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The olfactory ability of the convergent lady beetle, Hippodamia convergens Guerin-Meneville, was investigated using an 8-arm airflow olfactometer. Lady beetles tested were normal or had their antennae, antennal tips, or maxillary palps amputated. Normal beetles and those with their maxillary palps removed were highly attracted by the odor of radish leaves infested with green peach aphids, Myzus persicae (Sulzer). Beetles with their antennae or antennal tips removed were not attracted. In addition, the normal lady beetles were significantly attracted to clean radish leaves. These results indicate that H. convergens can perceive olfactory stimuli released by their prey and their prey’s host plant (or a combination of the two) and that the beetles’ olfactory receptors are located principally on the tips of their antennae. Also as part of this study, the antennal sensilla of male and female convergent lady beetles were examined using scanning electron microscopy. The sensilla were counted, the majority of which were located on the terminal segment, and 4 morphological classes were identified: chetiform, Bohm, basiconic, and trichoid. Chetiform sensilla were observed on all 11 antennal segments, while the Bohm sensilla were located only on the first two segments. The basiconic and trichoid sensilla were located exclusively on the terminal two segments. The most abundant sensilla on the terminal segment, trichoid sensilla, were suggested to function in olfaction.

Tuberculosis continues to be a major world health threat. The etiologic agent is among the vegetative organisms most resistant to chemical disinfection. Tuberculocidal efficacy testing for regulatory approval of chemical germicides has evolved considerably over the past decade. A method currently in use is the Environmental Protection Agency Tuberculocidal Activity Test Method, a suspension test using a Mycobacterium bovis culture grown under specific conditions and stored frozen until used. Differing tuberculocidal label claims on products with similar formulations have raised questions concerning the equivalence of test suspensions prepared by different laboratories. Five M. bovis suspensions from laboratories currently performing this test were compared against a battery of three disinfectants at a single test site. A significant difference between test cultures was found, with two of the five exhibiting a significant difference from the other three and also from each other. There was a significant culture-by-disinfectant interaction, indicating that the five cultures did not respond in a consistent manner across the different disinfectants used. However, these differences were due to cultures that were not prepared in accordance with the standard procedure or otherwise did not meet the test suspension criteria. In addition, a 0.55% sodium hypochlorite solution was found to be a sensitive indicator of culture variability. These data reinforce the need to adhere to published procedures and guidelines when growing and preparing a tuberculocidal test suspension and shed light on the variables associated with this type of testing.

Greenhouse experiments were conducted to help explain variations in chlorpyrifos activity against Russian wheat aphid, Diuraphis noxia (Mordvilko), in wheat, Triticum aestivuln L. When plants were held under different post-spray temperature regimes, chlorpyrifos was no more effective at 24°C than at 12°C or 2.5:10°C. The number of aphids was reduced when 2-leaf plants were sprayed compared with 3-leaf plants. Residue analysis showed higher chlorpyrifos deposits on the lower parts of the curled 2nd leaf (where the aphids located) compared with the corresponding parts of the curled 3rd leaf. The amount of leaf curl surrounding the aphids (30 versus 80% curled shut) had no effect on surviving aphid numbers because chlorpyrifos readily penetrates the leaf curl. Reducing the spray volume from 110 liters/ha to 55 or 20 liters/ha for chlorpyrifos applied to 3-leaf plants also had no effect on aphid numbers. Changing the spray nozzle angle to 45°, pointed ahead, did reduce aphid numbers on 3-leaf plants compared with the standard nozzle angle of 90° pointed down. Residue analysis indicated that chlorpyrifos deposits on the bottom half of the vertically orientated 3rd leaf (aphid location) were increased with the 45° nozzle angle.

Laboratory and greenhouse experiments were conducted to determine the mode of contact of chlorpyrifos with Russian wheat aphid, Diuraphis noxia (Mordvilko), in wheat. Triticum aestiuionm L. When infested plants were exposed to the vapor only from chlorpyrifos treatments, there was no significant aphid mortality. Apparently, the protective leaf curl surrounding the aphids shields them from toxic vapors generated during the spray operation. When aphids were exposed in vitro to the vapor only from chlorpyrifos-treated leaves, a definite, toxic effect was observed. Different pmts of infested, three-leaf stage plants were covered with plastic sleeves during spraying to determine which chlorpyrifos deposits caused a toxic effect. With the aphids located in the bottom of the third leaf, the only deposits causing significant mortality were those on the third leaf itself. Further leaf-cutting and leaf-painting experiments showed that aphid mortality was caused only by deposits on the bottom half of the third leaf. Toxicity from direct contact with dried chlorpyrifos residues on various leaf parts was generally low. A two-step process is postulated for the toxic action of chlorpyrifos against Russian wheat aphid. The initial mode of contact is as a penetrating vapor from the fresh spray deposited on the outside of the protective leaf curl. A secondary, more prolonged toxic action occurs as the dried surface residues on the leaf curl penetrate into the tissue, as a vapor or as dissolver! residue, and contact the aphids as they feed.

Current methods of characterizing spatial distributions of insects were applied to Russian wheat aphid, Diuraphis noxia (Mordvilko), data in winter wheat, Triticum aestivum L., plants sampled in the fall to derive information about the biology of this insect in the field and to develop sampling plans. The negative binomial fit well, but the k value was not constant, increasing rapidly and then remaining constant for mean densities > 5 per plant. Three dispersion indices indicated that the population was highly contagious initially but became less so as the population increased. Taylor’s power law and Iwao’s regression described similar relationships between the variance and the mean. Using Iwao’s method, a sequential sampling plan for the mean density was developed using a decision threshold of 0.7 aphids per plant. An acceptable operating characteristic curve was obtained with an average sample number of < 100 plants when the mean of aphids was near the threshold.

Field and greenhouse experiments were conducted to evaluate reduced rates of foliar insecticides for control of Russian wheat aphid, Diuraphis noxia (Mordvilko), on wheat, Triticum aestivum . L. In an initial field experiment on winter wheat, chlorpyrifos at 400 g (AI)/ha was the best treatment, achieving 100% control after 14 d. Subsequent greenhouse experiments indicated that, for chlorpyrifos applied to two-leaf plants using a cabinet sprayer, the rate could be reduced to 100 g (AI)/ha with 91–95% control after 7 d. The toxic action of chlorpyrifos against the aphids was rapid, with 33% control 2 h after spraying. When surviving aphids were removed from treated plants 2 h, 1 d, or 2 dafter spraying and incubated on untreated wheat, no further mortality occurred. Apparently, the Russian wheat aphid must receive prolonged exposure to the 0- to 2-d chlorpyrifos residues for adequate (>90%) control to occur. Chlorpyrifos applied to three-leaf wheat at 125 g (AI)/ha did not provide residual protection against Russian wheat aphid infesting treated plants 2, 4, and 7 d after spraying. Residue analysis showed that chlorpyrifos residues declined rapidly on the treated plants with a half-life of ≈1 d. Also, by 2 d after spraying, 90% of the residues had been absorbed into the leaves and may not have been available to the infesting aphids. When field applications using a bicycle sprayer were compared directly with cabinet-sprayer applications, better control (93–97% versus 80–83%) was achieved with field applications. In a subsequent aerially applied experiment to field-test reduced rates of chlorpyrifos, 240 g (AI)/ha gave 99% control of Russian wheat aphid on winter wheat after 14 d. We concluded that the recommended rate of chlorpyrifos for control of Russian wheat aphid in western Canada could be reduced from 480 to 240 g (AI)/ha.

This study examines the relationship between plant height, winterhardiness and genotype-by-environment interaction in the grain yield of winter wheat in western Canada. Positive correlations between plant height and winter survival ability (WSA) and between plant height and lodging score have persisted among entries in Western Hard Red Winter Wheat Cooperative Trials (WWC) for 33 yr. Progress has been made in developing winterhardy semidwarfs; however, no short cultivars have yet been isolated in the most hardy group. For Saskatchewan and Manitoba trials, correlations between WSA and yield (WSA:Y) were mostly positive, indicating widespread and intense cold stress. In southwest Alberta trials, WSA:Y ranged from significantly positive to significantly negative, indicating the wide range and unpredictability of cold stress in this area; in North and Central Alberta the distribution of WSA: Y was intermediate between southwest Alberta and Manitoba and Saskatchewan. In high stress trials (WSA:Y > 0.4), cultivar grain yield increased with increased cultivar height (on average, +0.024 tonnes ha−1 for each centimetre increase in height) but as stress levels declined, this relationship was reversed. In trials with WSA: Y < −0.4, cultivar yield was negatively related to cultivar height (average slope of −0.026 tonnes ha−1 per centimetre increase in height). Similar results were found in a trial of six winter wheat cultivars over three sites and 6 years within southern Alberta. In high stress trials, tall and hardy cultivars stabilized grain yield through high rates of survival while non-hardy cultivars performed poorly. Without damaging cold stress, short and non-hardy cultivars showed the highest yields and the greatest response to environmental productivity. Key words: Yield, winterhardiness, coldstress

Insect control measures can be effective not only by increasing mortality but also by affecting development and activity. Analysis of the simultaneous effects of a treatment on death times and development times is, however, complicated by difficulties that also arise in analyzing biomedical data in which there are competing causes of death. The theory that has been developed for dealing with these problems, competing risks theory, is reviewed in this article and applied to data from a laboratory study of the effects of Nosema locustae Canning and N. cuneatum Henry on mortality and development in Locusta migratoria migratorioides (Reiche & Fairmaire). Although the distributions of observed development times are similar among application rates, the use of competing risks methods showed that slower development is associated with increasing doses of both Nosema species. Further analysis of death times showed that N. locustae and N. cuneatum have quite different effects on development and mortality. N. locustae does not retard progression to the fifth instar as much as N. cuneatum , but for N. cuneatum , the death rate of inoculated locusts is greatly reduced at the onset of the fifth instar.

Efficacy of sprayed insecticides used for control of pale western cutworm, Agrotis Orlhogonia Morrison, is retarded by 3-5 d if a substantial proportion of the population is molting at the time of application. Cutworms are inactive during a molt and remain 1-3 cm below the soil surface. In natural infestations sampled before treatment, up to 50% of the cutworms were in a premolt or recent postmolt condition and not feeding. In the laboratory at constant temperatures, the molting time associated with the last two larval instars of pale western cutworm accounted for about one-third of the time between cessation of feeding by the antepenultimate instar and termination of feeding by the ultimate instar. Molting time comprises a large component of larval development in cutworms and its effect on behavior, including response to insecticides, has largely been ignored.

A binomial sampling model was developed for fall sampling of Russian wheat aphid, Diuraphis noxia (Mordvilko), in winter wheat, Triticum aestivum , in Alberta and Montana based on samples of whole plants collected from 24 fields over 2 yr. Percentage infestation was closely related to density, and the relationship was similar between Alberta and Montana. Measurement error regression models were discussed and used to develop new, less biased estimators of prediction equations for the density and a standard error of prediction. Using the new estimators, standard errors for whole plant, tiller, and complete count sampling were compared at various sample sizes. Whole-plant sampling with 80-100 plants per field was recommended for efficiently estimating aphid density. Under this procedure, the standard error was ≈30% of the mean throughout most infestation levels. Simulation studies showed that the new estimators were less biased than ordinary least-squares estimators and easily modified to accommodate sampling plans other than simple random sampling.

Permethrin was aerially applied at 78 g (AI)/ha in two experiments to control pale western cutworm, Agrotis orthogonia Morrison, in wheat, Triticum aestivum (L.). Despite low wind and favorable thermal lapse conditions during application, residue analyses showed that only 55 and 78% of the permethrin was deposited on the soil. Spray coverage, as indicated by water-sensitive papers placed on stakes above the crop canopy, was 26 and 22 droplets per cm2. Three days after application, cutworm control was only 9 and 55%. This low initial control was attributed to the proportion of the cutworm population, 50 and 34%, that was molting and therefore inactive at the time of treatment. Mortality of these cutworms was delayed until they resumed feeding and became exposed to the permethrin residues. By 7d after application, cutworm control had increased to 81 and 84%. The treatments reduced the initial populations of 5.4 and 20 cutworms per m2 to 0.6 and 2.6 cutworms per m2, respectively. The remaining populations were well below the economic threshold of 5 cutworms per m2. Daily counts of plant stand in one experiment showed that after an initial overnight loss of 16%, the permethrin treatment gave considerable crop protection. After 7d, 70% of the plants remained in the treated plots compared with only 40% in the unsprayed check plots. The linear relationship, y = -2.6 x + 76 ( r 2 = 0.70), between plant stand remaining ( y ) and number of cutworms per m2 ( x ) was improved by using cumulative insect-days as the indicator of cutworm survival.

Standard methods of obtaining absolute population estimates for the Russian wheat aphid, Diuraphis noxia (Mordvilko), are not feasible because of the insect’s small size, aggregated distribution, and difficulty in handling the samples. Because presence-absence information can be obtained easily, prediction of population density based on the proportion of sample units uninfested by the organism (Po) was investigated. Data on sample density ( m ) and Po for the Russian wheat aphid were obtained weekly in two winter wheat fields. The relationships between In( m ) and In(−In Po ) and between In(s2) and In( m ) were determined by regression. Several different published formulae for density predictions and their variances using the above regressions were examined analytically. New density predictor and variance estimators were developed and shown through simulation to be superior to existing estimators.

A binomial sampling plan for pest management of the stable fly, Stomoxys calcitrans (L.), was developed. Counts of stable flies on front legs of the same animal were independent and each leg from the same animal was considered a sample unit. The relationship between the mean number of flies per leg and the variance was determined and did not vary among farms. The relationship between the mean number of flies per leg and the proportion of legs with zero, one or less, and two or less flies (P0, P1, and P2) was determined and used as the basis of the binomial sampling plan. Predicted values of the mean number of flies per leg from P0, P1, and P2 were close to observed values of the mean number of flies per leg. Equations are presented for calculating the variance of a predicted value of the mean number of flies per leg using values of P0, P1 and P2 determined by sampling. Operating characteristic (OC) curves are also presented for determining the probability of making a treatment decision error at an economic threshold of one fly per leg (P0 = 0.47) using binomial sampling or direct counting. OC curves for binomial sampling with n = 50 legs were close to those for direct counting with n = 10 legs. Recommendations concerning the use of binomial sampling for stable flies are presented.

Uninfested cocoons of the alfalfa leafcutter bee, Megachile rotundata (F.), bare prepupae, and cocoons infested with the chalcidoid, Pteromalus venustus Walker, were exposed to vapor from dichlorvos resin strips at rates of 0.16, 0.37, 0.71, and 0.99 strip per 28.3 m3 during 4 days of incubation. For uninfested cocoons, there was no significant reduction in leafcutter bee survival at the dichlorvos rates tested. For bare prepupae, there was a significant linear trend of reduced survival with increased dichlorvos rate. Cocoons apparently protect the bees from dichlorvos vapor. For infested cocoons, 0.71 strip per 28.3 m3 reduced the parasitism from 40 to 13% which significantly increased bee survival. Adult parasites were placed in different housing environments and exposed to the 0.71 strip per 28.3 m3 rate. When parasites were directly exposed to dichlorvos vapor, mortality occurred within 2 h. When parasites were shielded by layers of cocoons, mortality was delayed 7 to 10 h. Because 25% parasitism can occur within 4 h of P. venustus emergence, it is unlikely that dichlorvos resin strips alone will totally control parasitism in a commercial operation.

Microclimate was found to affect the daily flight activity ofSimulium arcticum in a pasture situation in central Alberta, Canada. Vapour pressure, air temperature, light intensity, and wind gust velocity had the greatest correlation to flight activity. These variables were correlated to support the concept that they influence the energy and water balances of a black fly. Flight activity is a response of the black fly to alterations of its energy and water balances.

Field trials were conducted to determine deposition of deltamethrin applied to pastures by aircraft, and resulting effectiveness in controlling grasshoppers. Residue analysis indicated that 73% of 7.2 g (AI)/ha deltamethrin applied was deposited on vegetation and litter. Sampling via sweep net indicated considerably higher rates of control than did estimates of density based on trap catches 1 day after application, although both methods indicated a 65% reduction in grasshopper density after 4 days. The bias in sweep-net samples is due to reduced activity just after spraying. Contrary to earlier reports, efficacy of deltamethrin was unrelated to age distribution, species composition, or grasshopper movement. Estimates of mortality based on independent toxicological experiments in the laboratory agreed with field results, given the deposition measured at time of spraying.