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Remember when that guy stole a military tank and started mowing through neighborhoods in Southern California. He turned cars into pancakes, toppled telephone poles, drove through houses and flattened just about anything in his path. The situation started to look really grim when he headed for the Southern California Freeways. Hundreds of police officers were chasing him, but what could they possibly do to stop a tank. This real-life scenario is much like the problem that landscape professionals encounter with invasive species. They invade an area, infest the local fauna and seem unstoppable because they have no natural predators. What can a Contractor possibly do to combat such a formidable pest.

Though there are many insects that can be classified as invasive species, two types-red imported fire ants and the glassy-wing sharpshooter-are currently hot topics in the landscaping industry. Read on to learn some tricks of the trade to control the spread of these pesky critters.

Red Imported Fire Ants

Ants are one of the most numerous insects found on earth. They live in almost every place except the coldest and driest. Ants have adapted to live very well with humans and have become pests in their homes, gardens, yards, and other areas. In numerous sunbelt states, the red imported fire ant is creating havoc.

Red imported fire ants live in large colonies and build dome-shaped mounds that may contain more than 300,000 ants. If left undisturbed, mounds can reach 35 centimeters high and 25 centimeters in diameter. They like to build mounds in open, sunny areas like yards, pastures, and gardens. During very hot or dry weather, fire ants will dig deep into the soil to find cooler temperatures and water. It will seem like they just "disappear", but soon after rain or thorough watering, their mounds will "magically" reappear because they are trying to escape from the water flooding their mound.

Fire ants reproduce by swarming. On warm, sunny mornings after a rain shower, usually after 10 a.m., winged males and females fly up into the air from the mound and mate many feet above the ground. The newly mated queens drop back to the ground, cut off their wings, and find a nice quiet place to dig a hole and start their own colonies. Sometimes many queens form one colony together, or sometimes just one queen starts a colony. Male ants die after mating.

Fire ants are very aggressive and will protect their mounds from any threat. When their mound is disturbed, they will rush out in large numbers and sting anything within their reach. This aggressive attitude is the reason why many people have been stung-usually more than once. A few hours after the attack, the bites will form a red blister that contains pus. If these bites are scratched, they can get infected and cause more serious problems.

The worker ants are attracted to oily or greasy foods. They take these foods back to the colony and pass them along to other ants in the nest. Fire ants will also eat other insects, oily seeds, and sometimes during dry weather will dig up potatoes that are in the ground. Dog and cat food are among some of the favorite entrees that fire ants can find around the home.

Maintenance

Though fire ants cannot be eradicated completely, the pesky critters can be controlled, especially when Landscape Contractors are armed with information about how to discourage the spread of fire ant colonies. The key to effective fire ant management is knowing your situation and selecting your maintenance program accordingly.

Imported fire ant suppression in large acreage is currently only feasible using chemical methods that use broadcast applications of bait formulated insecticides. When properly applied, these products eliminate about 90 percent of the ant mounds within a period of weeks to months, and their effects can last up to a year, depending on the product selected. As a result, multiple broadcast applications of bait product(s) would be required in order to begin to approach 100 percent "control." Only in fairly small isolated areas of infestation (e.g., less than a few acres) should Landscape Contractors use the individual ant mound treatments.

Bait-formulated insecticides come in the form of defatted corn grit soaked in soybean oil to attract the ants. Generally, these baits are collected by foraging worker ants and taken back to the colony where they are distributed. The bait is fed to the queen, and she dies or is prevented from producing viable eggs. In general, baits are slower acting, but provide 80 percent to 90 percent suppression for 12 to 18 months.

Methoprene and similar-acting compounds (pyriproxyfen, fenoxycarb) are known as "Insect Growth Regulators" (IGR's). These have similar modes of action and do not kill adult stages of fire ants. Treatment with these IGR's prevent queen ants from producing new worker ants for months after treatment. Consequently, colonies decline slowly as the aged worker ants present at the time of treatment die off naturally and are not replaced by new worker ants. Several other bait products (hydramethylnon, spinosad, abamectin) have modes of action that can result in the mortality of worker ants and thus give a quicker suppression.

Treatment Methods

Fire Ants are very aggressive and will protect their mound by swarming and stinging anything within their reach. This photo shows a secondary infection that followed a fire ant attack.

For fast, thorough control of many mounds, researcher Charles Barr, with the Texas Agricultural Experiment Station at College Station recommends the Two-step method. This method works best in fully infested areas (five or more mounds for each quarter-acre of yard) or where there is little or no concern for preserving native ant species. The two-step method includes broadcasting a bait insecticide over your entire yard sometime between late August and mid-October, and then treating individual, problem mounds with an approved mound drench, granule, bait, or dust insecticide.

Step One: Baits

Calf eye ball showing fire ant stings on pupil. Many animals are being attacked by the Red Imported Fire Ants. The invasion is causing a serious problem among farmers in the infested areas.

Fire ant baits consist of pesticides on processed corn grits coated with soybean oil. Worker ants take the bait back to the colony, where it is shared with the queen, which then either dies or becomes infertile. Baits currently available include Amdro, Siege, Logic, Award, Ascend, or Raid Fire Ant Killer. Baits are slow-acting and require weeks to months to achieve 80% to 90% control. Bait products can be used to easily treat large areas effectively. They contain extremely low amounts of toxins. For best results:

Use fresh bait, preferably from an unopened container.

Apply when the ground and grass are dry and no rain is expected for the next 24 to 48 hours.

Apply when worker ants are actively looking for food, usually in late afternoon or in the evening. To test, put a small pile of bait next to a mound and see if the ants have found it with in 30 minutes.

Apply baits with hand-held seed spreaders. Don't apply baits mixed with fertilizer or seed.

Baits can be applied in summer/early fall because ants are still foraging and it's easier to predict weather patterns. Then the bait can take effect over the winter while you're indoors. Re-apply baits once or twice a year.

Step Two: Individual Mound Treatments

The Phorid Fly is being released as a biological control to the fire ant. The parasitic fly deposits an egg on the back of a worker ant. In about 3 weeks the ant dies.

Chemical. With dust products, no water is needed and they act fast. However, they leave a surface residue. Liquid drenches generally eliminate mounds within a few hours and leave little surface residue after application. Granular products are relatively fast acting and usually require putting granules on and around the mound and then sprinkling 1 to 2 gallons of water on without disturbing the mound. Closely follow directions on the label.

Organic. Pouring 2 to 3 gallons of very hot or boiling water on the mound will kill ants about 60% of the time. Otherwise, the ants will probably just move to another location. Very hot or boiling water will kill the grass or surrounding vegetation that it is poured upon. Other natural or organic methods include mound drench products containing plant-derived ingredients (e.g. botanical insecticides) and biological control agents.

Some additional treatment programs to select from include:

• For program initiation, applying an IGR bait first and a faster-acting bait several days or more afterward.

• For program initiation, applying a faster acting bait first and treating again six or more weeks later with an IGR bait.

• Hopper blend treatments of a 1:1 mixture of an IGR product plus a faster acting bait.

• Alternating an IGR bait with a faster-acting bait (Note: applying IGR baits within several months of the last application will not speed up control or improve performance; some faster-acting products have restrictions on the number of annual applications.

• Applying IGR baits twice per year (e.g., during drier, stressful parts of the year that increase natural worker ant mortality), with faster acting products applied during wetter, milder periods that prolong worker ant survival.

Any treatment program selected must use products in strict accordance to instructions provided on the product label or with full support from the manufacturer(s).

Biological Controls

Fire ants are sensitive to vibration or movement and tend to sting when the object they are on moves. The ants swarm up a person's leg when the mound is disturbed. A few hours after the attack, the bites will form red, pus-filled blisters.

The red imported fire ant came to the United States from South America around the 1930s. Scientists believe they entered the U.S. through Mobile, Alabama, probably in soil used for ships' ballast. Many of the fire ant's natural predators are native to South America but are not native to the American landscape. Lack of enemies is believed to be one factor that has allowed the fire ant to gain such a foothold in the States. Fire ant densities are five times greater in the U.S. than in South America, where this pest is attacked by a variety of natural enemies. Biological control, the use of natural enemies to suppress pest populations, offers an opportunity to re-establish these natural enemies in the U.S. and reduce the impact of fire ants.

The Phorid fly is one of the biological controls that the Texas Fire Ant Research and Management Plan is researching. Adult Phorid flies are about 1/16 inch long and fly rapidly. They hover above disturbed mounds or along foraging trails waiting for an opportunity to swoop down and deposit an egg on a fire ant worker. Once on the ant, the egg quickly hatches into a tiny maggot, which bores into the fire ant. The maggot feeds inside the ant for about three weeks before the parasitized ant dies. During the final stage of attack, the maggot consumes all of the head's contents and transforms to the pupa state. The ant's head then falls from its body as enzymes produced by the parasite dissolve the connecting tissue. The adult fly emerges from the ant's head about three weeks later.

The presence of Phorid flies causes the fire ant workers to quickly escape underground or assume a defensive posture. As a result, ants attacked by phorid flies spend less time searching for food. Other ant species, not attacked by the phorid flies, benefit by the greater food resource available to them. The decline in food collection and the increased competition from native ants will have a negative impact on a fire ant colony.

Integrated Pest Management

In this image, the worker ants are tending to their queen. Fire Ant baits consist of pesticides on processed corn grits coated with soybean oil. Worker ants take the bait back to the colony, where it is shared with the queen, which then either dies or becomes infertile. Baits currently available include Amdro, Siege, Logic, Award, Ascend or Raid Fire Ant Killer. Baits are slow-acting and require weeks to obtain 80-90% control.

There are several landscape practices and design elements that may make a landscape less attractive for foraging or colonization by red imported fire ants. By incorporating these elements into the landscape, a "choice" for habitat results. The ants in a colony may no longer prefer the modified site, leaving it uninfested, and move to a nearby site that may seem more preferable for nesting. The following IPM elements may be considered for management of fire ants:

Shade. Red imported fire ants nest in open, sunny areas. Numerous surveys have shown that relatively few fire ant colonies are found in shady wooded areas. Plant shade trees to increase shading and increase the diversity of the habitat. Shade trees around the home also regulate temperature inside the home, but they also require more water

Habitat diversity. Recognize that all ants are not bad and a diverse habitat encourages competitor ants. A number of non-pest ant species are known to attack and kill newly mated red imported fire ant queens, and they also have been observed to raid and kill off small fire ant colonies. A more diverse environment encourages and harbors these desirable ant species. Specific native ant predators can be encouraged by creating their ideal nesting sites (add small rock or board piles in shaded areas or leave thick, tall grass along landscape edges and bases of tree trunks). The selection of plant varieties or different plant species may also promote competitor ants.

Planting and maintaining pest-free plants. Imported fire ants eat caterpillars, beetles and other insects, chiggers, ticks, cockroach eggs and flea larvae found in the landscape. Grow plant species, varieties and cultivars that are not pest prone to indirectly provide less food for fire ants.

Access to water. Fire ants need water daily. In low maintenance or dry areas, lack of water can limit fire ant nesting and establishment. Fix leaky faucets and irrigation valves and heads, improve drainage, practice xeriscape techniques and conserve water to discourage fire ant infestations.

Mulches and nesting sites. Some mulches like cedar bark mulch may repel fire ants, although no studies confirm these claims. Using rough gravel instead of sand underneath brick or patio structures also may deter fire ants from nesting there.

Fertilization practices. Fertilization may have direct and indirect effects on fire ant colonization that can either encourage or discourage fire ant infestations. A lush turfgrass or other landscape plants are hosts to sucking insects and caterpillars that can serve as a sucrose and protein food source for the fire ant. Conversely, casual observation suggests that fire ants do not prefer to make mounds in taller, dense stands or grass, and/or their mounds seem to be less noticeable.

Mowing and disturbing ant mounds. Disturbing colonies frequently may cause the fire ants to move to a new location. In the landscape when the grass is mowed frequently at a low cutting height, the disturbed colonies will move to less disturbed areas in the fence row, adjacent to sidewalks and foundations or to hedge rows and trees. This is evident on putting greens and tees of golf courses as well. Fire ants are known as rapid reinvaders; they will rapidly reinvade the disturbed lands once these practices stop.

The Glassy-winged Sharpshooter

Glassy-winged sharpshooters overwinter as adults and begin laying eggs in late Feb. through March. This first generation matures as adults in late May through Aug. Second generation egg masses are laid in mid June to late Sept., which develop into overwintering adults.

The glassy-winged sharpshooter, Homalodisca coagulata, is native to the southeastern United States. It was first found in California in 1990 and is now found throughout Southern California and parts of Kern County. A large insect-almost 1/2 inch (12 mm) long- the glass-winged sharpshooter is dark brown to black with a lighter underside. The upper parts of the head and back are stippled with ivory or yellowish spots. Watery excrement often collects on either side of the insect, appearing as large white spots.

The glassy-winged sharpshooter can fly up to one-quarter of a mile, and it frequently appears in high numbers. The insect is able to survive winter temperatures dipping as low as 20 degrees Fahrenheit.

The insect overwinters as an adult. It begins laying egg masses from late February through May. The year's first generation matures as adults from May through August. The year's second generation begin as egg masses laid from June through September. It is this generation that produces the next year's offspring.

The sharpshooter feeds on a wide variety of ornamental and crop plants. On most plants, it feeds on stems rather than the leaves. When feeding it excretes copious amounts of watery excrement in a steady stream of small droplets. In urban areas, this "leafhopper rain" can be a messy nuisance. When dry, the excrement can give plants a white-washed appearance.

Oleander Leaf Scorch

The Glassy-Winged Sharpshooter gets its name from its transparent wings. A large insect-almost 1/2 inch (12 mm) long- the glass-winged sharpshooter is dark brown to black with a lighter underside. The upper parts of the head and back are stippled with ivory or yellowish spots. Watery excrement often collects on either side of the insect, appearing as large white spots.

The glassy-winged sharpshooter has severely impacted the oleanders in Southern California. Landscape professionals agree that it cannot be replaced. Oleander is frequently overlooked and under-appreciated because it is a common, drought tolerant, and requires little care. It can take different forms, from low shrubs to small trees, and blooms in different colors, including pink, salmon, red, white, and yellow. Oleander is used primarily as an ornamental, but also plays an important role as windbreaks, borders, and right-of-way plantings. The California Department of Transportation (CalTrans) maintains oleander in over 2,100 miles of freeway median, and it is found in 20% of all home gardens in California. Besides being important in California, oleander is used similarly in other states of the southwestern United States, including Arizona, New Mexico, Nevada, and Texas.

There are several factors that make disease control difficult. Symptoms of the disease may not appear for several months, and there is no known way to cure infected plants, which eventually die from infection. However, the University of Riverside is studying the affects that a tiny, stingerless parasitic wasp is having on the glassy-winged sharpshooter population. The non-native wasp, Gonatocerus triguttatus, parasitizes the sharpshooter by laying its eggs inside those of the larger insect. Once hatched, the wasps eat their way out.

David Morgan, a postdoctoral researcher, has raised the wasps and is releasing them in organic citrus groves and other locations, where they can begin to form field populations. "Our primary goal from these initial releases is to set up stable populations of the wasp in California," Morgan said. "We are also investigating the potential of other non-native parasites of the glassy-winged sharpshooter that we can use to bolster the natural enemy arsenal in California.

In the End

The University of Riverside is studying the affects that a tiny, stingerless parasitic wasp is having on the glassy-winged sharpshooter population. The non-native wasp, Gonatocerus triguttatus, parasitizes the sharpshooter by laying its eggs inside those of the larger insect. Once hatched, the wasps eat their way out.

Though the man who stole the tank looked unstoppable, it was by his own folly that his rampage on Southern California was finally brought to an end. A stroke of luck allowed the police officers to end the ordeal and prohibit any more destruction of property. There is no clear solution to the pest control issue, but know that research is ongoing and new technologies explored. As a Landscape Contractor, you can help out by staying informed about any new developments. LCM

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June 18, 2019, 8:43 am PDT

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