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The abundance of nine stored-product species found in crop residues in farm granaries in the Prairie Provinces was influenced by farm practices, kinds of crops stored in the granaries, and the materials used in the construction of the granaries.
Some species were found more frequently than expected on farms where there had been previous infestations (Pyralis farinalis L.), or where there was livestock (Cryptolestes ferrugineus [Stephens]).
Fewer samples than expected were found infested with Cryptophagus varus (W. & C.), where insecticidal sprays were used, but more C. ferrugineus than expected were found where fumigants or insecticidal sprays were used.
Fewer samples of canola residues than expected contained insects, but barley residues contained more insects than expected.
Wooden granaries contained more insects than expected, except for C. ferrugineus.
Cole’s coefficient of association showed that some species were often associated but other pairs of species such as Tribolium audax Halstead and Lathridius minutus L. were negatively associated.
These relationships between species and their environments can be used to reduce the abundance of stored-products insects in farm granaries.
E-Myrcenol reduced catches of the pine engraver, Ips pini (Say), to ipsdienol-baited, multiple-funnel traps in a dose-dependent fashion. The sex ratio was unaffected by E-myrcenol treatments. Lures containing E-myrcenol in ethanol solution failed to protect freshly cut logs of lodgepole pine from attack by I. pini. Rather, I. pini preferentially attacked logs treated with devices releasing E-myrcenol and ethanol, over nontreated, control logs. Our results demonstrate that E-myrcenol is a new pheromone for I. pini, and emphasize the importance of understanding basic pheromone biology before utilisation of a semiochemical in forest pest management.
The southern pine beetle, Dendroctonus frontalis Zimmermann, was studied in the laboratory to determine the influence of associated fungi on its reproduction. First-generation (P) surface-sterilized beetles associated with mycangial fungi (Ceratocystis minor [Hedgecock] Hunt var. barrasii Taylor or SJB 122) constructed more galleries and laid more eggs, at faster rates, than P beetles not associated with these mycangial fungi. No significant differences occurred among non-surface-sterilized P beetles associated with the phoretic blue staining fungus Ceratocystis minor (Hedgecock) Hunt and mycangial fungi or among progeny of P beetles (F1 generation) carrying mycangial fungi. P and F1 surface-sterilized beetles produced more eggs at a greater density than non-surface-sterilized beetles associated with blue stain, but gallery length and the rate of construction were not different. P and F1 surface-sterilized beetles laid more eggs and constructed galleries faster than surface-sterilized beetles that carried no mycangial fungi. The re-emergence rate of beetles was fastest for P beetles associated with C. minor and significantly slower for fungus-free P beetles, P beetles carrying only mycangial fungi, and F1 beetles, respectively. The F1 generation emerged fastest when associated with both mycangial fungi and slowest when associated with SJB 122, and C. minor var. barrasii or no fungus, respectively. This study employed a successful new rearing technique for isolating specific southern pine beetle/fungal associations.
No correlation was found between the size of male spruce budworm (Choristoneura fumiferana [Clem.]) moths and the duration of their flight in a sustained-flight wind tunnel. The numbers of male moths caught in traps baited with virgin female spruce budworm moths increased as the size of the females increased, but the relationship was significant in only one of eight experiments. Infection with the microsporidium Nosema fumiferanae (Thomson) resulted in smaller insects, but there were no significant relationships between the incidence of infection and male flight duration or female attractiveness.
Results of a field experiment indicate that adults of the pine weevil Hylobius pales (Herbst) respond to pheromones of bark beetles. Each sex of H. pales was more attracted to traps baited with the combination of a pine bolt infested with male Ips calligraphus Germar plus the synthetic Dendroctonus Erichson pheromones frontalin and exo-brevicomin, than to traps baited with pine bolts alone. The combined numbers of male and female H. pales caught in traps baited only with Ips calligraphus-infested bolts were significantly greater than numbers caught in traps baited with uninfested control bolts. The attraction of H. pales to bark beetle pheromones may represent a kairomonal response in which weevils exploit semiochemicals from other species that signify a suitable host resource.
Leafy spurge (Euphorbia × pseudovirgata [Schur]) is an herbaceous perennial and serious weed of European origin that has been accidently introduced into North America. The European anthomyiid flies Pegomya curticornis (Stein) and Pegomya euphorbiae (Kieffer) are found on several spurge species in Europe and also attack leafy spurge. The two flies induce identical galls on the subterranean stems of their host plants, and the shoots wilt and die. Eggs are laid on the shoot tip, and the larvae bore into the stem by eating pith which is later replaced by callus. This is a rare example of an insect with both boring and gall-inducing feeding strategies. Galls are induced when larvae feed on the ring of vascular tissue. There is no proliferation of nutritive cells but instead thick layers of gall parenchyma are produced. The vascular connections are broken at the gall level and concentric vascular bundles appear in the cortical and gall parenchyma. After pupation an inner periderm differentiates around the chamber surface.
The development of spruce cone axis midge, Dasineura rachiphaga Tripp, and its parasitoids, Platygaster lucida Fouts and Torymus sp., was studied in relation to the availability and development stage of black spruce, Picea mariana (Mill.) B.S.P., cones.
Spruce cone axis midge inhabiting black spruce cones appeared to undergo an extended diapause. This phenomenon probably was related to the production of cones. Platygaster lucida also appeared to undergo extended diapause and the proportion of P. lucida extending their diapause paralleled that of spruce cone axis midge which suggested a close dependance to their host.
Spruce cone axis midge, P. lucida, and Torymus sp. emerged from mature cones about the same time and were closely synchronized with the availability of black spruce flowers.
External morphological characters of the spruce cone axis midge that separate the two sexes in the pupal stage were described.
Twenty-one species of fleas, seven of which are considered true ground squirrel fleas, were collected by various means from Spermophilus richardsonii (Sabine), S. tridecemlineatus (Mitchell), and S. franklinii (Sabine) in Manitoba. Opisocrostis tuberculatus tuberculatus (Baker), O. labis (Jordan and Rothschild), Neopsylla inopina Rothschild, and Rhadinopsylla fraterna (Baker) are ground squirrel fleas reported from Manitoba for the first time. These, in addition to Oropsylla rupestris (Jordan) and Thrassis bacchi bacchi (Rothschild), were restricted to the southwestern region of the province, but Opisocrostis bruneri (Baker) was collected throughout the range of the ground squirrels, irrespective of location. Fourteen species collected were considered accidental on ground squirrels, one of which, Tamiophila grandis (Rothschild) (an eastern chipmunk parasite), was recorded for the first time in the province.
The performance of unbaited emergence traps and attractant-baited pitfall and flight traps was compared on the basis of suitability to produce population indices for two beetles, Steremnius carinatus (Boheman) and Hylastes nigrinus (Mannerheim), colonizing roots of Douglas fir in northern California. These beetles transmit Ceratocystis wageneri Goheen and Cobb, the fungus causing black stain root disease in Douglas fir. Trap sites were near stumps along transect lines through recently logged areas. Pitfall traps were judged the most promising for both species based on their relatively high catches and low expense. Although catch by emergence traps was low for both species, they appeared to catch the majority of S. carinatus. For both species, pitfall trap catches varied with date, study area, trapping line within study area, and stump within line. A number of variables, such as diameter of stump or type of ground cover, were significantly correlated with trap catch, and made significant contributions to linear models with catch as the dependent variable. Differences between study areas in the effect of variables on catch, and the possibility that pitfall trapping is subject to artifacts, suggested that the results of pitfall trapping need to be carefully scrutinized if they are to be used as a population index.
The arthropod and annelid fauna of a series of small, acidic pools in a domed, ombrotrophic bog on the Avalon Peninsula, Newfoundland, was studied over the ice-free season of 1986. Pools were assigned to four classes on the basis of their surface area (<1; 1.1–10; 10.1–100; >100 m2) and at least two 1-m2 (entire pool if area <1 m2) substrate samples, plankton samples, and moss samples were taken from pools of each size class biweekly. One hundred and thirty-one taxa, most identified to the species level, were collected. Taxa varied in abundance between pools of various size classes and, using Cluster Analysis and TWINSPAN, two principal communities were identified. Oligochaetes, beetles, and mosquitoes dominated small, astatic pools and odonates, chironomids, and several other taxa predominated in large, stable, vegetated pools. Water level stability is postulated to be the principal factor determining this community structure. Within large pools, odonate larvae were the dominant predators and comprised the majority of the standing crop. Odonate larvae have life cycles of 2 or more years; their slow growth is probably due to prey limitation. Odonate larvae potentially exert a powerful predation pressure within the large pool community, and may be the principal biotic factor determining abundance and distribution of prey taxa within the bog pool system.
Populations of pea aphid, Acyrthosiphon pisum (Harris), were sampled through the summer of 1984 on five cultivars and in 1985 and 1986 on six cultivars of field peas, Pisum sativum L., grown in field plots in southern Manitoba. Patterns of pea aphid population growth were generally similar among cultivars in any one year. Aphid populations on all cultivars in all years remained relatively low until mid-July, then increased rapidly, peaked at about the beginning of August, and declined sharply to low levels in late August. At the time of peak aphid numbers, significant differences in aphid population densities were found among cultivars in 2 years; the lowest densities were found on the cultivars Century and Tipu, and the highest densities on Triumph or Trapper. Pea aphid feeding was not detrimental to any yield parameters except 1000 seed weight. In 1984 Triumph and Tara, and in 1985 Triumph had significantly decreased 1000 seed weights in plots in which aphid densities were not controlled. Differences in the abundance of the aphid among cultivars were not reflected in their yield responses. Over 3 years the regression line of aphid densities upon Century seed weight was significantly steeper than those of Trapper, Lenca, or Tara. Trapper was least affected by aphid feeding. Results indicated that the economic threshold of pea aphids on peas other than Century needs to be re-evaluated.
One or more insects were captured during 1 week in probe traps placed in granaries holding wheat, barley, or oats in 51% (n = 116) of grain bulks in the fall of 1986, 88% (n = 111) in the summer of 1987, and 85% (n = 106) in the fall of 1987. Fungivorous insects were the most common and predominant group at all sampling times. Granivorous species were the rusty grain beetle, Cryptolestes ferrugineus (Stephens), and the red flour beetle, Tribolium castaneum (Herbst). Grain in galvanized steel and wooden granaries was usually infested with insects to the same extent; granaries with or without aeration systems usually contained the same number of species; small bulks of grain often were infested less frequently than large bulks; the presence of livestock feed on farms did not result in greater insect incidence; and insecticide use in granaries did not prevent re-infestation of grain and insecticide use increased from 24% in 1986 to 31% in the fall of 1987. The kinds of insects detected in grain stored with various farming practices, and co-occurrence with other arthropods in the grain provides baseline information on potentially changing patterns of infestation.
The accuracy of visual observations in estimating numbers of tuber flea beetles, Epitrix tuberis Gentner, on young potatoes was determined. Potential sources of observational error examined were as follows: (a) observer competence and experience; (b) time spent observing each plant; (c) time of day; (d) plant height; and (e) weather. Observational accuracy versus tuber flea beetle density on plants followed a linear relationship for both experienced and inexperienced observers. Marked differences between experienced and inexperienced observers generally were reduced after 2 h of sampling experience, but some observers were consistently less accurate at sighting beetles than others. When observing small plants, 5-s observations generally were more accurate at sighting beetles per second of observation than 2-, 8-, or 10-s observations. Under uniform weather conditions, accuracy was the same in the morning as in the afternoon. Observer accuracy was significantly reduced under the combined influences of observer fatigue and wind. The relationship of 5-s-per-plant sampling accuracy to plants between 14 and 56 cm in height was linear; however, a quadratic relationship is suspected for plants over the full range of plant heights (i.e. >1 cm). From these data, total tuber flea beetles per plant estimated by 5-s visual observations per plant would be: TFB = TFB0/EhE0n where TFB0 is the total number of flea beetles observed, n is the total number of plants sampled, Eh is a sampling accuracy constant for the mean plant height sampled, and E0 is the observer accuracy constant calculated as a proportion of the most proficient observer(s).
We propose a sequential sampling plan for adult tuber flea beetles, Epitrix tuberis Gent., in potato fields, which is based on a confidence interval calculated around a critical density value (Iwao 1975) and which uses Taylor’s Power Law (Taylor 1961) to estimate the variance. Because of the highly edge-biased gradients of density displayed by this insect, separate sequential expressions have been calculated for densities at the edges and centers of fields.
In a survey of 12 commercial potato fields, spring-generation E. tuberis densities in centers of fields were always far below the threshold level of one beetle per 10 plants employed at the time of sampling. The survey also indicated that fields that have been sown with potatoes for 2 consecutive years have higher beetle densities than fields sown with potatoes for a 1st year. Edge:center density ratios, however, were the same for the two categories of fields.
Eggs of western blackheaded budworm, Acleris gloverana (Walsingham), were found on the underside of needles of western hemlock, Tsuga heterophylla (Raf.) Sarg., with higher densities in the mid-crown area toward the outer tips of branches. Fringe and dominant trees were preferred oviposition sites over trees in lower crown classes or shaded positions. Vertical differences in needle density were considerable and led to high variability in insect densities when expressed on a per branch basis. When densities of eggs were based on a fresh branch weight basis there was a significant decrease in sample bias caused by the uneven distribution of foliage over the crowns.
Eggs of western blackheaded budworm, Acleris gloverana (Walsingham), are laid on the lower surface of western hemlock, Tsuga heterophylla (Raf.) Sarg., needles. A comparison was made of the following measures of sample branch size as a basis for expressing egg density: fresh branch weight, branch area, total twig length, branch volume, and number of buds. The criteria for selection of these measures were as follows: correlations of branch size with dry needle weight, variances of egg density and their relative contribution to sample size, and ease of measurement. Fresh branch weight was the best choice. A sequential sampling system was developed on this basis and was related to a scale of predicted defoliation. In addition, a transformation was provided for use in data analysis.
Promoresia elegans (LeConte), Optioservus fastiditus (LeConte), and Stenelmis nr. bicarinata LeConte coexist in Duffin Creek, Ont., making up 3.78–23.92% of the riffle fauna present.
Promoresia elegans and O. fastiditus appeared to have semi-voltine life histories. Stenelmis nr. bicarinata appeared to be univoltine but with overlapping generations and slow recruitment occurring from late summer to fall; growth was slow in winter but fast in spring and summer.
Based on the index of relative importance (Pinkas et al. 1971), detritus was identified as the most important food source for all size classes and all species throughout the year. Microinorganics ranked second, with diatoms, fungal hyphae, and vascular plant material being the least important food sources. There was no indication of ontogenic food switching in any of the species.
The Schoener (1970) niche overlap index indicated almost complete dietary overlap (Cxy = 0.78–0.97) among the three species throughout the year and the Hurlbert (1978) niche overlap index similarly indicated a convergence of diets (L = 1.31–3.54).
Niche breadth values were found to be high for all species on the rock surfaces (generalist diet) but were lower in the hyporheic zone indicating a higher degree of specialization there.
Coccinellids are a conspicuous group of aphidophagous predators in maize, Zea mays L., in the Northern Great Plains of the United States. Numerous studies have been conducted on the ecology of coccinellids in maize in North America (Ewert and Chiang 1966a, 1966b; Smith 1971; Foott 1973; Wright and Laing 1980; Corderre and Tourneur 1986; Corderre et al. 1987). However, there have been few long-term surveys of coccinellids in maize. Foott (1973) reported on the abundance of coccinellid species inhabiting maize in eastern Canada over a 4-year period; no surveys of this type have been reported for the Northern Great Plains. We sampled coccinellids in maize fields at three sites in eastern South Dakota for 13 consecutive years to determine the species inhabiting the crop and levels of variation in their abundances among sites and years.
Rangeland grasshoppers commonly are reared through a single generation in the laboratory from eggs collected in the field or produced by field-collected adults. These grasshoppers usually undergo an obligate egg diapause. The only exceptions are nondiapause strains of an economically important grasshopper, Melanoplus sanguinipes (F.) (Pickford and Randell 1969; Henry 1985).