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The efficacy of insecticides is often assessed in small-plot field trials that compare insect damage and yield loss relative to an untreated check, typically in a randomized complete block (RCB) design. When insect damage is not uniformly distributed across a field, differences among treatments might reflect differences in local pest pressure rather than differences in treatment efficacy. One potential way to account for patchy distributions is to use a “running check” in which each plot contains an insecticide treatment and its own untreated check. Any benefits of this approach must be weighed against the additional labor involved. Wireworms (Coleoptera: Elateridae) are soil-dwelling insects that typically exhibit patchy distributions that can confound insecticide efficacy trials. Several species of wireworms feed on potato tubers, causing damage that makes the tubers unmarketable and, aside from crop rotation, insecticides remain a cornerstone of wireworm management in potato. The current investigation evaluated insecticide efficacy trials targeting wireworms in potato by comparing two different analyses for the same data sets spanning five years and seven different studies. Data collected using the running check approach were analyzed using analysis of covariance and compared with analysis of variance as if the experiment were designed as a RCB. In a majority of cases, both methods resulted in similar levels of statistical power and similar conclusions; however, including data from the running check as a covariate did sometimes eliminate or reveal differences between treatments compared to ANOVA. Overall, given the similarity of the results and the additional labor involved in using running checks, the standard RCB design would have been appropriate for the experiments assessed here. However, for wireworms and other pests that exhibit patchy distributions, care must be taken when designing experiments and interpreting results.

The polyphagous larvae of click beetles (Coleoptera: Elateridae) are major pests of spring wheat in Montana, USA. Presently available insecticides are unable to provide control over wireworm populations, and the use of natural enemies has not been successful under field conditions. In this study, we examined the effect of seven trap crops: pea, lentil, canola, corn, durum, barley, and wheat, for their attractiveness to wireworms compared to spring wheat. Experimental plots were located in two commercial grain fields in Valier and Ledger, Montana, USA and the trials took place from May to August in 2015 and 2016. Wheat plants damaged by wireworms were recorded and their relative locations in wheat rows and adjacent trap crop rows within a plot were determined using destructive soil samples. In 2016, variable row spacing (0.25, 0.5, 0.75, and 1 m) between the trap crops (pea and lentil) and wheat was assessed. Shade house bioassays were conducted using potted pea, lentil, and wheat plants to support field trial results. Limonius californicus larvae, released at the center of each pot were sampled 4 and 10 days after sowing. Wheat intercropped with pea and lentil had significantly fewer damaged wheat plants. Wireworm numbers were lower in wheat intercropped with pea compared to the control for both locations and years. Shade house results corresponded with field results, with more wireworms collected from pea and lentil than wheat. In the spacing trials, wheat plant counts were also significantly higher when paired with pea and lentil, particularly at 0.5 m spacing. Regardless of inter-row spacing, significantly fewer wireworms were associated with wheat when intercropped with pea and lentil trap crops.

Wireworms, the larval stage of click beetles (Coleoptera: Elateridae), are economically important soil-dwelling pests that attack many field crops worldwide. Wireworms have become a serious threat to spring wheat in the Northern Great Plains because of lack of effective control measures, creating a need for alternative control methods such as biological control with entomopathogenic nematodes (EPNs). A laboratory bioassay was used to test ten EPN strains and identify infective EPN strains against the sugarbeet wireworm, Limonius californicus (Mannerheim) (Coleoptera: Elateridae). Steinernema carpocapsae (Weiser) (All and Cxrd strains) and S. riobrave Cabanillas, Poinar, and Raulston (355 and 7–12 strains) killed 60–70% of L. californicus larvae in four weeks when applied at 700 Infective juveniles (IJs) (25 IJs/cm2), 1400 IJs (50 IJs/cm2), 2800 IJs (100 IJs/cm2), and 5600 IJs (200 IJs/cm2) per larva in the laboratory. Also, Heterorhabditis bacteriophora (Poinar) VS strain and Steinernema rarum (Doucet) 17c + e strain caused 50–60% mortality to L. californicus larvae after four weeks when applied at 5600 IJs/larva. However, regardless of the concentration applied, the penetration rate of infective juveniles into the host did not exceed 33%. In shade house trials, S. riobrave and S. carpocapsae strains caused 34–56% L. californicus mortality after four weeks with 50 and 56% mortality caused by S. carpocapsae All and S. riobrave 355 strain, respectively when applied at the rate of 80,000 IJs/pot. These results suggest that S. carpocapsae and S. riobrave may have significant potential for protecting spring wheat crops from L. californicus.

Wireworms are an increasing threat to the sustainable production of cereal, potato and other crops in Montana since the delisting of lindane, an effective and inexpensive insecticidal seed treatment. With this study, we have initiated long term research to investigate the diversity of wireworm species infesting Montana's cropland. Canister-type bait traps were mailed to collaborating producers who buried them in established cereal fields for 10–14 days, and then returned them to Montana State University where the wireworms were identified to species. A total of 61 cereal fields in 12 counties were surveyed during 2011; 67 fields in 24 counties during 2012; and 66 fields in 16 counties during 2013. Wireworms were caught in 36.8% (46/125) of cereal fields with no prior known history of wireworms, averaging 0.5 larvae per trap. Wireworms were caught in 62.7% (37/59) of fields with a reported history of wireworms, averaging 4.1 larvae per trap. The prairie grain wireworm, Selatosomus aeripennis (Kir...

The basic principles of a reliable integrated pest management program include pest identification, monitoring, and distribution. Selecting the appropriate sampling protocol to monitor wireworm for research or applied entomology depends on the objective, including simply detecting the presence or absence of wireworm, surveying the composition of wireworm assemblages, or estimating spatial and temporal population densities. In this study, the efficacy of pitfall, stocking, pot, and canister traps baited with wheat and barley mixtures was evaluated for monitoring wireworm populations in four commercial cereal fields in Montana. Pitfall and stocking traps collected greater numbers of wireworm (1625 and 1575, respectively) followed by pot-type and canister-type traps (1173 and 725, respectively). The 5098 wireworm collected from four sites included seven species: Aeolus mellillus, Agriotes sp, Dalopius sp, Hypnoidus bicolor, Limonius californicus, Limonius infuscatus, and S. aeripennis.

The orientation response after selective bilateral amputation of the antennae, maxillary palps and labial palps was used to determine the location of the CO2-receptive sensilla of larval Agriotes lineatus-obscurus (L.) and Limonius californicus (Mannerheim). The maxillary palps appear to be the most important for CO2 perception followed by the labial palps. The antennae did not appear to be involved in the orientation response. The CO2-receptive sensilla are likely among the cluster of sensilla at the tip of each palp. Scanning electron microscopy showed that there are more than twice the number of sensilla on the tip of the maxillary palp than on the tip of the labial palp of L. californicus larvae. The possible involvement of some of these sensilla in CO2 perception is discussed.

In adult virgin females of the sugar beet wireworm, Limonius californicus (Mannerheim), the sex attractant (recently identified as valeric acid) is found primarily in the fifth and sixth abdominal segments. Ether extracts of virgin females and of females that had been mated for not more than 4 hours prior to death contained the highest concentration of the attractant. The concentration of attractant in mated females decreased as the post-copulatory interval increased. In the laboratory maximum sexual response was elicited from males exposed to as little as 0.008 female equivalent of attractant. Numerous thin-walled sensoria are present on the eight distal segments of the male antennae and apparently function as chemoreceptors. Response of males to the attractant was not affected by bilateral amputation of the five distal segments, decreased progressively with the amputation of segments 6 and 7, and was eliminated upon removal of segment 8. Males of L. californicus responded only to extracts of females of that species whereas males of Limonius canus (LeConte) responded to extracts of females of both species.

Granular fonofos, and granular AC 92100 [ O, O -diethyl S-( t -butylthio) methyl phosphorodithioate], each at 2 lb AI acre in-furrow, gave excellent protection of potatoes against wireworms in irrigated soils of southern Alberta. Fonofos was particularly effective over 2 consecutive years and provided better control than registered chlordane or carbofuran in-furrow broadcast. Chlordane and carbofuran were not significantly better than the checks in several tests, and HCS-3260 (alpha gamma chlordane) was no more consistent in its protection of potatoes than was chlordane. Fensulfothion, ( O, O -diethyl O-p -[(methylsulfinyl)phenyl] phosphorothioate), applied in-furrow or broadcast, gave variable tuber protection but appeared to be slightly better than chlordane or carbofuran. Fonofos, AC 92100, fensulfothion, and PP211 [ O, O -diethyl O -(2-diethyl-amino-4-methyl-6-pyrimidinyl) phosphorothioate] were as effective against the sugarbeet wireworm, Limonius californicus (Mannerheim), as against the prairie grain wireworm, Ctenicera aeripennis destructor (Brown).

Investigations on effect of method of application and placement of fonofos on its efficacy as a chemical control for wireworms, mainly Limonius californicus (Manner-heim), in Irish potatoes in Idaho were conducted at the Research & Extension Center, Aberdeen, for 3 years. Application methods used were broadcast, band-over, in furrow, and sidedress. Two areas of placement of sidedress treatments also were used: 50 mm to each side of the seed piece and at the same level; and 50 mm to each side and 50 mm above the seed piece. Significant differences in wireworm damage to potatoes due to different methods of application were noted in 2 of the 3 years. Furrow treatments resulted in less wireworm damage to tubers than any other method, with sidedress treatment giving control equal to or better than broadcast. Sidedress level with the seed piece resulted in significantly better results than sidedress 50 mm above in one of the years.

The sex attractant produced by adult females of the sugar beet wire-worm, Limonius californicus (Mannerheim) has been isolated and identified as valeric acid. In the laboratory, male wireworm beetles are repelled by the pure attractant but are drawn with intense sexual excitement to its dilute solutions; in the field, male beetles are lured from a distance of 12 meters. The pheromone occurs in unusually large amounts in the female's body.

In the course of recent field studies in southern Alberta on the behaviour of adults of the sugar-beet wireworm, Limonius californicus (Mann.), it has been observed that the males spend much of their time after emergence resting on small clods of earth with their heads pointed upward into the breeze and with their antennae waving as though testing for odours. When they appeared to scent a female they moved into the breeze, crawling or flying, depending on the velocity of the wind. As they neared the female they became increasingly agitated, but when in close proximity to her they seemed confused and often passed within an inchof her. Eventually one of them located her and mating occurred almost immediately. The remaining males finally dispersed after crawling repeatedly around and over the copulating pair. These observations suggested that the females, soon aftcr emerging, release a sex attractant.