Diaparsis carinifer was reported to be established in the US in 1970, at the Kellogg Biological Station in Michigan (Stehr and Haynes 1972). The authors described variation in colors of D. carinifer related to collection location in Europe, and later work showed there was another species, Diaparsis temporalis, was present in some locations in Europe and it was this species which had become established in North America (Miller 1977, Horstmann 1979).

Stehr and Haynes (1972) provided a description of the conditions for the release and establishment of larval parasitoids and for subcolonization of the parasitoids in other locations. They set as the primary conditions that there be no possibility the field would be sprayed, cereal leaf beetle larvae should be abundant (about 10/ft2 in oats), and the soil should not be disturbed until after emergence of the parasitoids the following spring. Additionally, at the insectary site, oats were planted at 2 to 4 week intervals to provide succulent growth for oviposition over a long period. Subcolonization was accomplished by hand-cutting grain after larvae had been parasitized and transporting the cut stems to the release field. Larvae then finished feeding on grain or grasses in the field border and pupated in the soil. It was felt that D. carinifer (temporalis?) was more active than T. julis, and would disperse from release sites more readily.

Lemophagus curtus was the last European larval parasitoid to become established in North America (Stehr et al. 1974). Little has been written about its population dynamics in the New World, perhaps because it was the last to become established, and studies of cereal leaf beetle and its parasitoids had concluded. During European collections, L. curtus was found in 11 European countries from Sweden to Italy and Yugoslavia, but never south of the Pyrenees in western Europe (Dysart et al. 1973). It was rarely the dominant species, and most often occurred at high host densities. This species is multivoltine with a facultative diapause (Dysart et al., 1973, Stehr et al. 1974). Those individuals which emerged in the summer did so when few CLB larvae were present, and Stehr et al. (1974) predicted that unless the parasitoid had exceptional searching abilities or an alternate host, summer emergence would be selected against. Additional larval parasitoids were collected in Europe in low numbers, but were not released in North America (Dysart et al. 1973).

Haynes (1973) discussed the species interaction and population management potential of the parasitoids which had become established in Michigan and surrounding states. Anaphes flavipes has excellent powers of dispersal and high reproductive potential, but because it is poorly synchronized with its host, and Haynes speculated that this species would have little direct influence on CLB. Because it is most numerous late in the season, Anaphes competes with T. julis for late CLB. Haynes predicted that with 2 generations per year, high reproductive potential, poor powers of dispersal, and better synchronization with the host, T. julis would play a major role in managing CLB. The author noted that a parasite with poor powers of dispersal can be protected, moved, managed and provisioned to overcome some inefficiency. Over 80% of the host population is present when either the first or second generation of T. julis. The impact of the newly established Diaparsis carinifer was uncertain. It appeared to be poorly synchronized with its host in Michigan, appearing late in the CLB life cycle with a low reproductive rate and intermediate powers of dispersal. In contrast, Miller (1977) showed that D. temporalis is well synchronized with the host. The difference may be attributed to the confusion of the two species; they occur together in some European locations, and were probably both released. It would appear, however, that only D. temporalis became established (Miller 1977). The specimens that were recovered in North America had dark abdomens, a characteristic of D. temporalis (Miller 1977).

As the cereal leaf beetle spread south and east from its original introduction in Michigan, surveys were conducted jointly by the USDA and NCDA in NC, and the first collections of CLB in the state occurred in 1977, in 19 counties, primarily along the Virginia border. The early cereal leaf beetle program in NC was aggressive, and its objectives were to map the spread of the pest, monitor population densities, locate potential parasitoid release sites, and to collect information on the life history of CLB in NC. Surveys continued in 40 counties in 1978, and when fields were found with adequate CLB egg densities, Anaphes flavipes, the egg parasitoid, was released in Stokes and Person Counties, both on the Virginia border. Surveys were conducted annually, and in 1980 a strategy was devised to use alternating survey methods. In 1980 and even years following, the objective of the surveys was to monitor changes in population density in infested areas and to select areas with adequate CLB egg and larva densities for parasitoid release. In odd years, the objective of survey activity was to monitor spread of the pest to new counties.

Additional A. flavipes (2 counties) were released in 1979 along with T. julis (10 counties) and D. temporalis (11 counties). A. flavipes was released annually in North Carolina from 1978 to 1981; approximately 66,000 were released in 9 counties, mostly in the central piedmont region. The release material was collected from various locations in the United States and reared at the Niles Biological Control Lab. This parasitoid species has become established in NC, and has apparently dispersed from release sites. It has been collected in at least 4 counties where it was not released (NCDA records).

The first recoveries of larval parasitoids (T. julis) occurred in 1979 in Stokes, Rockingham, and Wilkes Counties. Releases continued, and by 1982, all four species, A. flavipes, T. julis, D. temporalis, and L. curtus had been recovered in NC.

By the end of the CLB season in 1982, large numbers of parasitoids had been released in Northern Piedmont counties. Gladstone (1985a) reported that between 1978 and 1982, 66,860 Anaphes flavipes, 721 Lemophagus curtus, 2469 Tetrastichus julis , and 2473 Diaparsis temporalis had been released. In addition to survey and release work, an insectary was established at the Oxford Tobacco Research Station in 1983. The insectary was designed according to USDA guidelines and consisted of winter wheat followed by two plantings of spring oats. Larvae parasitized with T. julis were obtained from the Virginia Department of Agriculture and Commerce for release in the insectary in 1983 and 1984, and some parasitized by L. curtus were collected in Rockbridge Co., VA, and released in 1984 (Gladstone 1985a). The population density of CLB at the Oxford insectary was low, but considered typical of populations in that region of the state. The low density was attributed to parasitism by A. flavipes (18-20% in mid-May) and predation by coccinellids on eggs and small larvae (Gladstone 1985b). Parasitized larvae for release in Rowan and Davie Counties were obtained from Virginia.The Oxford insectary was discontinued in 1985 due to low CLB populations.

Cereal leaf beetle had spread through most of the grain growing regions of the state by 1984, but densities in fields statewide remained below the threshold of 40 larvae per square foot (Gladstone 1985a). The maximum density recorded that year was 5.3 larvae/sq ft. in an oat field in Guilford County. Highest populations were found in the western piedmont counties of Forsyth, Rockingham, Guilford and Alamance. The larval parasitoid Tetrastichus julis had become established in the Piedmont; it was found in 46% of the fields surveyed (8 counties), the highest occurrence to date. It should be noted that T. julis was not found in four counties where it had previously been collected.

Cereal leaf beetle continued to spread in the state, and T. julis appeared to spread along with it. Two new counties were found positive for CLB in 1986, Hoke and Lincoln, and in 1987, a collection in Onslow County brought the total infested counties to 80, representing most of the small grain producing counties in the state (Godfrey 1986, Godfrey and Keeley 1987, Watson 1987). The highest populations were found in the northern and central piedmont region. Tetrastichus julis was collected from 19.3% of fields sampled in 1986, and it was recorded from 5 new counties that year; no parasitoids had been released in any of these counties (Godfrey 1986).

A large insectary was initiated at the Piedmont Research Station in 1987, as that region of the state remained the most heavily infested with cereal leaf beetle (Godfrey 1986). Parasitized larvae were collected in Virginia for introduction to the Piedmont insectary; 1800 and 44,000 parasitized larvae were introduced in 1988 and 1989, respectively. Larvae from the insectary were dissected on 31 May 1989, and 100% were determined to be parasitized. Subsequently, collections were made from the insectary, and parasitized larvae were distributed to 14 growers in 3 counties (Keeley 1989). Collections of larvae continued through 1992, but numbers of CLB were declining in the insectary, despite annual introductions of adult CLB. Another insectary was started at a new site on the station, but large numbers of parasitoids were not available for "seeding".

USDA-APHIS/PPQ, through the Niles Biological Control Lab, renewed its involvement with cereal leaf beetle biological control in late 1992. Work at the federal level had concluded in 1978, but the continued spread of CLB throughout the south and to the western states of Montana and Utah prompted additional work on the pest. Parasitized eggs and larvae were collected in Europe, and A. flavipes was collected from several locations in the US for rearing in the lab at Niles. Insectaries to rear larval parasitoids were established in North Carolina, as well as in Utah and Montana. In North Carolina, the existing insectaries at the Piedmont Research Station near Salisbury and the Tidewater Research Station near Plymouth in the coastal plain were utilized for this cooperative work. The Tidewater insectary was in its beginning phase and contained no larval parasitoids, but the Piedmont station had an established population of T .julis.

Cereal leaf beetle and its parasitoids were monitored in the insectaries using standardized methodology. The Piedmont insectary consists of two plots, divided into subplots of fall wheat and three or more sequential plantings of spring oats. The Tidewater insectary consists of four plots, with two planted and two fallow. Plots are divided into subplots of fall wheat and spring oats (wheat was used 1993-1996). The presence of adult CLB in the wheat subplots was assessed with a sweepnet early in the spring, at 5 to 10 day intervals. After sweeping, a visual survey of at least 5 minutes was performed to detect eggs and larvae. If eggs were found, square foot counts were taken. Eggs and larvae were counted on all plants in 20.5 in. of row, at 3 locations spread across each subplot. Counts were totalled and recorded as number of eggs or larvae/ft2. The protocol from Niles required samples from the spring plantings only, although data were taken in the fall wheat plantings in some years. Samples of eggs and larvae for the determination of parasitism were collected after the first larvae were found. The protocol specified that 100 eggs and larvae be collected in each subplot. If either stage was scarce, we allotted 15 minutes for searching in each subplot per stage.

To determine if eggs or larvae had been parasitized, samples were returned to the lab. Larvae were placed in 20% ETOH and dissected by K.R. Ahlstrom of NCDA or sent to the laboratory at Niles for dissection. Eggs were placed on glass cover slips in a small petri dish lined with filter paper. These were held at room temperature and monitored for emergence of A. flavipes or other egg parasitoids.

Larval parasitoids were introduced into the insectaries in two ways. Cereal leaf beetle larvae parasitized with three species of larval parasitoids were shipped from Michigan to NC in 1994 for release at the Tidewater insectary. In 1995, adult Diaparsis sp. and T. julis were released in this insectary, but to date, none have been recovered. Adults of Diaparsis sp. and T. julis were released at the Piedmont insectary in 1996 to supplement the existing T. julis population. In addition to the larval parasitoids, approximately 17,000 A. flavipes were released in 5 counties in 1995. The insects had been collected in France, Greece and the US and reared at the Niles laboratory (NCDA lab records).

Work is continuing on this project. We currently have insectaries at Oxford, Tidewater and Piedmont Research Stations, and we are working with growers to monitor the parasitoids at release sites. This control method is best suited for no-till crops; as this cultural practice gains acceptance, we may see more success in establishing the larval parasitoids.

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A foreign exploration trip was made 13-30 May with the objective of collecting larval parasitoids of Oulema melanopus, the cereal leaf beetle. Using established methods, I collected larvae during the period of 15-28 May, and allowed them to pupate in the laboratory (Gruber, F., E. Rivet, and C. Prieto. 1972. A technique for obtaining cells of a soil-pupating insect, Oulema melanopus. J. Econ. Entomol. 65:904-906).Collections were initiated on 14 May, by visiting fields near the European Biological Control Laboratory (EBCL) near Montferrier, France. The area had been experiencing a drought, grain crops were small, and CLB populations low. The collection strategy which was recommended by personnel of the EBCL was to examine fields, and collect as many larvae as possible. On 20 May, large collections were not attempted because it was raining; instead, fields were screened, and small samples of 25 larvae were collected in fields with a population of CLB. Larvae were dissected in the laboratory, and ichneumonid parasitoids were found. Results: 17.8% parasitized larvae in one sample, 20.8% in the other. During the next 2 days, I concentrated on these and nearby fields for collections. This latter technique seems more suitable for future collections: make a large circuit to find candidate fields, sample, dissect, then collect as many as possible from specific fields, instead of merely collecting large numbers of larvae. Approximately 2400 CLB larvae were collected, and I also obtained about 6000 which had been collected by USDA personnel near Thessaloniki, Greece. Both collections were placed upon arrival in the NCDA quarantine facility. Adult CLB and other insects were collected as they emerged, and identified by K.R. Ahlstrom of NCDA. Voucher specimens were placed in the departmental collection. The remaining pupal cells were stored at approximately 2°C in an incubator in the quarantine facility for the fall and winter. In early April, the temperature was raised to 26°C. Parasitoids began emerging within 13 days. Total emergence for the summer (1997) and spring (1998) is reported below.

On 29 May, Alan Kirk, EBCL took me to collect ash whitefly natural enemies at the USDA greenhouse at LaValette, a botanical institute near the Agropolis. Encarsia inaron and Clithostetus (Coccinellidae) were present on leaves. I removed as many insects that were not AWF or Encarsia as possible in the lab. The remainder were shipped to the NCDA quarantine facility, but due to the unavailability of AWF at the time, the colony did not become established.

Cereal Leaf Beetle Collections, France and Greece, 1997-1998

*An additional 16 Tetrastichus sp. and 62 Diaparsis temporalis emerged from both boxes (1998). Other insects: 245 dipterans, 234 in Fam. Anthomyiidae, 10 hymenopterans in 5 families.