Augustine grass in Florida. Other lawn grasses are not seriously affected by this insect. The bug sucks the plant juices from grass resulting in yellowing and death of the plants in the affected area. The injured areas can be seen as brownish patches in the lawn. The problem can be more serious during dry weather periods or specific water-stressed areas in your garden.
The insect: Chinch bugs belong to the group of insects, which include the stink bugs, lace bugs and leaf bugs. In summer, eggs hatch in 10 days, and the young develop to adults in 3 weeks. When the nymphs are borne, they are about the size of a pinhead, red in color with a white band across the back, becoming darker as they mature. Adults are about 1/5 inch in length, black and have white, silvery wings. Three to four generations per year occur in central Florida.
Detection: The chinch bugs can be detected by using a soap solution. Mix one fluid ounce of dishwashing liquid in two gallons of water, and drench four square feet of this solution at the edge of the affected area. If the chinch bugs are present, they will emerge to the grass surface in about two minutes. The same procedure can be used to detect lawn caterpillars and mole crickets. In heavy infestations, they can be seen crawling over the grass blades or the soil surface.
Cultural practices: Turf management practices can influence the resistance or susceptibility of St. Augustine grass to chinch bugs. The susceptibility to chinch bug damage is increased if frequent applications of water soluble inorganic nitrogen fertilizers are used to produce succulent growth of the grass. Slow release nitrogen fertilizers decrease the incidence of chinch bug damage. Proper irrigation is also very important to control this insect problem. Large populations of insects tend to develop during dry periods, increasing the damage. Proper mowing practices can make the grass more tolerant to chinch bugs. The grass should be mowed often enough so that no more than 1/3 of the leaf blade is removed at each mowing. Regular St. Augustine grass varieties should be mowed to a height of 3-4 inches, semi-dwarf varieties 2 to 2 ? inches.
Biological control: The most important predator of chinch bugs is the black big-eyed bug. Another predator, an earwig, is also found frequently associated with chinch bug control. Many times these predators are not recognized and pesticides are usually applied when it is not needed.
Chemical control: Chinch bug populations of more than 20 insects per square foot should be treated with an insecticide to reduce the populations to non-damaging levels. Pyrethroids or Orthene are suggested for their control. When a spray is used, it is important to apply the insecticide in a large amount of water. The jar attachment to a garden hose is the suggested application device for homeowners. The recommended equipment should use 15 to 20 gallons of water passing through the hose to empty the quart-sized jar. The procedure is as follows: Put the amount of insecticide in the jar as directed on the label for 1000 square feet, and fill the rest of the way with water. Spray the contents over 1000 square feet of lawn. Spray evenly with a back and forth motion until the treated area is completely covered. The treated grass should be irrigated lightly to flush the insecticide into the thatch layer where the chinch bugs are feeding. Chinch bugs develop resistance to insecticides if only one type of product is used continuously. Granular formulations of the recommended insecticides can also be used. Granules should be applied with a drop-type spreader rather than the cyclone type for a better distribution of the granules. Irrigate after application of the granular insecticide.
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