Evidence of evolving carbaryl resistance in western corn rootworm (Coleoptera: Chrysomelidae) in areawide-managed cornfields in north central Kansas

Susceptibility of adult populations of the western corn rootworm, Diabrotica virgifera virgifera LeConte, to carbaryl was determined by a survey in 1996 before the implementation of an areawide management program near Scandia in north central Kansas. Subsequently, the susceptibility of western corn rootworm adults to carbaryl has been monitored throughout the program from 1997 to 2000 in both control and managed areas. In 1996, adults were highly susceptible to carbaryl with a mean LC50 value of 0.64 microg/vial. This value was comparable to those for adults collected from other regions within Kansas. However, adult susceptibility to carbaryl decreased rapidly within the managed area, where the cucurbitacin- carbaryl-based bait SLAM has been used as the primary tool to control adults in this project since 1997. In 1999, adults collected from the managed area were 9- and 20-fold less susceptible to carbaryl at the LC50 and LC90 levels, respectively, than those evaluated in 1996. In contrast, adults collected from the control area were only 2- and 3-fold less susceptible to carbaryl at the LC50 and LC90 levels, respectively, than adults evaluated in 1996. Although field adult populations of western corn rootworm were relatively low in 2000, evaluations showed trends similar to those in 1999 regarding their carbaryl susceptibility in the managed and control areas. These results provide evidence that western corn rootworm has been evolving carbaryl resistance rapidly in response to the use of SLAM in areawide-managed cornfields near Scandia.     

Effectiveness of corn rootworm (Coleoptera: Chrysomelidae) areawide pest management in South Dakota

Diabrotica barberi Smith & Lawrence and Diabrotica virgifera virgifera LeConte (Coleoptera: Chrysomelidae) are serious pests of maize, Zea mays L. To reduce the amount of toxicants released into the environment, the Agricultural Research Service implemented a 5-yr (1997-2001) areawide pest management program in five geographic locations, including one in South Dakota. The objective was to use integrated pest management tactics to suppress adult Diabrotica populations over a broad geographic area by using aerially applied semiochemical-baited insecticides. Suppressed populations theoretically should reduce oviposition, limit larval feeding damage to maize roots, and result in fewer beetles emerging in subsequent years. We used emergence cages, sticky traps, and CRW lure traps to monitor adult D. barberi and D. v. virgifera populations. We sampled for Diabrotica eggs, and we determined damage to maize roots. We sampled in several maize fields (control) located near the areawide site. The baited insecticides were effective in reducing adult populations 1 and 2 wk after application, and most remained low for the duration of the maize growing season. Fewer beetles were captured in both sticky and lure traps in the areawide site than in the control site. With a few exceptions, egg counts, adult emergence, and maize root damage were similar between the areawide and control sites; however, maize roots had greater fresh weight in the control site. Although not all goals were accomplished, when considering the amount of toxicant released into the environment, using semiochemical-baited insecticides to suppress adult pest Diabrotica populations seems to be an effective areawide management tool.     

Comparative susceptibility of western corn rootworm (Coleoptera: Chrysomelidae) adults to selected insecticides in Kansas

Susceptibility of adult populations of the western corn rootworm, Diabrotica virgifera virgifera LeConte, to several insecticides was evaluated in seven Kansas counties, including Dickinson, Ford, Finney, Pottawatomie, Republic, Riley, and Stevens, between 1996 and 2002. All populations surveyed were highly susceptible to methyl parathion with the largest difference in susceptibility of only three-fold based on 16 complete bioassays for the populations from six counties over a 5-yr period. Noticeable decreases in carbaryl susceptibility were found in populations collected from Republic County between 1997 and 2001 when the cucurbitacin-carbaryl-based bait SLAM was widely used as an areawide management approach for adult corn rootworm control. However, the lowered carbaryl susceptibility returned to previous levels 1 yr after the use of SLAM was halted in the managed (treated) cornfields. This change implies possible dispersal of insects into the relatively small managed area from surrounding untreated cornfields and / or some fitness cost associated with carbaryl resistance within the population. Relative susceptibility of western corn rootworm adults also was evaluated for seven commonly used insecticides, including bifenthrin, carbaryl, chlorpyrifos, cypermethrin, fipronil, malathion, and methyl parathion. They were tested with corn rootworm adults collected from a single cornfield. Methyl parathion and bifenthrin were highly toxic to corn rootworm adults, and cypermethrin, chlorpyrifos, carbaryl, and malathion were only slightly less toxic. Although fipronil was highly toxic to adult rootworms, its activity was much slower than that of other insecticides. Thus, bifenthrin and methyl parathion were among the most effective in killing corn rootworm adults.     

Consumption of residue containing cucurbitacin feeding stimulant and reduced rates of carbaryl insecticide by western corn rootworm (Coleoptera: Chrysomelidae).

Application of insecticide at a reduced rate with a cucurbitacin-based feeding stimulant is a viable alternative to a broadcast insecticide application for control of adult western corn rootworms, Diabrotica virgifera virgifera, LeConte. Because of the small amount of material applied, it is conceivable that a high density of beetles could consume all of the spray residue before economic control is achieved. A laboratory experiment was conducted to determine the amount of cucurbitacin-based spray residue consumed by beetles. Dried residue of four treatments were exposed to three groups of 10 rootworm beetles for 1 h each. Treatments consisted of a cucurbitacin-based adjuvant (Cidetrak CRW, Trécé, Salinas, CA) with carbaryl insecticide (Sevin XLR Plus, Rhone Poulenc, Research Triangle Park, NC) mixed at 0, 0.12, 1.2, and 12 g (AI)/liter. For the treatment with cucurbitacin adjuvant only (no insecticide), beetles consumed 0.029 mg beetle(-1) h(-1) of exposure. Approximately 54% of the beetles were recorded as feeding at any given time during the 60-min feeding period. However, when the spray residue contained carbaryl, no weight loss of treatment residue was measured, though the beetles were observed to feed from the residue during the first few minutes of exposure. When residue included insecticide, beetles quickly ceased feeding (within 20 min), and toxicity behavior was observed 30 min after initial exposure for up to 75% of the beetles, which were classified as moribund (unable to stand upright). Beetle mortality was recorded 24 h after exposure and demonstrated that male beetles (53% dead for three insecticide treatments) were more susceptible to carbaryl toxicity than female beetles (28% dead for three insecticide treatments). Regression analysis showed a significant positive relationship between mortality of female beetles and ovarian development. Based on the measurements of this experiment, it is unlikely that realistic beetle densities would consume enough spray residue to prevent economic control of the beetle population.     

Carbaryl resistance in populations of grape berry moth (Lepidoptera: Tortricidae) in New York and Pennsylvania

We collected grape berry moth, Endopiza viteana (Clemens) (from cultivated and wild Vitis along Lake Erie in Pennsylvania and New York), and measured carbaryl susceptibility in first instars. A model of susceptibility was based on the concentration-mortality curve of laboratory-maintained colonies originating from wild Vitis with no prior history of carbaryl exposure, and a noncommercial vineyard with modest previous exposure to carbaryl. We estimated LC50 and LC90 for susceptible grape berry moth larvae at 45.4 and 2319 microg/ml, respectively. Bioassays on field-collected larvae from commercial vineyards in both states, where grape growers were abiding by current pest management guidelines for carbaryl use, revealed carbaryl resistance ratios from 7 to 71 at the LC50 level. With the loss or restriction of alternative chemical control tactics in the Food Quality Protection Act era, resistance management programs for grape berry moth should be immediately developed and implemented to regain the efficacy of this once effective insecticide and other related chemical compounds.     

Nontarget arthropod abundance in areawide-managed corn habitats treated with semiochemical-based bait insecticide for corn rootworm (Coleoptera: Chrysomelidae) control

Impacts of semiochemical-based insecticidal bait applications on beneficial arthropod groups common to field corn, Zea mays L., habitats were assessed in areawide-managed field sites in South Dakota and Iowa during 1997 and 1998. Slam, a commercial bait formulation comprised of 87% cucurbitacin and 13% carbaryl insecticide, was used for management of adult rootworm, Diabrotica spp., and controls consisted of cornfield habitats without bait applications. Effects on beneficial organisms were variable, and negative impacts were infrequent. Coccinellidae, Staphylinidae, and Anthocoridae were usually more abundant in bait-treated plots than in controls that received at-plant soil insecticides, especially by 4 wk postapplication. Carabid beetle activity also had increased in bait-treated corn by proportionally greater rates than in control plots at 4 wk postapplication in two of the four site by year combinations in this study. Impacts of semiochemical-based adulticide applications on Formicidae were not consistently negative or positive. The relative lack of consistent negative impacts on nontarget arthropods suggests that other biotic and abiotic factors leading to natural population fluxes may have more influence on these groups of beneficial organisms than applications of semiochemical-based bait containing carbaryl. Overall, it seems that areawide applications of these baits for managing rootworm populations in corn are not likely to impose deleterious effects on the nontarget faunal groups we surveyed, especially in comparison with the at-plant applications of soil insecticides used as experimental controls in this study.     

Planting transgenic insecticidal corn based on economic thresholds: consequences for integrated pest management and insect resistance management

A simulation model of the western corn rootworm, Diabrotica virgifera virgifera LeConte, was used to investigate whether sampling and economic thresholds can improve integrated pest management (IPM) and insect resistance management (IRM) when transgenic insecticidal crops are used for insect pest management. When transgenic corn killed at least 80% of susceptible larvae, the calculated economic threshold increased linearly as the proportion of susceptible beetles surviving the toxin increased. The use of economic thresholds slightly slowed the evolution of resistance to transgenic insecticidal crops. In areas with or without rotation-resistant western corn rootworm phenotypes, the use of sampling and economic thresholds generated similar returns compared with strategies of planting transgenic corn, Zea mays L., every season. Because transgenic crops are extremely effective, farmers may be inclined to plant transgenic crops every season rather than implementing costly and time-consuming sampling protocols.     

Antifeedant discrimination thresholds for two populations of western corn rootworm

Abstract.Sensitivities to β‐hydrastine, strychnine and picrotoxinin were compared between two populations of western corn rootworm, Diabrotica virgifera virgifera LeConte (Coleoptera: Chrysomelidae), differing in their susceptibility to cyclodiene insecticides. The antifeedants are antagonists of γ‐aminobutyric acid (GABA) neuroreceptors that may mediate gustation and, in the case of picrotoxinin, interact directly with the target site for cyclodiene insecticides. In combination with cucurbitacin B, a specific Diabroticite phagostimulant, cyclodiene‐resistant beetles were two‐ to four‐fold less sensitive to hydrastine and strychnine. The discrimination threshold for picrotoxinin was higher for resistant beetles; however, overall dose–response profiles were similar. Beetles were more sensitive to hydrastine and strychnine in combination with L‐alanine, a general phagostimulant of less potency than cucurbitacin B. Dose–response slopes for the alkaloid‐alanine combinations were double those of respective cucurbitacin B slopes, which indicates that phagostimulatory input from l ‐alanine was more negatively affected by the alkaloidal antifeedants than the respective cucurbitacin B treatments. Picrotoxinin sensitivity was similar in mixtures with either phagostimulant. Comparison of chemosensillum responses to strychnine was inconclusive. Results are discussed in context of GABA receptor pharmacology.     

Flight behavior of methyl-parathion-resistant and -susceptible western corn rootworm (Coleoptera: Chrysomelidae) populations from Nebraska

Relative flight behavior of methyl-parathion-resistant and -susceptible western corn rootworm, Diabrotica virgifera virgifera LeConte populations, was studied as part of a larger effort to characterize the potential impact of insecticide resistance on adult life history traits and to understand the evolution and spread of resistance. A computer interfaced actograph was used to compare flight of resistant and susceptible individuals, and flight of resistant individuals with and without prior exposure to methyl-parathion. In each case, mean trivial and sustained flight durations were compared among treatments. In general, there were few differences in trivial or sustained flight characteristics as affected by beetle population, insecticide exposure, sex, or age and there were few significant interactions among variables. Tethered flight activity was highly variable and distributions of flight duration were skewed toward flights of short duration. Tethered flight activity was similar among resistant and susceptible beetles with the exception that susceptible beetles initiated more flights per beetle than resistant beetles. After sublethal exposure to methyl-parathion, total flight time, total trivial flight time, and mean number of flights per resistant beetle declined significantly. Because long-range flight was uncommon, short- to medium-duration flights may play an important role in determining gene flow and population spread of resistant D. v. virgifera. These results suggest that organophosphate-resistant beetles can readily move and colonize new areas, but localized selection pressure (e.g., management practices) and exposure to methyl-parathion may contribute to the small-scale differences in resistance intensity often seen in the field.     

The ineffectiveness of insecticide seed coatings and planting-time soil insecticides as Diabrotica virgifera virgifera LeConte population suppressors

Abstract:  The effect of any management strategy on pest population levels must be researched and determinations need to be made as to how that strategy might work based on the control objectives. In certain areas of Europe, the objective is to contain or eradicate the western corn rootworm (WCR), Diabrotica virgifera virgifera LeConte, population. In order to evaluate the impact of insecticide seed coatings and/or planting-time applications of insecticides as WCR population suppressors, plot trials and large field observations were carried out in Italy over a 5-year period. Larval, pupal and adult densities, along with root damage ratings, were estimated at different locations. Data from these studies revealed that the number of WCR adults emerging from untreated plots did not differ from the number of beetles emerging from those treated with insecticides, whether as seed coating or in-furrow applications. Both seed insecticide coatings (imidacloprid, fipronil, thiamethoxam, tefluthrin) and soil insecticides applied in-furrow (chlorpyrifos, diazinon, tefluthrin) did not reduce the number of beetles emerging from monoculture fields, either in plot trials or large field observations. Observations in the USA had previously shown that soil insecticides applied at planting time partially protected basal roots from economic damage, but did not reduce corn rootworm populations. Similarly, in Europe, it has been demonstrated that not only the application of soil insecticides at planting time but also insecticide seed coatings have no role in the containment and/or eradication of WCR. Although insecticide seed coatings and soil insecticides applied in-furrow may provide protection against economic damage to roots, these management strategies do not have an impact on WCR populations and therefore are useless in WCR containment and eradication programmes.     

Influence of Different Intensities of Pesticide Management on the Structure of Ground Beetle Communities (Coleoptera; Carabidae) During a Crop Rotation

Investigations were lead through in the years 1992 to 1995 at Halle (Saale) on a stand 24ha in size. Aim of the survey was to record the effects of graduate intensities of pest management on ground beetles. For this purpose 6 plots were installed on the field, 72 ‐ 200m each. Two plots served as control areas, without any application of pesticides. On two other plots intensive chemical pest management was applied. On the last two plots treatments were lead through considering the economic thresholds for weeds, fungal and insect pests according to the rules of integrated pest management. Ground beetles were sampled by using pitfall traps. In 1992 complementary methods to the pitfall trap catches, pick up of beetles after pesticide applications and semi-field-tests, on all plots were lead through. The graduate pest management was carried out 1992 and 1993 in winter wheat and 1994 in sugar beet stands. The last crop in 1995 was summer barley. In this year all plots were treated conventionally. In 1992 the differences between the total catches of ground beetles on the experimental sites were not high. In the following year most species were predominant on the control sites. In 1994 in sugar beet mechanical weed control was carried out on the control plots. The intensity of pesticide management between intensive and integrated plots differs only small. The amounts of ground beetles reached similar values on all experimental sites. In contrast to the expections the trap catches of ground beetles in the final investigations in summer barley were highest in the plots which had been treated integrated in the years before. The smallest amount was sampled in the former intensively managed sites. Renunciation of pesticides often is connected with economic losses which are not tolerable. If management is conducted considering the economic thresholds corresponding to the principles of integrated pest management negative effects on the economy of nature should not be expected for the longer term.     

Rainfastness and residual activity of insecticides to control Japanese beetle (Coleoptera: scarabaeidae) in Grapes

Field-based bioassays and residue profile analysis were used to determine the relative toxicity, rainfastness, and field degradation over time of five insecticides from five insecticide classes on adult Japanese beetles, Popillia japonica Newman (Coleoptera: Scarabaeidae), in grapes, Vitis labrusca L. Bioassays assessed Japanese beetle condition as alive, knockdown, or immobile when exposed for 24 h or 7-d field-aged residues of phosmet, carbaryl, bifenthrin, thiamethoxam, or indoxacarb after 0, 12.7, or 25.4 mm of rain had been simulated. We found that the two most toxic insecticides to Japanese beetle were phosmet and carbaryl, followed by bifenthrin, thiamethoxam, and then indoxacarb. The efficacy of phosmet decreased because of rainfall, but not because of field aging. The efficacy of carbaryl decreased because of rainfall and field aging. The efficacies of bifenthrin and thiamethoxam were not affected by rainfall but decreased because of field aging. The efficacy of indoxacarb was not affected by rainfall or field aging. This study will help vineyard managers make informed decisions on when reapplications of insecticides are needed with the aim of improving integrated pest management programs.     

Population patterns of Mexican corn rootworm (Coleoptera: Chrysomelidae) adults indicated by different sampling methods

The Mexican corn rootworm, Diabrotica virgifera zeae Krysan & Smith, is a serious pest of corn, Zea mays L., in several areas of Texas. Recent demonstrations of areawide adult control suggest this tactic has promise for rootworm management, but additional information regarding treatment thresholds and sampling methodology is needed. In 2000 and 2001 we examined the influence of distance into the field on rootworm captures by CRW and Pherocon AM traps, the fidelity of trap captures to population estimates from visual counts of beetles on plants (whole plant samples), and the seasonal population patterns indicated by each sampling method. Only the CRW trap consistently indicated reduced trap captures at the field margin compared with other distances. However, trends for the AM trap and whole plant samples suggested sampling on the field margin should be avoided. Population estimates at other distances into the field (2-30 m) were usually statistically similar. Thus, monitoring does not require trap placement far into the field. Both trap types indicated population peaks after flowering in corn, whereas plant samples indicated peak populations during tasseling and flowering. Both the CRW trap and plant samples showed the proportion of female beetles increased as the season progressed, but the CRW trap underestimated the proportion of females until after flowering. Regressions relating captures by traps to counts from plant samples indicated efficiency of both traps increased with increasing plant development. Our findings should increase acceptance of the CRW trap by producers and consultants and provide a rationale for development of improved, plant growth stage-specific treatment thresholds.     

Maxillary appendages used by western corn rootworms, Diabrotica virgifera virgifera, to discriminate between a phagostimulant and -deterrent

Ablation of maxillary appendages on western corn rootworm, Diabrotica virgifera virgifera LeConte (Coleoptera: Chrysomelidae), were used to determine which mouthparts were involved in discrimination between the phagostimulant, cucurbitacin B, and the phagodeterrent, strychnine. Strychnine deterred feeding in unablated beetles when its concentration on disks was equal to or higher than cucurbitacin B. Unilateral or bilateral lacinea ablation did not affect discrimination between cucurbitacin B and strychnine. Galeal ablations abolished strychnine deterrence at equimolar concentrations of both compounds but not at higher strychnine concentrations, whereas maxillary palp ablation had no effect. However, bilateral ablation of both galea and maxillary palps resulted in a loss of deterrence at all strychnine concentrations. These results indicated strychnine sensitive chemoreceptors were primarily located on the galeae and maxillary palps. However, beetles without galeae and palps still feed on disks suggesting that cucurbitacin B sensitive chemoreceptors were located on other mouthparts and contributed to cucurbitacin B phagostimulation.     

Selection for Cry3Bb1 resistance in a genetically diverse population of nondiapausing western corn rootworm (Coleoptera: Chrysomelidae)

Five short-diapause laboratory lines of western corn rootworm, Diabrotica virgifera virgifera LeConte (Coleoptera: Chrysomelidae), were selected for resistance to MON863, a variety of corn genetically modified with the Bacillus thuringiensis Berliner (Bt) transgene that expresses the Cry3Bb1 delta-endotoxin. Three of the selected lines were developed by incremental increase in the duration of exposure to MON863 over 11 generations (moderate selected lines). Two selected lines were developed from a control group by constant exposure to MON863 for at least 14 d posthatch over seven generations (intense selected lines). At the end of the experiment, survivorship, as measured by adult emergence, was approximately 4 times higher in each of the selected lines reared on MON863 compared with control lines. Estimates of realized heritabilities (h2) were 0.16 and 0.15 for the moderate and intense selected lines, respectively, and are consistent with h2 estimates reported previously from a variety of pest insects. These lines provide data necessary for evaluating the potential for Bt resistance within diabroticite beetles and will be useful for developing improved insect resistance management strategies.     

Evidence of Field-Evolved Resistance to Bifenthrin in Western Corn Rootworm (Diabrotica virgifera virgifera LeConte) Populations in Western Nebraska and Kansas

Pyrethroid insecticides have been used to control larvae or adults of the western corn rootworm (WCR), Diabrotica virgifera virgifera LeConte, a key pest of field corn in the United States. In response to reports of reduced efficacy of pyrethroids in WCR management programs in southwestern areas of Nebraska and Kansas the present research was designed to establish a baseline of susceptibility to the pyrethroid insecticide, bifenthrin, using susceptible laboratory populations and to compare this baseline with susceptibility of field populations. Concentration-response bioassays were performed to estimate the baseline susceptibility. From the baseline data, a diagnostic concentration (LC₉₉) was determined and used to test adults of both laboratory and field populations. Larval susceptibility was also tested using both laboratory and field populations. Significant differences were recorded in adult and larval susceptibility among WCR field and laboratory populations. The highest LC₅₀ for WCR adults was observed in populations from Keith 2 and Chase Counties, NE, with LC₅₀s of 2.2 and 1.38 μg/vial, respectively, and Finney County 1, KS, with 1.43 μg/vial, as compared to a laboratory non-diapause population (0.24 μg/vial). For larvae, significant differences between WCR field and laboratory populations were also recorded. Significant differences in mortalities at the diagnostic bifenthrin concentration (LC₉₉) were observed among WCR adult populations with western Corn Belt populations exhibiting lower susceptibility to bifenthrin, especially in southwestern Nebraska and southwestern Kansas. This study provides evidence that resistance to bifenthrin is evolving in field populations that have been exposed for multiple years to pyrethroid insecticides. Implications to sustainable rootworm management are discussed.     

Resistance of Colorado potato beetle (Leptinotarsa decemlineata Say) to commonly used insecticides in Iran

The Colorado potato beetle (CPB, Leptinotarsa decemlineata Say), is a major pest of potatoes in Iran and many other parts of the world. Injury is caused when adults and larvae feed on the foliage and stems of potato plants, resulting in poor yields and/or plant death. Adult beetles can also vector plant diseases. Historically, the CPB been controlled using different insecticides, but it is currently resistant to nearly all classes of insecticides and remains a serious pest in many parts of the world. All of the resistance mechanisms reported in insects have been demonstrated in CPB. L. decemlineata invaded Iran in the early 1980s, probably through the importation of infested potatoes. It has caused significant damage to potato crops in affected areas, and it accordingly remains a major threat to Iranian potato production. Regrettably, no IPM programs have been developed for managing CPB infestations in Iran. Furthermore, there are no organized CPB resistance monitoring programs in Iran, and the recommended insecticides for CPB control, endosulfan and phosalon, have not changed in over 22 years. Anecdotal evidence from local farmers suggests a reduction in the efficacy of control of CPB by commonly used insecticides, probably due to the reduced susceptibility to these insecticides. Given the economic significance of L. decemlineata infestations, the increasing prevalence of resistance in this species, the rate of spread of infestations, and the extent of the area infested, there is an urgent need to develop effective and sustainable integrated pest management programs for CPB in Iran.     

Evaluation of cucurbitacin-based gustatory stimulant to facilitate cucumber beetle (Coleoptera: Chrysomelidae) management with foliar insecticides in melons

The bitter plant-derived compounds cucurbitacins are known to stimulate feeding of adult cucumber beetles (Coleoptera: Chrysomelidae). A cucurbitacin-based gustatory stimulant applied as a flowable bait combined with either spinosad or carbaryl was compared with foliar sprays of spinosad and carbaryl for controlling two cucumber beetle species (Diabrotica undecimpunctata undecimpunctata Mannerheim and Acalymma trivittatum Mannerheim) in honeydew melons (Cucumis melo L.). Field studies were conducted on the University of California-Davis plant pathology farm in 2008 and 2009. Beetle densities after applications and fruit damage from beetle feeding were compared among treatments. In addition, beetle survival was compared within field cages placed over the treated foliage infested with beetles. Using all three measures of efficacy, we determined that the addition of cucurbitacin bait had no effect on the level of cucumber beetle control with carbaryl in either 2008 or 2009. In both years, spinosad did not significantly reduce cucumber beetle densities in either field cages or field plots and did not reduce fruit damage relative to the untreated control. The addition of the bait to spinosad did not improve its efficacy. A laboratory bioassay of the spinosad formulation used in the field showed it had significant lethal effects on adults of both cucumber beetle species. Results indicated that the bait formulation used did not improve cucumber beetle control but may benefit from the addition of floral attractants or using a different type of cucurbitacin.     

Sublethal effects of deltamethrin exposure of parental generations on physiological traits and overwintering in Leptinotarsa decemlineata

Although the evolution of insecticide resistance has received a lot of attention, less is known about sublethal effects of insecticide stress experienced by the preceding generations on the performance of pest populations. We investigated whether three generations of parental exposure to a deltamethrin insecticide influences physiological traits and overwintering success of offspring in Leptinotarsa decemlineata (Say) (Coleoptera: Chrysomelidae). Beetles descending from insecticide‐exposed parents had lower adult body mass but higher relative lipid content and resting metabolic rate than those descending from non‐insecticide‐exposed parents. Also, a higher proportion of beetles descending from insecticide‐exposed parents than from control parents overwintered on the soil surface, which was associated with very low overwintering survival. When burrowed into the soil for overwintering, both groups had similar probability to survive the overwintering period. Parental insecticide exposure can reduce overall overwintering survival in the next generation by disturbing overwintering behaviour. Although beetles descending from insecticide‐exposed parents were small, the overwintering conditions seem to select for high lipid content, which could override the negative effects of small weight, and possibly improve fitness in the following growing season. Thus, insecticide application may have unintended consequences, which should be considered in pest management.     

Water solutions of boric acid and sugar for management of German cockroach populations in livestock production systems

Pest management in confinement swine production relies primarily on calendar-based applications of broad-spectrum insecticides. However, regulatory restrictions imposed by the U.S. Food Quality Protection Act of 1996, the large financial obligation of pesticide registration, and development of insecticide resistance have led to a renewed search for alternative control methods. Boric acid dust has long served as an insecticide in urban pest management and has been shown an effective alternative for use in sensitive environments such as swine production. However, dust formulations are difficult to apply and require specialized equipment. The purpose of this study was to evaluate the efficacy of liquid baits containing boric acid for the control of German cockroaches in a commercial swine nursery. Bait, consisting of 1 or 2% boric acid and 0.5 M sucrose, was deployed in 21 bait delivery tubes per room. Results of a 2-yr study showed significant reductions in cockroach populations. When baits were withdrawn in the summer, the cockroach population increased significantly faster than when the baits were removed during the winter. These data indicate that liquid formulations of boric acid effectively reduce the burden of cockroach infestation in swine production. This approach should have applications in structures in other urban and agricultural environments.