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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 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.

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.