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Integrated Pest Management Program

Department of Plant Science and Landscape Architecture, Department of Extension

Fact Sheets > Greenhouse > Insect and Mite Pests

Beetles

Although not usually greenhouse pests, beetles can be found feeding on plants in outdoor production and retail yards, cut flower fields, and customer’s gardens in Connecticut. Beetles are a large group of insects characterized by hardened forewings. Both adults and larvae have chewing mouthparts that cause damage to a wide range of plants. Leaf feeding beetles such as lily leaf beetles and scarab beetles are important pests in herbaceous perennial production. Some other damaging beetles include tortoise beetles, flea beetles, various spotted and striped cucumber beetles, larvae of click beetles (wireworms), and blister beetles. During weekly plant inspections, look for chewed leaves, or pinholes from flea beetle feeding.

Leaf feeding beetles

Lilyleaf beetles 

The lily leaf beetle (Liloceris lilii) was introduced into the U.S. in 1992, and has since spread throughout Connecticut. Adults are 1/4–3/8 inch long, bright scarlet-red in color, with black legs, head, and antennae. Larvae are orange, brown, or yellow. They resemble a fragment of soil as they transport their excrement on their backs. Both adults and larvae feed on Fritillaria, Lilium, Polygonatum, and Nicotiana. Insect growth regulators may be effective in killing the early instar larvae. However, applications must be performed before the larvae start covering themselves with their excrement

Biology and Life Cycle

  • Overwintering adult beetles emerge from the soil in early spring.
  • Females lay up to 250 eggs (over two growing seasons) on the underside of lily leaves.
  • Larvae, which feed for approximately two weeks before entering the soil to pupate, cause most of the damage to plants.
  • Adults emerge from pupae in 3–4 weeks and feed on plants until fall.
  • Adults overwinter in soil and plant debris.

Tortoise Beetles

Golden Tortoise Beetles adults (Metriona bicolor) are shiny, golden beetles, less than ¼” long with thin margins that extend out from their body and a shield-like structure covering their head. They are sometimes mistaken for ladybird beetles and may also be known as “goldbugs”. Both adults and larvae can feed upon plants in the morning glory family (Convulvulaceae) (Ipomoea sp.) causing distinct round circular holes. Contact insecticides labeled for leaf feeding beetles may be applied in production where the damage may be unsightly.

Biology and Life Cycle

  • Tortoise beetles overwinter as adults.
  • There is one generation a year. 
  • During late spring and early summer, adults lay their eggs on leaves.
  • Eggs hatch into yellowish to oval brown, broad, spiny flattened larvae that use their rear spines to hold debris and excrement over their back.  

Scarab beetles

Scarab beetles are large brightly colored beetles with lamellated tips to the antennae. Asiatic garden beetles, Oriental beetles and Japanese beetles feed on many different herbaceous perennials, annuals, woody ornamentals, and vegetables. European chafer adults are not foliage feeders. Their fleshly legless larvae are known as ‘white grubs” and develop on the roots of many different plants. The identification of the particular grub species is important because the effectiveness of chemical controls and beneficial nematodes varies according to species. Species can be identified by the pattern of hairs (rasters) on the tip of the rear end of the grubs.

Asiatic garden beetle adults (Maladera castanea) are about 3/8 inch long and cinnamon-brown in color. Asiatic garden beetles feed at night on Aquilegia, Aster, Chrysanthemum, Dahlia, Delphinium, Helianthus, Heuchera, Phlox, Physostegia, Rosa, Rudbeckia, Salvia and Zinnia. Their nighttime feeding causes c-shaped notches on the edges of leaves. During the day, adults burrow into mulch or soil or can be found under pots. They are often found near the roots of plants when one is hand pulling weeds in the garden. Immature white grubs feed on the roots of grasses and flowering plants. Asiatic garden beetles overwinter as grubs in the soil and adults emerge the following summer (mid-July to mid-August). There is one generation a year. Contact insecticides may be applied against adults; however, repeat applications may be needed. Grubs can be managed in grassy areas.

Oriental beetle adults (Anomala orientalis) are about 1/2 “long, straw-colored or dark brown with dark markings on their wing covers. Adults emerge from the soil in mid-June and are present until August. They are active during the day and night. Adult beetles do very little foliage feeding. The white grubs feed on the roots of herbaceous perennials, and woody ornamentals. 

Adult Japanese beetles (Popillia japonica) are from 1/3 to ½ “  long, metallic green with copper colored wing covers and white patches of hair near the end of the abdomen. Adults can feed during the day many different woody and ornamental herbaceous plants. Adults emerge from the soil in June and July and feed for about 30-45 days. Eggs are laid in the soil in grassy areas and hatch into white, c-shaped grubs that feed on turf grass roots. Japanese beetles overwinter as grubs in the soil below the frost line. There is one generation per year.

Japanese beetles are extremely mobile, and once feeding begins, the pests emit feeding or aggregation pheromones attracting other beetles to the same location. Look for feeding between the leaf veins (called “skeletonization”) on favored hosts.

Contact insecticides can be applied as soon as the adult beetles are observed. Many of the contact insecticides may be harmful to bees, predatory mites and insects. Apply grub control to larvae in grassy areas surrounding the production areas. 

Biological and Cultural Controls

Good weed control in and around production areas helps to eliminate potential food sources.

Shade cloth can be used to exclude adults from hoop houses. Japanese beetles are strong fliers. Japanese beetle traps are not recommended. Although they attract adult beetles they only increase feeding damage on nearby plant hosts.

The female winsome fly (Isocheta aldrichii) is a natural enemy of adult Japanese beetles that parasitizes adults. Look for the distinct white eggs on the thorax of adult beetles. The spring Tiphia (Tiphia vernalis) is a parasitic wasp that attacks Japanese beetle and Oriental Beetle grubs. A recent survey in CT, found that the spring Tiphia wasps are widely distributed in the state. Beneficial nematodes (Heterorhabditis sp.) are commercially available for use against white grub larvae. Scarab beetle species vary in their susceptibility to infection and white grubs also have some defenses against nematode infection.

References:

  • Capinera, J. 2009. Golden Tortoise Beetle. Featured Creatures. University of Florida Institute of Food and Agricultural Sciences, Department of Entomology and Nematology and Florida Department of Agriculture and Consumer Services. 4 pp.
  • Hiskes, R. Managing White Grubs in Home Lawns. 2005. Connecticut Agricultural Experiment Station Fact Sheet. 6 pp. Link
  • Pundt, L. and T. Smith. 2003. Integrated Pest Management Handbook for Herbaceous Perennials. University of Connecticut Extension Publication. 42 pp.
  • Smith, T. 2009. Lily Leaf Beetle Fact Sheet. UMASS Extension. 2 pages. Link
  • Hazzard, R. 2010. Scarab Beetle Update: Japanese, Oriental and Asiatic Garden Beetles are Active. Adapted from Turf Management Update, Pat Vittum, Turf Entomologist, UMass, Beth Bishop, Michigan State University, Michael Seagraves, Cornell Cooperative Extension, and Ann Hazelrig, University of Vermont. UMASS Extension Vegetable Notes. 21(12). 6-7.  Link
  • Ramoutar, D. and A. Legrand. 2007. Surveyof Tiphia vernalis (Hymenoptera:Tiphiidae) a parasitoid wasp of Popillia japonica(Coleoptera: Scarabaeidae) in Connecticut. Florida Entomologist 90(4): 780-2. Link

By: Pundt, L. , Extension Educator, University of Connecticut and T. Smith, University of Massachusetts. August 2010.

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