A strain of the fungus Beauveria bassiana (Balsamo) Vuillemin (Deuteromycota: Hyphomycetes) isolated from varroa mites, Varroa destructor Anderson & Trueman (Acari: Varroidae), was used to treat honey bees, Apis mellifera L. (Hymenoptera: Apidae), against varroa mites in southern France. Fungal treatment caused a significant increase in the percentage of infected varroa mites compared with control treatments in two field experiments. In the first experiment, hives were treated with a formulation containing 0.37 g of B. bassiana conidia per hive and in the second experiment with a dose of 1.0 g of conidia per hive. The percentage of infected varroa mites also increased in the nontreated (control) hives, suggesting a movement of conidia, probably via bee drift, among the hives. Mite fall was significantly higher among treated hives compared with control hives on the sixth and eighth days after treatment in the first experiment. These days correspond to previously published data on the median survivorship of mites exposed to that fungal solate. The interaction of treatment and date was significant in the second experiment with respect to mite fall. Increases in colony-forming unit (cfu) density per bee were observed in all treatments but were significantly higher among bees from treated hives than control hives for at least a week after treatment. The relationship between cfu density per bee and proportion infected was modeled using a sigmoid curve. High levels of infection (>80%) were observed for cfu density per bee as low as 5 × 10² per bee, but the cfu density in hives treated with 0.37 g generally dropped below this level less than a week after treatment.

By applying insecticides at lower rates of active ingredients per unit area, survival rates of the pests’ natural enemies can be enhanced, whereas pest mortality can remain high. The effects of reduced application rates of the insecticides lambda-cyhalothrin and dimethoate on the mortality of bird cherry-oat aphid, Rhopalosiphon padi (L.), and lacewing Micromus tasmaniae Walker were determined in the laboratory and field. Cholinesterase (ChE) and glutathione S-transferase (GST) activities in survivors provided a measure of sublethal effects and general fitness. In the laboratory, lacewings were less sensitive than aphids to both insecticides, and dimethoate was more toxic than lambda-cyhalothrin. However, these results could not be recreated in the field, in part due to very low recapture rates. In summary, lambda-cyhalothrin seemed to have no effect on aphids, but it was toxic to lacewings. Dimethoate was far less toxic in the field, but aphids were still more sensitive than were lacewings. Cholinesterase activity was reduced by dimethoate exposure in the laboratory in both species, but there were species-specific differences. Dimethoate and lambda-cyhalothrin had no effects on GST activity in either species. The high mortality rate for lacewings and aphids exposed to dimethoate in the field suggests that the application rate could be reduced to as low as 10% of that recommended by manufacturers, and this should still be highly efficacious against aphids, while protecting the predatory lacewing. Measurement of enzyme activity could provide a useful indicator of “fitness” of survivors.

Xestia c-nigrum granulovirus (XcGV) was tested for its ability to increase Spodoptera litura nucleopolyhedrovirus (SlNPV) infection in larvae of S. litura (F.). The interaction of XcGV with peritrophic matrix and SlNPV in S. litura also was studied to account for the synergism. In dose-response bioassays with a constant XcGV concentration of 5-mg/ml capsules and SlNPV concentration that varied from 10³ to 10⁷ polyhedral inclusion bodies (PIB) per larva, XcGV increased the virulence of SlNPV infection in fifth instars of S. litura. The lethal concentration of 50% individuals (LC₅₀) of SlNPV combined with XcGV was 3.35 × 10⁵PIB/ml, which was significantly lower than that of SlNPV alone (2.17 × 10⁶). Compared with 10⁷ PIB/ml SlNPV alone, the lethal time of 50% individuals (LT₅₀) of 10⁷ PIB/ml SlNPV combined with XcGV was not significantly shortened. In addition, no significant improvement in the activity and killing speed of SlNPV progeny was noted after propagation with XcGV, indicating that native characters of SlNPV associated with viral potency were not altered by XcGV. Investigation via environmental scanning electronic microscopy showed that the peritrophic matrix (PM) of S. litura exposed to XcGV or XcGV enhancin, or the combination treatment, was markedly disrupted. The outer surface of the PM was loose, or ruptured, which potentially facilitated the passage of virions through the PM. Therefore, it is reasonable to conclude that the synergy between XcGV and SlNPV was closely associated with the disruption of the PM in S. litura.

We evaluated the possibility of using the eggs laid out of host to rear Exorista larvarum (L.) (Diptera: Tachinidae), a larval parasitoid of Lepidoptera, on artificial media. In a first experiment, eggs oviposited on a plastic sheet (either by inexperienced or experienced females) showed the same in vitro hatching capability as those removed from the larvae of the factitious host Galleria mellonella L. Subsequently, eggs laid on the host integument or out of host, either by inexperienced or experienced females, were removed from the oviposition substrate and placed on a skimmed milk-based artificial medium. The percentages of hatched eggs, of puparia and adults, as well as the puparial weights did not differ significantly among the three treatments. These findings suggested that E. larvarum may be successfully reared in vitro with a total exclusion of the host insect. In a further test, no difference for the in vitro hatching time was found between the eggs oviposited either on a plastic sheet or on G. mellonella larvae in the same length of time (60 min). This result suggested that at oviposition the out-of-host eggs were unincubated, similarly to those that had been laid on the host larvae.

We determined that spinosad interacts synergistically with the biocontrol agent Metarhizium anisopliae (Metch) Sorokin to increase the mortality of two wild-collected wireworm species, Agriotes lineatus (L.), and Agriotes obscurus (L.). Bioassays were performed using a M. anisopliae isolate originally acquired from a local wireworm cadaver. M. anisopliae was applied as a soil drench at 3.3 × 10² and 10⁴ conidia per gram sand, respectively. Soil drenches also were prepared using a commercial formulation of the actinomycete toxins spinosyn-A and spinosyn-D (common name spinosad) at sublethal doses of 1.5, 3, and 6 ppm active ingredient per gram sand. Combined treatments of spinosad and M. anisopliae were synergistic in causing mortality for all spinosad concentrations. Wireworm feeding activity was reduced after exposure to both spinosad and M. anisopliae and was found to be concentration dependent. The high mortality and reduced rate of wireworm feeding suggest that spinosad and M. anisopliae treatment combinations should be tested in the field.

Organic lettuce, Lactuca sativa L., producers on California’s Central Coast rely on endemic syrphid flies (Diptera: Syrphidae) to suppress populations of Nasonovia ribisnigri Mosley (Homoptera: Aphididae) and other aphids affecting lettuce. Growers are using various forms of habitat manipulation to enhance biological control. We surveyed syrphids collected from organic romaine in and around the Salinas Valley from March through September 2005 to gain a better understanding of the species responsible for aphid suppression and to examine possible implications for biocontrol. The primary species of syrphid fly reared were Toxomerus marginatus (Say) (39%), Platycheirus stegnus (Say) (27%), Sphaerophoria sulfuripes (Thomson) (13%), and Allograpta obliqua (Say) (10%). Syrphus opinator Osten Sacken (2%), Toxomerus occidentalis (Curran) (1.3%), and Eupeodes volucris Osten Sacken (1%) were less common. Sphaerophoria pyrrhina Bigot, Scaeva pyrastri (L.), Platycheirus obscurus Say, Allograpta exotica Wiedemann, and Eupeodes americanus Wiedemann each made up <1% of the syrphids reared. T. marginatus and Sphaerophoria sulfuripes were commonly collected from romaine plants with few or no detectable aphids. P. stegnus was observed to deposit in clusters of eggs, and was only reared in significant numbers from highly infested fields. Approximately 5% of syrphid larvae overall were parasitized by either Diplazon sp. (Hymenoptera: Ichneumonidae) or Pachyneuron sp. (Hymenoptera: Pteromalidae).

We examined the amount of maturation feeding and transmission of pinewood nematodes, Bursaphelenchus xylophilus (Steiner et Buhrer) Nickle (Nematoda: Parasitaphelenchidae), to healthy pine (Pinus spp.) trees by pine sawyer Monochamus alternatus Hope (Coleoptera: Cerambycidae) adults infected with Beauveria bassiana (Balsamo) Vuill. (Deuteromycotina: Hyphomycetes). Inoculated beetles fed less than noninoculated beetles, probably because feeding by inoculated beetles began to decrease at about 4 d postinoculation and inoculated beetles ceased to feed for several days before their death. In inoculated beetles carrying >1,000 nematodes, some beetles died before nematode departure. The remaining heavily nematode-infested beetles lived until the beginning of nematode departure, but they had stopped feeding, preventing the nematodes from entering pine twigs. We suggest that microbial control of pine sawyer adults by B. bassiana may be effective in preventing transmission of pine wilt disease to healthy pine trees.

Pheromone-baited traps were used to monitor the movement of the Mexican rice borer, Eoreuma loftini (Dyar) (Lepidoptera: Crambidae), through the Texas rice belt from 2000 to 2005. Based on location of discovery in each county and year, the average rate of spread from 1980 to 2005 was 23 km/yr. From 2000 to 2005, the leading edge of the infestation has moved 16.5 km/yr toward Louisiana. The 1.8-fold increase (99% confidence interval) of the area occupied from 2000 to 2005 in the Texas rice belt indicates an expansion of the distribution of E. loftini. If movement continues to occur at similar rates, E. loftini will reach Louisiana by 2008.

Laboratory studies were conducted to determine the sublethal effects of exposure to selected larvicides on the critical swimming speed (U_crit) of crimson-spotted rainbowfish, Melanotaenia duboulayi (Castlenau). This native fish is common throughout southeastern Queensland, and it is increasingly being distributed as a biological control agent of mosquitoes. The selected larvicides included, two organophosphate (OP) compounds (temephos and pirimiphos-methyl), two microbial larvicides (Bacillus thuringiensis spp. israelensis [Bti] de Barjac and Bacillus sphaericus [Bs] Neide), and an insect growth regulator (IGR) (s-methoprene). Exposure to the OP temephos at 10 times the effective field concentration (EFC; 0.33 mg/liter), and OP pirimiphos-methyl at the EFC (0.50 mg/liter), resulted in a significant reduction in the U_crit of M. duboulayi under controlled conditions. Conversely, exposure to the microbial (Bti and Bs) and IGR (s-methoprene) larvicides at 10 times the EFC had no effect on the U_crit of M. duboulayi. Accordingly, these products are suitable for integrated pest management programs in Australia.

A 2-yr field study was conducted to evaluate a botanical natural product, AkseBio2, for control of pear psylla, Cacopsylla pyri L. (Homoptera: Psyllidae). Three applications were made each year. Whereas the first application was applied at the dormant period (just before the first eggs were deposited by overwintered females), the second and third applications, respectively, were against the first and second summer generations of pear psylla. The first application deterred winterform females from depositing eggs until the clusterbud stage (buds expanded but no blossoms open) of tree development. In the second and third applications, the product reduced the number of psyllid eggs and young (first and second) instars, causing up to 79.4 and 81.1% mortality, respectively. However, it was less active against the older (third–fifth) instars and achieved only up to 52.7% mortality. Reduction in egg laying was greater than that caused by amitraz, the most commonly used conventional pesticide for psylla control in Turkey. There were no significant horticultural changes on treated plants up to 7 d after treatment in any trial, nor was there any phytotoxicity on plant tissue as a result of AkseBio2 treatments.

The chemical communication (female attractiveness and male responsiveness) of adult oriental fruit moth, Grapholita molesta (Busck) (Lepidoptera: Tortricidae), exposed to surfaces treated with the ecdysteroid agonist methoxyfenozide for 48 h were investigated in two laboratory wind tunnel assays. The recapture assay examined the ability of treated males to orient to a single cage of treated females, and the data gathered were mean percentage of males recaptured per treatment. The male sexual behavior assay examined some specific orientation behaviors (associated with sexual excitability) of treated males when they were given a choice of two competing pheromone sources (cages of treated females), and the data gathered were mean time males spent in upwind plume orientations and at source contact (female cage) per treatment. Data from the recapture assay suggests that exposure to methoxyfenozide impacts male responsiveness more than female attractiveness. In contrast, data from the sexual behavior assay strongly revealed that exposure to methoxyfenozide-treated surfaces does negatively impact both the ability of calling females to attract males and of aroused males to display sustained upwind flight behavior and time spent at the female cages.

The wheat stem sawfly, Cephus cinctus Norton (Hymenoptera: Cephidae), has reached outbreak status at most locations in the southern Canadian prairies. Solid-stemmed wheat, Triticum aestivum L., cultivars, which are less susceptible to damage, remain the primary management option. This article quantifies the effect of wheat stem sawfly damage on grain yield and quality at harvest and determines how cultivar selection affects harvest losses. Solid-stemmed cultivars were compared with hollow-stemmed cultivars and with blends of a 1:1 ratio of each. The hollow-stemmed cultivars with the exception of ‘McKenzie’, which had intermediate levels of stem cutting, were all significantly more susceptible to stem cutting than solid-stemmed cultivars. Cultivar blends had lower damage but were still significantly higher than the solid-stemmed cultivars. The solid-stemmed ‘AC Eatonia’ and ‘AC Abbey’ had the lowest levels of stem cutting and ranked second and third overall for yield in 2001 and 2002. McKenzie ranked first, which reflects its yield potential in combination with its partial resistance to stem cutting. Lower cutting in AC Eatonia, AC Abbey, McKenzie, and the blend of AC Abbey/McKenzie was significantly correlated with lower grain losses. Grain lost at harvest has major economic implications if sawfly pressure is moderate to high and susceptible cultivars predominate.

Rotations, tillage, and fertilizer treatments can affect yield, costs, and profitability in sorghum, Sorghum bicolor (L.) Moench, depending on their effects on pests. Rotation or planting different crops reduces soil erosion and pests that build up when a field is planted to the same crop each year. Minimum tillage reduces the number of trips over a field, lessening soil compaction and reducing costs. We examined the effects of fertilizer, tillage, and rotation with cotton, Gossypium hirsutum L., on sorghum head insects during three sampling periods each year from 2000 to 2003. We found that fertilizer treatments did not affect pests or predators. Also, predators were unaffected by rotation and tillage, which some years affected Helicoverpa zea (Boddie) and Oebalus pugnax (F.), both pests that feed on developing sorghum kernels, thereby reducing yield. In 2000, H. zea densities were greater in continuous sorghum, regardless of tillage practice, than in sorghum–cotton rotation. However, in 2003, H. zea densities were greater in minimum tillage plots within sorghum–cotton rotation than minimum tillage plots within continuous sorghum. In 2000, in sorghum–cotton rotation, O. pugnax densities were greater in minimum tillage than conventional tillage plots, whereas in continuous sorghum the opposite was true, O. pugnax were greater in conventional tillage. Also, O. pugnax were greater in sorghum–cotton rotation than in continuous sorghum. In 2002, O. pugnax densities were greater in conventional than minimum tillage plots. These results suggest that rotation of sorghum with cotton can sometimes reduce H. zea, but this reduction may occur with increased density of O. pugnax. Also, reducing tillage may reduce O. pugnax in some instances.

Cultural and chemical controls were evaluated to determine their ability to deter feeding by Japanese beetles, Popillia japonica Newman (Coleoptera: Scarabaeidae), on floribunda type roses, Rosa ‘Acadia Sunrise’. Roses were arranged in field plots and exposed to resident adult beetle populations. Cultural controls were designed to block the feeding-induced aggregation response by manually removing beetles and/or damaged blooms from rose plants. Azadirachtin, carbaryl, and imidacloprid were evaluated in field and laboratory trials. In no-choice laboratory assays, foliar applications of azadirachtin caused low rates of morbidity to adult beetles and were unable to deter feeding. Foliar-applied carbaryl and soil-applied imidacloprid caused high rates of morbidity and reduced feeding injury. In the field, foliar sprays of azadirachtin and carbaryl, deterred feeding on foliage under low beetle pressure (maximum of 29% defoliation in untreated controls), when applied weekly after first beetle flight or every 2 wk after 5% injury was reached. A single foliar application of these materials at the 5% injury level did not significantly reduce peak defoliation. Soil applications of imidacloprid also deterred foliar feeding in the field. Blooms were more difficult to protect with both foliar- and soil-applied insecticides with only weekly application of foliar insecticides providing significant reductions in bloom injury. Removing beetles and/or blooms provided marginally greater reductions in leaf and flower injury. This suggests that blocking the feeding-induced aggregation response of Japanese beetles can provide only modest levels of control in roses where both flowers and feeding-induced volatiles recruit beetles to plants.

Japanese beetle traps baited with the Popillia japonica Newman (Coleoptera: Scarabaeidae) pheromone lure and a eugenol feeding attractant were placed at five golf courses in Korea to determine how well they work for detecting activity of a closely related species, Popillia quadriguttata (F.) (Coleoptera: Scarabaeidae), a turf pest in Korea. The traps also were used to determine the time of day and time of year that P. quadriguttata is most active. Nineteen scarab species of 13 genera were attracted to the Japanese beetle traps with P. quadriguttata clearly being the most abundant (383 beetles per trap), followed by Adoretus tenuimaculatus Waterhouse (10 per trap), Popillia flavosellata Fairmaire (seven per trap), Exomala orientalis Waterhouse (four per trap), and Maladera japonica (two per trap). Other scarab species were trapped at a rate of <1.0 per trap. Popillia quadriguttata adults were active over a 5-wk period in late June and early July. At Yongwon Golf Club in 2002, peak adult activity was during the last week of June in visual counts and ≈1 wk later in the Japanese beetle traps. In Korea, P. quadriguttata adults are most active between 12:00 p.m. and 4:00 p.m. This information should be helpful to golf course superintendents in Korea and to entomologists interested in finding natural enemies of P. quadriguttata to evaluate as potential biocontrol organisms for the very closely related species, the Japanese beetle.

The parasitoid Encarsia formosa Gahan (Hymenoptera: Aphelinidae) has been used successfully for the control of Trialeurodes vaporariorum (Westwood) (Homoptera: Aleyrodidae). The development of UV-blocking plastic films has added a new component to future integrated pest management systems by disrupting insect pest infestation when UV light is excluded. Because both T. vaporariorum and E. formosa are reported to have similar spectral efficiency, there was a need to identify the impact of UV-blocking films on the dispersal behavior of both the pest and the natural enemy. In field studies, using choice-chamber experiments, E. formosa showed some preference to disperse into compartments where less UV light was blocked. However, further studies indicated that the effect was primarily attributable to the different light diffusion properties of the films tested. Thus, unlike its whitefly host, when the UV-absorbing properties of the films were similar, but the light diffusion properties differed, E. formosa adults preferred to disperse into compartments clad with films that had high light diffusion properties. When the plastic films differed most in their UV-absorbing capacity and had no light-diffusion capability, the initial dispersal of E. formosa between treatments was similar, although a small preference toward the environment with UV light was observed over time. When parasitoid dispersal was measured 3 h after release, more parasitoids were found on plants, suggesting that the parasitoids would search plants for whitefly hosts, even in a UV-blocked light environment. The potential for the integration of UV-blocking films with E. formosa in an advanced whitefly management system is discussed.

Azadirex (azadirachtin and other biologically active extracts from neem trees) has been shown to have considerable potential to be used in integrated pest management systems based on its growth regulator/insecticide properties. Less well known are the antifeedant properties. The feeding-deterrent properties of a commercial azadirex formulation (Azatrol EC) were evaluated using both no-choice and choice tests, the American grasshopper, Schistocerca americana (Drury), and four host plants [savoy cabbage, Brassica oleracea variety capitata L.; cos (romaine) lettuce, Lactuca sativa variety longifolia Lam.; sweet orange, Citrus sinensis variety Hamlin L.; and peregrina, Jatropha integerrima Jacq.]. These studies demonstrated that azadirex application can significantly affect the feeding behavior of grasshoppers. Some degree of protection can be afforded to plants that differ markedly in their innate attractiveness to the insect, although the level of protection varies among hosts. The tendency of grasshoppers to sometimes feed on azadirex-treated foliage suggests that it will be difficult to prevent damage from occurring at all times, on all hosts. No evidence of rapid habituation to azadirex was detected. Rapid loss of efficacy was observed under field conditions, suggesting that daily retreatment might be necessary to maintain protection of plants from feeding.

Economic injury level (EIL) and economic threshold (ET) were established for Aulacorthum solani (Kaltenbach) (Hemiptera: Aphididae) in greenhouse pepper, Capsicum annuum L. The high toxicity of the salivary secretion of A. solani produces deformation and decoloration of leaves, complete plant defoliation, and unmarketable deformed fruits at high densities. Low, high and null infestation rate treatments provided a broad range of population densities to determine the relationship between yield and the cumulative A. solani-days (CAD). In all infested compartments, A. solani reached a very high population density that eventually produced the complete defoliation of the plants and losses in total and marketable yield. At low A. solani density, pepper plants showed a tolerance response. Generalized Additive Models (GAM) and Gompertz equation were used to determine the relationship between yield and CAD. Both models explained a high proportion of the variance and described well the relationship between the two variables. However, GAM predicted the tolerance phase of the yield–CAD relationship more satisfactorily. The theoretical damage curve predicted by GAM describes a tolerance, compensation and a linearity part. EIL was estimated at 57 CAD. ET was established at 20 CAD to prevent aphid density from reaching EIL within the gap between sampling periods.

In conjunction with efforts to identify efficient insect pollinators for seed multiplication of cross-pollinated plant species stored and maintained by USDA–ARS Western Regional Plant Introduction Station (WRPIS), experiments were conducted to assess and compare the efficiency of the house fly, Musca domestica L. (Diptera: Muscidae), and Calliphora vicina Robineau-Desvoidy (Diptera: Calliphoridae), and different densities of each fly species, to pollinate leek, Allium ampeloprasum L., plant inventory (PI) accessions in field cages for seed yield maximization and high germination. Cages with flowering plants were exposed to 0 flies or stocked with 100, 250, and 500 M. domestica or C. vicina pupae per week for 6 (2002) and 7 (2004) wk. Seed yield (weight per cage) increased linearly as fly densities (C. vicina or M. domestica) increased from 0 to 500 pupae per week, with 500 fly cages averaging 340.7 g (C. vicina) and 70.5 g (M. domestica) of seed in 2002 (PI 368343) and 615.3 g (PI 168977) and 357.5 g (PI 368343) in 2004 when only the C. vicina was used. For 0, 100, and 250 fly cages, seed yields averaged between 2.3 and 175.3 g in 2002 and 10.7 and 273.1 g in 2004. Mean 100-seed weights between treatments ranged narrowly between 0.4 and 0.5 g in 2002 and 0.3 and 0.4 g in 2004, and germination rates of seed lots from “fly cages” were mostly ≥80% in both years. The C. vicina is an efficient and cost-effective pollinator ($388.97 for pupae and shipping, compared with $2,400 for honey bee, Apis mellifera L. [Hymenoptera: Apidae], nuclei) for caged leek accessions, with 250 and 500 C. vicina pupae per week required to produce sufficient seed (130 g) to fill an accession storage bag in the WRPIS gene bank.

A 2-yr study was conducted to document the influence of selected buffalograss, Buchloë dactyloides (Nuttall) Engelmann, management practices (three mowing heights and five nitrogen levels) on the seasonal abundance of the western chinch bug, Blissus occiduus Barber (Heteroptera: Lygaeidae), and its beneficial arthropods. Vacuum, pitfall, and sticky traps samples were collected every 14 d from the middle of May through October from western chinch bug-resistant (‘Prestige’) and -susceptible (‘378’) buffalograss management plots. In total, 27,374 and 108,908 western chinch bugs were collected in vacuum and pitfall traps, respectively. More than 78% of all western chinch bugs were collected from the highly susceptible buffalograss 378. Significantly more bigeyed bugs (Geocoridae: Geocoris spp.) were collected from the 378 buffalograsss management plots than the Prestige plots. In contrast, buffalograss cultivar had little influence on the abundance of other beneficial arthropods collected. Statistically, western chinch bugs were least abundant at the lowest mowing height (2.5 cm) and increased in abundance with increasing fertility. Numerically, however, differences among management levels on western chinch bug abundance were minimal. Numerous beneficial arthropods were collected from buffalograss management plots, including spiders, predatory ants, ground beetles (Carabidae), rove beetles (Staphylinidae), bigeyed bugs, and several species of hymenopterous parasitoids. In general, beneficial arthropods were essentially unaffected by either mowing height or nitrogen level. Scelionid wasps represented 66.3% of the total parasitoids collected. The total number of scelionid wasps collected among the three mowing heights and five nitrogen levels were approximately equal.

The Argentine ant, Linepithema humile (Mayr), and the red imported fire ant, Solenopsis invicta Buren, are natural agonists in their country of origin. Since the first report of L. humile in California in 1907 its range expanded statewide, displacing native ant species wherever it spread. Since the discovery of established populations of S. invicta in southern California in 1998, it has been restricted to discrete areas of southern California. However, as these discrete populations expand, they are encountering large populations of L. humile, which are effective competitors for available resources and are particularly aggressive in their encounters with other ant species such as S. invicta. Most Dolichoderine ants such as L. humile do not prefer to forage on baits made with defatted corn grit and soybean oil typically used in red imported fire ant control programs. Applications of these baits in areas where distributions of these species overlap might selectively affect populations of S. invicta and give L. humile a competitive advantage. Three laboratory experiments were conducted to determine the competitive outcomes between S. invicta pitted against L. humile: 1) agonistic behavior of workers in small arenas, 2) colony interactions with different population ratios, and 3) the effects of pyriproxyfen on the competitiveness of S. invicta against L. humile. Populations of S. invicta consisting of major workers killed more L. humile than did minors or a mixture of majors and minors. When paired against L. humile colonies consisting of 1,100 workers, colonies consisting of 38 S. invicta workers were easily defeated by L. humile. Colonies consisting of 450 S. invicta workers plugged their nest entrances, but they were ultimately defeated by L. humile after 13 d. The S. invicta colonies consisting of 1,100 workers took control of the bridge connecting the colonies, invaded the L. humile colony, killed the Argentine ant queens, and removed their brood. Pyriproxyfen-treated fire ant workers took significantly longer to chase the Argentine ants from a connecting bridge than did untreated fire ants. Thus, fire ant baits may have long-term effects on intercolonial aggression between S. invicta and L. humile, especially when Argentine ant populations are high in the summer.

The activity of spinosad, imidacloprid, and methomyl baits and technical actives were assessed against susceptible house flies, Musca domestica L. (Diptera: Muscidae). In a feeding assay, imidacloprid affected flies more rapidly than methomyl or spinosad, but spinosad was 2.7 times more potent than methomyl and 8 times more potent than imidacloprid. The profile of technical actives correlated with their respective fly bait formulations in laboratory assays. Although having the most rapid onset of activity in laboratory tests, up to 50% of flies remained alive after exposure to imidacloprid bait. In contrast, <5% of flies survived 24-h exposure to spinosad or methomyl baits. High temperature reduced the knockdown activity of imidacloprid bait and slowed the speed of kill for spinosad and methomyl baits over a 24-h exposure period. Spinosad and methomyl baits were also superior to imidacloprid when applied to the floors of environmentally controlled rooms at label recommended rates, providing good fly control for up to 21 d. The fact that a significant percentage of flies exposed to imidacloprid were rapidly knocked down but subsequently remained alive in all of the assays suggested that flies were recovering from initial exposure to this compound. Given its favorable safety profile, a high degree of initial and residual activity comparable with methomyl and lack of cross-resistance to other chemistries, spinosad bait may be a valuable component of house fly control programs to help control or delay the emergence of resistant populations.

Transgenic maize, Zea mays L., expressing the Bacillus thuringiensis (Bt) Cry1Ab toxin has been planted to extensive areas across the United States and several other countries, but no resistance has been documented in field populations of lepidopteran target pests. This article describes the first report of resistance alleles to commercially available Cry1Ab Bt maize in a Louisiana population of sugarcane borer, Diatraea saccharalis (F.) (Lepidoptera: Crambidae). Two hundred thirteen two-parent isolines of D. saccharalis were screened for Cry1Ab resistance on Bt maize leaf tissue using an F₂ screening technique. Larvae representing three isolines survived >15 d on Bt tissue in the F₂ generation. The second generation backcross progeny (B₁F₂) derived from isoline 52 completed larval development on Bt maize in the greenhouse. Segregation and resistance frequency analysis associated with isoline 52 suggested that Bt resistance is probably determined by a nearly completely recessive allele at a single locus. With this assumption, the estimated resistance allele frequency in this population is 0.0023, within a 95% confidence interval of 0.0003–0.0064.

Transgenic potato, Solanum tuberosum L., plants containing a synthetic cry1Ac gene coding for the Bacillus thuringiensis (Bt) crystalline insecticidal protein were produced and evaluated for resistance to Tecia solanivora Povolny (Lepidoptera: Gelechiidae), the larvae of which attack potato tubers. In total, 43 transgenic lines of commercial Andean potato varieties Diacol Capiro, Pardo Pastusa, and Pandeazúcar were obtained. These transgenic lines were found to have one to four copies of cry1Ac per genome and expression levels of Cry1Ac protein varying from 0.02 to 17 μg/g fresh tuber tissue. Bioassays of T. solanivora larvae on these transgenic potato tubers showed 83.7–100% mortality, whereas the mortality levels on nontransgenic lines were 0–2.67%. Our data indicate the capability of Bt transgenic technology to control the T. solanivora while reducing the use of chemical insecticides. Further studies under controlled field conditions will be helpful in exploring the potential of Cry1Ac potatoes in the insect pest management strategies.

One susceptible and three Cry1Ac-resistant strains of tobacco budworm, Heliothis virescens (F.) (Lepidoptera: Noctuidae), were used in laboratory studies to determine the level of cross-resistance between the Bacillus thuringiensis (Berliner) toxins Cry1Ac and Vip3A by using concentration–mortality and leaf tissue experiments. Concentration–mortality data demonstrated that the three Cry1Ac-resistant H. virescens strains, YHD2, KCBhyb, and CxC, were at least 215- to 316-fold resistant to Cry1Ac compared with the susceptible strain, YDK. Results from Vip3A concentration–mortality tests indicated that mortality was similar among all four H. virescens strains. Relative larval growth on Cry1Ac reflected concentration–mortality test results, because YHD2 larval growth was mostly unaffected by the Cry1Ac concentrations tested. Growth ratios for KCBhyb and CXC indicated that they had a more moderate level of resistance to Cry1Ac than did YHD2. Relative larval growth on Vip3A was highly variable at lower concentrations, but it was more consistent on concentrations of Vip3A above 25 μg/ml. Differences in larval growth among strains on Vip3A were not as pronounced as seen in Cry1Ac experiments. Mortality and larval growth also was assessed in leaf tissue bioassays in which YDK, CxC, and KCBhyb neonates were placed onto leaf disks from non-Bt and Bt cotton, Gossypium hirsutum L., for 5 d. Three Bt lines were used in an initial bioassay and consisted of two Vip3A-containing lines, COT203 and COT102, and a Cry1Ac-producing line. Mortality of KCBhyb and CXC was lower than that of YDK larvae in the presence of leaf tissue from the Cry1Ac-producing line. Additionally, increased larval growth and leaf tissue consumption on Cry1Ac-containing leaf disks was observed for KCBhyb and CXC. Mortality and larval weights were similar among strains when larvae were fed leaf tissue of either non-Bt, COT203, or COT102. A subsequent leaf tissue bioassay was conducted that evaluated four cotton lines: non-Bt, Cry1Ab-expressing, Vip3A-expressing, and pyramided-toxin plants that produced both Cry1Ab and Vip3A. Mortality levels were similar among strains when fed non-Bt, Vip3A-expressing, or pyramided-toxin leaf tissues. Mortality was higher for YDK than for KCBhyb or CXC on Cry1Ab-expressing leaf tissues. No differences in larval weights were observed among strains for any genotype tested. Results of these experiments demonstrate that cross-resistance is nonexistent between Cry1Ac and Vip3A in H. virescens. Thus, the introduction of Vip3A-producing lines could delay Cry1Ac-resistance evolution in H. virescens, if these lines gain a significant share of the market.

The evolution of pest resistance to transgenic crop plants producing insecticidal toxins from Bacillus thuringiensis (Bt) Berliner poses a continuing threat to their sustainable use in agriculture. One component of the U.S.-wide resistance management plan for Bt cotton, Gossypium hirsutum L., involves monitoring the frequency of resistance alleles in field populations. However, existing methods are expensive and may not detect recessive resistance alleles until their frequencies are too high for countermeasures to be effective; therefore, more sensitive methods are needed. The first Bt resistance-causing mutation described at the molecular level was a retrotransposon insertion into the gene encoding a 12-cadherin-domain protein expressed in the midgut of larval Heliothis virescens (F.). We report the first large-scale screen for this mutation using a polymerase chain reaction (PCR)-based approach on >7,000 field-collected individuals. The specific insertion was not detected in any of these samples, nor was it detected in three progeny-tested, field-caught males thought to carry a Bt resistance gene. Unlike the targets of many chemical insecticides where a limited number of resistance-causing mutations compatible with viability can occur; a very large number of such mutations seem possible for the 12-cadherin-domain gene. However, even if these mutations are viable in the laboratory, they may not threaten the effectiveness of transgenic crops because of a high fitness cost in the field. The challenge remains to detect the subset of possible resistance-conferring alleles that are still rare but are viable in the field and increasing due to selection by Bt cotton. This situation will complicate PCR-based Bt resistance monitoring strategies.

The high-dose/refuge strategy is considered as the main strategy for delaying resistance in target pests to genetically modified crops that produce insecticidal proteins derived from Bacillus thuringiensis Berliner. This strategy is based on a key assumption that resistance alleles are initially rare (<10⁻³). To test this assumption, we used an F₂ screen on natural populations of Sesamia nonagrioides Lefebvre (Lepidoptera: Noctuidae) from Greece and Spain. In total, 75 lines from Greece and 85 lines from Spain were screened for survival of F₂ larvae on Cry1Ab corn, Zea mays L., leaves. No major resistance alleles were found. The frequency of resistance alleles in the Greek population was <9.7 × 10⁻³ with 95% probability, which was very similar to that of the Spanish population (<8.6 × 10⁻³ with 95% probability), and the expected frequencies were 3.2 × 10⁻³ (0–0.0097) and 2.9 × 10⁻³ (0–0.0086) in Greece and Spain (pooled 1.5 × 10⁻³). The experiment-wise detection probability of resistance was 94.0 and 97.5% for the Greek and the Spanish population, respectively. Evidence of alleles conferring partial resistance to Cry1Ab was found only for the Greek population. The frequency of alleles for partial resistance was estimated as 6.5 × 10⁻³ with a 95% credibility interval between 8 × 10⁻⁴ and 17.8 × 10⁻³ and a detection probability of 94%. Our results suggest that the frequency of alleles conferring resistance to Cry1Ab, regarding the population of S. nonagrioides, may be rare enough so that the high-dose/refuge strategy could be applied with success for resistance management.

Intersimple sequence repeat (ISSR) amplification was used to analyze genetic relationships among silkworm, Bombyx mori L., strains. Nineteen primers containing simple sequence repeat (SSR) motifs were tested for amplification on a panel of 42 strains, representative of the diversity of silkworm germplasm; 12 of the primers amplified distinct, reproducible bands. The primers amplified a total of 108 bands, of which 85 (78.7%) were polymorphic. The ISSR results suggested that within the dinucleotide class, the poly(CA) motif was more common than the poly(CT) motif. The ISSR amplification pattern was used to group the silkworm strains into seven subclusters based on their origin in an unweighted pair-group method with arithmetic average cluster analysis by using Nei’s genetic distance. Seven major ecotypic silkworm groups were analyzed. Principal component analysis of the ISSR data supported the unweighted pair-group method with arithmetic average clustering. Therefore, ISSR amplification is a valuable method for determining genetic variability among silkworm varieties. This efficient genetic fingerprinting technique should be useful for characterizing the large numbers of silkworm strains held in national and international germplasm centers.

Resistance to corn borers, Ostrinia nubilalis (Hübner) (Lepidoptera: Crambidae) and Sesamia nonagrioides (Lefebvre) (Lepidoptera: Noctuidae) in maize, Zea mays L., populations is partial, and more resistant populations are needed. The objective of this research was to compare resistance to corn borers of the main maize races from North America. Twenty open-pollinated maize populations belonging to the races Southern Dent, Corn Belt Dent, and Northern Flint, and three check populations, were evaluated under artificial infestation with S. nonagrioides and O. nubilalis. None of the populations had complete resistance. Northern Flint had the lowest yield under corn borer infestation, whereas Southern Dent had the highest yield but also the largest damage. Corn Belt Dent had a shorter growing cycle and similar yield of infected plants than Southern Dent. The checks had intermediate yield and resistance and were not significantly different from Corn Belt Dent for any trait. The Southern Dent populations Tennessee Red Cob and White Dent (PI221885 and PI311232) could be used as sources of tolerance to corn borers, although they are not expected to provide great gains compared with the levels of tolerance already present in some Corn Belt Dent and European Flint populations and would require adaptation to short growing cycle. The Corn Belt Dent synthetic BS17 had the highest yield and general agronomic performance under corn borer infestation, along with Rustler and Silver King, and the European Flint composite EPS13.

Selecting insect-resistant plant varieties is a key component of integrated management programs of oligophagous pests such as diamondback moth, Plutella xylostella (L.) (Lepidoptera: Plutellidae), but rigorous research on important life history parameters of P. xylostella in relation to host plant resistance is rare. We evaluated six conventional brassicaceous species, namely, Brassica napus L. ‘Q2’, B. rapa L., B. juncea (L.) Czern., B. carinata L., B. oleracea L., and Sinapis alba L., and two herbicide-tolerant cultivars, namely, B. napus ‘Liberty’ and B. napus ‘Conquest’ for their resistance against P. xylostella. Brassicaceae species and cultivars varied considerably in their susceptibilities as hosts for P. xylostella. Sinapis alba and B. rapa plants were highly preferred by ovipositing females and trichome density on adaxial and abaxial leaf surfaces had nonsignificant effects on P. xylostella oviposition. Larval survival was similar on the genotypes we tested, but host plants significantly affected larval and pupal developmental time, herbivory, pupal weight, silk weight, adult body weight, forewing area and longevity (without food) of both male and female P. xylostella. Larval and pupal development of females was fastest on B. juncea and S. alba, respectively. Specimens reared on B. napus Liberty and B. oleracea, respectively, produced the lightest female and male pupae. Defoliation by both female and male larvae was highest on B. rapa, whereas least herbivory occurred on S. alba. Females reared on S. alba were heavier and lived longer in the absence of food than their counterparts raised on other tested host plants. Brassica oleracea could not compensate for larval feeding to the level of the other species we evaluated. B. napus Conquest, B. napus Q2, B. carinata, B. rapa, and S. alba produced, respectively, 1.6-, 1.8-, 1.8-, 3.9-, and 5.5-fold heavier root systems when infested than their uninfested counterparts, suggesting that these species were better able to tolerate P. xylostella infestations.

Scouting techniques combining rapid counting methods must be developed to help growers with immediate decision making in integrated pest management programs. We evaluated a method for estimating densities of western flower thrips, Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae), one of the most damaging insect pests of greenhouse cucumber, Cucumis sativus L., and rose, Rosa × hybrida crops in southeastern France. This method is based on abundance classes of thrips observed on sampling units of flowers and foliage during a period of <1 min. Classes were calibrated using actual counts, and precision was improved by introducing additional predictive variables into multivariate nonparametric regression models. Regression models using infestation variables with and without climatic variables significantly increased calibration precision and made possible the accurate description of population dynamics. Rapid visual scouting methods could be combined for surveys of different pests and diseases. When calibrated, they provide growers or technicians with accurate tools guiding crop protection decisions.

Binomial sampling based on the proportion of samples infested was investigated for estimating mean densities of citrus rust mite, Phyllocoptruta oleivora (Ashmead), and Aculops pelekassi (Keifer) (Acari: Eriophyidae), on oranges, Citrus sinensis (L.) Osbeck. Data for the investigation were obtained by counting the number of motile mites within 600 sample units (each unit a 1-cm² surface area per fruit) across a 4-ha block of trees (32 blocks total): five areas per 4 ha, five trees per area, 12 fruit per tree, and two samples per fruit. A significant (r² = 0.89), linear relationship was found between ln(−ln(1 −P₀)) and ln(mean), where P₀ is the proportion of samples with more than zero mites. The fitted binomial parameters adequately described a validation data set from a sampling plan consisting of 192 samples. Projections indicated the fitted parameters would apply to sampling plans with as few as 48 samples, but reducing sample size resulted in an increase of bootstrap estimates falling outside expected confidence limits. Although mite count data fit the binomial model, confidence limits for mean arithmetic predictions increased dramatically as proportion of samples infested increased. Binomial sampling using a tally threshold of 0 therefore has less value when proportions of samples infested are large. Increasing the tally threshold to two mites marginally improved estimates at larger densities. Overall, binomial sampling for a general estimate of mite densities seemed to be a viable alternative to absolute counts of mites per sample for a grower using a low management threshold such as two or three mites per sample.

A highly absorbent cellulose fiber from recycled paper was tested and compared with a polyacrylate gelling agent, Aquatain, normally used for bulking and solidifying larval rearing medium of screwworm, Cochliomyia hominivorax (Coquerel) (Diptera: Calliphoridae). The absorbent fiber, when mixed with water and dietary ingredients, produced a diet medium of homogeneous texture that supported larval growth and development comparable with the standard gelled diet. Larval and pupal weights from two concentrations of cellulose fiber-based diet were significantly higher than those obtained using gelled diet. The number of pupae per tray, percentage of adult emergence, oviposition, percentage of egg hatch, and adult longevity obtained from the insects reared in the cellulose fiber-based diet were comparable or slightly better than the biological parameters recorded from flies reared in the gelled diet. Moreover, results indicate that a lesser amount of the cellulose fiber-based diet than the normal amount of gelled diet per tray would support normal larval growth. Physical properties and texture of the new diet seem to allow the larvae to move and feed more freely than they do on the semisolid gelled diet, resulting in less wasted diet. The cellulose fiber is biodegradable and inexpensive, whereas the polyacrylate gel polymer is not biodegradable and is relatively expensive. Replacing gel with cellulose fiber in the screwworm larval diet for mass rearing should result in substantial cost savings in material and labor as well as eliminating concern of environmental pollution due to diet waste disposal.

Xenorhabdus nematophila is the symbiotic bacterium of an entomopathogenic nematode, Steinernema carpocapsae. When the nematode enters a target insect, the symbiotic bacteria are released into the hemocoel. After inducing host immunosuppression, the bacteria multiply in the hemocoel and cause fatal septicemia. For optimal field application to control insect pests, culturing mass numbers of the nematodes would be costly. In this study, Bacillus thuringiensis (Bt) was chosen as an alternative natural vector, which would be relatively economical for field application. Bt infection of gut epithelium would form a bacterial passage between the gut lumen and hemocoel, which facilitates the orally fed X. nematophila to infect the hemocoel. Diamondback moth, Plutella xylostella (L.) (Lepidoptera: Plutellidae), used in this study was tolerant to Bt because only 10% mortality was noted in response to 2 times higher concentration than recommended for commercial B. t. kurstaki, although this species was susceptible only during early instars. The orally fed X. nematophila caused significant mortality to early instars of P. xylostella, but not late instars. When both X. nematophila and Bt were fed to late instars of P. xylostella, they showed significantly enhanced mortality, in which X. nematophila cells were recovered from the hemocoel of the treated P. xylostella. However, when only X. nematophila was fed, no cells were recovered from the hemolymph. This study suggests that X. nematophila can be applied to control P. xylostella in a mixture with Bt in the field without its nematode host.