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Agricultural systems are often simultaneously impacted by multiple stressors. In our study, we investigated the effects of two commonly occurring viruses of potato, Potato virus Y (PVY) and Potato leafroll virus (PLRV) on host plant selection and utilization across various spatial scales by the Colorado potato beetle. Adult beetles selected PLRV-infected foliage in the cage choice trails, and larvae that fed exclusively on PLRV-infected foliage developed into larger adults. PVY-infected foliage was avoided in the cage trials and had no effect on the weight of developing adults. In field trials, preference and utilization of potato plants was more dependent on plant size than on virus infection. These results demonstrate that while virus-infected plants can cause physiological changes that influence beetle preference, beetle abundance and/or distribution is driven by a more complex array of factors at the field level. Additionally, this study demonstrates the importance of investigating the applicability of laboratory findings at the field level.

Cannibalism, or intraspecific predation, can play a major role in changing individual fitness and population processes. In insects, cannibalism frequently occurs across life stages, with cannibals consuming a smaller or more vulnerable stage. Predation of adult insects on one another is considered to be uncommon. We investigated adult cannibalism in the Colorado potato beetle, Leptinotarsa decemlineata (Say), which is an oligophagous herbivore specializing on plants in family Solanaceae, and an important agricultural pest. Under laboratory conditions, starvation and crowding encouraged teneral adults to feed upon each other, which reduced their weight loss during the period of starvation. However, pupae were attacked and consumed before adults. Injured beetles had a higher probability of being cannibalized than intact beetles. Males were more frequently attacked than females, but that appeared to be a function of their smaller size rather than other gender-specific traits. Cannibalizing eggs at a larval stage did not affect beetle propensity to cannibalize adults at an adult stage. When given a choice between conspecific adults and mealworms, the beetles preferred to eat conspecifics. Cannibalistic behavior, including adult cannibalism, could be important for population persistence in this species.

Applications of remote sensing are important in improving potato production through the broader adoption of precision agriculture. This technology could be useful in decreasing the potential contamination of soil and water due to the over-fertilization of agriculture crops. The objective of this study was to assess the utility of active sensors (Crop Circle&trade, Holland Scientific, Inc., Lincoln, NE, USA and GreenSeeker&trade, Trimble Navigation Limited, Sunnyvale, CA, USA) and passive sensors (multispectral imaging with Unmanned Arial Vehicles (UAVs)) to predict total potato yield and phosphorus (P) uptake. The experimental design was a randomized complete block with four replications and six P treatments, ranging from 0 to 280 kg P ha&minus, 1, as triple superphosphate (46% P2O5). Vegetation indices (VIs) and plant pigment levels were calculated at various time points during the potato growth cycle, correlated with total potato yields and P uptake by the stepwise fitting of multiple linear regression models. Data generated by Crop Circle&trade, and GreenSeeker&trade, had a low predictive value of potato yields, especially early in the season. Crop Circle&trade, performed better than GreenSeeker&trade, in predicting plant P uptake. In contrast, the passive sensor data provided good estimates of total yields early in the season but had a poor correlation with P uptake. The combined use of active and passive sensors presents an opportunity for better P management in potatoes.

Microalgae feed production is a major cost in bivalve aquaculture. Its efficiency is increased by scaling it up under automated control of environmental conditions. The initial cost of commercially available systems can be prohibitive. Therefore, a large volume full-scale photobioreactor built of low-cost, readily available materials was developed and tested. A cone-bottom, polyethylene tank was internally illuminated with submersible fluorescent lamps and equipped with a monitoring and control system that measured temperature, pH and optical density of the microalgal culture. Injection of CO2 was automated to maintain pH within a target range. System performance was evaluated by growing four batch cultures of Tetraselmis chuii. Temperature inside the photobioreactor was 29.5 ± 2.38 °C (mean ± SD, range 21−35 °C) and pH was 7.56 ± 0.87 (mean ± SD, range 5.29–8.97). Optimal harvest time was after 300 h (12.5 days) of growth, yielding 1700 L of microalgae at a density of 2500 cells/ μl (1200 cells/ μl/ m2 illuminated surface area). With 24 h illumination, the fluorescent lights, air pump and monitoring/ control device consumed 14.9, 1.9 and 0.1kwh/ day, respectively. Assuming the microalgae are harvested at their optimal density after 12.5 days, each batch would consume 211kwh or 0.124kwh/ liter. The photobioreactor described provides an economical option for growing large amounts of microalgae for aquaculture feed and other purposes.

The Colorado potato beetle is an important pest of solanaceous plants in the Northern Hemisphere. Better understanding of its physiological responses to temperature stress and their interactions with still-prevalent chemical control has important implications for the management of this insect. We measured mortality and expression of the Hsp70 heat shock proteins in the Colorado potato beetle larvae exposed to sublethal concentration of the commonly used insecticide imidacloprid, and to supraoptimal temperatures. Both turned out to be significant stress factors, although induction of Hsp70 by imidacloprid observed in the present study was low compared to its induction by the heat. The two factors also interacted with each other. At an extreme temperature of 43 °C, exposure to a sublethal dose of imidacloprid resulted in a significant rise in larval mortality, which was not observed at an optimal temperature of 25 °C. Heat-stressed larvae also failed to respond to imidacloprid by producing more Hsp70. These findings suggest that when field rates of insecticides become insufficient for killing the exposed beetles under optimal temperature conditions due to the evolution of resistance in beetle populations, they may still reduce the probability of resistant beetles surviving the heat shock created by using propane flamers as a rescue treatment.

Mineral oil is a product used to reduce Potato Virus Y transmission in potato fields. However, there is little information available about other effects that oil may have on insect pests of potato. To better understand how mineral oil affects potato pests, we performed a series of experiments testing the effects of oil on mortality, behavior, and development of potato aphids, Macrosiphum euphorbiae (Thomas) (Hemiptera: Aphididae), green peach aphids, Myzus persicae (Sulzer) (Hemiptera: Aphididae), and Colorado potato beetles, Leptinotarsa decemlineata (Say) (Coleoptera: Chrysomelidae). All three species showed negative behavioral responses to oil-treated potato foliage. Oil treatment also increased aphid mortality. Colorado potato beetle mortality was not affected, but developing on oil-treated potato plants resulted in prolonged development and smaller adults. Additionally, oil acted synergistically with the entomopathogenic fungus Beauveria bassiana (Balsamo) Vuillemin (Hypocreales: Clavicipitaceae); Colorado potato beetle larvae were killed more rapidly when sprayed with both products compared with when sprayed with B. bassiana alone. Based on these results, mineral oil has the potential for expanded use in potato IPM programs.

Neonicotinoid insecticides have been the most common management tool for Colorado potato beetle, Leptinotarsa decemlineata (Say), infestations in cultivated potato for nearly 20 yr. The relative ease of applying neonicotinoids at planting coupled with inexpensive, generic neonicotinoid formulations has reduced the incentive for potato growers to transition from these products to other mode of action (MoA) groups for early-season L. decemlineata control. Continuous use of neonicotinoids has resulted in resistant L. decemlineata populations in some production areas of the eastern United States. Continued reliance on neonicotinoids will accelerate L. decemlineata resistance development and result in additional insecticide inputs to manage these populations. Resistance management recommendations for L. decemlineata have focused on rotation of insecticides within the growing season. Growers using at-plant neonicotinoids for early-season L. decemlineata control are encouraged to rotate MoAs for later generations to delay resistance development. Although this short-term insecticide rotation has likely prolonged the utility of neonicotinoid insecticides, reducing reliance on a single MoA soil application at planting will improve the longevity of newer, more reduced-risk alternatives. The objectives of this article are twofold: 1) to provide a review of the current status of L. decemlineata neonicotinoid resistance, and 2) to propose long-term resistance management strategies that arrange reduced-risk MoA groups into several, multiyear sequences that will maximize L. decemlineata control and reduce the probability for resistance development. This recommendation maintains practical and economical approaches for L. decemlineata control, but limits reliance on any single MoA group to minimize selection pressure for resistance development. Wisconsin Potato Industry Board, Distinguished Graduate Student Fellowship; R. Keith Chapman and Jeffrey A. Wyman-Wisconsin Distinguished Graduate Fellowship in Vegetable Entomology; National Potato Council-State Cooperative Potato Research Program [FY09-13] We thank cooperating growers for generously providing insecticide application records and allowing us to conduct research on their farms. We also thank the research programs of Jeffrey A. Wyman and R. Keith Chapman for generating L. decemlineata screening data used to determine sustainability improvements of insecticide tools in Wisconsin. We thank the Wisconsin Potato and Vegetable Growers Association (WPVGA) and the New York Empire State Potato Growers Association for continued support of our research efforts. Funding was provided by Wisconsin Potato Industry Board, Distinguished Graduate Student Fellowship 2009 & 2011, R. Keith Chapman and Jeffrey A. Wyman-Wisconsin Distinguished Graduate Fellowship in Vegetable Entomology 2010, and National Potato Council-State Cooperative Potato Research Program FY09-13.

The Colorado potato beetle, Leptinotarsa decemlineata (Say) is a very serious pest of potatoes which is highly mobile and capable of rapid evolution of resistance to chemical control. Insect movement, resulting in gene flow between resistant and susceptible populations, is considered to be an important factor affecting the development and spread of insecticide resistance. We investigated the movement of adult Colorado potato beetles by flight and by walking following the treatment with a sublethal dose of imidacloprid in the laboratory. Imidacloprid had a pronounced negative effect on beetle mobility. The proportion of beetles flying and walking, as well as the number and duration of performed flights, were significantly decreased for the treated beetles. Since local selection followed by long-distance dispersal have been reported to lead to serious area-wide problems with the insecticide-resistant Colorado potato beetle, long-term suppression of flight activity recorded in our study suggests that imidacloprid applications may reduce outflow of resistant alleles.

Phosphite is a general term used to describe the salts of phosphorous acid H 3 PO 3 . It is effective in suppressing a number of plant diseases caused by oomycetes and has been shown to reduce populations of several insect species. We investigated the effects of phosphite on the Colorado potato beetles in the field and laboratory. Beetle numbers and defoliation on phosphite-treated plots were lower compared to the control plots during one out of two years of the study. No phosphite effects were detected in the field during the second year of the study. However, larval mortality was significantly higher the second year in the laboratory when larvae were fed on potato foliage excised from the potato plants treated with phosphite in the field. Laboratory tests with excised leaves dipped in a solution of phosphite revealed lower beetle survivorship and prolonged development on the treated foliage. Because of its dual properties as a fungicide and an insecticide, as well as its low toxicity to vertebrates, phosphite is a potentially good fit for integrated pest management programs.

Colorado potato beetle, Leptinotarsa decemlineata (Say), is a major pest of potatoes in North America, Europe, and parts of Asia. It adapts quickly to adverse environments, thereby limiting the longevity of control strategies. Better understanding of variability among geographically isolated populations of this insect might create an opportunity to customize control techniques for local conditions. We investigated insecticide resistance, heat tolerance, and growth potential in six beetle populations collected from different locations in the United States. Significant differences were detected in insecticide resistance, egg mass size, and egg hatchability among the tested populations. Large egg mass size appeared to be offset by lower egg hatchability. We also observed a female-biased sex ratio at least in one of the strains. Population growth rates were different among the strains, but this parameter was not correlated to insecticide resistance. This suggests that using allopatric populations in comparative studies of insecticide resistance might result in confusing effects of geographic isolation with the effects of selection toward resistance.

Aims Integrating multiple soil and disease manage- ment practices may improve crop productivity and disease control, but potential interactions and limita- tions need to be determined. Methods Three different potential disease-suppressive management practices, including a Brassica napus (rapeseed) green manure rotation crop, conifer-based compost amendment, and three biological control or- ganisms (Trichoderma virens, Bacillus subtilis, and Rhizoctonia solani hypovirulent isolate Rhs1A1) were evaluated alone and in combination at sites with both organic and conventional management histories for their effects on soilborne diseases and tuber yield. Results Rapeseed rotation reduced all observed soil- borne diseases (stem canker, black scurf, common scab, and silver scurf) by 10 to 52 % in at least one year at both sites. Compost amendment had variable effects on tuber diseases, but consistently increased yield (by 9 to 15 %) at both sites. Biocontrol effects on disease varied, though Rhs1A1 decreased black scurf at the conventional site and T. virens reduced multiple diseases at the organic site in at least one year. Combining rapeseed rotation with compost amend- ment both reduced disease and increased yield, where- as biocontrol additions produced only marginal addi- tive effects. Conclusions Use of these treatments alone, and in combination, can be effective at reducing disease and increasing yield under both conventional and organic production practices.

Seasonal patterns of abundance and population variability were determined for Macrosiphum euphorbiae (Thomas), Myzus persicae (Sulzer), and Aphis nasturtii (Kaltenbach) (Hemiptera: Aphididae) in potato plots from weekly samples for 28 years. All species showed a single annual peak, but arrived and reached peak abundance at different times. Population variability (PV, a proportion between 0 and 1) for the week of peak abundance was close to that of other sample weeks and mean seasonal abundance. Based on mid-season abundance, PV of 0.76 for M. persicae differed significantly from 0.80 for A. nasturtii, as well as from 0.59 for M. euphorbiae. A weekly time scale for abundance, initiated at an early stage of plant growth, produced slightly different estimates of PV early and late in the season than a scale centred on peak abundance for each species. PV at the time of invasion differed from estimates for the rest of the summer. The annual abundance used to estimate PV was best determined in the context of aphid life history. Nevertheless, PV provided a robust and precise metric for comparing population variability among the three species, regardless of their seasonal patterns of abundance.

Cultural practices such as organic amendments, rotations, and use of biological control organisms are regularly investigated for their effects on controlling plant diseases but their effects on soil microbial populations are often unexplored. In this study, three different sustainable disease management practices, use of compost amendment, biocontrol organisms, and a potentially disease-suppressive rotation, were established in potato field trials at two sites under different management regimes and histories, and evaluated over three potato cropping seasons for their effects on soil microbial communities. Specific management factors assessed included the presence or absence of a conifer-based compost amendment, addition of one of three different biocontrol organisms (Trichoderma virens, Bacillus subtilis, and Rhizoctonia solani isolate Rhs1A1), and a Brassica napus (rapeseed) green manure rotation crop preceding potato, and treatments were assessed in all factorial combinations. The two farm sites represented organic and conventional potato production practices in Aroostook County, Maine. Compost amendment and rapeseed rotation had the greatest impacts on soil microbial communities, with both treatments increasing total populations of culturable bacteria at both sites over the course of the study, as well as causing detectable shifts in soil microbial community characteristics as determined by sole carbon-source substrate utilization and fatty acid methyl ester (FAME) profiles. Compost amendment generally led to increased utilization of complex substrates and increased levels of Gram-positive bacteria and fungi, and compost effects were more pronounced at the conventional site. Rapeseed rotation often resulted in somewhat different effects at the two different sites. Consistent overall effects were observed with the biocontrol amendments Rhs1A1 and T. virens, including increased microbial activity and bacterial populations. Combined effects of multiple treatments were greater than those of individual treatments and were generally additive. These results indicate that each treatment factor had significant and specific effects on soil microbial communities, and that combined effects tended to be complementary, suggesting the potential of combining multiple compatible management practices and their associated changes in soil microbial communities.

Abundance, persistence, and variability of populations of Macrosiphum euphorbiae (Thomas), Myzus persicae (Sulzer), and Aphis nasturtii Kaltenbach (Hemiptera: Aphididae) in potato plots for intervals of 58 years (n = 1), 29 years (n = 2), 19–20 years (n = 3), and 9–10 years (n = 6) were compared. The abundance of M. euphorbiae showed no trend among decades and varied 2.4-fold, whereas that of M. persicae and A. nasturtii declined and showed 54-fold and 3700-fold variation, respectively. All three aphid species persisted through the first five decades and M. euphorbiae also persisted through the sixth (last) decade, but M. persicae and A. nasturtii failed to persist for 1 and 3 years of the last decade, respectively. Population variability (a proportion between 0 and 1) measured over a 58-year interval was high: 0.585 for M. euphorbiae, 0.771 for M. persicae, and 0.830 for A. nasturtii. During the first three but not the last three decades, population variability increased with sampling interval, owing to dramatic declines in abundance for M. persicae and A. nasturtii and one stable decade for M. euphorbiae, but no evidence of a more-time — more-variation effect was detected. Persistence was not related to population variability, but declined with abundance. Populations did not reach equilibrium, because of declining abundance for M. persicae and A. nasturtii and changes in population variability from decade to decade for M. euphorbiae. Populations of M. persicae and A. nasturtii from this crop monoculture were less stable than previously studied natural populations of a native aphid species. In contrast, the population of M. euphorbiae, a native species, had variability in a potato crop similar to that of the previously studied native species. The high population variability of M. persicae and A. nasturtii may be associated with their status as introduced species. The dynamic and species-specific characteristics of population variability require that interspecific comparisons be considered cautiously.

Novaluron is a chitin synthesis inhibitor (a benzoylphenyl urea) that kills larval stages and causes reversible cessation of laying viable eggs in adults of the Colorado potato beetle, Leptinotarsa decemlineata (Say). Previous studies also suggest that it has ovicidal properties, but not on all tested egg masses. We investigated if egg maturity at the time of exposure affects its susceptibility to novaluron. Novaluron application significantly reduced the hatch of eggs that were 0–24 h old at the moment of treatment, but had no effect on the eggs that were 96–120 h old. Novaluron also interfered with the development of the hatched larvae regardless of the egg age at the time of treatment, probably due to chorion feeding by neonates. Ovicidal properties of novaluron may contribute to Colorado potato beetle control, but their effect will be limited to newly laid eggs. If that window of susceptibility is missed, hatching larvae will be exposed to a fairly old novaluron residue that might be weathered down to sublethal levels. This supports the current recommendations to apply novaluron as a larvicide.

The acceptability of four different aphid species Macrosiphum albifrons (Essig), Macrosiphum euphorbiae (Thomas), Macrosiphum pseudorosae Patch, and Myzus persicae (Sulzer) (Hemiptera: Aphididae), as prey for four lady beetle species, one native species Coccinella trifasciata L, and three non-native Coccinella septempunctata L, Harmonia axyridis Pallas, Propylea quatuordecimpunctata L (Coleoptera: Coccinellidae) were tested in the laboratory. The relative field abundance of adults of the same lady beetle species on host vegetation, Lupinus polyphyllus Lindley (Fabales: Fabaceae), Solanum tuberosum L (Solanales: Solanaceae), and Rosa multiflora Thunberg (Rosales: Rosaceae), both with and without aphids present was also observed. In the laboratory, H. axyridis generally consumed the most aphids, while P. quatuordecimpunctata consumed the fewest. The exception was P. quatuordecimpunctata, which consumed a greater number of M. albifrons nymphs, and C. trifasciata, which consumed a greater number of M. albifrons nymphs and adults, compared with the other two beetle species. Lady beetles consumed fewer M. albifrons compared with the other three aphid species, likely because of deterrent compounds sequestered by this species from its host plant. In the field, P. quatuordecimpunctata was the most abundant species found on L. polyphyllus and S. tuberosum.

Response to odours plays an important role in resource location by natural enemies, particularly by parasitoid wasps. While a considerable research effort has been dedicated to studying the effects of insecticide intoxication on natural enemy search behaviour, it is yet unknown if the odours themselves interfere with distant chemoreception. We investigated this issue using the food-searching behaviour of Microplitis croceipes (Cresson)(Hymenoptera: Braconidae) in laboratory arenas as a model system. Odours of imidacloprid (Genesis®), spinosad (Entrust®), esfenvalerate (Asana®), methamidophos (Monitor®), and vanilla were tested for their ability to interfere with wasp response to the odour of honey. The wasps did not contact the chemicals. Honey odour was generally effective in triggering food-searching behaviour in both honey-fed (and thus conditioned to associate honey odour with food) and unfed, naive wasps. Mixing honey with imidacloprid and spinosad did not affect wasp responses. The remainin...

The Colorado potato beetle, Leptinotarsa decemlineata (Say), is one of the most damaging insect pests of potato, Solanum tuberosum L. Novaluron is a relatively new benzoylphenyl urea insect growth regulator with good activity against this pest. Earlier studies revealed that feeding on potato foliage treated with novaluron induces reversible egg hatch inhibition in adult Colorado potato beetles. We investigated whether novaluron effects depend on physiological state of the beetles at the time of exposure. The following four treatments were created: young beetles unmated at the beginning of the experiment and feeding on potato foliage treated with novaluron, young beetles unmated at the beginning of the experiment and feeding on untreated foliage, older beetles mated at the beginning of the experiment and feeding on foliage treated with novaluron, and older beetles mated at the beginning of the experiment and feeding on untreated foliage. The beetles were exposed to the respective treatments for 5 d. After that, both young and older beetles feeding on novaluron-treated leaves were switched onto untreated leaves and monitored for another 5 d to test their ability to recover. Young beetles unmated at the beginning of the experiment produced more eggs after feeding on the treated foliage, possibly indicating the presence of a pesticide-induced homeostatic modulation. No such effect was observed in the older beetles. Regardless of beetle physiological state at the beginning of the experiment, eggs produced on treated foliage did not hatch. The beetles eventually resumed laying viable eggs after being switched onto untreated foliage, with the recovery being delayed by approximately 24 h in young beetles compared with older beetles. Our results corroborate that novaluron reduces fertility of treated adults.

Interactions between lady beetles and the European fire ant (Myrmica rubra L.) tending potato aphids [Macrosiphum euphorbiae (Thomas)] were compared in the laboratory. Lady beetle species native to North America (Coccinella trifasciata perplexa Mulsant, Coleomegilla maculata lengi Timberlake, Hippodamia convergens Guérin-Méneville) and non-native species of Palearctic origin [Coccinella septempunctata L., Harmonia axyridis (Pallas), Hippodamia variegata (Goeze), Propylea quatuordecimpunctata L.)] were evaluated. Harmonia axyridis consumed a significantly greater number of aphids compared with all other species but C. septempunctata. Ant stings affected H. variegata and C. septempunctata to a greater extent than other species. Ants showed a significantly greater amount of aggression toward H. convergens and H. variegata compared with P. quatuordecimpunctata. P. quatuordecimpunctata, C. trifasciata, and H. axyridis reacted significantly less to ants compared with H. variegata, H. convergens, C. maculata, and C. septempunctata. Differences in interactions with natural enemies may explain, in part, the successful establishment of some non-native coccinellids in new habitats.

Several studies suggest the possibility that non-native lady beetles may have replaced native lady beetles in some agricultural habitats. There is relatively little information, however, about lady beetle species composition outside of agricultural habitats. Evans (2004) suggested that native species have retreated to nonagricultural habitats in response to the arrival of non-native lady beetles (habitat compression hypothesis). To test this hypothesis, a survey of lady beetles was conducted in 2004 and 2005 in different habitats in Maine. From May to October, lady beetles were sampled in a variety of agricultural and nonagricultural habitats. In total, 3,487 and 2,903 lady beetles were collected in 2004 and 2005, respectively. Non-native lady beetles were found in a variety of habitats, including the habitats that would have likely served as a refuge for native species if the habitat compression hypothesis applied to the surveyed areas. Native species were found in a higher proportion in agricultural habitats compared with nonagricultural habitats and in very low numbers in all of the habitats surveyed. Hippodamia tredecimpunctata tibialis (Say) and Coccinella transversoguttata Brown, the two native species that were once dominant here, made up only 1.09 and 0.07% of the total lady beetles collected, respectively. In this survey, we failed to detect evidence that native lady beetles have retreated to nonagricultural habitats in response to the arrival of non-native lady beetles.

The Colorado potato beetle, Leptinotarsa decemlineata (Say), is widely regarded as the most important insect defoliator of potatoes. Its current range covers about 16 million km2 in North America, Europe, and Asia and continues to expand. This insect has a complicated and diverse life history, which is well-suited to agricultural environments, and makes it a complex and challenging pest to control. Dispersal, closely connected with diapause, feeding, and reproduction, allow the Colorado potato beetle to employ “bet-hedging” reproductive strategies, distributing its offspring in both space (within and between fields) and time (within and between years). The Colorado potato beetle played a large role in creating the modern pesticide industry, with hundreds of chemicals tested against it. High selection pressure, together with natural propensity to adapt to toxic substances, eventually resulted in a large number of insecticide-resistant Colorado potato beetle populations. Since the middle of the last century, the beetle has developed resistance to 52 different compounds belonging to all major insecticide classes. Resistance levels vary greatly among different populations and between beetle life stages, but in some cases can be very high (up to 2,000-fold). Known mechanisms of Colorado potato beetle resistance to insecticides include enhanced metabolism involving esterases, carboxylesterases and monooxygenases, and target site insensitivity, as well as reduced insecticide penetration and increased excretion. There is also some evidence of behavioral resistance. Resistance mechanisms are sometimes highly diverse even within a relatively narrow geographical area. Resistance is usually inherited as an incompletely dominant or incompletely recessive trait, with one or several genes involved in its determination. Because of pleiotropic effects of resistant alleles, insecticide-resistant beetles often have reduced relative fitness in the absence of insecticides. Rotating different classes of insecticides and reducing insecticidal pressure on pest populations by provision of temporal and spatial refuges from exposure to toxins have been proposed to delay evolution of resistance. However, insecticide resistance in this insect will likely remain a major challenge to the pest control practitioners. Still limited understanding of beetle biology, its flexible life history, and grower reluctance to adopt some of the resistance management techniques create impediments to successful resistance management. Overcoming these obstacles is not an easy task, but it will be crucial for sustainable potato production.

Assessing learning outcomes in general education is increasingly important to accrediting bodies. A fertile area of assessment is measuring changes in student attitudes/values in response to general education. University of Maine faculty experimented with such an attitude assessment. The results reveal interesting questions about general education and values education.

Cannibalism, or intraspecific predation, can play a major role in changing individual fitness and population processes. In insects, cannibalism frequently occurs across life stages, with cannibals consuming a smaller or more vulnerable stage. Predation of adult insects on one another is considered to be uncommon. We investigated adult cannibalism in the Colorado potato beetle, Leptinotarsa decemlineata (Say), which is an oligophagous herbivore specializing on plants in family Solanaceae, and an important agricultural pest. Under laboratory conditions, starvation and crowding encouraged teneral adults to feed upon each other, which reduced their weight loss during the period of starvation. However, pupae were attacked and consumed before adults. Injured beetles had a higher probability of being cannibalized than intact beetles. Males were more frequently attacked than females, but that appeared to be a function of their smaller size rather than other gender-specific traits. Cannibalizing eggs at a larval stage did not affect beetle propensity to cannibalize adults at an adult stage. When given a choice between conspecific adults and mealworms, the beetles preferred to eat conspecifics. Cannibalistic behavior, including adult cannibalism, could be important for population persistence in this species.

Repeated use of neonicotinoid insecticides has resulted in the first reported cases of Colorado potato beetle (Leptinotarsa decemlineata (Say)) resistance to imidacloprid. In the laboratory we determined susceptibility of the imidacloprid-resistant Colorado potato beetles from a population in Southern Maine to other insecticides currently registered for use on potato. This population was about 30-fold resistant to imidacloprid and could not be effectively controlled by its applications. Control mortality was significantly higher for the imidacloprid-resistant larvae than for the susceptible larvae, suggesting that fitness disadvantages may be associated with the resistance trait. Resistant larvae exhibited significantly less mortality than susceptible larvae when exposed to cyfluthrin, carbaryl, azinphosmethyl, and methamidophos. Their susceptibility to oxamyl was also somewhat reduced, although it did provide nearly 100% mortality at the highest concentration tested. Disulfoton was highly toxic to the resistant larvae. Oxamyl killed about 40% of the adults in greenhouse assays with potted potato plants, altered their feeding behavior (fewer adults up on plants), and reduced defoliation by more than 90%. Disulfoton was not lethal to adults, but significantly suppressed their feeding. In field trials with the resistant population, oxamyl and imidacloprid + spinosad provided the best beetle control. Novaluron had no detectable effect on beetle densities. There was little difference between the plots treated with imidacloprid or thiamethoxam and the untreated control. Our results suggest that insecticide rotation may be a valuable option for managing imidacloprid-resistant Colorado potato beetle populations. We also had a good consistency between the results of the Petri dish, greenhouse, and field experiments, indicating that screening under laboratory confinement may be useful when developing initial recommendations to potato growers in areas affected by resistance to neonicotinoids.

Potato aphid, Macrosiphum euphorbiae (Thomas), is a highly mobile aphid species that dominates aphid communities in Maine potato fields and may contribute to virus transmission between potato plants. We studied effects of simulated rain, wind, mechanical raking, fungicide application, reflective mulch, and predator [lady beetle, Harmonia axyridis (Pallast)] on the interplant movement of wingless adult potato aphids in greenhouse experimental arenas that imitated small segments of a potato field. The number of aphids dispersing from the central plant in the arena after a tested perturbation was recorded. Experiments were repeated with 3- to 4-wk-old plants with nonoverlapping canopies and with 4- to 5-wk old plants with canopies overlapping within rows. Aphids moved between potato plants even when canopies did not overlap and without any environmental perturbations. However, more aphids moved between larger plants with overlapping canopies. Rain significantly encouraged aphid movement between plants with nonoverlapping canopies. Wind, rain, and mechanical raking significantly encouraged aphid movement between plants with overlapping canopies. Regardless of canopy overlap, most aphids moved within the rows of potato plants. However, there was also considerable movement between the rows, even though the aphids had to walk over bare soil.

Potato aphid, Macrosiphum euphorbiae (Homoptera: Aphididae), is an abundant potato pest and vector of potato leaf-roll virus and potato virus Y in Maine and other potato growing areas. We investigated the circadian rhythmicity of its movement towards host plant odor. Effects of daily cycle (day or night) and illumination (light or dark) on the proportion of aphids colonizing potato leaflets were determined in a Petri plate arena and in a Y-tube olfactometer. In Petri dishes, both daily cycle and light had a highly significant effect on plant colonization. Increasing temperature reduced aphid colonization of the leaflets. In the olfactometer, light had a significant effect on the proportion of aphids walking towards the host plant. Interaction between time and light was also statistically significant, with the effect of illumination being smaller during the day than during the night. Our results suggest that circadian rhythm in host-finding behavior of the potato aphid is regulated by both exogenous and endogenous mechanisms.

Colorado potato beetle, Leptinotarsa decemlineata (Say), is the most important insect defoliator of potatoes and is infamous for its ability to develop insecticide resistance. Sperm precedence is an important consideration in developing resistance management plans. We determined the precedence of sperm from a postdiapause spring mating by using irradiated sterile males. We also investigated whether spring mating (with or without fertilization) affects reproduction of overwintered females. Precedence of sperm from spring matings versus overwintered sperm from fall matings was almost complete. Some fertilization from fall matings did take place in this experiment, but it exceeded 10% in only one of the 22 pairings. Females mated only the previous fall laid fewer eggs than spring-mated females, but spring mating did not seem to improve the hatch rate of deposited eggs. On average, mated females started laying 1.6 d sooner than fall-mated females, but this difference was not significant. Hatch rate did not change with time. Precedence of spring matings over stored sperm can help compensate for assortative summer mating among resistant individuals due to differences in developmental time between refuges and treated areas.

Scarcity of long-term (over 30 years) data series represents a major challenge for an accurate estimation of the role of density-dependent processes in population regulation. We analyzed population densities of the wingless parthenogenic morphs of buckthorn aphid (BA), Aphis nasturtii Kaltenbach, potato aphid (PA), Macrosiphum euphorbiae (Thomas), and green peach aphid (GPA), Myzus persicae (Sulzer) from 1949 to 2003 for signs of density-dependent regulation. We found strong evidence of density-dependent regulation, with detection of density dependence being fairly consistent among the different statistical techniques. Direct density dependence was detected for the populations of all three species. There was also evidence of delayed density dependence for PA. The periodicity of population fluctuations for BA and GPA was 6.1 years and 3.9 years, respectively. The periodicity for PA was not explicit, being highly variable throughout the time series. Effects of density-independent weather factors were relatively minor compared to density-dependent regulation. The BA populations experienced a significant reduction in both density and annual oscillations starting in 1995, while GPA populations experienced a similar reduction in 1991. No such change was apparent for PA. The most likely explanation for the observed phenomenon is a change in the composition of the lady beetle community following the establishment of two alien coccinellid species, and/or changes in insecticide use by commercial growers in the area of the study.

A number of recent studies indicated that establishment of exotic lady beetles (Coleoptera: Coccinellidae) may have adverse affects on native lady beetle species. In the present study, we analyzed changes in coccinellid community inhabiting potato crops in northern Maine over the past 31 years. Prior to 1980, lady beetle communities were comprised almost exclusively of the two native species, Coccinella transversoguttata Brown and Hippodamia tredecimpunctata(Say). Starting 1980, an exotic species Coccinella septempunctata L. became permanently established in potato crops and quickly started to dominate lady beetle community. Two other exotic species, Harmonia axyridis(Pallas) and Propylea quatordecimpunctata(L.) became prominent members of the lady beetle community in 1995 and 1996. Invasion by exotic species was followed by a significant decline in the abundance of C. transversoguttata and H. tredecimpunctata, and a significant increase in the overall diversity of lady beetle community. The abundance of aphid prey was substantially reduced after the establishment of H. axyridis. The observed trends demonstrate the profound effects that exotic natural enemies may have on target and non-target native species, and highlight the importance of their thorough evaluation before initiating biological control programs.

Imidacloprid is a commonly used insecticide that is highly effective in controlling insect pests of potato. The relatively high cost of imidacloprid provides commercial growers with a strong incentive to reduce field application rates. In the present study, we investigated the impact of reduced imidacloprid rates on aphid abundance and potato virus Y transmission within potato fields. Infurrow applications of imidacloprid provided better aphid control even at a reduced rate when compared to threshold-based foliar applications, but did not suppress the spread of the non-persistently transmitted potato virus Y. Virus transmission was significantly decreased in foliar-sprayed plots, possibly because foliar applications incapacitated aphid vectors probing or feeding on infected plants. Despite these generally encouraging results, we still observed 2.3 to 2.7 fold increase in virus infection at foliar-treated plots at the end of the growing season.

The Colorado potato beetle is an important pest of solanaceous plants in the Northern Hemisphere. Better understanding of its physiological responses to temperature stress and their interactions with still-prevalent chemical control has important implications for the management of this insect. We measured mortality and expression of the Hsp70 heat shock proteins in the Colorado potato beetle larvae exposed to sublethal concentration of the commonly used insecticide imidacloprid, and to supraoptimal temperatures. Both turned out to be significant stress factors, although induction of Hsp70 by imidacloprid observed in the present study was low compared to its induction by the heat. The two factors also interacted with each other. At an extreme temperature of 43 °C, exposure to a sublethal dose of imidacloprid resulted in a significant rise in larval mortality, which was not observed at an optimal temperature of 25 °C. Heat-stressed larvae also failed to respond to imidacloprid by producing more Hsp70. These findings suggest that when field rates of insecticides become insufficient for killing the exposed beetles under optimal temperature conditions due to the evolution of resistance in beetle populations, they may still reduce the probability of resistant beetles surviving the heat shock created by using propane flamers as a rescue treatment.

Cannibalism can have a large effect on population growth and survival in stressful environments, possibly including those created by insecticide use. In this study, we collected Colorado potato beetles from three isolated areas in the northeastern United States known for high levels of resistance to neonicotinoids. We measured resistance to imidacloprid in each of those populations, a laboratory susceptible population, and in hybrids between the three field populations and the laboratory susceptible population. We fed neonates eggs from resistant dams fed either imidacloprid-treated or untreated foliage to determine whether cannibals are exposed to toxins sequestered in eggs. We measured egg cannibalism by hatchlings within the clutch in each population and hybrids, and examined how fecundity and several variables associated with egg development varied among populations and with cannibalism, to see which traits might enhance or reduce cannibalism. Cannibalism varied significantly among populations, accounting for most of the variation in hatching success. Variability in egg development time and hatch rate in the absence of cannibalism in some populations affected rates of cannibalism. Resistance varied significantly among the field populations but was not related to cannibalism. Neonates fed eggs from dams on treated foliage showed signs of intoxication or death. Cannibalism appears to be part of a varying life history strategy in this species, with some populations laying larger and more cannibalistic clutches and the New York population laying smaller clutches with higher hatching success owing to reduced cannibalism.

The flower-head feeding fly Acinia picturata (Diptera: Tephritidae) was deliberately introduced from Mexico into Hawaii in 1959 for biological control of the exotic weed Pluchea odorata (Snow) (Asteraceae). Neither field efficacy nor possible non-target effects of the fly have been evaluated in the 40 years since the introduction. We assessed the impact of the fly on both its target host and on seven non-target plant species. The impact on the target weed was limited, with only 5-13% of the developing seeds in P. odorata flowerheads being destroyed by larval feeding. We did not detect any host range expansion of A. picturata onto flowerheads of two exotic or 5 endemic non-target plant species in the family Asteraceae.

Originally designed to reconcile insecticide applications with biological control, the concept of integrated pest management (IPM) developed into the systems-based judicious and coordinated use of multiple control techniques aimed at reducing pest damage to economically tolerable levels. Chemical control, with scheduled treatments, was the starting point for most management systems in the 1950s. Although chemical control is philosophically compatible with IPM practices as a whole, reduction in pesticide use has been historically one of the main goals of IPM practitioners. In the absence of IPM, excessive reliance on pesticides has led to repeated control failures due to the evolution of resistance by pest populations. This creates the need for constant replacement of failed chemicals with new compounds, known as the 'insecticide treadmill'. In evolutionary biology, a similar phenomenon is known as the Red Queen principle - continuing change is needed for a population to persevere because its competitors undergo constant evolutionary adaptation. The Colorado potato beetle, Leptinotarsa decemlineata (Say), is an insect defoliator of potatoes that is notorious for its ability to develop insecticide resistance. In the present article, a review is given of four case studies from across the United States to demonstrate the importance of using IPM for sustainable management of a highly adaptable insect pest. Excessive reliance on often indiscriminate insecticide applications and inadequate use of alternative control methods, such as crop rotation, appear to expedite evolution of insecticide resistance in its populations. Resistance to IPM would involve synchronized adaptations to multiple unfavorable factors, requiring statistically unlikely genetic changes. Therefore, integrating different techniques is likely to reduce the need for constant replacement of failed chemicals with new ones.

Incorporating our knowledge of fundamental evolutionary processes into pest control practices is essential for maximizing their efficiency. The insect pest complex of potato is characterized by a high degree of plasticity and adaptability. In particular, the Colorado potato beetle quickly expanded its host range to include cultivated potato, and has shown a remarkable ability to evolve resistance to a wide variety of chemicals. Another major pest of potatoes, the green peach aphid, is also very adaptable to insecticides. Both of these insects can also develop resistance to non-chemical methods of their suppression, such as biological control and crop rotation. In addition, understanding insect adaptation to abiotic conditions (temperature, water availability, solar irradiation, etc.) is essential for forecasting future pest outbreaks under the current conditions of extensive human traffic among previously geographically isolated areas and changing climate.

The Colorado potato beetle is a very important defoliator of potatoes in many potato-growing areas of the world. This insect has a diverse and flexible life history that is well-suited to a variety of environmental conditions. It is also extremely adaptable to adverse conditions, including those created by humans in an attempt to control the pest. The beetles integrate diapause, dispersal, feeding, and reproduction into an ecological “bet-hedging” strategy, distributing their offspring in both space (within and between host habitats) and time (within and between seasons). As a result, they are a very challenging pest to manage.