First report of redbacked cutworm damage to cow cockle [Vaccaria hispanica (Mill.) Rauschert], a potential new crop for western Canada

Willenborg, C. J. and Dosdall, L. M. 2011. First report of redbacked cutworm damage to cow cockle [ Vaccaria hispanica(Mill.) Rauschert], a potential new crop for western Canada. Can. J. Plant Sci. 91: 425–428. We report the effects of redbacked cutworm Euxoa ochrogaster (Guenée) on cow cockle [Vaccaria hispanica (Mill.) Rauschert] plant height, seed yield, and 1000-seed weight (TSW). Euxoa ochrogaster damage to plots varied considerably among genotypes, with some genotypes exhibiting <10% damage and others >45%. Seed yield also varied significantly among genotypes and exhibited a strong linear relationship with the extent of E. ochrogaster damage. This is the first known report of any insect pest feeding on cow cockle. Results suggest that E. ochrogaster has the potential to cause significant losses in cow cockle crops.

Moths trapped in Alaska with feeding attractant lures and the seasonal flight patterns of potential agricultural pests

Traps baited with two types of chemical feeding attractants yielded 97 species of macrolepidoptera at three areas in Alaska (Fairbanks, Delta Junction, and Palmer). These were 16 geometrid, 1 thyatirid, and 76 noctuid moth species and 4 species of nymphalid butterflies. Potential crop pests trapped included Apamea devastator (Brace) (glassy cutworm), Xestia c-nigrum L. (spotted cutworm), Xestia smithii (Snellen) (Smith's dart), Euxoa ochrogaster (Guenée) (redbacked cutworm), and Discestra trifolii (Hufnagel) (clover cutworm). The clover cutworm was captured early in the season (May into June), while Smith's dart, glassy cutworm, spotted cutworm, and redbacked cutworm were captured in traps in mid to late summer. Many more species and greater numbers of moths were captured in traps baited with acetic acid and 3-methyl-1-butanol than in traps baited with a multicomponent floral lure (phenylacetaldehyde, methyl salicylate, methyl-2-methoxy benzoate, and β-myrcene). However, most of the geometrid moths captured (12 of 16 species) were in floral lure traps, while one species of Hadeninae (Noctuidae) and both species of Plusiinae (Noctuidae) were trapped exclusively in floral lure traps. The one thyatirid, both Catocalinae noctuid species, and most Amphipyrinae, Cuculliinae, Hadeninae, and Noctuinae noctuid species were captured in traps baited with acetic acid and 3-methyl-1-butanol. In addition, large numbers of bumblebees were captured in traps baited with the floral lure, while large numbers of yellowjackets were captured in traps baited with acetic acid and 3-methyl-1-butanol.

PHENOLOGY AND REPRODUCTIVE STATUS OF ADULT REDBACKED CUTWORMS, EUXOA OCHROGASTER (GUENÉE) (LEPIDOPTERA: NOCTUIDAE), IN SOUTHERN MANITOBA

The phenology and reproductive status of adults of the redbacked cutworm, Euxoa ochrogaster (Guenée), were determined from blacklight (BLT) and sex-attractant (SAT) trap catches at four locations in southern Manitoba in 1987 through 1989. The flight period was of 9–12 weeks duration, extending from late June to early October. The first male and female moths were captured at about the same time in the BLT and SAT. The peak catches of the BLT occurred during the first 3 weeks of August (weeks 5 and 6 of the flight period) and those of the SAT about 1 week later. The SAT continued to capture male moths for 2–3 weeks after the last moths appeared in the BLT. Most females captured during the first 2–3 weeks of the flight period were virgins who had not yet initiated egg development. Most mating, egg development, and oviposition took place during a 3- to 4-week period that included the 2 weeks before, the same week as, and the week after the peak BLT catches (weeks 3–7 of the flight period); these activities occurred in the 3–4 weeks before the peak SAT catches. The data suggested that there was competition between SAT and females in attracting males and, consequently, the SAT catch data may not be providing accurate measurements of the sizes of breeding populations of males in the field. The BLT catches underestimated the length of the flight period by about 1.5–3 weeks.

EFFECTIVENESS OF STEINERNEMATID AND HETERORHABDITID NEMATODES AGAINST NOCTUID, PYRALID, AND GEOMETRID SPECIES IN SOIL

Larvae of one pyralid, five noctuid, and one geometrid species were exposed to six species/strains of steinernematid and two species of heterorhabditid nematodes applied to soil surface in the laboratory. The most parasitic nematodes were Steinernema bibionis Bovien for the wax moth (Galleria mellonella L.) and the bertha armyworm (Mamestra configurata Wlk.), Heterorhabditis heliothidis (Khan, Brooks, and Hirschmann) for the cereal armyworm [Pseudaletia unipuncta (Haw)], S. feltiae Filipjev Mexican for the variegated cutworm [Peridroma saucia (Hbn.)], and S. feltiae All for the red-backed cutworm [Euxoa ochrogaster (Gwen)] and the spring cankerworm [Paleacrita vernata (Peck.)]. When both LD50 values and rates of parasitism of the hosts were considered together, the most promising nematode for soil applications was S. feltiae against the bertha armyworm.

VIRULENCE OF ENTOMOPATHOGENIC NEMATODE–BACTERIA COMPLEXES FOR LARVAE OF NOCTUIDS, A GEOMETRID, AND A PYRALID

Nine entomopathogenic nematode–bacteria complexes were screened for their virulence against larvae of six noctuids, a geometrid, and a pyralid. Ninety-six-hour LD50’s of steinernematids (and heterorhabditids) ranged from 1 to 3 (1–8) infective juveniles in Galleria mellonella (L.), 1–71 (2) in Peridroma soucia (Hbn.), 1–10 (1–3) in Mamestra configurata (Wlk.), 1–28 (3–7) in Euxoa ochrogaster (Gn.), 19 in Lacanobia radix (Wlk.), 22–60 (4) in Pseudaletia unipuncta (Haw.), 2–95 (111) in Agrotis ipsilon (Hufn.), and 3–28 in Paleacrita vernata (Peck). The nematode, Steinernema feltiae LIC, a cold-hardy strain isolated in Newfoundland, was highly virulent for G. mellonella and M. configurata, but not for P. soucia and E. ochrogaster. The number of nematodes invading larvae and the number produced were greater in G. mellonella than in other insects tested. Nematode–bacteria complexes that showed potential for controlling cutworms included S. feltiae, S. glaseri, S. bibionis, Heterorhabditis bacteriophora, and H. heliothidis.

THE RESPONSE OF FLAX TO DIFFERENT POPULATION DENSITIES OF THE RED-BACKED CUTWORM, EUXOA OCHROGASTER (GN.) (LEPIDOPTERA: NOCTUIDAE)

Controlled field studies carried out in plots within a field of NorMan flax, Linum usitatissum L., showed that the loss of flax plants caused by the red-backed cutworm was proportional to the number of cutworm larvae present. A density of 16 larvae per 0.5 m2 destroyed most plants by severing the plant stems at the soil surface. The loss of only some plants at larval densities lower than 16 larvae per 0.5 m2 resulted in a small but significant increase in per plant yield but the increase did not completely compensate for the yield reductions caused by plant loss. The larvae removed plants in blocks with the result that the density of the remaining plants was unchanged and the opportunity for compensating plant growth was limited. An equation defining this relationship between larval densities and yield is presented. Ancillary experiments in which the population of cutworm larvae was sequentially sampled showed that, after an initial loss of about 20% when the plots were established in the field, the larval population remained constant. The proportion of the larvae found around damaged plants also remained constant until the larvae became immobile through preparation for pupation. Because of this stable relationship, reliable estimates of potential crop loss from cutworm larvae in flax should be possible by sampling for cutworms only around damaged plants within a specified row length.

MONITORING POPULATION LEVELS OF EIGHT SPECIES OF NOCTUIDS WITH SEX-ATTRACTANT TRAPS IN SOUTHERN ALBERTA, 1978–1983: SPECIFICITY OF ATTRACTANTS AND EFFECT OF TARGET SPECIES ABUNDANCE

The abundances of eight species of cutworm and armyworm moths were monitored with sex-attractant traps at 81 locations in a 13 000-km2 area of southern Alberta from 1978 to 1983. The life history and economic status of each species is summarized and the monitoring methodology is described. The attractants for redbacked cutworm (Euxoa ochrogaster), darksided cutworm (Euxoa messoria), pale western cutworm (Agrotis orthogonia), and army cutworm (Euxoa auxiliaris) were highly specific and > 99% of the moths caught were of the target species. Specificity of the attractants for clover cutworm (Discestra trifolii) and Leucania commoides was also high, averaging 98.3 and 96.6%, respectively, over 6 years. The attractants for variegated cutworm (Peridroma soucia) and bertha armyworm (Mamestra configurata) were less specific but the proportion of target species exceeded 80% in those years when either species was relatively abundant. For those species that were monitored over a wide range of population levels, the apparent specificity of the attractant varied directly with the number of target species moths caught. The use of efficient attractants in combination with high-capacity nonsaturating traps is clearly of advantage in enhancing specificity.