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European chafer (Rhizotrogus majalis), June beetle (usually one of the following in S-W Ontario- Phyllophaga futilis, P. fusca, P. rugosa and P. anxia in Eastern Canada), Japanese beetle(Popillia japonica) All three are members of the Sarabaedae Family

Description:

Grubs are the larvae of many species of beetles belonging mainly to one family. The European chafer has infected the Toronto region. The June beetle is present in pockets around Toronto. So far only a few small areas of the province of Ontario have experienced infestations of the Japanese beetle.

The European chafer larva is a 3/4 inch long, grayish white, C-shaped grub with a brown head and three pairs of prominent long legs. The hind part of the body is smooth and shiny with dark body contents showing through the skin. The adult chafer is a small, shiny, golden to fawn-coloured oval shaped beetle, approximately 1/2 inch long. They can reach up to 23 mm in their 3rd instar stage with their pupa reaching up to 16mm long.

The June beetle larva is slightly larger than the larva of the European chafer and, as an adult, is dark brown and about 3 cm long.

The larva of the Japanese beetle is similar to that of the June beetle, but half the size when mature. When mature the Japanese beetle adult is metallic green and bronze in colour, oval in shape and 8 - 12 mm long.

Life Cycle and Habits:

The European chafer completes its life cycle in one year. The adult swarms in trees on warm evenings in late June and early July. The females drop out of trees and lay their eggs in the surrounding sod. The larvae emerge in early August and reach their second instar stage by the middle of that month. By mid-October they have reached the third instar stage and they overwinter in that form. Being more cold tolerant than those of the June beetle, they can be a problem right through into November. From mid-May to June 1 the larvae pupate, and the adults start to emerge two weeks later.

The June beetle requires three years to develop into an adult while feeding under the soil. The larva, referred to as a white grub, is also crescent shaped with a brown head and three pairs of legs. The adult beetle is black or dark brown in colour, about 3 cm long and is often seen at night near lights in late May or early June. It feeds on the foliage of trees and shrubs.

The Japanese beetle completes its life cycle in one year. The insect winters as a 1/2" gray grub 8 to 10 inches deep in the soil, moving up in the spring to feed on grass roots. The grub pupates in late spring and emerges in early July as an adult beetle.

Symptoms of Grub Infestation:

Grubs feed on the crowns of grass but they find the fibrous root system of turfgrass a particularly enticing treat. As the grubs destroy the grass root system irregular patches of lawns gradually turn yellow, then brown and can be easily pulled back from the soil. Loose mats or clumps of dying turf are evident.

Raccoons and skunks often damage the turf as they tear it up in search of grubs. Damage is usually more severe in the late spring and fall when the moisture in the soil is high and grubs are feeding near the surface.

The degree of damage will depend on the vigour of the turf and soil moisture content. Grubs feeding in spring and fall do not cause visible damage as the temperatures are cooler and root growth by the turf grasses is more active than at other times.

Plants Affected:

The European chafer larvae are serious pests of nursery stock (ornamentals in pots) as well as lawn grasses and forage crops but the adults do little or no damage. Adults feed on fibrous roots of plants but leave the taproots alone. When feeding it can be found about 1 to 2 inches below the soil's surface and like the June beetle, sinking lower when pupating or hibernating. The adult swarms in trees in late July or early July to lay eggs. The highest density of the grubs will be found within a radius of 75 inches or 2.3 metres of the tree that the adults flew to, to lay eggs. Higher density will also be found in dry, sandy soils. Most serious damage will occur in the fall, but this may not always be noticed unless there are periods of drought.

The June beetle, in the larval stage, feeds on lawns and forage crops. Turf will be damaged in mid-to-late summer of the second year after the grub has been feeding since early spring. Adult June beetles can also cause considerable damage when feeding on the foliage of trees (e.g. oak, maple, ash) and shrubs, preferably those with tender leaves. They feed at night and higher densities of them will be found in dry sandy soils.

The Japanese beetle is a very serious pest where it occurs. It feeds on lawn grasses in the larval stage and when it emerges, to lay eggs in July, it eats over 300 species of plants in the adult form, including vegetables, fruits, ornamental plants as well as forage and food crops. Damage occurs from mid to late fall (grubs hatch mid-July).

Organic Management and Control Strategies:

The City of Toronto adopted a new municipal by-law (spring 2004) that restricts the use of pesticides. For details about the by-law visit the Pesticide by-law page on Toronto Public Health's Web site at www.city.toronto.on.ca/pesticides or www.toronto.ca/health. Questions may be e-mailed to pesticide@toronto.ca.

Natural Control:

A natural method to eliminate white grubs is beneficial nematodes (marketed under the name Biosafe by Plant Products). Nematodes search through the soil, locating a host and then enter through natural body openings. A natural bacterium is released that is fatal only to the insect, which dies within 24 to 48 hours. The nematodes reproduce and continue to eliminate grubs as long as soil moisture conditions allow (6 to 8 weeks). Application should be done when soil temperatures are above 10°C, preferably above 15°C. The lawn must be kept moist for two weeks after application. The solution must be able to penetrate to the root zone area, thus a properly dethatched lawn is advisable. There are no harmful residues left in soil that could contaminate water supplies.

Milky spore disease (Bacillis popilliae), another natural control for Japanese beetles, has not been approved for use in Canada.

If renovating a turf area after a severe infestation, consider using new cultivars that are resistant to infestations of grubs.

Mechanical Control:

The use of cultural practices such as proper mowing (mow higher to encourage root growth), correct fertility, thatch control, and adequate irrigation help to ensure a dense, vigorous, actively growing lawn. Rake the lawn after mowing to remove clippings and reduce the buildup of thatch. Healthy turf can sometimes outgrow the effects of a low to moderate number of grubs.

If grubs are detected during warm, dry periods of the growing season, irrigating and fertilizing will help maintain turf vigour and compensate for the root feeding caused by grubs.

To monitor, cut about ten 4" circles about your lawn at the beginning of August to the middle of August. Five to ten grubs per .1m² in non-irrigated turf, or 15-20 per .1m² in irrigated turf indicates a problem.

Mechanical Control of Animals:

The only permanent solution to raccoon and skunk problems is to alter or eliminate an attractive food source. In addition to the natural or mechanical controls suggested some simple deterrents can be used. Both raccoons and skunks can be somewhat discouraged by the use of bright landscaping lights especially ones with a swaying motion. Use two 100-watt light bulbs for every 15 square metres (50 x 50 ft) of garden.

Live trapping in towns and cities may rid a homeowner of nuisance skunks or raccoons. In some areas live traps may be rented from Humane Societies or local pounds. Some sporting goods stores sell live traps. Plans and a list of materials for a simple trap may be obtained from the nearest Ministry of Natural Resources District Office. Bait for traps includes canned pet food, sardines, and crisp bacon. Skunks should be released at least 16 kilometres from point of capture and raccoons 32 kilometres away.

References:

• The Toronto Master Gardener Weston Family Library is an excellent source for horticultural information.
• Tashiro, Haruo. Turfgrass Insects of the United States and Canada. Ithaca, New York, U. S.A.: Cornell University Press, 1987.
• Yepson, Roger B.Jr. ed. The Encyclopedia Of Natural Insect and Disease Control. Pennsylvania, U.S.A.: Rodale Press, 1984.
• Cranshaw, Whitney. The Ultimate Guide to Backyard Bugs. Princeton, U.S.A.: Princeton University Press, 2004.
• Alford, David V. A Colour Atlas of Pests of Ornamental Trees, Shrubs and Flowers. Portland, Oregon: Timber Press, 2003.
• The Gardener's Handbook - An Integrated Approach to Insect and Disease Control, Toronto, Canada: Publication 64. Ontario Ministry of Agriculture, Food and Rural Affairs, Queen's Printer for Ontario, 1998.

Factsheets are produced by the Toronto Master Gardeners in association with the Toronto Botanical Garden. They provide introductory information about a broad range of horticultural topics and are intended for personal use and study purposes. Should your gardening group or organization wish to use multiple copies we ask that you inform the Toronto Botanical Garden at info@torontobotanicalgarden.ca.

Date revised: January 8, 2006