Recommended Field Concentration Research Articles

Additive and dose-dependent mixture effects of Flumite 200 (flufenzin, acaricide) and Quadris (azoxystrobin, fungicide) on the reproduction and survival of Folsomia candida (Collembola)

Chemical plant protection is still a dominant agricultural practice in the world, and usually fields are treated with several pesticides many times per year. This means that not only the single substances affect the environment and the non-target organisms, but their mixtures. Our model organism was Folsomia candida (Collembola). We aimed to gain information on the toxicity of Quadris (azoxystrobin) and Flumite 200 (flufenzine aka. diflovidazine) on survival and reproduction and whether the animals can mitigate the toxicity with soil and/or food avoidance behaviour. Also, we aimed to test the effect of the mixture of these two pesticides. We used the OECD 232 reproduction test, a soil avoidance test, and a food choice test for both single pesticides and their mixture. We prepared the mixtures based on the concentration addition model, so the 50% effective concentrations (EC50) of the single materials were used as one toxic unit with a constant ratio of the two materials in the mixture. In the end, the measured mixture EC and LC (lethal concentration) values were compared to the estimate of the concentration addition model. Both materials were toxic to the Collembola in much higher concentrations than the recommended field concentrations (Flumite 200 EC50: 1.096, LC50: 1.561, Quadris EC50: 65.568, LC50: 386.165 mg kg−1). The springtails did not consistently avoid the polluted soils, this only happened in higher concentrations. The mixtures seemed to have additive effects on the reproduction and we found dose-dependent interaction with the survival (EC50: 1.022 Toxic Unit, 0.560 Flumite 200 and 33.505 Quadris; LC50: 1.509 Toxic Unit, 0.827 Flumite 200 and 49.471 mg kg−1 Quadris). The deviation from the concentration addition model suggests that the curve starts with a synergy. but above EC50 it becomes antagonistic. We conclude that both Quadris and Flumite 200 are safe for springtails until the recommended field concentration is respected. However, if higher concentrations are used the animals cannot avoid Flumite 200 and the toxic effects can fully manifest. Consequently, the dose-dependent deviation from the concentration addition model is a reason for caution as the low concentrations were synergistic for survival. That means the field concentrations can possibly cause synergistic effects. However, to clarify that further tests are necessary.

Efficacy of single and combined applications of entomopathogenic fungi and nematodes against the pupae of colorado potato beetle (Leptinotarsa decemlineata [Say]), (Coleoptera: Chrysomelidae)

BackgroundThe lethal effects of different entomopathogenic fungi (EPF) and nematodes (EPN) on the pupae of the Colorado Potato Beetle, Leptinotarsa decemlineata (Say) (Coleoptera: Chrysomelidae) were investigated in a two-step study when used separately or together. In the first step, Nostalgist (Beauveria bassiana strain Bb-1, Agrobest Co.), Steinernema feltiae (Filipjev) (Rhabditida: Steinernematidae), Heterorhabditis bacteriophora Poinar, 1976 (Rhabditida: Heterorhabditidae) (Bioglobal Co.), 2 Turkish isolates of Beauveria bassiana BIM-001 and BY2 were applied separately to the pupal stage of pest in the soil. In the experiments, 3 different concentrations (150, 200, and 250 million infective juveniles (IJs)/100 l water) of EPN and a single concentration (1x108 spores/ml for and maximum recommended field dose 1 × 108 CFU/ml) of EPF were used. In the second step, BIM-001 and BY2 isolates of B. bassiana were combined with both EPN species; S. feltiae + B. bassiana BIM-001, S. feltiae + B. bassiana BY2, H. bacteriophora + B. bassiana BIM-001, H. bacteriophora +B. bassiana BY2 were applied to pupae. At this stage, 150 million IJs/100 l water which was the maximum recommended field concentration for EPN and 1 × 108 spores/ml for local EPF isolates were used.ResultsAccording to the study results, pupae deaths were significantly higher in Nostalgist (74%) than those of B. bassiana BIM-001, B. bassiana BY2, S. feltiae, and H. bacteriophora (P<0.05). While both EPN caused higher mortality than B. bassiana BY2, B. bassiana BIM-001 had the highest mortality rates. The combination of S. feltiae + B. bassiana BIM-001 at the highest mortality rate (80%) was found statistically different and significant from other EPF + EPN treatments on pupae. Moreover, there were non-statistical differences between the other EPF and EPN combinations.ConclusionIt was found that the combined use of EPF and EPN was more effective on the pupae of L. decemlineata than a single application. According to the results of the study, it may be promising to use EPN and EPF together for the control of the Colorado Potato Beetle pupae.

Role of Some Nanoformulations in Suppression of Silver Whitefly, Bemisia tabaci Population in Compared with Their Conventional Formulations in Tomato Fields

Background: Scientific research will continue to search for the best methods to control the insect pests and at the same time reduce insecticide concentrations used. Using of nanoinsecticide formulations may be resolving this problem. Methods: In this work two types of formulations were used; nanoformulations and their conventional formulations. Three common insecticides were used against the silver whitefly, Bemisia tabaci; indoxacarb, spirotetramat and thiacloprid in tomato fields. The nanoparticle sizes were ranged between 210 and 290 nm. The loading capacities were 70.6, 71.2 and 69.1% for indoxacarb, spirotetramat and thiacloprid, respectively. The recommended field concentration for each insecticide was used. The concentrations of nanoformulations were one-fifth of conventional one. Result: The obtained results showed that indoxacarb was the most effective insecticide against the B. tabaci in tomato field with the both formulations (nano and conventional) followed by thiacloprid and spirotetramat. By using of nanoformulations, the percent of reduction after the third application were 97.7, 38.2 and 44.8%, for indoxacarb, spirotetramat and thiacloprid, respectively. While, the corresponding results with the conventional formulation were 97, 39.8 and 49.2%, respectively. The obtained results also, showed that there were no difference between the nano and conventional formulations. The per cent of B. tabaci reduction after the third application were 97.7 and 97.0; and 38.2 and 39.8; and 44.8 and 49.2% for nano and conventional indoxacarb, spirotetramat and thiacloprid, respectively. These results may be throw some light in the advantages of using nanoformulations compared with the conventional formulations.

Toxic effects of seven pesticides to aphid parasitoid, Aphidius gifuensis (Hymenoptera: Braconidae) after contact exposure

The toxic effects of pesticides have been widely reported on aphid parasitoids, but few studies have been devoted to assessing the toxicity of chemicals to parasitoid, Aphidius gifuensis. In this study, A. gifuensis was exposed to seven commonly used pesticides at their highest recommended field concentrations and the toxic effects were evaluated. All the seven pesticides decreased the parasitism rates after the adults were exposed, especially thiamethoxam and dinotefuran by 35.3 and 32.3%, respectively. In addition, thiamethoxam, dinotefuran, emamectin benzoate and profenofos shortened the longevity of next generation with 59.3h, 64.7h, 66.8h and 61.9h, respectively. However, pymetrozine and azoxystrobin had a low toxicity to the wasps. In the persistent toxicity test, at 1–14 DAT (day after treatment), thiamethoxam, bifenthrin and dinotefuran greatly affected the survival and parasitism of adults; followed by profenofos and emamectin benzoate. After the mummies were exposed to the pesticides, the egg and larval stages were more susceptible than the pupal stage of A. gifuensis. The sex ratio of newly emerged A. gifuensis was not affected. The findings of the present study provide informative data for the implementation of biological and chemical control strategies in the integrated pest management of aphids. In addition, our findings contribute to the determination of an effective time interval for the release of parasitoids when a specific pesticide is applied in the field.

Effect of selective and non-selective insecticides on survival and feeding behavior of the spiders Hogna cf. bivittata and Lycosa poliostoma (Araneae: Lycosidae)

An important aspect of implementing Integrated Pest Management programs is evaluating the compatibility of insecticides with the biological attributes of the natural enemies used for pest control. In this study, we evaluated the effects of selective and non-selective insecticides on the survival and feeding behavior of Hogna cf. bivittata and Lycosa poliostoma (C. L. Koch, 1847), present in soybean crops. We used residual exposure to contaminate adult females of both spider species with the broad-spectrum insecticide thiamethoxam+lambda-cyhalothrin and the selective insecticide methoxyfenozide using concentrations of 20%, 10% and 5% of the maximum recommended field concentration. The survival rate after 120 hours post treatment and the prey acceptance rate in survivors were assessed as ecotoxicological parameters. Methoxyfenozide did not show any disruption to survival of either spider at any of the concentrations evaluated. We did not find significant differences related to mortality between the evaluated concentrations of methoxyfenozide and the control groups for both species. Nevertheless, all the concentrations of broad-spectrum insecticides we used caused mortality rates significantly higher when compared to the selective insecticide. The highest percentages with thiamethoxam+lambda-cyhalothrin were recorded for 20% and 10% concentration. Although we observed moderate mortality rates for the lowest concentrations, the exposed spiders showed a lower acceptance rate when compared to all the concentrations of methoxyfenozide and the control group; the two latter treatments were not significantly different. These results suggest that the selective insecticide can be used in different concentrations without affecting the survival or feeding behavior of either spider species.

Lethal and sublethal effects of two new insecticides spirotetramat and flupyradifurone in comparison to conventional insecticide deltamethrin on Trichogramma evanescens (Hymenoptera: Trichogrammatidae)

Abstract The effects of three insecticides including deltamethrin, spirotetramat and flupyradifurone on pre-imaginal stages of Trichogramma evanescens Westwood (Hymenoptera: Trichogrammatidae) were investigated using dipping method. The mean emergence rate of T. evanescens when exposed to the recommended field concentrations of deltamethrin, spirotetramat and flupyradifurone were 62.8, 84 and 86.1%, respectively while 94.3% of the wasps emerged in the control group. According to the concentration–response experiments, the LC50 values of deltamethrin, spirotetramat and flupyradifurone were 262.9, 274.8 and 334.8 ppm, respectively. The results indicated that lethal (LC50) and sublethal (LC30) concentrations of three tested insecticides significantly reduced the fecundity and longevity of T. evanescens. However, LC30 of spirotetramat and flupyradifurone didn’t influence the oviposition duration of the wasps when compared with the control group. The gross reproductive rate (GRR), intrinsic rates of increases (r), net reproductive rate (R0), and finite rate of increase (λ) were significantly lower in all the treated wasps in comparison with control. However, the mean generation time (T) was not affected by the sublethal concentrations of tested insecticides. According to our findings, all insecticidal treatments have adverse effects on the population of T. evanescens, notwithstanding sublethal concentration of flupyradifurone followed by spirotetramat were more compatible with adults T. evanescens in comparison with deltamethrin. However, further studies under the field conditions are required to confirm the results.

Side effects of chlorantraniliprole, phosalone and spinosad on the egg parasitoid, Trichogramma brassicae.

The combined use of chemicals and biological control is not always a successful strategy owing to the potential side effects on biocontrol agents. Lethal and sublethal effects of three commonly used insecticides were assessed on adult and immature stages of the egg parasitoid Trichogramma brassicae Bezdenko (Hymenoptera: Trichogrammatidae). Recommended field concentrations of chlorantraniliprole, phosalone and spinosad caused mortality on preimaginal stages by 24, 87, and 98%, respectively. Lethal effects on parasitoid adults exposed to the insecticide dry residues were estimated as median lethal concentrations (LC50) that were 13.28, 0.25, and 0.03 µg a.i. ml-1 for chlorantraniliprole, phosalone, and spinosad, respectively. The effect of a low lethal concentration (LC30) of the compounds was evaluated on various adult biological traits, such as longevity, fecundity, emergence rate and other life table parameters. All compounds caused detrimental effects on all the estimated demographical indexes. Chlorantraniliprole affected the net reproductive rate, mean generation time and doubling time in comparison to the control; while, phosalone and spinosad adversely affected all assessed parameters. Phosalone and spinosad significantly reduced gross reproductive rate, net reproductive rate, intrinsic rate of increase, finite rate of increase, mean generation time and doubling time and reduced longevity, fecundity, emergence rate related to other biological parameters in comparison with control. The results suggest that all compounds are not fully compatible with the activity of T. brassicae, and that the inclusion of chlorantraniprole, spinosad and phosalone into Integrated Pest Management (IPM) involving this parasitoid has to be avoided. Nevertheless, further studies in open field conditions and on a multiple generation scale are necessary for providing a more definitive conclusion on the IPM suitability of the three tested insectcides.

Distinct changes in the life-history strategies of Folsomia candida Willem (Collembola: Isotomidae) due to multi- and transgenerational treatments with an insecticide

Chronic exposure of soil animals with insecticides over multiple generations can induce modifications to their life-history. Moreover, insecticide effects over generations may be substantially different if subsequent generations get direct exposure repeatedly (multigenerational effect), or direct exposure affects only the parent generation, but the subsequent ones not (transgenerational effect). These are essential but understudied aspects of the environmental risk assessment. The present study assessed the multi- and transgenerational effects of the insecticide Trebon® 30 EC (active ingredient etofenprox) on 15 life-history traits (initial length, final length, absolute growth, total number of eggs, number of clutches, time of maturation, ratio of egg diameters, egg volume, unhatched ratio, reproduction investment, mortality, food consumption, velocity, movement energy, growth-reproduction trade-off) of the collembolan Folsomia candida Willem, 1902 in a four-generation long laboratory study. In the multigenerational treatment, all four generations were treated by the insecticide, while in the transgenerational one, only the parent generation was treated, but the consecutive three generations were not. When a generation was treated with the insecticide, six sublethal concentrations of the Trebon® 30 EC (0, 0.766, 1.303, 2.215, 3.765, and 6.4 ml insecticide L−1 water) were applied to see dose-response effects. In the multigenerational treatment, dose-dependent effects of the insecticide were pronounced from the parent to the F2 generation, with high mortality, especially in the highest concentration. Conversely, in the transgenerational treatment the most effects on life-history traits were found in the F3 generation. The results show that in the multigenerational treatment, either the population becomes resistant, or it could compensate for the effects of the insecticide in the long term. In the F1 generation, the number of eggs and clutches decreased, the mortality increased, and the growth-reproduction trade-off shifted in the direction of growth. Rather similar results were found in the F2 generation, with the difference that all animals died in that case if the insecticide was applied for consecutive generations repeatedly, and five to eight times higher than the recommended field concentration (0.766–1.303 ml L−1). Furthermore, our experiment detected evidence of an apparent transgenerational effect. While in the F1 and F2 generation of the transgenerational treatment, few effects were found, in the F3 generation, 10 out of the 15 traits showed a dose-response relationship. This finding indicates the long-term transgenerational effects of the Trebon® 30 EC insecticide on several F. candida life-history traits. We concluded that the influence of both treatment methods on life-history traits is strong but appreciably distinct. Our results support the view that transgenerational epigenetic heritability should be taken into account in environmental risk assessment.

Contact application of neonicotinoids suppresses the predation rate in different densities of prey and induces paralysis of common farmland spiders

Neonicotinoids are very effective in controlling crop pests but have adverse effects on predators and pollinators. Spiders are less sensitive to neonicotinoids compared to insects because of the different structure of their acetylcholine receptors, the binding targets of neonicotinoids. We tested whether short-term exposure to neonicotinoids affected the predation rate in different densities of prey of spiders and led to their paralysis or eventual death. To examine these effects, we topically exposed dominant epigeic, epiphytic and sheet-weaving farmland spiders to four widely used neonicotinoids (imidacloprid, thiamethoxam, acetamiprid and thiacloprid). We applied the neonicotinoids at concentrations recommended by the manufacturers for spray application under field conditions. Short-term exposure to the formulations of all four tested neonicotinoids had adverse effects on the predation rate of spiders, with imidacloprid (Confidor) associated with the most severe effects on the predation rate and exhibiting partial acute lethality after one hour (15–32%). Acetamiprid also displayed strong sublethal effects, particularly when applied dorsally to Philodromus cespitum. Day-long exposure to dorsally applied acetamiprid or thiacloprid led to paralysis or death of multiple Linyphiidae spp., with the effects particularly prominent in males. To conclude, we provided multiple lines of evidence that short-term exposure to neonicotinoids, which were applied at recommended field concentrations, caused severe health effects or death in multiple families of spiders. Even acetamiprid caused strong effects, despite being subject to less strict regulations in the European Union, compared with those for imidacloprid because of claims of its negligible off-target toxicity.

Comparative susceptibility of two Neotropical predators, Eriopis connexa and Chrysoperla externa, to acetamiprid and pyriproxyfen: Short and long-term effects after egg exposure

Compatibility assessments between selective insecticides and the natural enemies of pests are essential for integrated-pest-management programs. Chrysoperla externa and Eriopis connexa are two principal Neotropical predators of agricultural pests whose conservation in agroecosystems requires a toxicity evaluation of pesticides to minimize the impact on those beneficial insects on the environment. The objective of this work was to evaluate the toxicity of the insecticides pyriproxyfen and acetamiprid on C. externa and E. connexa eggs exposed to the maximum recommended field concentrations of each along with three successive dilutions. The survival and the immature developmental time were assessed daily until adulthood and the mean survival time calculated over a 10-day period. The cumulative survival of E. connexa was reduced at all concentrations of both insecticides, while that of C. externa was significantly decreased by ≥50 mg L−1 of acetamiprid and ≥37.6 mg L−1 of pyriproxyfen. In both species, the reductions occurred principally on the eggs and first larval instar. Survival curves, in general, differed from those of the controls, with the mean survival time of E. connexa being significantly shorter in insecticides treatments than that of the controls. Certain concentrations of each of the insecticide lengthened the egg and first-larval-instar developmental periods of E. connexa and C. externa, respectively. Also, pyriproxyfen reduced the first-larval-instar period and lengthened the fourth of E. connexa. Acetamiprid was more toxic to E. connexa than to C. externa at the two highest concentrations. Conversely, at those same concentrations of pyriproxyfen, the relative toxicity to the two species was reversed. The present work represents the first investigation on the comparative susceptibility of two relevant Neotropical biological control agents to acetamiprid and pyriproxyfen. Also, it highlights the necessity of assessing long-term effects in the compatibility studies between natural enemies of agricultural pests and insecticides.

An evaluation of the effect of botanical insecticide, palizin in comparison with chemical insecticide, imidacloprid on the black citrus aphid, Toxoptera aurantii Boyer de Fonscolombe and its natural enemy, Aphidius colemani Viereck

AbstractThe black citrus aphid,Toxoptera aurantiiBoyer de Fonscolombe (Hemiptera: Aphididae), an important pest of citrus species, feeds by sucking sap from plant leaves. It causes some leaf distortion and malformation of growing leaves and shoot tips. In this study, the effects of the botanical insecticide, palizin onT. aurantiiand its parasitoid,Aphidius colemaniViereck (Hymenoptera: Brachonidae) were compared with the chemical insecticide, imidacloprid. The compounds were evaluated at maximum recommended field concentrations: palizin 2,000 ppm, imidacloprid 500 ppm, water (as control) on adult aphids. Spraying was done with a 100-l engine Honda sprayer (GX120T1, 160T1, 200T) until run-off. The number of dead aphids was recorded 24, 48 and 72 hours after treatment. According to the results, statistically significant differences were found between treatments (p ≤ 0.05). Twenty-four hours after treatment, imidacloprid was more effective than palizin in reducing theT. aurantiipopulation. Palizin showed high efficiency (95% mortality) 72 hours after treatment. However, at that time, there was no statistically significant difference between the mean mortality percentages of imidacloprid and palizin. This shows that botanical insecticide, palizin can effectively controlT. aurantii. Also, palizin caused low mortality (10.86%) onA. colemaniwhile imidacloprid was more toxic (31.1% mortality). The results of the present study indicated that palizin can be used instead of chemical insecticide, imidacloprid in control programs ofT. aurantii.

Effects of emamectin benzoate and cypermethrin on the demography of Trichogramma brassicae Bezdenko

The Effects of two insecticides were evaluated on the immature and adult stages of Trichogramma brassicae. The recommended field concentrations of emamectin benzoate and cypermethrin caused 72.0 and 80.7% mortality of immatures, respectively. LC50 values were 2.7 and 0.5 μg a. i/ml, respectively, estimated by the dry film residue method. Longevity and population parameters were assessed after exposure to the LC30 concentration of each insecticide. Results showed that sublethal concentrations affected the life history parameters of the wasp adversely compared to controls. The intrinsic rate of increase values for emamectin benzoate, cypermethrin and the control were 0.252, 0.248 and 0.272 day−1, respectively. Moreover, R0 values were 31.2, 28.9 and 44.7, respectively. The mean generation time was significantly affected by the insecticides compared to control. In conclusion, both insecticides may interfere with biological control of pest, based on their acute and sublethal effects on T. brassicae.

Toxicity of nine insecticides on four natural enemies of Spodoptera exigua.

Spodoptera exigua, which feeds on various crops worldwide, has natural enemies that are susceptible to the insecticides used against S. exigua. We investigate the toxicity and residue risk of 9 insecticides on the development of H. axyridis, C. sinica, S. manilae and T. remus. S. manilae and T. remus adults were sensitive to all 9 insecticides (LC50 less than 2.75 mg a.i. liter−1), while H. axyridis and C. sinica adults were less sensitive (LC50 between 6 × 10−5 mg a.i. liter−1 and 78.95 mg a.i. liter−1). Emamectin benzoate, spinosad, indoxacarb, alpha-cypermethrin, chlorfenapyr and chlorantraniliprole showed no toxicity on H. axyridis, C. sinica, S. manilae and T. remus pupae with the recommended field concentrations. The risk analysis indicated that chlorantraniliprole is harmless to larvae of four natural enemies and adult of H. axyridis, C. sinica and S. manilae. Emamectin benzoate and spinosad had higher safety to the development of H. axyridis, C. sinica, S. manilae and T. remus with the risk duration less than 4d. Indoxacarb, tebufenozide, chlorfenapyr, methomyl, alpha-cypermethrin and chlorpyrifos showed dangerously toxic and long risk duration on S. manilae and T. remus adults.

Effect of Three Entomopathogenic Fungi on Three Species of Stingless Bees (Hymenoptera: Apidae) Under Laboratory Conditions.

Development of alternative strategies for pest control with reduced effect on beneficial organisms is a priority given the increasing global loss of biodiversity. Biological control with entomopathogenic fungi arises as a viable option to control insect pests. However, few studies have focused on the consequences of using these organisms on pollinators other than the honey bee ( Apis mellifera L.) or bumble bees ( Bombus spp). We evaluated the pathogenicity of commercial formulations of three widely used entomopathogenic fungi, Metarhizium anisopliae (Metschnikoff) Sorokin, Beauveria bassiana Vuillemin, and Isaria fumosorosea (Wize), to three species of stingless bees: Tetragonisca angustula Latreille, Scaptotrigona mexicana Guérin-Meneville, and Melipona beecheii Bennett. Bioassays consisted of exposing groups of bees to the recommended field concentration of each fungus using a microspray tower under laboratory conditions. Susceptibility to fungi varied greatly among species . Isaria fumosorosea (strain Ifu-lu 01) and the two formulations of B. bassiana (Bea-TNK and BotanicGard) caused <30.3% mortality in all bee species. Metarhizium anisopliae (Meta-TNK and strain Ma-lu 01) was highly active against T. angustula (94.2% mortality) and moderately active against M. beecheii (53.0% mortality) and S. mexicana (38.9% mortality). Though our laboratory-derived results suggest a moderate to high impact of these entomopathogenic fungi on stingless bees, further field studies are required to support this finding.

Lethal and sublethal effects of three insecticides on the aphid parasitoid, Lysiphlebus fabarum Marshall (Hymenoptera: Aphidiidae)

Lysiphlebus fabarum Marshall is the main parasitoid of the black bean aphid, Aphis fabae Scopoli. Lethal and sublethal effects of insecticides, thiacloprid+deltamethrin, pirimicarb and pymetrozine were evaluated on the parasitoid under laboratory conditions. One-day-old mummies were exposed to the recommended field concentration of either insecticides via dipping method. Adult emergences were reduced by 82.67, 19.98 and 10.67 % for thiacloprid+deltamethrin, pirimicarb and pymetrozine treatments, respectively. Thiacloprid+deltamethrin had the most adverse effect on the fecundity of the emerged females, while pirimicarb and pymetrozine did not have such effects. According to International organization for biological control (IOBC) insecticide toxicity classification, thiacloprid+deltamethrin resulted to be moderately harmful (E = 97.39%), whereas pirimicarb (E = 15.78%) and pymetrozine (E = 5.15%) were harmless. Thiacloprid+deltamethrin negatively affected five of the estimated demographic parameters (GRR, R0 , rm, λ and T ). Pirimicarb negatively affected GRR, R0 and T, while it had no adverse effects on rm and λ. None of the studied demographic parameters were affected by pymetrozine. Our results suggest that pirimicarb and pymetrozine can be considered as safe for L. fabarum, but that thiacloprid+deltamethrin can have serious detrimental of this parasitoid in the field.

A new threat to bees? Entomopathogenic nematodes used in biological pest control cause rapid mortality in Bombus terrestris.

There is currently a great deal of concern about population declines in pollinating insects. Many potential threats have been identified which may adversely affect the behaviour and health of both honey bees and bumble bees: these include pesticide exposure, and parasites and pathogens. Whether biological pest control agents adversely affect bees has been much less well studied: it is generally assumed that biological agents are safer for wildlife than chemical pesticides. The aim of this study was to test whether entomopathogenic nematodes sold as biological pest control products could potentially have adverse effects on the bumble bee Bombus terrestris. One product was a broad spectrum pest control agent containing both Heterorhabditis sp. and Steinernema sp., the other product was specifically for weevil control and contained only Steinernema kraussei. Both nematode products caused ≥80% mortality within the 96 h test period when bees were exposed to soil containing entomopathogenic nematodes at the recommended field concentration of 50 nematodes per cm2 soil. Of particular concern is the fact that nematodes from the broad spectrum product could proliferate in the carcasses of dead bees, and therefore potentially infect a whole bee colony or spread to the wider environment.

Survival and behavior of the insecticide-exposed predators Podisus nigrispinus and Supputius cincticeps (Heteroptera: Pentatomidae)

Pentatomid stinkbugs are important predators of defoliating caterpillars in agricultural and forestry systems, and knowledge of the impact of insecticides on natural enemies is important information for integrated pest management (IPM) programs. Thus, we assessed the toxicity and behavioral sublethal response of the predators Podisus nigrispinus and Supputius cincticeps exposed to deltamethrin, methamidophos, spinosad and chlorantraniliprole, insecticides commonly used to control the velvetbean caterpillar (Anticarsia gemmatalis) in soybean crops. With the exception of deltamethrin for S. cincticeps, all insecticides showed higher acute toxicity to the prey than to these natural enemies providing effective control of A. gemmatalis. The recommended field concentration of deltamethrin, methamidophos and spinosad for controlling A. gemmatalis caused 100% mortality of P. nigrispinus and S. cincticeps nymphs. Chlorantraniliprole was the less toxic and the most selective insecticide to these predators resulting in mortalities of less than 10% when exposed to 10× the recommended field concentration for a period of 72h. Behavioral pattern changes in predators were found for all insecticides, especially methamidophos and spinosad, which exhibited irritability (i.e., avoidance after contact) to both predator species. However, insecticide repellence (i.e., avoidance without contact) was not observed in any of the insects tested. The lethal and sublethal effects of pesticides on natural enemies is of great importance for IPM, and our results indicate that substitution of pyrethroid and organophosphate insecticides at their field rates by chlorantraniliprole may be a key factor for the success of IPM programs of A. gemmatalis in soybeans.

Laboratory Evaluation of the Toxicity of Proteus, Pymetrozine, Deltamethrin, and Pirimicarb on Lady Beetle Hippodamia Variegata (Goeze) (Col.: Coccinellidae)

Abstract The implementation of an Integrated Pest Management (IPM) program requires selecting and using chemicals which are least harmful to natural enemies. In this study, the acute toxicity of the recommended field concentration of four conventional insecticides was evaluated in reference to the different life stages (L3, L4 and adult) of the variegated lady beetle Hippodamia variegata (Goeze) (Coleoptera: Coccinellidae). The evaluated insecticides were Proteus, pymetrozine, deltamethrin, and pirimicarb. A completely randomized design (CRD) with four replications was used as the experimental design. The means were separated by the least significant difference (LSD). The mortalities of those predators treated with the field recommended concentrations of various insecticides, were significantly different. Proteus showed strong toxicity toward the different life stages of the predator. However, pymetrozine and pirimicarb caused less than a 50% mortality. Based on the lethal concentration (LC50) values at 24 h after treatment, the adult predator was the most susceptible to proteus, followed by deltamethrin, pymetrozine, and pirimicarb values of 35.977, 358.757, 915.667, and 2616.113. Based on sublethal concentrations (LC30), these values were 22.718, 261.957, 569.879, and 1521.424. Based on International Organization of Biological Control (IOBC) classification, the insecticides pirimicarb and pymetrozine were both categorized as having a Class 1 toxicity level (harmless), deltamethrin as having a Class 2 level (slightly harmful), and Proteus, a Class 4 toxicity level (harmful).

Effect of fenitrothion on different life stages of black pine bast scale, Matsucoccus thunbergianae

Black pine bast scale, Matsucoccus thunbergianae, is one of the most destructive pests of black pine trees throughout Korea. Toxicities of five commercially available insecticides for scale insects were compared in the laboratory with that of buprofezin 40SC, which is currently used to treat the disease in Korea. Fenitrothion 50EC and buprofezin 40SC significantly suppressed the adult emergence of intermediated male nymphs when exposed to the recommended-field concentrations (RFCs) of 500 and 4,000ppm, respectively. Fenitrothion 50EC was effective against male pupae even at one-fifth of the RFC, and showed no significant difference from buprofezin 40SC. Fenitrothion 50EC caused significantly higher mortality than buprofezin 40SC towards intermediate female nymphs and eggs, even at half RFC, and on female adults at one-tenth of its RFC. In a field test in a black pine arboretum, 50ppm of fenitrothion 50EC was equally effective to its RFC (500ppm) on the settled crawlers. Toxicities of fenitrothion 50EC and buprofezin 40SC to humans, other mammals, and non-target organisms are discussed. Fenitrothion 50EC can be used for urgent control of M. thunbergianae in limited outbreak areas at lower concentrations than its RFC.

Locomotor Behavioral Responses of Anopheles minimus and Anopheles harrisoni to Alpha-Cypermethrin in Thailand

Excito-repellency responses of 3 test populations, representing 2 sibling species within the Minimus Complex, Anopheles minimus and An. harrisoni, were characterized for contact irritant and noncontact repellent actions of chemicals during and after exposure to alpha-cypermethrin at half the recommended field (0.010 g/m2), the recommended field (0.020 g/m2), and double the recommended field concentration (0.040 g/m2), using an excito-repellency escape chamber system. Two field populations of An. minimus and An. harrisoni collected from the malaria-endemic areas in Tak and Kanchanuburi provinces in western Thailand, respectively, were tested along with a laboratory population of An. minimus maintained since 1993. Females of all 3 test populations rapidly escaped after direct contact with treated surfaces for each concentration. In general, increased escape responses in the An. minimus test populations were proportionate to increased insecticide dosages. The greatest escape response for An. harrisoni was observed at the operational field concentration of alpha-cypermethrin. The noncontact repellency response to alpha-cypermethrin was comparatively weak for all 3 test populations, but significantly different from each paired contact test and respective noncontact controls. We conclude that strong contact irritancy is a major action of alpha-cypermethrin, whereas noncontact repellency plays no role in the escape responses of 2 species in the Minimus Complex in Thailand.