Integrated Pest Management

IPM Manual for Landscape Pests in British Columbia

Chapter 6: IPM for Insects in Turf

Learning Objectives

When you have completed this lesson, you should be able to:

1. Classify common types of turf sites into three categories according to maintenance level.
2. List methods that prevent insect problems in turf.
3. Know where to look for help in identifying insects.
4. Describe two monitoring methods used for turf insects.
5. Describe the use of insect parasitic nematodes to control turf insects.
6. List general guidelines for using insecticides to control turf insects.
7. Describe the role of evaluation in an IPM program for turf insects.
8. Describe monitoring methods, give examples of treatment thresholds and treatments for European cranefly, white grubs, black turfgrass Ataenius and sod webworms.

Introduction

Insects are generally less of a problem in turf in BC than in other areas of Canada. The most common problems are: `leatherjackets´, which are the larvae of the European crane fly (Tipula paludosa); white grubs, which are the larvae of May or June beetles (Phyllophaga spp.); black turfgrass Ataenius (Ataenius spretulus) and sod webworms (Crambinus spp.). Cutworms (larvae of Noctuid moths), leafhoppers and chinch bugs can also be a problem.

Given good management, turf usually out-grows moderate insect damage without need for treatment. It is not uncommon, however, for raccoons, crows and other animals, to dig up turf in search of insects, causing much more damage than the insects.

As described in Chapter 2, using a system for categorizing sites according to maintenance level can help in planning an IPM program.

Facility Categories

Examples of turfgrass sites that might be included in each category include:

Class A - High level of service: fine ornamental lawns, golf and lawn bowling greens, irrigated sports field.

Class B - Moderate level of service: general park areas, residential and commercial lawns, boulevards, recreational fields, golf fairways.

Class C - Low level of service: meadows, picnic areas, rough grass, undeveloped and naturalized areas.

The following section describes the general steps in an IPM program for turf insects and gives examples of techniques currently available to turf managers. Examples of IPM information about four common turfgrass insects is also included at the end of the chapter. This information is intended as a starting point, to be adapted to suit specific sites and improved as new products and methods are developed.

Prevention

The elements of prevention (also called "cultural controls" in some references) for turf pests involve using optimum site design and management. When designing and planting turf areas, plan for long-term insect management by starting with the correct drainage, soil preparation and choice of turfgrass cultivars adapted to the conditions. Follow this with turf management practices that ensure healthy, vigorous turf (see Chapter 5 for additional management methods that contribute to healthy turf).

Plant Pest-resistant Turfgrasses

On sites where chewing insects, such as sod webworm, are a chronic problem, consider renovating and reseeding with grasses containing endophytic fungi. Some cultivars of perennial rye grass and tall, turf-type fescues have high levels of endophytic fungi in the leaves. These fungi produce toxins that repel or kill leaf- and stem-feeding insects (they do not affect root-feeding species, such as leatherjackets or white grubs). Endophytic grasses must not be planted where livestock may graze.

Identification

Correct identification of turf pests is essential because monitoring and treatment methods must be tailored to a particular species. Once a problem species is identified, then information about it´s life cycle can be used to pinpoint when treatments will have the greatest effect and what preventative measures would be most effective.

If you suspect an insect problem, search carefully among leaves and in thatch. Fold back a section of sod or use a soil probe or cup cutter to remove a section of turf. Inspect the thatch layer, roots and soil for larvae, pupae and adult insects. Collect insects and identify them from guides and other references or preserve them for later identification by an expert.

Identification resources include:

• reference books, plant guides (suggestions are listed at the end of the chapter)
• resources on the internet
• staff at garden centres, community colleges, botanical gardens
• professional diagnostic services

Note: Professional services and companies can send samples to the provincial Plant Diagnostic Laboratory, Ministry of Agriculture and Lands, 1767 Angus Campbell Road, Abbotsford, B.C. V3G 2M3. Phone: 604-556-3126 (there is a charge for this service).

Monitoring

Turf insect populations can be estimated by visual inspections or determined more accurately using one of the counting methods described below.

Visual Inspections

Walk over the turf areas, noting:

• damaged areas, which may show up as patches of wilting, yellowing, or browning turf or bare areas
• signs that birds or other animals are pulling up the turf, indicating the possible presence of insects
  Record information on a map or diagram for future reference.

For close visual inspections, use a hand lens and a soil probe or other tool to search deep in the thatch layer and root zone. Look for:

• life stages of insects, such as larvae or pupae, on the surface or among the roots in the soil
• symptoms of chewing or sucking on leaf blades, missing leaf blades
• silken webbing in the thatch layer

Counting Methods

• Fold back a measured section of sod or remove a plug of sod with a golf course cup cutter or other tool, then count and record the insects found among the roots. Replace the sod.
• Soak a measured area of turf with soapy water or a pyrethrins solution (see text box). This irritates insects and drives them to the surface where they can be counted.
• Cut out a measured section of sod and soak in a bucket filled with a saturated solution of salt water (add salt until no more will dissolve). Count the larvae that float to the top. This is a destructive sampling method that would not be appropriate for most landscape turf.

For future reference, it is important to keep written records of counts as well as notes and maps of damage from visual inspections. Some turf managers also find it useful to keep photographs as a record.

Which Method: The choice of monitoring method depends on the site, the user and the suspected pest problem. For example, soap drenches work well to drive out active larvae, but not white grubs. Once a method is chosen, the same method should be used each time so that counts and averages can be compared from one year to the next.

When and How Often: The monitoring schedule depends on the category of the site and the life cycle of the problem insect. Intensive monitoring may be necessary for a few weeks in the spring for several species, but may not be necessary at other times of the year.

Action Decisions

On general use turf, in parks and other public facilities, injury levels depend on what the users will tolerate and how vigorously the turf is growing. On sports turf, safety considerations also influence treatment decisions because bare patches can increase the slipping hazard. Injury levels also depend on the category of site. For example:

• Class A Sites: There is low tolerance for infestations of insects because of the potential for deterioration of playing surfaces, safety and aesthetic values.
• Class B Sites: Higher insect counts are tolerable unless their presence is attracting secondary pests, such as crows, ravens and raccoons to dig up the turf.
• Class C Sites: Generally insects are not a concern.

Treatments

Insect populations in turf rarely reach levels that require treatment in most areas of BC, especially where turf is growing vigorously. Avoiding insecticide use in favour of improved cultural methods has the advantage of preserving the naturally occuring beneficial insects and mites that control pests.

Biological Controls

Insect parasitic nematodes are the only type of biological control produced commercially at this time for turf pests. These are microscopic worms that move through the soil to attack insects (for more detailed information, see Chapter 3). Depending on the species of nematode available (it varies from year to year), they may be used for leatherjackets, white grubs, black turfgrass Ataenius, cutworms and other turf pests.

Nematodes are sold in a dormant stage, which is mixed in water and applied to the soil. They can also be applied through irrigation systems. They must be applied with sufficient water (at least 1.5 cm) to carry the nematodes down to the root zone where the pests are feeding. Irrigating both before and after applying nematodes has given better results than irrigation only after application.

Note: Nematodes are not active in cold soil conditions and most species are only effective when soil temperatures are above 12°C. Always consult suppliers for advice on which species to use and methods of application.

Chemical Controls

Where possible, avoid broadcast or blanket applications of insecticides. These have been shown to reduce the natural populations of the beneficial insects and mites that eat the eggs and larvae of turf pests. Where possible, use spot treatments with selective insecticides. This reduces treatments costs and protects beneficial species.

If an insecticide treatment is judged necessary, make sure the product selected is:

• effective and registered for the specific insect,
• applied as a spot treatment instead of broadcast application wherever possible, and
• applied at the right time to have the greatest effect on target species. For example, timing pesticide applications for larval control is critical and must be determined by monitoring, since chemical treatments are more effective when larvae are actively feeding in the root zone.

For more precautions and guidelines for using pesticides in landscapes, see Chapter 11.

Evaluation

At the appropriate interval after any type of treatment, use visual inspections or counting methods to assess the effect. Check problem areas the following season at the right time in the life cycle of the insects to look for damage or count populations.

Use this information, along with other monitoring records, observations from field staff, feedback from clients, budget records, etc. to assess the effectiveness of the turf IPM program and find ways to improve it for next year.

IPM Examples

Following are descriptions of four common turf pests with notes on monitoring, action decisions and treatments that could be incorporated into an IPM program. In any IPM program, correct identification of the pests before taking action is critical, as is the evaluation step to determine how to improve the program in the future.

European Cranefly (Tipula paludosa)

The larvae, or ´leatherjackets´, of European cranefly are dull gray, legless, and up to 3 cm long when they reach full size. They feed in the top 2-3 cm of soil among the roots of grasses. In severe infestations their feeding leaves ragged brown patches in the turf.

The adult cranefly is a large (2.5 m long), two-winged insect with extremely long, fragile legs. The females lay eggs in turf in August-September and the tiny larvae feed for a month or two in the fall. At this stage, however, they are so small that they do very little damage. The larvae over winter in the soil, where many are killed by natural enemies and winter weather. Those that survive, start feeding again in early spring. They grow to full size by mid-June, then stop feeding for a few weeks and pupate in early July. The adults emerge in late August to September. Outbreaks of this species were severe in BC 15-20 years ago. Now damaging numbers are usually found only in highly managed or stressed turf (i.e., golf course greens).

Recently another species of cranefly, Tipula oleracea, has been identified in south coastal BC. The most noticeable difference is that adults appear in April and May. This species may have two generations a year, but the need for treatment is not known. Current recommendations are to manage them as for European cranefly.

Monitoring

Three methods of monitoring for leatherjackets are:

• In early spring, drench 1 m² areas of sod that shows signs of damage, with soapy water or pyrethrins solution (see text box under Monitoring in this chapter). Count the leatherjackets that wiggle to the surface.
• In spring or fall, pull back measured sections of sod and pick through the soil and roots to count larvae and pupae.
• Soak sections of sod in a saturated solution of salt water. Count the larvae that float to the top.
  For all methods, take 5-10 samples per site and average the counts.

Action Decisions

Example of injury levels used by turf managers for leatherjackets are:

• Class A Sites: 20-25 larvae/m² in spring
• Class B Sites: 50-100 larvae/m² in spring
• Class C Sites: over 100 larvae/m² in spring or 300 larvae/m² in fall (the higher level in the fall is acceptable because many larvae die over winter)

Treatments

Control measures are directed toward the larval (leatherjacket) stage. Treatments must be made when they are actively feeding in the roots in October or from April to early June. Treatments applied at other times of year are not effective.

Biological Control

Apply insect parasitic nematodes (Steinernema feltiae) in the fall or as soon as the soil warms in the spring. Nematode products vary, therefore follow label recommendations for release rates and methods.

Chemical Control

Although not usually recommended for general use turf because of the long-term harm to beneficial insects and mites that control craneflies (and other pests), diazinon can be used for leatherjacket control where high larval counts justify treatment. Fall treatments are usually not usually recommended because so many leatherjackets die over winter that treatments may not be needed.

White Grubs - May or June Beetles (Phyllophaga spp.)

"White grubs" are the larvae of May or June beetles. The larvae are large (up to 3 cm long), "C"-shaped grubs with reddish brown heads. They feed on the roots of grasses. Common species take three years to develop, moving deeper in the soil for the winter and rising to the root zone again in the spring. Full-grown grubs burrow 20-25 cm below the surface during July to pupate. The adults stay there to spend the winter and emerge from the soil in the spring.

Monitoring

Lift sections of damaged sod, up to 10 cm deep, and search through the roots. Count and record the number of grubs, then replace sod. Count larvae in May or early June, before they burrow deeply to pupate.

Action Decisions

Examples of injury levels:

• In healthy, irrigated turf, average counts of up to 15 larvae/0.1 m², in spring, may be acceptable.
• In stressed turf, average counts of 5-10 larvae/0.1 m² may require treatment.

Treatment

Biological Control

Some species of insect parasitic nematodes (e.g., Steinernema carposapsae, Heterorhabditis glaseri) have been shown to be effective in controlling white grubs. Apply nematodes after soil temperatures have warmed and use sufficient water to flush nematodes down into the root zone of the turf. Always check with suppliers for availability of species and methods of applications.

Chemical Control

Spot treatments of pesticides where sampling had identified high populations may be sufficient because white grubs usually occur in patches. Diazinon products are registered for white grubs in turf.

Black Turfgrass Ataenius (Ataenius spretulus)

The larvae of this small, 5 mm long beetle, are white grubs that feed on the roots of grasses. Damage appears as irregular dead patches in turf and can look like damage some turf diseases. The adult beetles over-winter in the soil and emerge in April and May. They are mainly a pest of golf courses and in BC have been found on courses in the Okanagan Valley.

Monitoring

Visual Inspections

• Look for adult beetles around outdoor lights, which strongly attracts them; check irrigation valve boxes, where beetles congregate in moist conditions.
• Inspect the top layer of turf, particularly following heavy irrigation when they are more visible.
• Inspect thatch in the fall, along the perimeters of greens, which is an area preferred by the beetles.

Counting Methods

• Pour soapy water into a large, bottomless tin can, pressed into the turf (see text box) to drive larvae to the surface for counting.
• Use a golf course cup cutter or other tool to remove sod samples. Look for larvae at the point where the soil and thatch layer meet.

Counting the numbers of larvae in the soil can be done in the fall to anticipate the numbers likely to appear the following spring. Counts for larvae can also be started two weeks after the adult beetles are first found in visual inspections.

Action Decisions

• Action levels used in Ontario are 30-40 larvae/0.1 m² (300-400 larvae/m²), especially if turf is under stress.
• Experience has shown that heavy damage occurs when there are 250-300 larvae/0.1 m² (2500-3000 larvae m²).

Treatment

To prevent spreading beetles to other areas, wash mowers and clean out clippings catcher to remove adult beetles (don't forget to kill the collected beetles).

Biological Control

Research in California has found that some species of insect parasitic nematodes are effective against the larvae. Applications should be made as soon as the soil has warmed in the spring, before adults begin to emerge.

Sod Webworms or Lawn Moths (Crambinus spp.)

Sod webworms are small, whitish caterpillars (6-19 mm long), covered with short bristles. They are the larvae of small, light brown moths, which lay eggs in the turf. The larvae live in short, silk-lined tunnels at the base of grass plants, where they feed at night, chewing off the leaf blades. Damage appears as small, dollar-sized circular patches of thin turf. The last generation of larvae spends the winter in these tunnels and starts feeding again in the spring.

Monitoring

• Inspect turf closely for missing leaf blades and green pellets of caterpillar excrement. Probe deeply into the thatch for signs of webbing and for larvae in silken tubes.
• Drench a measured area of turf with soapy water to drive larvae out of their tubes and make them easier to see (see text box).
• Count the number of larvae in measured areas of sod in several sample sites.

Action Decisions

• Healthy turf may support up to 2-3 larvae/0.1 m² (20-30 larvae/m²). High populations are usually temporary and turf can usually withstand high populations when it is growing vigorously.
• Stressed turf may be damaged by as few as 1 larvae/0.1 m².

Treatment

Reduce thatch if it is over 2 cm deep, as webworms prefer thick layers of thatch. Where sod webworms are a chronic problem, reseeding with endophytic grasses may be an option for long-term control.

Biological Control

Some species of insect parasitic nematodes (e.g., Steinernema carpocapsae) have been found to control larval stages of sod webworm.

Chemical Control

Treatment is usually not necessary, however, both diazinon and carbaryl are registered for sod webworms.

Further Reading

Anon. 1987. Scott´s Guide to the Identification of Turfgrass Diseases and Insects. O.M. Scott & Sons. Marysville, Ohio 43041.

Leslie, A. R. 1989. Handbook of Integrated Pest Management for Turf and Ornamentals. Lewis Publishers, Boca Raton. 660 pp.

MacDonald, L. and H. Gerber. 1996. Turfgrass Disease and Pest Management Guide for Professional Turfgrass Managers in B.C. BC Ministry of Agriculture and Lands . 80 pp. (From: Western Canada Turfgrass Association, 22097 Isaac Crescent, Maple Ridge, BC V2X 0V9. Tel: 604-467-2564).

Olkowski, W., S. Daar, H. Olkowski, 1991. Common-Sense Pest Control. The Taunton Press, Newtown, CT. (From: Bio-Integral Resource Center, PO Box 7414, Berkeley, CA 94707. Tel: 510-524-2567.