Project Methods and Materials

1. Detection Survey
Goals for the 2001 detection survey focused on sampling counties that 1) were not previously surveyed in eastern Washington by WSDA (Okanogan, Columbia, Franklin, Chelan, Yakima, Benton, and Ferry), and 2) were considered high priority western counties along the southern I-5 corridor (Lewis, Pierce, Thurston, Cowlitz, and King). The survey also included high priority counties previously surveyed (Adams, Clark, Douglas, Garfield, Grant, Kittitas, Klickitat, Lincoln, Pend Oreille, Spokane, Stevens, Walla Walla, Whitman). High priority counties were defined as areas with high economic risk, with suitable habitat, and adjacent to previously detected populations.

The western Cereal Leaf Beetle Working Group (CLBWG) serves as an informal scientific forum and regional partnership to aid in the exchange and redistribution of biological control agents. The group represents 10 western states/provinces, whose members include industry representatives, federal and state agricultural entomologists, and university researchers and extension agents. In 2001, members of the CLBWG met to review the survey methodology used for the detection of cereal leaf beetle. The group developed a list of survey guidelines and standardized methods for field sampling during CLB detection surveys.

Essentials of survey methods include both visual inspection and sweep netting. For survey purposes, a "sweep" was defined as one pass through the upper foliage with a 15" diameter sweep net. A "sample" was defined as 30 sweeps taken at a moderate walking pace 10-15 ft. inside the border of the field. Four samples were taken from each site, totaling 120 sweeps per site. The contents of each sample were visually inspected for life stages of CLB and all suspect specimens were retained for verification and reference. Guidelines advise surveying a minimum of 5 high priority fields per county, and a maximum of 20 sites per county, or until a detection is made. WSDA survey efforts concentrated on "high priority" sites which included commercial grain and grass fields such as oats, wheat, barley and rye. In areas with little grain production, sampling focused also on wild and cultivated grasses such as timothy, orchard grass, bluegrass, wild oats, corn, brome, and ryegrass.

2. Delimiting Survey
A delimitation survey was conducted as a multi-year effort to monitor growth and movement of the localized CLB populations in the State. Because of limited resources, inspections were focused on fields adjacent to previously surveyed sites. Special attention was placed on potential avenues of natural and human-assisted dispersal such as river corridors, railway systems, and highways. Sampling methods for each site were identical to those used for the detection survey.

3. Biological Control
In 2000, the WSDA began a biological control program aimed at the long-term management of cereal leaf beetle. With the cooperation of a local farmer, the WSDA has established one CLB field insectary, located at Nine Mile Falls in Spokane County. The insectary site is located on approximately 600 acres of irrigated grain and grass farmland, bordered by forested slopes and waterfront. Later that same year, with the support of the USDA and WSU, the WSDA conducted the initial release of the parasitic wasp species Tetrastichus julis. Renowned for its efficacious control of CLB, T. julis wasps locate young CLB larvae and deposit eggs into the host's body. After the eggs hatch, the emerging parasitic larvae begin to feed and develop slowly within the living host. The CLB larvae continue feeding and eventually move to the soil and build a pupal cell. After the pupal cell is constructed, the T. julis larvae grow rapidly, killing the CLB host. Some T. julis larvae will complete development immediately, emerge as wasps and disperse to attack new hosts. Another portion of the T. julis larvae will enter diapause and overwinter within the remaining host pupal cell, emerging as adults the following spring. (Gage and Haynes 1975, Stehr 1970).

In 2000 and 2001, Washington received shipments of the bioagent T. julis from university and federal cooperators in Utah and Montana . During the first year, shipments were received and screened by the Northwest Biological Control Insectary/Quarantine (NWBIQ). Adult wasps were reared from the parasitized CLB and released at the Nine Mile Falls insectary site. In 2001, instead of rearing and releasing adult wasps, the parasitized CLB larvae were released directly at the Nine Mile Falls insectary site. This was done in order to 1) increase survivability of the parasitoid, 2) encourage synchronized emergence of T. julis wasps with local field conditions, and 3) make use of the diapausing bioagents that may be dormant in the samples. To further facilitate rapid establishment of T. julis, a "conservation strip" strategy was initiated in 2001. The main purpose of this strategy is to reduce mortality of over-wintering T. julis caused by routine farm management practices. The conservation strips were defined as a 1-meter wide strip along the edge of a field, running parallel with the crop row. Each conservation strip was located in heavily infested areas of the farm, adjacent to winter and spring grains, and grass varieties. Shipments of parasitized CLB larvae were opened on site and releases were concentrated in these managed areas.

Pre-release Monitoring
A "pre-release" study was conducted to monitor for naturally occurring larval parasitoids and to evaluate the success of the previous years biocontrol release. In June, prior to any 2001 bioagent releases, the WSDA and WSU personnel conducted a pre-release survey at the Nine Mile Falls field insectary by collecting CLB larvae from three winter wheat fields. Collected larvae were stored in 20% ethyl alcohol at 45°F for 1 week. Most larvae were sent directly to the USDA-APHIS-PPQ Niles Biological Control Laboratory (NBCL) for dissection and examination. Dissection techniques were also applied to screen for the presence of larval parasitic wasp larvae. A number of dissections were also completed by the WSDA.

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