September 13, 2012
Although more than 800,000 different species of insects creep and crawl across the Earth, the vast majority do not harm turf grass. However, there are a select few that prefer to feast on a lush, green lawn. The following suggestions can help homeowners reclaim their lawns from these unwelcome dinner guests.
Outnumbered, But Not Outsmarted
With an estimated 40 million insects in a typical acre, it's impossible to completely eradicate them. And that's good, as most insects are considered beneficial because they eat other harmful insects and provide food for birds and other animals. Therefore, identifying turf-damaging insects and controlling them selectively is the best strategy.
Most insects only damage grass at certain points during their life cycle. Once the pest has been identified, the best approach is to control it at the insect's most susceptible life stage, which is usually during the immature or larval stage.
Keep in mind that an insect problem usually (but not always) occurs as a result of a breakdown in proper lawn maintenance. Stressed grass is more predisposed to insect invasion. Healthy lawns can coexist with a higher level of insect invasion, so check mowing, fertilizing, irrigation and cultivation practices before resorting to pesticides, as these were likely contributing to the problem, and will contribute the next time as well.
Turf-damaging insects can attack three different areas in a lawn: the upper leaf surface, at the thatch/soil interface or underneath the turf in the soil. Insects above ground are either chewing grass blades or sucking fluids from plant parts. If they are underground, they are feeding on roots. Three of the most common turf-damaging insects in the U.S. include sod webworms, chinch bugs and grubs. Each are described below along with control suggestions.
Sod webworms are caterpillars of the common lawn moth often seen flying around homes in the evening. They live in silk-lined tunnels in thatch and are mainly a nuisance to cool-season grasses.
This insect attacks lawns at night by chewing off and eating grass leaves and stems. Damage is rarely detectable in healthy grass, but expect to see small patches of closely cropped grass in more severely damaged areas and in dormant grass. At first glance, the damaged areas may resemble the rest of the dormant lawn, but after rainfall, the chewed areas will remain brown.
Sod webworm damage can often be mistaken for the dreaded 'dog spot' damage, but can be identified by chewed grass leaves and stems. Inspect south facing slopes first or areas under the most stress. Walk the area at night and look for moths flying low to the ground. If moths are present, it's a sign that they are laying eggs and caterpillars will appear 10 to 14 days later.
The best control for sod webworms are beneficial insects that prey on them. In addition, proper lawn fertilization, mowing and watering will often mask symptoms and eventually correct the damage.
However, if sod webworms have infested the lawn and stricter control methods are needed, treat the area with products labeled for sod webworms. Apply it in the late afternoon or evening before the caterpillars emerge. Products that sit on the grass surface – rather than those watered into the soil – tend to be the most effective.
Chinch bugs are thirsty creatures that prefer to suck fluid from grass leaves and stems. The Hairy chinch bug attacks cool season grasses and prefers fine fescues and perennial ryegrasses in open, sunny areas. The Southern chinch bug attacks warm season grasses like St. Augustine grass. They attack lawns from early on in their life cycle through the adult stage, typically appearing in mid- to late summer during hot, dry periods.
Turf damaged by chinch bugs often appears dry, but won't recover from rain or irrigation. What initially looks like irregular, small patches of stressed grass will grow larger as the damage progresses.
Chinch bugs are small and hard to detect (measuring only 3 mm long). The best way to identify if they are present is to "float" them out of the lawn. Take a coffee can and cut out both ends. Hammer one end into the ground about two inches deep, fill the can with water and wait three to four minutes. If chinch bugs are present, they will float to the top. If there are more than five chinch bugs in the can, a control method is necessary.
Several insecticides are effective against chinch bugs. For best results, water the lawn 20 to 25 minutes before applying a liquid or granular product. Watering the lawn regularly helps control damage and a small amount of fertilizer will speed up the recovery.
White grubs, put simply, are the larval stage of beetles. They wreak havoc on lawns throughout the U.S. by feeding on grass roots just below the surface. A variety of species exist, including the Japanese beetle, June beetle, European chafer beetle, masked chafer beetle and Oriental beetle
Grubs have a complex life cycle. The beetles lay eggs every year in mid- to late summer. These eggs hatch into grubs that feed in the fall before they go deep into the soil for winter. In spring, they return as mature grubs feeding again before they become adult beetles in early summer.
Because grubs are a food source, skunks, raccoons, birds and moles may dig up the lawn looking for them. Damage from grubs looks like wilted grass with small, brown dead areas that quickly spread. Turf will feel spongy underneath because it's not anchored to the ground. If grubs are present, the infested area can literally be rolled back like a carpet because they feed on the roots near the surface. If more than 15 grubs per square foot are present, there is need for control.
The best way to help grass recover from grub damage is regular irrigation that encourages rooting. If watering does not eliminate the problem, products containing chemicals such as Dylox (carbaryl) or Sevin (trichlorfon) can help. They need to be watered in and work best on young grubs in early August and later in the year in northern regions.
For areas prone to grub attack (particularly with Japanese and European chafer beetles), a new preventative approach is effective if timed correctly. Apply Merit or Mach II from mid-June to mid-July. These chemicals will eliminate grubs as they hatch in August before they can cause damage and without harming other beneficial insects.
Following proper lawn care practices can help control and more importantly, prevent damage from insects. If more control is necessary, the right insecticide will be sure to have insects turning elsewhere for their dinner.