Southern Chinch Bug Management on St. Augustine Grass
October 22, 2009 by Brian Brown
Filed under Plant Problems
Intro
The southern chinch bug, Blissus insularis Barber, is currently the most difficult-to-control and damaging insect pest of St. Augustinegrass 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. Homeowners and lawn care companies seek to prevent this damage by repeatedly applying insecticides to keep chinch bug numbers low. However, numerous chinch bug populations have developed resistance to every major chemical class that has been used against them and host plant resistance has been overcome. An integrated pest management program, or resistance management program, must be implemented to keep chinch bug populations under satisfactory control and keep St. Augustinegrass as a viable lawn turfgrass in Florida.
Biology & Behavior
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.
Several insects live in St. Augustinegrass lawns, so proper insect identification is important before deciding that a problem exists. Adult southern chinch bugs (Figure 1) are about 1/8 to 1/10 of an inch long. The wings are folded flat on the back and are shiny white with a triangular-shaped black marking in the middle of the outer edge of each wing. Adults may have long or short wings, and populations often contain both. Their bodies are black.
Figure 1. Southern chinch bug adult and fifth instar.
Adult females may live up to 2 months, laying 4 or 5 eggs a day, or 250-300 eggs in a lifetime. Tiny eggs are laid singly or a few at a time in leaf sheaths, soft soil, or other protected areas. The eggs are white when first laid and turn bright orange or red just before hatching. Eggs hatch within 6-13 days (average: 10 days), and nymphs mature in 4-5 weeks. Young nymphs are reddish-orange with a white band across the back (Figure 2), darken in color as they mature (fourth instar), and turn black before becoming adults (fifth instar; Figure 1).
Figure 2. Southern chinch bug nymphs.
Southern chinch bug populations tend to be clumped, rather than randomly dispersed throughout lawns. Usually more than one chinch bug can be found in the bottom leaf sheath on a plant and among surrounding plants. Infestations may occur in open, sunny areas near sidewalks and driveways, but also in the middle of lawns. Infested plants have slower growth, turn yellow, and die. As their host plants die, individuals will walk to neighboring St. Augustinegrass plants to continue feeding. Thus, dead patches of grass seem to get larger over time (Figure 3). The speed of turf death probably depends on chinch bug density and the turf’s overall health. Southern chinch bugs rarely disperse by flying.
Figure 3. St. Augustinegrass yard killed by southern chinch bugs.
Detecting Infestations
Other factors, such as disease, nematodes, nutritional imbalances, and drought can cause off-color areas to occur in lawns. Therefore, the lawn should be carefully examined to determine which corrective measures may be needed. Especially in areas where pesticide resistance is suspected, monitor before and after any treatments to determine if control has been achieved. If more than about an 80% reduction in chinch bug numbers has occurred, then the treatment was successful.
Several methods can be used to find southern chinch bugs. The easiest and fastest is to part the grass near yellowed areas and look at the soil surface and thatch. Pull out individual grass plants and look inside the bottom leaf sheath. Examine several different areas if chinch bugs aren’t immediately found. Heavy infestations are easy to identify because large numbers of chinch bugs may migrate across sidewalks and driveways. Insects are most active on warm, sunny days in mid-afternoon.
Another option is to use a Dust Buster or hand-held vacuum cleaner (AC- or DC-operated) to suck up any chinch bugs near damaged areas. Remove the filter, empty the contents on the sidewalk or into a plastic bag, and look for nymphs and adults. Repeat in several damaged areas.
A flotation technique can also be used to detect infestations. Cut both ends out of a metal can and push one end 2-3 inches into the soil on green or yellowing grass (not dead grass). Slowly fill with water and count the number of chinch bugs that float to the top within 5 minutes. Keep the water level above the grass surface. If nothing emerges in the first area, examine at least 3 or 4 other areas.
Cultural Control
Cultural practices may influence the susceptibility of St. Augustinegrass to chinch bug damage (See ENH-5: St. Augustinegrass for Florida Lawns). Rapid growth resulting from frequent applications of water soluble nitrogen fertilizers may increase southern chinch bug survival, development time, and the number of eggs that can be laid rather than help plants outgrow any damage. Responsible use of slow-release nitrogen fertilizers may help reduce pest population build-up.
Excessive watering, fertilizing, and/or fungicide use can cause lawn grasses to develop a thick thatch layer. Insecticide treatments can also bind to the thatch layer, instead of reaching soil-dwelling pests. Thatch is a layer of accumulated dead plant roots, stems, rhizomes, and stolons between the live plant and the soil. Excessive thatch should be mechanically removed (vertical mowing, power raking, aerating, etc). Proper mowing practices can make grass more tolerant to chinch bugs and greatly improve the appearance of the lawn. St. Augustinegrass should be mowed to a height of 3 – 4 inches.
Southern chinch bugs feed on fluids within the grass plants. Thus, it is likely a myth that chinch bugs are attracted to drought-stressed areas of lawns. It is more likely that they develop faster in areas that have higher temperatures (e.g., not in shade). If plants are wilting from drought, they are probably not good food plants. However, chinch bug damage could easily resemble drought-stress. Proper diagnosis of the problem is essential to growing healthy turfgrass.
Host Plant Resistance
Several varieties of St. Augustinegrass are available for use in Florida, but the most common one is Floratam. Floratam was released in 1973, but populations of southern chinch bugs could develop on it and damage it by 1985. All other varieties are fairly susceptible. Screening for resistant varieties continues, and NUF-76 is considered resistant and is in development. For more information on different St. Augustinegrass varieties see ENH-5: St. Augustinegrass for Florida Lawns. If control failures repeatedly occur in an area, another alternative is to change the turfgrass species being grown (e.g., switch to centipedegrass or zoysiagrass). Keep in mind that other turfgrass species also have other pest complexes.
Biological Control
Common natural enemies of the southern chinch bug are big-eyed bugs (Geocoris spp.), a predatory earwig (Labidura ripara), and spiders. A small wasp, Eumicrosoma benefica Gahan, parasitizes chinch bug eggs. Big-eyed bugs (Figure 4) and anthocorids (another group of predators) are similar to chinch bugs in size and shape and are often mistaken for them. Unnecessary insecticide use can reduce these natural enemies and their ability to suppress pest populations. Natural enemies are often not abundant and efficient enough to keep chinch bug populations under control by themselves. However, their populations may build after chinch bug populations increase.
Figure 4. Southern chinch bug and big-eyed bug adults.
Chemical Control
Southern chinch bug management is currently dependent on insecticides (Tables 1 and 2). Efforts should be made to reduce the amount and frequency of pesticide use against this pest, given its track record of developing resistance to insecticides. Researchers are studying various aspects of controlling this pest, so keep up-to-date on technology changes. The warning signs of product failure include having to increase the number of applications, the rate of product being used, or needing to use an insecticide in another chemical class or mode of action.
In areas where pesticide resistance does not seem to exist, try to use spot treatments when infestations are first noticed and damage is minimal, rather than broadcast applications. Treat dead and dying St. Augustinegrass and about a 5-foot buffer area around the damage. This is because most populations are localized. Chinch bugs that were not exposed to the insecticide can interbreed with any chinch bugs that survive the treatment and dilute the resistance genes in the population. This should help delay further resistance.
In areas where resistance is suspected, be sure to monitor before and after any applications to see if the insecticides worked. This will be important information when discussing the problem with a client. Be sure pesticide applicators are properly trained and are not applying sublethal doses by either walking too fast, not applying enough product, using improperly calibrated equipment, doing an application when windy (results in drift and smaller droplets), etc. Use the highest labeled rate of the chosen insecticide, rotate insecticides with different modes of action, consider using a non-ionic wetting agent or adjuvant to increase penetration into the leaf sheaths and thatch, and determine if the spray solution needs to be buffered to have a neutral pH. If the label requires post-treatment irrigation (watering-in), be sure to communicate that with the client and provide instructions on how and when to apply the proper amount of water. If the insecticides bind tightly with organic matter (e.g., leaf blades, thatch), then watering-in should be done soon after an application. The insecticides must get to where the insects are living and feeding to be effective. On the other hand, be careful that some insecticides might wash off with excessive rain or irrigation within a day of application.
Pyrethroids, carbamates, and organophosphates will only kill nymphs and adults, and their residuals may last from about 1 day to roughly 2 months or so, depending on the product and environmental conditions. Know the strengths and limitations of the products that are used. Many contact products will kill the insects within 3-5 days of treatment, but others (e.g., neonicotinoids like clothianidin or imidacloprid) require the insects to feed on treated tissue, and affected insects might die more slowly (up to 7 or more days). Avoid using products that are not specifically for use on turfgrass for controlling turf-feeding insects or that have been made illegal for use on residential turfgrass (e.g., Orthene or acephate). Creative label-interpretation is not in the industry’s best interest and will only bring greater regulation. All directions and the insecticide label should be read and understood before a product is used, particularly the dosage rates, application procedures, and precautions. Homeowners are discouraged from applying their own insecticides to control chinch bugs if they have a professional lawn care maintenance company.
Footnotes
1.
This document is ENY-325 (LH036), one of a series of the Department of Entomology & Nematology, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. First Printed October, 1993. Revised: April 2007. Please visit the EDIS Web site at http://edis.ifas.ufl.edu.
2.
Eileen A. Buss, assistant professor, Entomology and Nematology Department, Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, 32611.
The use of trade names in this publication is solely for the purpose of providing specific information. UF/IFAS does not guarantee or warranty the products named, and references to them in this publication does not signify our approval to the exclusion of other products of suitable composition. All chemicals should be used in accordance with directions on the manufacturer’s label. Use pesticides safely. Read and follow directions on the manufacturer’s label.
Thrips on Ornamental Plants
October 5, 2009 by Brian Brown
Filed under Plant Problems
Thrips are very small, yellow, brown or black, slender insects ranging from 1/16 to 1/8 inch in length (Figure 1). Adults and larval thrips feed using a punch and suck technique. Their life cycle includes an egg stage, two larval instars, two pupal stages, and an adult stage.
Depending on the species, thrips feed on fully expanded leaves, young tissue in the bud, flowers, and/or small fruit. Infested leaves dry out and have a stippled or silver-flecked appearance. Small brownish specks of excrement will usually be noticed on the underside of the leaves. Infested flower buds fail to open or the flowers are deformed. Damaged flowers become streaked and discolored. Flowers or leaves suspected of being infested with thrips should be shaken over a white sheet of paper to better observe the insects. A 10X magnifying glass or hand lens will aid in their detection. Thrips may also cause minor irritation if they get on human skin.
Thrips populations are at their peak in the spring. They damage both foliage and flowers of many ornamental plants. The most important thrips species attacking flowers and buds in Florida are flower thrips and the gladiolus thrips. Red-banded thrips, Cuban-laurel thrips and greenhouse thrips are the most common species on foliage. A new invasive species is the Chilli thrips.
Flower thrips are yellow in color with brown blotching. Larvae are lemon yellow and lack wings. The Florida flower thrips (Frankliniella bispinosa) occur in Florida, Georgia, and Alabama. The western flower thrips (Frankliniella occidentalis) is also pest in Florida. Thrips attack hundreds of plant species, including oaks, roses and other plants in the Rosaceae, citrus, and vegetables. White or yellow flowers are apparently preferred, as well as flowers with an open structure, where the stamens and pistils are easily accessible. Feeding and damage occur on buds, flowers, and leaves, resulting in discoloration and premature dropping.
Feeding by the gladiolus thrips, Thrips simplex (Figure 2), discolors flowers and foliage, and the corms (bulbs) become soft and prone to decay. Seriously damaged flower buds fail to open. The thrips may be seen on foliage during overcast days, but hide in flower buds and beneath leaves on sunny days. The gladiolus thrips occurs wherever gladiolus are grown, but also attack iris, carnation, lily, narcissus, freesia, amaryllis, tigerflower, poker plank, tomato, begonia, primula, snapdragon, chrysanthemum, and geranium. Females lay up to 200 eggs in leaves, and larvae develop rapidly. Nine or more generations may occur outdoors each year. Immatures are pale yellow with red eyes, and adults are dark brown, have a grey band on their folded wings, and are about 1/16 inch long.
Immature and adult red-banded thrips, Selenothrips rubrocinctus (Figure 3), produce a lot of honeydew, and their feeding causes premature defoliation. This species attacks fruit and shade trees, shrubs and vines, such as avocado, lychee nut, tung, acacia, persimmon, sweetgum, Brazilian pepper tree, and pyracantha. Breeding occurs continuously and there are overlapping generations in southern Florida. Eggs are inserted singly in the tissue on the underside of leaves, and are covered with excrement. Only larvae have red bands. Adults have dark brown to black bodies (3/64 inch long).
Adult and immature Cuban-laurel thrips, Gynaikothrips ficorum (Figure 4), feed on expanding leaves, creating purplish red spots on the undersurfaces, causing foliage to severely curl or roll and drop prematurely. Common hosts are Ficus spp. Adults are black, about 3/64 inch long, and actively fly on hot days. Breeding is continuous. Females lay eggs on the upper surface of curled leaves.
The greenhouse thrips, Heliothrips haemorrhoidalis (Figure 5), is a common pest of greenhouse- and nursery-grown plants. It has many hosts, including maple, azalea, citrus, dogwood, Ficus, fuchsia, toyon, St. Johnswort, Grecian laurel, magnolia, mango, alligator pear, rhododendron, and viburnum. Unlike many thrips species, the greenhouse thrips openly feeds on the lower surface of leaves first, rather than on blossoms, buds, or growing shoots. It prefers shaded conditions, and does not thrive in hot, dry areas. It lives in dense colonies as immatures and adults. Its feeding causes a flecking, bleaching, or silvering to leaves, and young foliage may become distorted. Damaged foliage becomes papery and wilts, then drops prematurely. These thrips also produce large quantities of varnish-like excrement, which sticks to foliage. Adults (3/64 inch long) are black with a silver sheen. Eggs hatch within 2-3 weeks. Larvae are translucent and white, and feed only for 2-3 weeks. Adults are not strong fliers, despite having wings, and may be wind-dispersed. Wings are narrow and fringed with long hairs.
Biological Control
Several arthropods help keep thrips populations under control, including green lacewing larvae, big-eyed bugs, damsel bugs, insidious plant bugs (Orius insidiosus), ladybird beetles, parasitic wasps, other predaceous thrips, and predatory mites. Also, a fungal pathogen, Verticillium lecanii, may be purchased and used to reduce thrips numbers. Some thrips are parasitized by insect-parasitic nematodes in the genus Thripinema.
Cultural Control
Plants that are commonly attacked by thrips should be monitored carefully and frequently (Figure 6). Blue, yellow or white sticky cards or traps are effective monitoring tools (color varies with the thrips species).
Chemical Control
If thrips are beginning to damage plants, apply one of the suggested insecticides (Table 1). Treat foliage or flowers as soon as thrips are found. Weekly applications may be needed until control is achieved. Spray the plants to the point of run-off. Be especially careful to cover the undersides of the leaves. Continue to inspect the plants periodically and apply an insecticide if plants become re-infested. Soaps are safe and effective.
Several systemic insecticides are applied as soil drenches, so that the roots take up the toxicant and spread it to where the insects are feeding. They may achieve control within several weeks, but are effective for a longer time than most contact insecticides.
Be sure to wear the appropriate protective clothing when using insecticides, as described on each containers label. Read and understand each label before doing an application.
Footnotes
1.
This document is ENY-333 (MG327), one of a series of the Department of Entomology and Nematology, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. Date first published October 1993. Revised: June 2006. Please visit the EDIS Website at http://edis.ifas.ufl.edu.
2.
Eileen A. Buss, assistant professor, Entomology and Nematology Department, Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, 32611.
