CIS 994

Stuart C. Parkinson, Robert L. Stoltz, Jay Karren, Michael E. Cooper

History and spread

Boundary The cereal leaf , 1994 melanopus, has been recognized as a pest of small grains in Europe since Bonner 1737. It was first identified in the 1998 Figure 1. Idaho Cereal - United States in 1962 in Berrien Infested Counties, 1992-2000.

County, Michigan. Since then it has Kootenai Source: Idaho State Department of Agriculture spread to many states in the eastern 1998 and midwestern United States and Benewah parts of eastern and western Canada. Shoshone

This first appeared in Idaho Latah in Franklin County in 1992. Infestations Clearwater Nez now occur in 29 counties in Idaho (fig- Perce ure 1); the northern half of Utah; parts Lewis Infested Counties of Montana; Malheur, Baker, Umatilla, Counties Surveyed Negative Union, Columbia, Multnomah, Wash- Idaho ington, and Yamhill counties in Oregon; Spokane County, Washing- ton; Elko County, Nevada; and parts of Adams Lemhi British Columbia. 2000 Valley 2000

Host plants Washington Custer Clark 1998 Fremont The cereal leaf beetle feeds on oats, Payette 1998 Boise Gem 1997 Jefferson barley, wheat, rye, and corn as well as 1998 Madison Teton 1998 1998 Canyon Butte on weeds such as wild oat and 1997 Bonneville Ada Camas Blaine quackgrass. It also feeds on forage Elmore 1995 1996 1998 1995 Bingham grasses, such as timothy, ryegrass, 1997

M 1995

Gooding inidoka orchardgrass, and reed canarygrass. Its Lincoln 1996 1997 1997 Caribou Bann preferred hosts are spring-seeded small Power 1996 Jerome 1994 1996 1995 ock grains–especially oats and barley. Owyhee Twin Falls Bear 1996 1996 Cassia Lake Oneida 1995 Franklin 1995 1995 1992

Cooperative Extension System • Idaho Agricultural Experiment Station CIS 994 Cereal Leaf Beetle Description covered with this slimy material when woody or brushy locations, especially they are working in an infested field. areas adjacent to infested fields. They Adults. The adult beetle is small but Pupae. Pupae are yellow to yellow- have also been found under the easy to identify. It is a hard-shelled ish brown. They are rarely seen be- siding of homes and farm buildings beetle, 1/4- to 3/16-inch long, with a cause they are under the soil surface and behind fence boards. metallic blue head and wing covers, a encased in earthen cells. In the spring, when maximum daily red pronotum, and yellowish-orange temperatures reach about 50°F, the legs (figure 2). Life cycle and damage overwintered adults become active. Eggs. Newly laid eggs are elliptical, Cereal leaf overwinter as Full adult activity (mating and flight) yellow, and about the size of a pinhead adults in grass stems and debris, un- occurs when temperatures reach (less than 1/16-inch long). Before der bark, and in the crowns of grasses. about 66°F. Adults are active fliers and hatching, they turn almost black. Eggs In some areas, the beetles survive in move around in search of acceptable are laid on their sides rather than on host plants. Heavy feeders, they con- their ends. They are never laid in clus- sume up to 3.5 times their body weight ters but are deposited singly or in rows in a single day as they prepare for egg of up to three or four. Normally they laying, but rarely cause economic are found close to the mid-rib on the damage. upper surface of the host plant leaf The adults mate and begin to lay (figure 3). Economic thresholds eggs on host plant leaves within 10 Larvae. Mature larvae are slightly for chemical control days of breaking diapause. One larger than adults and look much like female may lay up to 300 eggs. slugs. Their skin is yellow or yellow- Before Boot Eggs take from 4 to 23 days to hatch, ish brown and is covered by a mass of depending on temperature. Larval popu- slimy, dark fecal material (figure 4). 3 larvae per plant or lations peak in early summer (mid to late This fecal deposit is thought to protect 3 eggs per plant or June) depending on altitude and tem- the larvae from desiccation and preda- perature. With a warm, early spring, tors. It also appears to attract some of both these populations may peak up to 1 the beetle’s host-specific parasites. month early. Immediately after a molt is the only After Boot Larvae eat the upper layer of green time larvae are found without this ex- mesophyll cells, which create the green crement. Disturbed larvae easily cast 1 per flag leaf leaf color and generate plant energy. off this fecal covering. Field workers’ They feed down to the cuticle, staying shoes, pants, and shirts often become between leaf veins. This feeding pattern ADULT LARVA EGG

Figure 2. Adults are hard-shelled Figure 4. Larvae normally are covered beetles with metallic blue head and in a mass of slimy, dark feces. wing covers, red pronotum, and yellowish orange legs.

Figure 3. Cereal leaf beetle eggs, typically one per leaf, rest on their sides rather than on their ends. Cereal Leaf Beetle gives the leaves a frosted appearance Quarantines Control recommendations when viewed from a distance (figure 5). This feeding pattern is characteristic of California has imposed quarantines Cultural control practices that suc- the cereal leaf beetle and is one way of on products from the infested areas to cessfully reduce populations of cereal detecting its presence. This pattern can prevent this insect from spreading. leaf beetle have not been identified. also be detected late in the season on Current quarantines involve barley and The economic threshold for chemi- old, brown, dried-up leaves. wheat hays and grains. Clean alfalfa cal control is based on insect popula- After 10 to 14 days and three to four hay is exempt. Please consult the Idaho tion densities and growth stage of the instars, the mature larvae pupate in State Department of Agriculture or the grain crop: small, hardened, mucous-lined cells University of Idaho extension agricul- Before boot stage. Prior to boot they construct in the soil. The pupal tural educator in your county to deter- stage, do not spray cereal crops un- stage requires from 10 to 21 days, de- mine the current quarantine status. less populations reach an average of pending on environmental conditions. three larvae per plant, three eggs per Newly emerged adults feed on a vari- plant, or both. When counting, be cer- ety of material, but prefer succulent tain to inspect all the tillers in each grasses, grain, and young corn. Even plant. It is best to walk a wide circle though their numbers can reach several through the field, taking 10 to 20 hundred per plant, newly emerged Current sample counts to ensure accuracy. adults rarely cause economic damage After boot stage. After boot stage, because they feed for such a short time. the economic threshold becomes one Adults feed entirely through the leaf quarantines larva per flag leaf. If control is required, surface. They eat between the leaf consult the current edition of the Pa- veins, staying in a straight line. This involve barley cific Northwest Insect Management produces a stripping effect instead of Handbook for specific recommenda- the frosted appearance created by tions. larvae (figure 6). and wheat hays Toward fall, after about two weeks of feeding, adults go into a resting stage, or diapause. They seek shelter and grains. and become quiescent until the follow- ing spring. The cereal leaf beetle has only one generation per year.

Figure 5. Heavy laval feeding gives the leaves a Figure 6. Adults feed through the leaf frosted appearance. surface, between leaf veins, producing a stripping effect. Biological control A concentrated effort by state and federal agencies the past several years has produced a successful parasite introduction program in the midwestern and eastern United States. Several species of parasitic wasp have been used in this biologi- cal control program. The species Tetrastichus julus has been the most successful at becoming established where it has been released. Once es- tablished, this parasite typically re- duces beetle populations by about 60 percent and grain losses to less than 1 percent without chemical control. Studies show that 30 to 40 percent parasitism results in a controlling population. Populations of cereal leaf beetle usually disappear soon after this level is reached. Presently the USDA, Idaho State De- partment of Agriculture, and Univer- sity of Idaho are working together to establish parasite populations in Idaho. Egg and larval parasite releases have been made in several counties. Egg parasites have proven to be very difficult to establish. Larval parasites have been recovered from several re- The authors – Stuart C. Parkinson, University of Idaho lease sites. Complete introduction and Agricultural Extension Educator, Franklin County; Robert L. establishment of the parasites will Stoltz, Extension Entomologist, University of Idaho Twin Falls take several years. Research & Extension Center; Jay Karren, Utah State Univer- Even with the establishment of sity Extension Entomologist, Logan; Michael E. Cooper, parasites the cereal leaf beetle contin- Bureau of Feeds & Plant Services, Idaho State Department of ues to spread to new areas. In areas Agriculture, Boise. where the parasites have been re- cently introduced, chemical spraying should be limited to protect the grow- ing parasite population. Limited spray- ing may be necessary for three to five Copies of the annually revised Pacific Northwest Insect Management Hand- years while parasites build up in the book are available by contacting Ag Publications, University of Idaho, P.O. new beetle population and reduce it Box 442240, Moscow, ID 83844-2240; telephone (208) 885-7982; email to a level that does not seriously af- [email protected]; Web site http://info.ag.uidaho.edu fect yields.

Issued in furtherance of cooperative Extension work in agriculture and home economics, Acts of May 8 and June 30, 1914, in coopera- tion with the U.S. Department of Agriculture, LeRoy D. Luft, Director of Cooperative Extension System, University of Idaho, Moscow, Idaho 83844. The University of Idaho provides equal opportunity in education and employment on the basis of race, color, religion, national origin, gender, age, disability, or status as a Vietnam-era veteran, as required by state and federal laws.

Revised February 2001 $2.50