Know Your Turf Grass Thugs

Almost every Saturday morning on my show I will get the inevitable turf grass question, What is wrong with my lawn? Why? Well remember that our lawns make up a very large proportion of our garden. This large area is also a monoculture of various turf grass species and as such any small discrepancy in colour, height or texture is easily noticed even by the most novice of gardeners. If the question is not about a turf grass disease or weeds then it will be about insects. The question is by far almost always about those turf grass thugs – insects.

Insects are always feeding on our lawns. This is natural but when a turf area is stressed by adverse environmental conditions then our turf grasses can not grow faster than the destruction caused by the insects. The other possibility is that the insect population has just exploded because their environmental conditions are perfect.

The Top Seven Turf Grass Thugs


The armyworm larvae feed on the shoots of the turf grasses.

Armyworm drawing.

They are nocturnal feeders that produce somewhat circular patches of defoliated turf. The moths fly at night and are attracted to light sources. The females begin depositing eggs on your turf grass in May. The eggs upon hatching as larvae start feeding immediately. The armyworm larvae migrate from place to place as a large group eating voraciously. In fact they will even feed on cloudy dull days as well as at night. Normally though they can be found hiding in the thatch layer during the day. Armyworms may have as many as three generations per growing season.

Control: Apply a turf grass insecticide at the first sign of the tattered grass.

Bluegrass Bill Bugs

The Bill Bug larvae burrow into the stems where there is moisture.

Bluegrass Bill Bugs.
Bluegrass Bill Bugs.

They then feed on the turf grasses roots, rhizomes and shoots puncturing the plants tissues as they go. As the turf grass' stems and crowns die they form irregular brown patches. The Bill Bug adults feed on the stems and leaf blades causing only minor damage. In late May the females deposit their eggs in the stem area just above the crown. Their newly hatched larvae appear in late May and June feeding inside the turf grass' stem. It is at this stage that the most damage is done.

Control: Apply a soil insecticide (Diazinon or Chlorpyrifos) in May.

European Chafer

The larvae of the European Chafer feed on the roots and rhizomes of your turf grass in the midsummer. The turf grass roots are unable to regenerate at this time and thus creating irregular brown patches. The European Chafer has a one year life cycle and swarm in the trees in late June to early July.

  • European Chafer.
    European Chafer.
  • Spines on the raster of the European Chafer.
    Spines on the raster of the European Chafer.

To identify them look at the arrangement of the spines on their raster. This arrangement will be two rows of spines that diverge near the tip of the abdomen. Their threshold is 5-10 grubs per .1 square meter on non-irrigated turf. 10-20 grubs per .1 square meter on irrigated turf.

Control: Merit® in spring or Chlorpyrifos in August.

The Life Cycle of the Annual White Grub

Life cycle of the Annual White Grub.
Life cycle of the Annual White Grub.

Japanese Beetle

The larvae of the Japanese Beetle feed on the roots and the rhizomes of your turf grasses in the summertime. It is during this time that the grass finds it difficult to regenerate roots and soon dies in irregular brown patches. The Japanese Beetle has only one life cycle per growing season.

  • Japanese Beetle.
    Japanese Beetle.
  • Arrangement of spines on the raster of the Japanse Beetle.
    Arrangement of spines on the raster of the Japanse Beetle.

The adult with its metallic green and bronze colour is seen in July feeding on fruit and on shrubs. It absolutely loves to eat your hostas and roses. To identify them look at the arrangement of the spines on their raster. There are two "V" shaped short rows of spines. Their threshold is 8-10 grubs per .1square meter.

Control: Apply Merit® in the spring or Chlorpyrifos in August.

June Beetle

The larvae of these beetles feed on the roots and the rhizomes of the turf grass during the summer time.

  • June Beetle.
    June Beetle.
  • Spines on the raster of the June Beetle.
    Spines on the raster of the June Beetle.

Then without any roots your turf grasses die in an ever increasing irregular brown patch. The June beetle grub (larvae) is larger than that of the other root feeding grubs and has the characteristic "C" shape typical of all of the white grubs. Their life cycle is at best irregular. There maybe or two generations of grubs per growing season or as few as one generation every three years. The June Beetle feeds on the foliage of your trees and shrubs. It is often seen flying around your lights at night. To identify them look at the arrangement of the spines on their raster. The spines are almost parallel. Their threshold is 3-5 grubs per .1 square meter before control is necessary.

Control: A soil insecticide (Chlorpyrifos) during the growing season.

Hairy Chinch Bug

The Hairy Chinch Bug sucks the juices from your turf grasses.

Hairy Chinch Bug.
Hairy Chinch Bug.

This weakens them to form large irregular yellow to brown patches. The Nymphs are small, red and first seen in May. The Nymphs emerge in May and June. They go through five stages (instars) in approximately thirty days. A second generation develops in September. As the Hairy Chinch Bug feed, they inject a salivary fluid into the plant that disrupts the conductivity of water causing the plant to wilt and eventually die. In July and up until October look for areas of dead sunken turf.

Control: Apply Carbaryl (Sevin), Chlorpyrifos, or Diazinon in early July.

Sod Webworm

The larvae of the Sod Webworm feed nocturnally on the grass shoots.

Sod Webworm.
Sod Webworm.

They will consume the grass right down to the soil level leaving large irregularly shaped brown patches . The Sod webworm adults are small buff coloured moths. They construct silk-lined tunnels through the thatch layer and down into the soil. The moths hide in the grass during the day and usually fly at dusk or when disturbed by foot traffic. They will fly in a zig zag pattern close to the ground. It is the females that drop their eggs like little bombs throughout these flights to spread their species.

Control: Apply Carbaryl (Sevin), Chlorpyrifos or Diazinon when you first notice them. Do not water or mow the lawn for several days after you apply one of these.

Always Read the Label

  • Please remember the pesticide label is a legal document.
  • Always follow the label directions.
  • When in doubt always ask a professional.
  • Merit® can only be applied by a licensed professional.

How to Minimize Turf Disease & Insect Problems

The following information should help you to minimize your turf disease and insect problems.

  • You should provide adequate, but not excessive fertility. Excessive nitrogen application, particularly in the spring results in lush , succulent growth which is more susceptible to diseases and insects. An Autumn application of a significant portion of the fertilizer is highly recommended. A fertilizer application in hot weather may also burn the turf and be wasteful if the turf is not actively growing to utilize the nutrients.
  • Water the turf thoroughly in the early morning hours to encourage deep rooting. This makes your turf less susceptible to drought. Watering in the evening will only encourage diseases.
  • Mow your turf early in the day, as often as necessary, with a sharp lawn mower. Using a dull mower and evening mowing leaves open wounds which are more readily infected by disease causing fungi.
  • Collect or remove grass clippings if thatch build up is a problem. Do not remove more than one-quarter to one-third of the leaf surface in one mowing. Excessive removal reduces the turfs ability to regrow after mowing especially in the summer heat. This will also make it more vulnerable to disease and insects.
  • Remove excessive thatch. This layer of brown accumulated organic material found between the leaves and the soil should be less than 2.5 centimeters thick. You can remove it by raking it out or by composting it on your lawn. Composting is done by providing adequate moisture, nitrogen and cutting your turf frequently so that the clippings are very small. This will allow them to decompose quickly.
  • Turf-type perennial rye grass varieties such as Barry, Blazer, Fiesta, Fiesta II, Manhattan II, Omega II, Palmer and Yorktown are among the many varieties that are recommended for over-seeding problem turf areas. Please note that perennial rye grasses look very different than other turf grass varieties. Therefore you should over-seed the entire turf area. Do not seed just the dead areas.
  • Endophyte producing turf grass varieties will discourage those insects that feed at or above the soil surface.
  • To reduce the insect populations on your turf at or above the soil surface you can use an old vacuum cleaner to vacuum up the insects.
  • Spike sandals are available for you to wear. You then walk all over your turf with them. This will aerate the turf and puncture the white grubs below the soil surface.
  • Predatory nematodes are also available to be watered into the turf. They will then hunt out the white grubs and kill them.
  • In the U.S.A. there is a product called milky spore available which infects the white grub and kills them. This naturally occurring disease is resident in the soil for many years.
  • Birds are also a natural predator of turf grass insects so encourage the birds: see my article on Attracting Birds and Butterflies to Your Garden.

The method that you choose to control your turf grass problems is up to you. You will find that not just one method will solve your problems. Choose the best combination of methods for your needs and level of expectations.

Related Posts

View More Articles