Effects of sterilized flax seed and sterilized soil on feeding behaviour and growth of larvae of Ctenicera aeripennis aeripennis (Kby.) (Coleoptera: Elateridae)

Medium sized (average 43.1 mg) and large (average 110.6 mg) wireworm larvae (Ctenicera aeripennis aeripennis) were reared in sterilized or unsterilized soil, with sterilized or unsterilized flax seed supplied as food. Sterilized flax was a better food than unsterilized flax, but unsterilized soil improved the results obtained with unsterilized flax.

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Sommaire Dans un effort de détérminer les différences biologiques entre le taupin des graminées, Ctenicera aeripennis destructor (Brown), et celui de Puget Sound, Ctenicera aeripennis aeripennis (Kby), les effets sur les larves de ce dernier de la semence de lin et du sol sterilisés fut observés pendant 30 semaines. Contraire aux résultats obtenus avec les larves de C. a. destructor, le lin sterilisé autant que le lin non-sterilisé prouva attrayant et efficace pour la croissance aux larves de taille moyenne de C. a. aeripennis. Les larves de C. a. aeripennis de grosse taille ne différèrent de celles de C. a. destructor que par une plus grande augmentation de poids quand le lin sterilisé ou non-sterilisé fut présent en sol nonsterilisé. La survivance des larves de grandeur moyenne fut meilleure avec le lin sterilisé qu'avec le lin non-sterilisé tandis que celle des grosses larves ne fut pas influencée.Les résultats obtenus sans le lin avec les larves des deux espèces suggèrent que les microorganismes dans le sol ne sont probablement pas utilisés dans l'alimentation de ces espèces. Dans le cas des larves de C. a. aeripennis de grosse taille, il est fort probable que les microorganismes dans le sol rendent plus accessibles aux larves des facteurs alimentaires du lin, ce qui leur permet une croissance meilleure que d'ordinaire.Pourvues du lin, 25 p.c. des larves de grandeur moyenne mangèrent hebdomadairement. A peu près de 5 p.c. muèrent chaque semaine, même sans lin. Avec le lin non-sterilisé, 17 p.c. des larves survécurent dans le sol sterilisé, tandis que 55 p.c. survécurent en sol non-sterilisé. Avec le lin sterilisé, plus de 90 p.c. survécurent, et dans le sol non-sterilisé et dans le sol sterilisé. Pourvues du lin, les larves prirent du poids; sans lin, elles en perdirent.Avec le lin sterilisé dans le sol sterilisé, 31 p.c. des larves de grosse taille mangèrent chaque semaine et seulement 16 p.c. dans tout autre cas. A peu prés 4 p.c. muèrent chaque semaine. Seulement 37 p.c. des larves de cette taille survécurent dans le sol non-sterilisé avec le lin non-sterilisé, mais plus de 98 p.c. survécurent avec du lin sterilisé dans le même sol et plus de 65 p.c. dans le sol sterilisé pourvu de lin ou sans lin.

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Contribution No. 22, Canada Department of Agriculture Research Station, Saskatoon, Canada.     

The influence of soil moisture and some soil physical factors on the ovipositional behavior of the prairie grain wireworm, Ctenicera destructor

Soil moisture, texture, cracks and compaction all influenced the ovipositional behavior of Ctenicera destructor. In oviposition choice-chambers, most eggs were laid in soil with a range of moisture content about halfway between the field capacity and the permanent wilting percentage. In cylinders of soil, beetles usually burrowed to reach moist soil before ovipositing, but laid close to the surface, if the soil within 2 cm of the surface was moist and the underlying soil was dry. Soil cracks enhanced oviposition and increased the survival time of beetles in field cages. Beetles were unable to penetrate field soil unless a crack was present.Eggs laid under natural conditions were found under soil lumps in a cultivated field and under partially dried cow manure in pastures.

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Zusammenfassung Bodenfeuchtigkeit, Struktur, Verdichtung und Spalten beeinflußten das Eiablageverhalten von C. destructor. Bei Wahlkammer-Versuchen im Laboratorium reagierten die Käfer in einer Reihe von Bodenfeuchtigkeitsstufen etwa halbwegs zwischen dem permanenten Welke-Prozentsatz und der Feldkapazität. Die Tiefe der Eiablage wurde ebenfalls von der Bodenfeuchtigkeit beeinflußt. In Zylindern mit Bodenfüllung begannen die Käfer so lange nicht mit der Eiablage, bis sie in Berührung mit einer feuchten Bodenschicht kamen.Nahe der Bodenoberfläche erfolgten Eiablagen besonders dann, wenn die Bodenoberfläche feucht und der darunter liegende Boden trocken war.Die Tiefe der Eiablage im Boden wurde in Feldkäfigen von der Verdichtung und von Spalten beeinflußt. Die Lebensdauer der Weibchen und deshalb das Gesamtgelege waren um so größer die Tiefe der Spalten wurde, sowohl in gesiebten wie in ungestörten Feldböden.Unter natürlichen Bedingungen wurden ablegende Weibchen und Eigelege in einem Kulturfeld unter dem Schutz von Bodenklumpen und auf Weiden unter teilweise getrocknetem Kuhdung gefunden. Solche Art der Bodenbedeckung bietet sowohl Käfern wie Eiern Schutz und dürfte einen wichtigen Eiablageplatz im Freiland darstellen.

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Contribution No. 273, Canada Agriculture Research Station, Saskatoon, Saskatchewan     

Effects of variations in casein and dextrin content of a synthetic diet on larvae of Ctenicera aeripennis destructor (Brown) (Coleoptera: Elateridae)

Larvae reared aseptically on pellets of synthetic diet in which the ratio of casein to dextrin was varied over the full range, gained most weight in a two-month period when the ratio was either 20:80 or 70:30. When the ratio was varied by smaller amounts in the region of these concentrations, the larvae gained most weight in a narrow range of 21 to 23 parts casein and also in a broad range of 65 to 71 parts casein. This bimodal response may occur because deleterious effects of large quantities of casein or dextrin in the diet are counteracted by small quantities of the corresponding component.

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Sommaire Des larves du taupin des graminées, Ctenicera aeripennis destructor (Brown), ont été élevées individuellement et aseptiquement sur des régimes synthétiques dans des éprouvettes pourvues de coton humide. D'une part, les régimes variaient de l'un à l'autre par une augmentation de 10 parties de caséine depuis 0 jusqu'à 100, pendant que la dextrine diminuait également par 10 parties depuis 100 jusqu'à 0. D'autre part, elles augmentaient de deux parties de caséine, à partir de 15 jusqu'à 25 parties et de 65 jusqu'à 75, pendant que la concentration de dextrine diminuait également de 85 jusqu'à 75 parties et de 35 jusqu'à 25 parties. Ces régimes étaient donnés sous forme de boulette sur le coton.Les larves étaient pesées à 0.1 mg près au commencement des essais et la différence entre les poids initial et final de chacune était exprimée en quantités de milligrammes par milligramme de poids initial.Les larves ont également bien survécu avec tous les régimes. La meilleure augmentation pondérale était obtenue avec un régime contenant 21, 23, ou 67 parties de caséine. Ce dernier résultat n'était pas du tout surprenant. Il est probable que ni un manque complet ni une surabondance de protéine ou d'hydrates de carbone ne profite aux taupins. Si les petites quantités peuvent favoriser l'accroissment des larves, il est fortement probable que 20 parties de caséine soient suffisantes pour détruire n'importe quel effet défavorable d'un surcroît de dextrine (80 parties). De même, une teneur de 30 parties de dextrine pourrait donner assez de vigeur aux larves pour surmonter l'effet d'un niveau alimentaire de 70 parties de caséine. Aux autres concentrations, l'action de l'un est antagoniste de l'autre et probablement leurs effets réciproques s'annulent.

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Contribution No. 94, Canada Department of Agriculture Research Station, Saskatoon, Sask.     

Food habits of pasture wireworm,Conoderus exsul (Coleoptera: Elateridae)

Abstract

The food preferences and rates of growth of the omnivorous pasture wireworm, Conoderus exsul (Sharp) were studied. Larvae of soil-living insects were preferred to germinating maize seed, and wireworm growth rate was greater on insect compared with plant food. In glasshouse pot trials, wireworms increased their attack rate as the density of grass grub (Costelytra zealandica (White)) or white-fringed weevil (Graphthognathus leucoloma Boheman) larvae was increased. In field experiments that compared grass grub numbers in cages accessible to wireworms or protected from predators, predation varied with season from a low of 15% in late summer up to 82% in late autumn. White-fringed weevil larval mortality was increased by addition of wireworms in two field experiments, but not affected in a third trial where initial white-fringed weevil density was low. Grass grub mortality was increased by the presence of wireworms in field plots. Adult C. exsul were observed feeding on sweetcorn pollen.     

环境因子对沟金针虫呼吸代谢的影响

为了探讨沟金针虫Pleonomus canaliculatus对不同环境条件的适应性, 应用多通道昆虫呼吸仪测定了不同温度、O₂浓度、光照强度和湿度条件下沟金针虫的呼吸率。结果显示: 沟金针虫的呼吸模式为不规则波动型。温度和光照强度对沟金针虫的CO₂释放率影响突出, 不同处理间差异显著; 不同温度条件下, CO₂释放率最小和最大值分别为5℃时的7.22 μL/h和35℃时的180.74 μL/h, 两者间存在极显著差异（P<0.01）; 强光条件下的沟金针虫呼吸代谢强度大约是无光条件下的2倍（P<0.05）。不同的O₂浓度和空气相对湿度对沟金针虫的CO₂释放率无明显影响。同时确定了沟金针虫呼吸速率对温度的敏感性——Q₁₀值。结果表明沟金针虫在呼吸代谢过程中对温度和光照反应敏感, 对低氧和湿度环境的适应性较强。     

Influence of preceding crop on wireworm (Coleoptera: Elateridae) abundance in the coastal plain of North Carolina

Three studies were conducted to determine the effect of preceding crop on wireworm (Coleoptera: Elateridae) abundance in the coastal plain of North Carolina. In all three studies, samples of wireworm populations were taken from the soil by using oat, Avena sativa L., baits. Treatments were defined by the previous year's crop and were chosen to reflect common crop rotations in the region. Across all three studies, eight wireworm species were recovered from the baits: Conoderus amplicollis (Gyllenhal), Conoderus bellus (Say), Conoderus falli (Lane), Conoderus lividus (Degeer), Conoderus scissus (Schaeffer), Conoderus vespertinus (F.), Glyphonyx bimarginatus (Schaeffer), and Melanotus communis (Gyllenhal). The effect of corn, Zea mays L.; cotton, Gossypium hirsutum L.; fallow; soybean, Clycine max (L.) Merr.; sweet potato, Ipomoea batatas (L.) Lam.; and tobacco (Nicotiana spp.) was evaluated in a small-plot replicated study. M. communis was the most frequently collected species in the small-plot study and was found in significantly higher numbers following soybean and corn. The mean total number of wireworms per bait (all species) was highest following soybean. A second study conducted in late fall and early spring assessed the abundance of overwintering wireworm populations in commercial fields planted to corn, cotton, peanut (Arachis hypogaea L.), soybean, sweet potato, and tobacco in the most recent previous growing season. C. lividus was the most abundant species, and the mean total number of wireworms was highest following corn and soybean. A survey was conducted in commercial sweet potato in late spring and early summer in fields that had been planted to corn, cotton, cucurbit (Cucurbita pepo L.), peanut, soybean, sweet potato, or tobacco in the most recent previous growing season. C. vespertinus was the most abundant species, and the mean total number of wireworms per bait was highest following corn.     

Relative susceptibility of two sweetpotato varieties to storage root damage by sweetpotato flea beetle (Coleoptera: Chrysomelidae) and wireworm (Coleoptera: Elateridae)

The feeding of soil dwelling insects on storage roots is one of the most serious management issues faced by sweetpotato, Ipomoea batatas (L.) Lam. (Convolvulaceae), growers in the southern United States. Field studies were conducted to evaluate the relative susceptibility of two commonly grown sweetpotato varieties to sweetpotato flea beetle, Chaetocnema confinis Crotch (Coleoptera: Chrysomelidae), and wireworms (Coleoptera: Elateridae, various species). The incidence and severity of sweetpotato flea beetle damage was significantly lower in the variety Covington than Beauregard in two small plot replicated studies. Surveys conducted in commercial sweetpotato fields also showed significantly less sweetpotato flea beetle damage in fields planted to Covington compared with those planted to Beauregard. There was no clear evidence of varietal effect on the incidence of wireworm damage in the study. Results indicate that the severity of wireworm damage as measured by the size of feeding scars may be less in Covington than Beauregard.     

Mortality of a wireworm, Agriotes obscurus (Coleoptera: Elateridae), after topical application of various insecticides

Ten insecticides representing seven chemical groups were applied at various concentrations topically by using a Potter Spray Tower to evaluate their relative toxicities on the European wireworm Agriotes obscurus L. (Coleoptera: Elateridae). Wireworms were stored at 15 degrees C after exposure to organophosphate (OP) (chlorpyrifos, diazinon), pyrethroid (tefluthrin), thianicotinoid (thiamethoxam, clothianidin), chloronicotinoid (imidacloprid, acetamiprid), phenyl pyrazole (fipronil), organochlorine (lindane), and spinosyn (spinosad) insecticides, and their postapplication health was evaluated weekly for up to 301 d. LC50, LC90, LT50, and LT90 values were calculated for each chemical except acetamiprid, and compared with those of lindane, clothianidin, and chlorpyrifos. Wireworms exposed to OPs died or recovered more quickly (LT50 < 20 d, LT90 < 50 d), than those exposed to all other insecticides tested except tefluthrin (LT50 = 25.5 d, LT90 = 66.5 d). Wireworms exposed to sublethal concentrations of all neonicotinoids quickly became moribund after application but made a full recovery. Wireworms exposed to fipronil at concentrations near the LC90 value showed no intoxication symptoms for up to 35 d, and they did not recover after symptoms developed. For each chemical, increasing the concentration increased the time required for wireworms to recover but decreased the time required to kill wireworms. Fipronil was highly toxic to wireworms (LC50 = 0.0001%), but acetamiprid (LC50 = 1.82%), imidacloprid (LC50 = 0.83%), tefluthrin (LC50 = 0.23%), diazinon (LC50 = 0.54%), and spinosad (LC50 = 0.51%) were not. The toxicity of both clothianidin (LC50 = 0.07%) and thiamethoxam (LC50 = 0.17%) were similar to those oflindane (LC50 = 0.06%) and chlorpyrifos (LC50 = 0.10%).     

Microbial population of the digestive tract of click beetle larvae (Elateridae,Coleoptera)

The composition and functional structure of the intestinal microflora of three wireworm species (Agriotes obscurus (L.), Selatosomus aeneus (L.), and Ampedus pomorum (Herbst)) with different dietary regimes were studied. The total abundance of the microorganisms was evaluated by fluorescent microscopy, the group composition was assessed by inoculation on a solid glucose-peptone-yeast medium, and the functional diversity was estimated by multisubstrate testing. It was noted that, in the intestine of the larvae, the total number of microorganisms was lower by 1–2 orders of magnitude than in the soil and decaying wood. It was found that the composition of the intestinal microbial communities of wireworms was radically different from that of the substrate: the Bray-Curtis coefficient did not exceed 0.25. It was found that native forms accounted for more than half of the total number of saprotrophic bacteria: in the larvae, Gram-positive cocci, enterobacteria, Vibrionaceae, Acinetobacter, and some genera of coryneform bacteria, which were absent in the soil and wood, prevailed. The micromycetes were either absent (Agriotes) or were found in insignificant quantities (Selatosomus, Ampedus). In Selatosomus, apart from the intestinal forms, representatives of Mezorhizobium, Nocardioides, and Erwinia, occurring on plant substrates, were observed.     

Repellency of a wireworm, Agriotes obscurus (Coleoptera: Elateridae), on exposure to synthetic insecticides in a soil-less bioassay

A soil-less bioassay arena to test repellency of wireworms (A. obscurus) to insecticides and carrier solvents is described. The bioassay and variables measured distinguish between shorter-range (contact and/or volatile) and longer-range (volatile) repellency. Wireworm positions are recorded every 3 s for 20 min, and average speed, rate of slowing, and longer- and shorter-range repellent behaviors calculated. Shorter-range repellency is determined with a Wireworm Repellency Score (WRS, range 0-100), calculated before contact and after contact with test chemicals. Of two carrier solvents tested, wireworms were strongly repelled by acetone (WRS = 57) but not by water (WRS = 1) when introduced to the bioassay arenas immediately after chemical inoculation. When bioassay arenas were assembled/sealed 2 min after inoculation, acetone elicited no repellency (WRS = 2). When dissolved in acetone in bioassays assembled with a 2-min delay, imidacloprid, chlorpyrifos, lindane, and tefluthrin elicited slight to moderate repellency at the highest concentrations tested (WRS = 30, 48, 42, and 49, respectively). Both longer- and shorter-range repellency increased over the duration of the observation period for lindane and tefluthrin, and shorter-range repellency also increased over the duration of the observation period for chlorpyrifos. Removal of volatiles in the bioassay arena by vacuum considerably affected wireworm movement in the arena, with the repellency elicited by acetone and lindane being significantly reduced. Clothianidin elicited no longer- or shorter-range repellency.     

Serological identification of wireworm and staphylinid predators of the Australian soldier fly (Inopus rubriceps) and wireworm feeding on plant and animal food

Pasture wireworm, Conoderus exsul (Sharp) fed more on larvae of the Australian soldier fly (Inopus rubriceps (Macquart)) than on germinating wheat seed when given a choice in the laboratory. Conversely, Agrypnus variabilis (Candeze), another wireworm found in New Zealand pastures, fed more on wheat seed. As determined by a serological technique (immuno-osmophoresis), 19% of C. exsul larvae, 20% of A. variabilis larvae and 80% of the adults of a staphylinid, Thyreocephalus oxthodoxus, (Olliff) collected in a pasture, had fed on I. rubriceps larvae. A predation rate of 12 soldier fly larvae/m²/day was estimated for C. exsul larvae.

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Résumé Pour déterminer la valeur de Conoderus exsul Sharp comme prédateur d'Inopus rubriceps Macquart, ravageur des prairies en Nouvelle Zélande, cet élatéride a été sur nourri des végétaux et animaux. En 72 heures, il s'est alimenté plus abondamment sur I. rubriceps que sur grains de blé. Par contre, un autre élatéride des prairies, Agrypnus variabilis Candeze, a consommé plus de grains de blé que de I. rubriceps.Une technique sérologique, l'immuno-osmophorèse, a montré que 19% des larves de C. exsul, 20% de celles de A. variabilis et 80% des adultes du staphylin, Thyreocephalus orthodoxus Olliff récoltés dans la nature, avaient consommé des larves de I. rubriceps.En se basant sur la densité en Elatérides, sur le pourcentage de réactions positives, sur les taux de consommation quotidiens, et la période d'observation de proies dans le tube digestif des prédateurs, on peut estimer que 12 larves/m²/jour de I. rubriceps ont été détruites par les larves de C. exsul pendant les 7 semaines de la période utilisée.

     

Feeding behaviour of Epilachna vigintioctopunctata (Coleoptera: Coccinellidae) on Luffa aegyptiaca

Observations on adult Epilachna vigintioctopunctata Fabr. on Luffa aegyptiaca show that these insects prefer flowers in light and leaves and flowers in dark. Probably physical and chemical stimuli, originating from the flowers, guide beetles to them in light. In darkness the insects' comparatively greater preference to leaves and flowers suggests that the attractants and arrestants present in both these parts of the plant are mainly in the form of chemical stimuli bearing equal intensity. These insects prefer to feed on the corolla of the flower of L. aegyptiaca. This preference is affected by stimulants in these parts of the plant. The nature and characteristics of these stimuli are unknown.

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Comportement alimentaire d'Epilachna vigintioctopunctata (Coleoptera, coccinellidae) sur Luffa aegyptiaca

Résumé Cette étude expose les résultats d'observations sur l'orientation et sur le préférendum alimentaire de la coccinelle Epilachna vigintioctopunctata Fabr. à l'égard des diverses parties de sa plante hôte: Luffa aegyptiaca. Les expériences réalisées sont décrites et les données numériques obtenues ont été soumises au calcul statistique. Il a été établi que dans des conditions d'obscurité les insectes se portent en nombre presque égal sur les fleurs et sur les feuilles, alors qu'à la lumière, les fleurs sont nettement plus attractives. En ce qui concerne leur alimentation, les insectes préfèrent se nourrir aux dépens de la corolle de la fleur.Les divers facteurs, chimiques ou visuels, pouvant intervenir dans l'orientation de l'insecte et dans son comportement alimentaire, sont discutés.

     

Aggregation and mortality of Agriotes obscurus (Coleoptera: Elateridae) at insecticide-treated trap crops of wheat

Agriotes obscurus (L.) wireworms assembled in increasing numbers at rows of treated (Agrox DL Plus seed treatment) and untreated wheat, Triticum aestivum L., planted at increasing densities (0, 0.15, 0.30, and 0.60 seeds/cm). In treated wheat plots at all planting densities, no wireworm damage to seedlings was apparent, and total wireworms taken in core samples in wheat rows increased according to the asymptotic equation y = B0(1 -e(-Blx)), where B0 is the asymptote, B1 is the slope of the initial rise, and x is the seeding density. The number of dead wireworms in treated plots increased linearly and intercepted the asymptotic models (theoretical point at which 100% mortality of assembled population occurs) at 0.95 seeds/cm on 11 June and 1.14 seeds/cm on 18 June 1996. Untreated wheat at all densities planted had severe wireworm damage and significantly reduced stand. Populations that had assembled at the surviving untreated wheat were fewer than in the treated wheat plots, and although increasing with seeding density, did not follow the asymptotic model. The data suggest that A. obscurus populations can be assembled and killed in fallowed fields in large numbers at treated trap crops of wheat over a 19-d period when planted in rows spaced 1 m apart at a linear seeding density of 1.5 seeds/cm.     

Wireworm (Coleoptera: Elateridae) identity, monitoring and damage in sugarcane

Abstract Wireworms (Coleoptera: Elateridae) damage the eyes and young shoots of germinating cane setts in many growing regions. Insecticides can be applied at planting to avoid damage. However, there are no guidelines for deciding on whether treatment is warranted and a sampling method to detect wireworms before planting has not been developed. Baits of rolled oats were tested as a method for detecting wireworms in preplant fallows. In 1995 at Bundaberg, the reduction in crop establishment when treatment was withheld was positively correlated with the catch of wireworms at baits before planting. However, no similar relationship was seen in 1996 or at Mackay in either 1995 or 1996: severe damage was recorded on one farm at Mackay where no wireworms had been found. A sampling plan was developed to estimate wireworm numbers at baits with a fixed level of precision. Wireworms collected at the baits and in samples from established canefields in Queensland and New South Wales included five named and 21 unnamed species from five genera, the most abundant being Agrypnus , Conoderus and Heteroderes . Possible barriers to the adoption of baiting as a decision-support tool are discussed. Development of a reliable monitoring system would require considerably more research, which could not be justified at present.