(Coleoptera: Chrysomelidae)

The sunflower beetle, Zygogramma exclamationis, is a native pest of the sunflower. It closely resembles the Colorado potato beetle but is smaller, differently colored, and does not feed on sunflowers. Adult sunflower beetles are 6-8 mm long and 4-5 mm wide.

The head is reddish-brown and the pronotum (or shoulder) is pale yellow with a reddish-brown patch at the base. Each wing-cover has 3 dark-brown stripes that extend the length of the back. The fourth stripe ends at the middle of the wing in a small dot that resembles an exclamation point, giving the sunflower beetle its scientific name. Note that the Colorado potato beetle has 5 stripes on each wing cover.

The cigar-shaped eggs are yellow to orange in color and are about 2 mm long.

The humpbacked larvae are dull yellow-green with a brown load and, when fully grown, are about 10mm long. Colorado potato beetle larvae are brick-red.

The yellowish pupae are about the size of the adult.

Sunflower beetles occur throughout southern Manitoba, wherever commercial sunflowers are grown for seed, oil, or confection.

All stages of this pest are closely associated with their host.

Sunflower beetles feed on a variety of wild and cultivated sunflowers in the genus Helianthus across the prairies.

Sunflower beetles overwinter as adults in the soil. They emerge in the spring (anytime from late-April to late-June, depending on weather conditions). Usually, their emergence from the soil coincides with the time that sunflower seedlings begin to appear in late-May (Westdal,1975; Charlet, 1991). The beetles feed throughout the day on the emerging seedlings, mate within a week, and begin egg-laying.

The eggs are laid singly on the underside of leaves or on the stem, at a rate of about 15 eggs per day (Gerber et al, 1979). Egg-laying may continue for 6-7 weeks, resulting in the production of up to 1000 eggs per female. However, most female beetles probably lay fewer than 200 eggs.

Eggs hatch in about a week and the young larvae feed on the leaves at night. They hide among the bracts of the flower bud and in the axils of the leaves during the day. The larvae feed for about 2 weeks but, because of the long egg-laying period, larvae may be present in the field for about 6 weeks.

When mature, larvae drop to the ground, enter the soil, and pupate in earthen cells. The pupal stage lasts about 2 weeks. Adults of the now generation emerge and feed for a short period in late-August and early-September. They feed on the uppermost leaves or bracts of the plant before re-entering the soil to overwinter. There is only one generation per year on the prairies.

6. Seasonal Abundance:

Larval sunflower beetle populations are at their highest immediately after egg-hatch is complete. They are at their lowest in the spring, when only the surviving adults are present.

7. Responses to Environmental Factors:

Cold winter temperatures may reduce the survival of overwintering adults (Charlet, 1983, 1991).

Adult sunflower beetles injure the plants by chewing on the edges of the newly-formed leaves of the seedlings. They may completely defoliate plants if the population is large enough. The larvae feed at night on the upper leaves and chew holes through the inner portion of the leaf rather than the margins as is the case with the adult beetles. Feeding by adult beetles and larvae may result in extensive defoliation. This, in turn, causes poor seed set or seed filling, reduced yields, and delayed maturity. Damage by the adults in late summer is not usually a problem.

Predators (e.g., ladybird beetles, lacewings) and parasites (e.g., tachinid flies) may keep sunflower beetle populations below damaging levels. Larval parasitism by tachinids (e.g., Doryphoraphaga doryphorae) can be quite high in some years.

Noticeable damage is often first seen on plants near the margins of sunflower fields. Both the larvae and adults are easily seen and counted on seedlings and young plants.

Control may be necessary if defoliation, caused by either the adults or the larvae, reaches 25-30%, especially if more defoliation may occur. One or 2 adults per seedling or 10-15 larvae per plant, on the top 8-12 leaves, will probably warrant control (Charlet, 1983, 1991).

In those years when adult control is necessary, larval control will also usually be required. One application of insecticide, after all the eggs have hatched, should give good larval control.

Control is probably required if there are 1-2 adults/2-3 seedlings or if there are over 12 larvae/plant. Severe leaf damage may occur to plants in the 2 to 6 leaf stage when adults are numerous. Severe leaf damage may occur on growing plants, throughout the season, when larvae are numerous.

No non-chemical controls were suggested in any of the available scientific and technical literature.

Permethrin has a low acute mammalian toxicity. Very toxic to bees and fish. Do not contaminate ponds, lakes or streams during sprayer filling or while spraying. Avoid spraying when bees are foraging.

Azinphos-methyl...... 280

Carbofuran

Larvae........... 70 60

Adults........... 140 60

Cypermethrin......... 25 70

Endosulfan........... 560 60

Methidathion......... 260-525 50

Deltamethrin......... 5-7.5 70

Restrictions and Precautions -

Do not apply insecticides after plants are 60 cm high or after heads begin to form.

Azinphos-methyl: Do not apply more than twice per season, 7-14 days apart. Do not apply after heads begin to form. Do not re-enter treated fields without protective equipment within 2 days of application.

Carbofuran: Do not apply more than 280 g/season. Do not apply by aircraft. Do not apply Furadan to areas where bees are actively foraging or near apiaries. Do not spray sunflowers after plants are more than 60 cm in height or after heads have started to form. The use of Furadan 480F may be hazardous to burrowing owls. Do not apply within 250 meters of known burrowing owl nests.

Cypermethrin: Avoid application at temperatures above 27C. May be applied by ground or air (but only one application by air per year). Observe a 100 m setback from water bodies and sensitive areas when applying by air.

Endosulfan: May be applied by air or ground equipment. Do not apply more than once per season. Do not feed treated foliage to livestock. Thiodan has a high acute mammalian toxicity, is toxic to bees and is highly toxic to fish.

Methidathion: May be applied by air or ground equipment. Works as a contact and stomach poison. Toxic to birds, bees, fish and other wildlife. Observe a 100 m setback from any body of water or environmentally sensitive area when applying by air. Do not apply to crops in bloom. Do not enter treated fields on the same day of application. Do not feed or allow animals to graze on treated crops.

Deltamethrin: Do not make more than three applications/yr. (Only one application per year by air.) Do not apply at temperatures above 25C.