Utilizing the assassin bug, Pristhesancus plagipennis (Hemiptera: Reduviidae), as a biological control agent within an integrated pest management programme for Helicoverpa spp. (Lepidoptera: Noctuidae) and Creontiades spp. (Hemiptera: Miridae) in cotton

Helicoverpa spp. and mirids, Creontiades spp., have been difficult to control biologically in cotton due to their unpredictable temporal abundance combined with a cropping environment often made hostile by frequent usage of broad spectrum insecticides. To address this problem, a range of new generation insecticides registered for use in cotton were tested for compatibility with the assassin bug, Pristhesancus plagipennis (Walker), a potential biological control agent for Helicoverpa spp. and Creontiades spp. Indoxacarb, pyriproxifen, buprofezin, spinosad and fipronil were found to be of low to moderate toxicity on P. plagipennis whilst emamectin benzoate, abamectin, diafenthiuron, imidacloprid and omethaote were moderate to highly toxic. Inundative releases of P. plagipennis integrated with insecticides identified as being of low toxicity were then tested and compared with treatments of P. plagipennis and the compatible insecticides used alone, conventionally sprayed usage practice and an untreated control during two field experiments in cotton. The biological control provided by P. plagipennis nymphs when combined with compatible insecticides provided significant (P<0.001) reductions in Helicoverpa and Creontiades spp. on cotton and provided equivalent yields to conventionally sprayed cotton with half of the synthetic insecticide input. Despite this, the utilization of P. plagipennis in cotton as part of an integrated pest management programme remains unlikely due to high inundative release costs relative to other control technologies such as insecticides and transgenic (Bt) cotton varieties.     

Susceptibility of pest Nezara viridula (Heteroptera: Pentatomidae) and parasitoid Trichopoda pennipes (Diptera: Tachinidae) to selected insecticides

Susceptibility of the southern green stink bug, Nezara viridula (L.) (Heteroptera: Pentatomidae), and its endoparasitoid Trichopoda pennipes (F.) (Diptera: Tachinidae) to acetamiprid, cyfluthrin, dicrotophos, indoxacarb, oxamyl, and thiamethoxam was compared in residual and oral toxicity tests. In the residual toxicity test, cyfluthrin, dicrotophos, and oxamyl were highly toxic to N. viridula. Thiamethoxam was moderately toxic to these insects. Each of the four insecticides was highly toxic to T. pennipes after prolonged tarsal contact with dried residues of these chemicals. In the oral toxicity test, where N. viridula fed on food covered with insecticide residues, none of the insecticides were toxic to adults of this stink bug, but acetamiprid, dicrotophos, and thiamethoxam were moderately toxic to the nymphs. In the oral toxicity test, where N. viridula fed on a gel-food containing insecticides, cyfluthrin, dicrotophos, oxamyl, and thiamethoxam were highly toxic to this stink bug. In an oral toxicity test using contaminated sugar water, all of the insecticides were highly toxic to T. pennipes. Because insecticides were as toxic, or more toxic, to T. pennipes than to N. viridula, it is extremely important to conserve this parasitoid by applying these insecticides for control of southern green stink bugs only when the pest reaches economic threshold.     

Effect of selected insecticides on the natural enemies Coleomegilla maculata and Hippodamia convergens (Coleoptera: Coccinellidae), Geocoris punctipes (Hemiptera: Lygaeidae), and Bracon mellitor, Cardiochiles nigriceps, and Cotesia marginiventris (Hymenoptera: Braconidae) in cotton

We evaluated the toxicity of three insecticides (lambda cyhalothrin, spinosad, and S-1812) to the natural enemies Bracon mellitor Say, Cardiochiles nigriceps Viereck, Coleomegilla maculata De Geer, Cotesia marginiventris (Cresson), Geocoris punctipes (Say), and Hippodamia convergens Guérin-Méneville, in topical, residual, and field assays. Lambda cyhalothrin exhibited the greatest toxicity to the natural enemies. In topical toxicity tests, lambda cyhalothrin adversely affected each natural enemy species studied. Residues of lambda cyhalothrin on cotton leaves were toxic to B. mellitor, C. nigriceps, C. maculata, and C. punctipes. Interestingly, residues of this insecticide were not very toxic to C. marginiventris and H. convergens. Geocoris punctipes and C. maculata numbers in the field generally were significantly lower for lambda cyhalothrin treatments than for the other four treatments, substantiating the previous tests. Although cotton aphids began to increase over all treatments around the middle of the test period, the number of cotton aphids in the lambda cyhalothrin plots was significantly higher than the number in any of the other treatments. As cotton aphids increased in lambda cyhalothrin field plots, the predator H. convergens also increased in number, indicating that lambda cyhalothrin did not adversely affect it in accordance with the residual tests. Spinosad exhibited marginal to excellent selectivity, but was highly toxic to each parasitoid species and G. punctipes in topical toxicity tests and to B. mellitor in residual tests. Spinosad generally did not affect the number of G. punctipes, H. convergens, and C. maculata in the field except for one day after the second application for G. punctipes. S-1812 exhibited good to excellent selectivity to the natural enemies. Some reduction of G. punctipes occurred for only a short period after the first and second application of this insecticide in the field. H. convergens and C. maculata were affected very little by S-1812.     

Susceptibility of immature stages of Homalodisca coagulata (Hemiptera: Cicadellidae) to selected insecticides

Susceptibility of immatures of the glassy-winged sharpshooter, Homalodisca coagulata (Say) (Hemiptera: Cicadellidae), to 10 insecticides that included chlorpyrifos, dimethoate, endosulfan, bifenthrin, cyfluthrin, esfenvalerate, fenpropathrin, acetamiprid, imidacloprid, and thiamethoxam was evaluated in the laboratory. All five instars were exposed to different doses of each foliar insecticide by the petri dish technique, whereas a systemic uptake method was used to assess the toxicity to imidacloprid and thiamethoxam. All test insecticides exhibited high toxicity to all immature stages of H. coagulata at concentrations below the field recommended rates of each insecticide. Although all five instars were susceptible to test insecticides, mortality was significantly higher in first instars than in the older immatures based on low LC50 values (ranging from 0.017 to 5.75 ng(AI)/ml) with susceptibility decreasing with each successive stage. Fifth instars were generally the least sensitive (LC50 values ranging from 0.325 to 216.63 ng (AI)/ml). These results show that mortality was directly related to age of the insect and suggest that chemical treatment at early stages is more effective than at late stages. Acetamiprid (neonicotinoid) and bifenthrin (pyrethroid) were the most toxic to all five instars, inducing most mortality within 24 h and showing lower LC50 values ranging from 0.017 to 0.686 ng/ml compared with other insecticides (LC50 values ranging from 0.191 to 216.63 ng(AI)/ml). Our data suggest that a diverse group of very effective insecticides are available to growers for controlling all stages of H. coagulata. Knowledge on toxicity of select insecticides to H. coagulata immatures may contribute to our understanding of resistance management in future for this pest by targeting specific life stages instead of the adult stage alone.     

Field bioassay to evaluate contact and residual toxicities of insecticides to carabid beetles (Coleoptera: Carabidae)

A 2-yr field study evaluated the effects of selected insecticides on Bembidion obscurellum Motschulsky and Bembidion quadrimaculatum L., carabid predators of the wheat midge, Sitodiplosis mosellana (Géhin). A bioassay method using caged beetles indicated that insecticides differed significantly in their contact and residual toxicities when applied at maximum recommended field rates. Deltamethrin, the least toxic insecticide, caused approximately 30% mortality in both beetle species, but its residual toxicity on the soil remained constant for 1 wk. Dimethoate was initially more toxic (73% mortality) than deltamethrin but less toxic after 1 wk (12% mortality). Carbofuran and chlorpyrifos, the most toxic contact sprays, caused 83 to 100% mortality. After 1 wk, the residual toxicity of carbofuran had declined markedly (5% mortality) whereas the toxicity of chlorpyrifos remained high (82% mortality). Pitfall trapping was an inconclusive method of evaluating the toxicity of insecticidal sprays to carabid adults. In plots treated with carbofuran, pitfall catches of Bembidion species were not significantly different from those in control plots during a 6-wk period after spraying. In plots treated with chlorpyrifos, catches of Bembidion species were significantly lower than those in control plots 3-16 d after spraying, but not thereafter. Results suggested that adult immigration and residual toxicity influence pitfall catches and recovery of carabid populations after spraying.     

不同类型杀虫剂对烟粉虱捕食性天敌日本刀角瓢虫的毒力

采用试管药膜法,测定了不同类型杀虫剂对日本刀角瓢虫Serangium japonicum Chapin的毒力。结果表明,灭多威和敌敌畏对日本刀角瓢虫具有极强的毒力,其25%推荐剂量即可导致日本刀角瓢虫全部死亡;氯虫苯甲酰胺、吡虫啉和噻虫嗪对日本刀角瓢虫也具有很强的毒力,其田间推荐剂量可导致日本刀角瓢虫全部死亡,其50%推荐剂量对日本刀角瓢虫的致死率也高达73.33%～100.00%;乐果、烯啶虫胺、丁醚脲田间推荐剂量对日本刀角瓢虫的致死率分别为40.00%、56.67%、50.00%,预示着上述这些杀虫剂的田间应用对刀角瓢虫具有很高的直接杀伤风险。高效氯氰菊酯、联苯菊酯、毒死蜱、甲氰菊酯、高效氯氟氰菊酯、虫螨腈、阿维菌素、吡蚜酮、噻嗪酮、定虫隆和氟虫脲对日本刀角瓢虫的毒力较低甚至没有直接致死作用。研究结果将为合理使用杀虫剂,协调利用化学防治与生物防治对烟粉虱进行综合防治提供依据。     

Comparison of susceptibility of pest Euschistus servus and predator Podisus maculiventris (Heteroptera: Pentatomidae) to selected insecticides

Susceptibility of the brown stink bug, Euschistus serous (Say), and the spined soldier bug, Podisus maculiventris (Say), to acetamiprid, cyfluthrin, dicrotophos, indoxacarb, oxamyl, and thiamethoxam, was compared in residual and oral toxicity tests. Generally, susceptibility of P. maculiventris to insecticides was significantly greater than or not significantly different from that of E. servus. Cyfluthrin and oxamyl were more toxic to the predator than to E. servus in residual and feeding tests, respectively. Dicrotophos is the only compound that exhibited both good residual and oral activity against E. servus, but even this toxicant was more toxic to the predator than to the pest in oral toxicity tests. Feeding on indoxacarb-treated food caused high mortality for both nymphs and adults of P. maculiventris. In contrast, E. servus was unaffected by feeding on food treated with this compound. Insecticide selectivity to P. maculiventris was detected only with acetamiprid for adults in residual toxicity tests and for nymphs in oral toxicity tests. Because insecticide selectivity to P. maculiventris was limited, it is extremely important to conserve P. maculiventris in cotton fields by applying these insecticides for control of brown stink bugs only when the pest reaches economic threshold.     

八种新烟碱类杀虫剂对地熊蜂工蜂的毒性及风险评估

【目的】评价新烟碱类杀虫剂对地熊蜂Bombus terrestris工蜂的毒性和生态风险性,为温室施用新烟碱类杀虫剂提供科学依据。【方法】分别采用饲喂法和接触法测定了噻虫嗪、噻虫胺、啶虫脒、吡虫啉、烯啶虫胺、呋虫胺、噻虫啉和氟吡呋喃酮8种新烟碱类杀虫剂对地熊蜂成年工蜂的急性经口和急性接触毒性。同时评估了8种新烟碱类杀虫剂对地熊蜂工蜂的生态风险性。【结果】8种杀虫剂经饲喂法测定,噻虫胺对地熊蜂成年工蜂的毒性最高,24 h和48 h的LD 50值分别为0.0433和0.0330μg a.i./蜂;氟吡呋喃酮毒性最低,24 h和48 h的LD 50值分别为72.4119和67.9079μg a.i./蜂。接触法测定的毒性与饲喂法测得的结果一致,噻虫胺的毒性最高,24 h和48 h的LD 50值分别为0.0220和0.0192μg a.i./蜂;氟吡呋喃酮的毒性最低,24 h和48 h的LD 50值分别为141.7641和130.3062μg a.i./蜂。生态风险评估表明,啶虫脒、噻虫啉和氟吡呋喃酮对地熊蜂成年工蜂的经口毒性和接触毒性均表现为低风险,吡虫啉、烯啶虫胺和呋虫胺的毒性表现为中等风险。噻虫嗪和噻虫胺对地熊蜂成年工蜂的经口毒性表现为中等风险,而接触毒性则表现为高风险。【结论】检测的8种新烟碱类杀虫剂中啶虫脒、噻虫啉与氟吡呋喃酮对地熊蜂成年工蜂的毒性为低毒,而噻虫嗪、噻虫胺、吡虫啉、烯啶虫胺、呋虫胺这5种杀虫剂均为高毒。在设施蔬菜花期使用地熊蜂授粉时,建议禁用这5种中、高风险的新烟碱类杀虫剂,以避免对熊蜂授粉的危害,而另3种低风险药剂可根据田间试验情况合理施用。     

Toxicity of several pesticides used in Tunisia, for Aphanius fasciatus Nardo, 1827 (Pisces, Cyprinodontidae.)

The acute toxicity of some pesticides used in Tunisia is determined for the species Aphanius fasciatus (Pisces - Cyprinodontidae). Bioassays conducted at temperature (19-20 degrees C) and salinity (37-38%) have allowed to calculate the CL50 48 h and 96 h. The classification of these pesticides, based on the CL50 96 h, and according to their toxicity for the test species, shows that the organic phosphorus (Murphotox, Bazudin, Dursban, Zithiol, Lebaycid, Imidan, Oleoparathion, Folimat; Nuvan, Actellic, Carbicron, Nexion, Dimecron, Roxion) have all the degrees of toxicity, but the majority are among the most toxic; the carbamates (Betanal, Dimetilan, Baygon), are generally less toxic than the organic phosphorus tested, except Nexion which is less toxic than the Betanal and Roxion less toxic than the three carbamates tested; the herbicides (2,4-D, Basagran, Printan) have a very low toxicity, and are less toxic than the insecticides tested, except Betanal and Suffix of which the toxicity is higher than some insecticides (Nexion, Dimecron, Baygon, Dimetilan, Roxion); Calixin (Fongicide) is more toxic than the herbicides tested but it is generally less toxic than the insecticides used. At higher temperature (28-29 degrees C) A. fasciatus is more sensible to organic phosphorus (Dursban, Folimat) than to carbamate (Betanal). The variation change of salinity (from 37 to 6.5 %) don't modify the sensibility of the test species face to face of three pesticides: Dursban, Folimat (organic phosphorus insecticide) and Betanal (carbamate herbicide). A. fasciatus is suitable for acute and chronic bioassays.     

Mediation of pyrethroid insecticide toxicity to honey bees (Hymenoptera: Apidae) by cytochrome P450 monooxygenases

Honey bees, Apis mellifera L., often thought to be extremely susceptible to insecticides in general, exhibit considerable variation in tolerance to pyrethroid insecticides. Although some pyrethroids, such as cyfluthrin and lambda-cyhalothrin, are highly toxic to honey bees, the toxicity of tau-fluvalinate is low enough to warrant its use to control parasitic mites inside honey bee colonies. Metabolic insecticide resistance in other insects is mediated by three major groups of detoxifying enzymes: the cytochrome P450 monooxygenases (P450s), the carboxylesterases (COEs), and the glutathione S-transferases (GSTs). To test the role of metabolic detoxification in mediating the relatively low toxicity of tau-fluvalinate compared with more toxic pyrethroid insecticides, we examined the effects of piperonyl butoxide (PBO), S,S,S-tributylphosphorotrithioate (DEF), and diethyl maleate (DEM) on the toxicity of these pyrethroids. The toxicity of the three pyrethroids to bees was greatly synergized by the P450 inhibitor PBO and synergized at low levels by the carboxylesterase inhibitor DEF. Little synergism was observed with DEM. These results suggest that metabolic detoxification, especially that mediated by P450s, contributes significantly to honey bee tolerance of pyrethroid insecticides. The potent synergism between tau-fluvalinate and PBO suggests that P450s are especially important in the detoxification of this pyrethroid and explains the ability of honey bees to tolerate its presence.     

Effects of methoxyfenozide, indoxacarb, and other insecticides on the beneficial egg parasitoid Trichogramma nr. brassicae (Hymenoptera: Trichogrammatidae) under laboratory and field conditions

Trichogramma nr. brassicae is a common egg parasitoid of Helicoverpa species in Australian processing tomatoes, but its effectiveness can be severely curtailed by insecticide applications. To identify insecticides that are potentially compatible with this species, the effects of seven insecticides, including newly introduced compounds and a surfactant, were screened in laboratory and glasshouse assays for their toxicity to the wasps. Assays involved direct applications on adults, residual effects on adults, and applications on life stages still inside the host. Methoxyfenozide and indoxacarb were not toxic to Trichogramma in any assay when applied at field rates. Naled and chlorfenapyr caused 100% mortality when directly applied to adults, and 95% mortality when adults were exposed to residues of these chemicals within 24 h of application. The effects of naled residues were short lived (<48 h). Naled and chlorfenapyr were also toxic when applied to Trichogramma developing inside host eggs, reducing emergence of adults by >25%. Imidacloprid, emamectin, and tau-fluvalinate were toxic in some experiments; they caused >97% mortality in adults 1 h after direct application and in residue assays they caused 23-64% mortality during the first 24 h. In field trials, methoxyfenozide had no harmful effects on emergence from sprayed parasitized eggs, whereas indoxacarb had a small impact (<8%) on emergence. Methoxyfenozide and indoxacarb are potentially suitable for inclusion in integrated pest management strategies for management of Helicoverpa because they do not influence adult survival or development of immature stages, whereas other chemicals need to be treated cautiously.     

Susceptibility to insecticides of Glyptapanteles militaris (Hymenoptera: Braconidae), a Parasitoid of Pseudaletia unipuncta (Lepidoptera: Noctuidae)

The susceptibility of cocoons and adults of Glyptapanteles militaris (Walsh) were studied. One organophosphate insecticide (trichlorfon), one organochlorine insecticide (endosulfan), one pyrethroid (deltamethrin) and a commercial formulation of Bacillus thuringiensis subsp. Kurstaki were selected for testing. All the tests were carried out with fresh solutions of commercial insecticides applied on host larvae at the recommended concentration. One- and 6-day-old cocoons were sprayed with the insecticide solutions by means of a Potter Tower and held for adult emergence. Adults were exposed to residues of insecticides inside plastic vials. The B. thuringiensis formulation had no harmful effect on the cocoons nor on the adults. Trichlorfon and endosulfan were highly toxic to all the tested stages. Deltamethrin was highly toxic to adults but relatively safe when applied on parasitoid cocoons. Based on these results, field applications of deltamethrin would be least disruptive of tested insecticides to populations of G. militaris.     

Augmentation of the assassin bug Pristhesancus plagipennis (Walker) (Hemiptera: Reduviidae) as a biological control agent for Helicoverpa spp. in cotton

Third-instar nymphs of the Australian assassin bug, Pristhesancus plagipennis (Walker), were released into cotton plots at two release densities and two crop growth stages to test their biological control potential. Release rates of 2 and 5 nymphs per metre row resulted in field populations of 0.51 and 1.38 nymphs per metre row, respectively, indicating that over 70% of nymphs died or emigrated within two weeks of release. Effective release rates of 1.38 nymphs per metre row reduced the number of Helicoverpa spp. larvae in the plots for a 7-week period. Crop yields were significantly greater in the plots to which P. plagipennis nymphs were released, with the effective release rate of 1.38 nymphs per metre row providing equivalent yields as insecticide treated plots. The data suggest that P. plagipennis has the capacity to reduce Helicoverpa spp. larvae densities in cotton crops when augmented through inundative release.     

The susceptibility and resistance of fry and fingerlings of Oreochromis mossambicus Peters to some pesticides commonly used in Sri Lanka

The acute toxicity (48 hr LC₅₀) of seven herbicides, three acaricides and eight insecticides used in the Control of agricultural pests in Sri Lanka to the fry and fingerlings of Oreochromis mossambicus Peters were investigated in freshwater at 28–29°C under static laboratory conditions. The fry were more susceptible to the pesticides tested than were the fingerlings. Most of the pesticides tested induced severe behavioural changes in the exposed fish. Exposure to some herbicides and insecticides resulted in lateral and upward bending of the body, while higher concentrations of some pesticides caused excessive mucous secretions, rupturing of eyes and production of haemmorrhagic patches. Of the pesticides tested on fry and fingerlings, Ronstrar, Elsan and Endosulfan are the most toxic herbicide, acaricide and insecticide, respectively, while Basfapon, Rogor and Azodrin 60 are, respectively, the least toxic herbicide, acaricide and insecticide.     

Life stage toxicity and residual activity of insecticides to codling moth and oriental fruit moth (Lepidoptera: Tortricidae)

The codling moth, Cydia pomonella (L.), and oriental fruit moth, Grapholita molesta (Busck), are two key pests of apple (Malus domestica Borkh.) in North Carolina. Growers extensively relied on organophosphate insecticides, primarily azinphosmethyl, for > 40 yr to manage these pests. Because of organophosphate resistance development and regulatory actions, growers are transitioning to management programs that use new, reduced-risk, and OP-replacement insecticides. This study evaluated the toxicity of a diversity of replacement insecticides to eggs, larvae, and adults, as well as an assessment of their residual activity, to codling moth and oriental fruit moth. Laboratory-susceptible strains of both species were used for all bioassays. Fresh field-harvested apples were used as a media for assessing the ovicidal activity of insecticides. For larval studies, insecticides were topically applied to the surface of lima bean-based diet, onto which neonates were placed. Toxicity was based on two measures of mortality; 5-d mortality and development to adult stage. Ovicidal bioassays showed that oriental fruit moth eggs were generally more tolerant than codling moth eggs to insecticides, with novaluron, acetamiprid, and azinphoshmethyl having the highest levels of toxicity to eggs of both species. In contrast, codling moth larvae generally were more tolerant than oriental fruit moth to most insecticides. Methoxyfenozide and pyriproxyfen were the only insecticides with lower LC50 values against codling moth than oriental fruit moth neonates. Moreover, a number of insecticides, particularly the IGRs methoxyfenozide and novaluron, the anthranilic diamide chlorantriliprole, and the spinosyn spinetoram, provided equal or longer residual activity against codling moth compared with azinphosmethyl in field studies. Results are discussed in relation to their use in devising field use patterns of insecticides and for insecticide resistance monitoring programs.     

Toxicity of seventeen insecticides to Camponotus sericeus (Hymenoptera: Formicidae)

The success of chemical control depends on toxicity of insecticides against insect pests. Camponotus sericeus is an important urban pest with the ability to cause substantial damage to wooden structures, but there is a lack of information on toxicity of insecticides against C. sericeus. To determine the insecticide toxicity, workers of C. sericeus were exposed to 17 insecticides from different classes: carbamate (methomyl, bendiocarb), organophosphate (chlorpyrifos, profenofos, temephos), pyrethroid (bifenthrin, deltamethrin, permethrin), neonicotinoid (acetamiprid, imidacloprid, thiamethoxam), avermectin (abamectin, emamectin), pyrrole (chlorfenapyr), phenylpyrazole (fipronil), and spinosyn (spinosad and spinetoram), via residual bioassay method. The LC₅₀ ranged from: 0.15 to 0.20 µg/vial for carbamates, 0.09 to 0.27 µg/vial for organophosphates, 0.09 to 0.44 µg/vial for pyrethroids, 0.02 to 0.67 µg/vial for neonicotinoids, 0.54 to 0.82 µg/vial for avermectins, 0.78 µg/vial for pyrrole, 0.62 µg/vial for phenylpyrazole, and 1.96 to 2.05 µg/vial for spinosyns. Overall, acetamiprid was the most toxic one among the tested insecticides followed by permethrin, temephos, profenofos, bendiocarb and methomyl, while spinosad and spinetoram were the least toxic insecticides. Considering the potential toxicity of different insecticides against C. sericeus, future studies could investigate the practical application of these insecticides in order to design an effective management plan.     

Towards the on-farm conservation of the assassin bug Pristhesancus plagipennis (Walker) (Hemiptera: Reduviidae) during winter using crop plants as refuges

Abstract Habitat instability associated with seasonal crop succession in broad-acre farming systems presents a problem for the conservation and utilisation of beneficial insects in annual field crops. The present paper describes two experiments used to measure the potential of seven plant species to be utilised as winter refuges to support and conserve the predatory bug Pristhesancus plagipennis (Walker). In the first experiment, replicated plots of canola ( Brassica napus ), red salvia ( Salvia coccinea ), niger ( Guizotia abyssinica ), linseed ( Linum usitatissimum ), lupins ( Lupinus angustifolius ), and lucerne ( Medicago falcata ) were planted in a randomized experiment during Autumn 1998. Upon crop establishment, adults and nymphs of P. plagipennis were released into treatment plots and their numbers were assessed, along with those of their potential prey, throughout the ensuing winter months. Post-release sampling suggested that canola and niger retained a proportion of adult P. plagipennis , while niger, lucerne and canola retained some nymphs. The other plant species failed to support P. plagipennis nymphs and adults postrelease. In the second experiment, niger was compared with two lines of sunflower ( Helianthus annus ). Both sunflower lines harboured significantly higher ( P  < 0.05) densities of P. plagipennis nymphs than did niger. The more successful refuge treatments (sunflower, niger and canola) had an abundance of yellow flowers that were attractive to pollinating insects, which served as supplementary prey on which P. plagipennis were observed to feed. Sunflower and niger also supported high densities of the prey insect Creontiades dilutus (Stål) and provided protective leafy canopies which supplied shelter during the winter months. The potential and limitations for using each plant species as a winter refuge to retain P. plagipennis during winter are discussed.     

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.     

Insecticide susceptibility level of Anopheles arabiensis in two agrodevelopment localities in eastern Ethiopia

Anopheles arabiensis strains reared from larvae and pupae collected from two different localities, Metehara and Melka-Worer, eastern Ethiopia, were evaluated against three insecticides. Resistance states of adult females were determined using the WHO test kits under field condition. The insecticides used were WHO discriminating doses of 4% DDT, 0.75% permethrin and 0.1% propoxur. The study revealed that 42.5% of the An. arabiensis population was resistant to DDT in Melka-Worer while only 30% of the species was resistant in Metehara to the same insecticide. In Metehara, 25% of An. arabiensis was also resistant to permethrin while the population was highly susceptible to the insecticide in Melka-Worer. Propoxur, which was not evaluated in Melka-Worer, was highly toxic to An. arabiensis in Metehara. The knocked-down time (KD50) for permethrin was 14.5 and 12.5 minutes in Metehara and Melka-Worer, respectively. The implications of these findings are discussed.     

Toxicity of thiamethoxam and mixtures of chlorantraniliprole plus acetamiprid, esfenvalerate, or thiamethoxam to neonates of oriental fruit moth (Lepidoptera: Tortricidae)

To assess the toxicity ofthiamethoxam and three mixtures of insecticides to oriental fruit moth, Grapholita molesta (Busck) (Lepidoptera: Tortricidae), we added the insecticides to diet and fed it to neonates of two laboratory colonies; mortality was assessed after 96 h. Thiamethoxam was much less toxic than insecticides previously tested. Five of six analyses of the joint action of chlorantraniliprole plus acetamiprid, esfenvalerate, or thiamethoxam indicated that toxicity was not independent and not correlated. For chlorantraniliprole plus acetamiprid, mortality was slightly lower than expected at low concentrations and greater than expected at high concentrations. For chlorantraniliprole plus esfenvalerate, mortality was less than expected at nearly all concentrations, suggesting antagonism despite the two compounds' different modes of action. For chlorantraniliprole plus thiamethoxam, observed mortality exceeded expected mortality at low concentrations, but this trend did not continue at higher concentrations. Although the null hypothesis of independent and uncorrelated toxicity was rejected for chlorantraniliprole plus acetamiprid and chlorantraniliprole plus thiamethoxam in three of four analyses, differences between observed and expected mortality were minor and inconsistent over the range of concentrations tested. We do not expect these mixtures to exhibit significant synergism or antagonism in the field. Apparent antagonism between chlorantraniliprole and esfenvalerate is particularly relevant because these insecticides (or chlorantraniliprole plus a different pyrethroid) may be used together in apples or peaches for control of oriental fruit moth and hemipteran pests. The effectiveness of each insecticide against oriental fruit moth might be reduced in such applications.