Cereal Leaf Beetle

Damage

Photo: Cereal BeetleBoth adults and larvae of the cereal leaf beetle damage grain crops with the larvae stage being the most damaging and the target of control measures. Generally, the newer plant tissue is preferred with feeding occurring on the upper leaf surface causing characteristic elongated slits.

Life Cycle and Description

Adults are the overwintering stage, moving into grain fields and feeding for about 10 days on small grain and grass foliage after they become active in the spring. Adults prefer spring grains over winter grains. The adults are about 1/4 inch in length with brightly colored orange-red thorax, yellow legs and metallic blue head and wing covers. It is important to correctly identify the adults since other beetles, common in cropland, resemble the CLB. Eggs are laid end to end singly or in groups of 2 or 3 on the upper leaf surface near the base of the leaf. Newly laid eggs are bright yellow, darkening to orange-brown and finally to black before they hatch. Egg hatch may take from 4 to 23 days depending on temperatures.

Photo: Cereal BeetleThe larvae has a yellow body with brown head and legs. The body is protected by a layer of slimy, fecal material which makes them look like a slug. When working or walking in an infested field the slimy covering will rub off on your clothing. Although both adults and larvae cause feeding damage, the larvae is responsible for majority of the damage. They feed on the leaf surface between veins, removing all the green material down to the lower cuticle resulting in an elongated windowpane in the leaf. Severe feeding damage can give a frosted appearance to the field. The larvae has 3 pairs of legs located close to the head end of the immature insect. When larvae have completed their feeding they shed their slimy covering and drop to the ground, hollowing out an earthen cell for pupation. The pupal stage takes from 10 to 14 days to complete. When new adults emerge from pupation they feed briefly on grasses, before leaving the field and finding a suitable protected overwintering site. Adults are strong, active flyers and can move some distance.

Monitoring

The first sign of damage in the spring is due to adult feeding on the plant foliage. While this is the first sign of adult activity, adults are not the target of control. Eggs and larvae are monitored by plant inspection since thresholds are expressed as egg and larvae numbers per plant or per stem. Examine 10 plants per location and select 1 location for every 10 acres of field. Count number of eggs and larvae per plant (small plants) or per stem (larger plants) and get an average number of eggs and larvae, based on the samples you have taken.

Plant growth stage should be noted because the treatment threshold changes with plant growth stage (3 eggs and larvae or more per plant in smaller plants; 1 larvae per flag leaf in larger plants). Both eggs and larvae can be found by examining the upper leaf surface.

Economic Threshold

Boot stage is a critical point in plant development and impact of cereal leaf beetle feeding damage can be felt on both yield and grain quality. Before boot stage, the threshold is: 3 eggs and larvae or more per plant (including all the tillers present before emergence of the flag leaf). Larvae feeding in early growth stages can have a general impact on plant vigor. When the flag leaf emerges, feeding is generally restricted to the flag leaf which can significantly impact grain yield and quality. The threshold is decreased at the boot stage to: 1 larvae or more per flag leaf.

Host Plants

Cereal leaf beetle has a wide host range including cultivated grass hosts: barley, oats, wheat speltz, rye. Adults may feed on corn, sorghum and sudangrass. Beetles may use resident or grass weeds including: wild oats, quackgrass, timothy, canary grass, reed canary grass, annual and perennial ryegrass, foxtail, orchard grass, wild rye, smooth brome and fescues. The above information was taken from: http://scarab.msu.montana.edu/ipm/clbnotes.htm@A3 (pictures are available on website)

Cereal Leaf Beetle Update

by Diana Roberts, Area Extension Agent WSU Extension

The cereal leaf beetle (CLB) has caused crop damage at a number of hotspots across eastern Washington the past few years. Most of these sites are in irrigated areas. However, in 2006 the pest is becoming more visible in dryland regions such as Columbia and Walla Walla Counties . It has also been reported for the first time in Yakima County .

The adult CLB are about ¼ inch long with blue/black, shiny, rectangular abdomens. The legs and prothorax (head) must be red/orange (or it is a different, beneficial species). The beetles overwinter as adults and emerge in spring when temperatures reach around 50 degrees Fahrenheit for several days. You will find them first in winter wheat, where they seldom cause much damage. By now they are mostly on young and lush oats, spring wheat, or barley.

Research has shown that it is not economic to spray early in the season but insecticides are more effective when CLB is in the larval stage. The larvae appear as dark, slimy, stubby “caterpillars” that cover themselves in their own fecal material and feed up and down the upper leaves. They leave whitish streaks between the leaf veins as they remove the chlorophyll layer but they seldom eat all the way through the leaf, unlike the adults that may chew longitudinal holes in the leaf.

The most effective time to spray is when most of the larvae are about 1/8 inch long. If you spray too early there may still be a lot of unhatched eggs in the field and it may be necessary to reapply insecticide. The eggs appear as individual, tiny (1 mm) orange/brown specks on the upper surface of the leaf at the midrib about 1 inch from the plant stem.

It is also important to determine whether you have an economic threshold of the pest. Up to the boot stage this occurs when there are 3 larvae or eggs per plant. After the boot stage heavier infestations are required before there is economic loss - at least 1 larva per flag leaf. You should also scout across the whole field as CLB infestations are often heavier on borders than within the field.

It is tempting to use insecticide on new infestations in hopes of eradicating the population, but this is not likely to happen. Attempts to eliminate the pest were unsuccessful when it was first found in Michigan in the 1960's. Some reports indicate that premature use of insecticides may actually cause an increase in CLB the following season as the chemicals also kill predatory species such as ladybird beetles.

WSU Extension is coordinating a biocontrol project intended to keep CLB populations below the economic threshold. The biocontrols we are using are two species of wasps (which are tiny and harmless to people, pets, livestock, and other plants and animals). They lay their eggs in the larvae or eggs of CLB and prevent further development of the pest. In areas where the biocontrols are multiplying we recommend that farmers not spray the whole field but leave buffer strips so that the beneficial insects can survive and multiply.

Currently we have field insectaries at Nine Mile Falls , Peone Prairie, Colville , Deep Creek, Warden, and Connell. Farmers who have large populations of CLB and who would be interested in managing an insectary should contact Mary Corp at 541-278-5403. For pictures, labeled insecticides, and further information on CLB, go to www.spokane-county.wsu.edu/smallfarms/index.htm and click on the Integrated Pest Management button on the left.

From the Archive

Cereal Leaf Beetle (CLB) adults are beginning to infest spring grains, including oats, barley and wheat in the Nyssa - Adrian areas according to Ben Simko, OSU Extension Agent in Malheur County. Adults and eggs were observed, particularly in preferred hosts of oats and spring barley. Field consultants and growers are advised to monitor populations of CLB and the larval hatch to assess potential economic damage to their crop later this season.

Photo: Cereal Leaf Beetle Damage

Cereal Leaf Beetles were found in Umatilla County at one location in 1997. No additional CLB have ever been found. There is a sizable infestation in the La Grande area, and it would seem likely that we would eventually find it again in Umatilla County. It likes to hitchhike it's way around and prefers spring grains.

See CLB Reference Page for more information on identification, action thresholds and crop protection chemicals. USDA APHIS staff are looking for a field in Oregon for potential biocontrol release site of beneficial CLB parasites. For more information contact the Malheur County extension office at 541.881.1417.

Cereal Leaf Beetles Found in Umatilla County

Cereal leaf beetles have been found in Umatilla County this spring, according to Dick Jackson, Oregon Department of Agriculture entomologist. Three locations have been found. Populations at all sites are low. One site is the original site from 1999 at the foot of Cabbage Hill. The other two sites are in Adams and Athena areas.

Biological control agents are effective controllers of this cereal pest. The agents, a wasp and a larval parasitoid, should be available from insectaries in Union County to introduce as the CLB continues to expand in our area. 

Cereal Leaf Beetle in Malheur County

Cereal leaf beetles (CLB) have been found at several sites in Malheur County, Oregon, according to Dick Jackson, entomologist at the Oregon Department of Agriculture (ODA). Adult beetles were found on April 21, 1999. Jackson says they were found in winter wheat, oats and barley in low numbers.

The ODA will be surveying in Umatilla County and other adjacent counties this year. The adult beetles are good flyers and can move significant distances under their own power. Larvae and eggs can also be moved with contaminated hay over even longer distances.

I would encourage everyone in eastern Oregon to watch for this insect this season.