Biological effects of combining carboxin,organomercury fungicides and insecticides as seed dressings for wheat,and the effect of these combinations on adherence of the pesticides to the seed

When seeds of winter wheat were carefully dressed in the laboratory with combinations of fungicides (organomercury alone or organomercury plus the systemic fungicide carboxin) and insecticides (aldrin, carbophenothion or chlorfenvinphos as liquid formulations, or a γ-BHC powder formulation) so as to ensure that nearly all the recommended amounts of the active ingredients stuck to them, the insecticides gave good insect control, but γ-BHC with organomercury fungicide decreased the number of plants that germinated, and γ-BHC with carboxin and organomercury was even more damaging. Commercially dressed seeds had only about 30 to 60% of the target dose of fungicides, but more than 80% of the target doses of the liquid insecticides aldrin, carbophenothion and chlorfenvinphos. With combinations of powder fungicide and liquid insecticide, greater amounts of pesticide on the seed were obtained if the insecticide was put on first. Because of unusually late sowings and little fungal infestation, neither laboratory nor commercially treated seeds provided good tests for control of smut.     

Incorporation and stability of chlorfenvinphos,chlorpyrifos, diazinon and phorate in peat blocks

Factors likely to influence the uniformity of treatment and the stability of the insecticides incorporated into peat blocks were investigated. When an Adelphi horizontal mixer was used, 90% of the blocks contained the mean dose (±10%) after dry-mixing the diazinon granules for 3 min. Treatment was slightly less uniform using a concrete mixer or a spade. Between-block variability was greatest when diazinon was applied to the wet surfaces of prepared blocks; in this process, sprinkling granules by hand was less erratic than spraying a liquid formulation. When granular, wettable powder, or emulsifiable concentrate formulations of diazinon were incorporated using the Adelphi mixer, neither the between-block variability nor the subsequent stability of the insecticide were significantly influenced by the formulation used. Insecticide stability was studied by incorporating chlorfenvinphos, chlorpyrifos, diazinon and phorate at 10 mg a.i. per block in January, March, May and July. The relative order of persistence was chlorfenvinphosChlorpyrifos > phorate≫diazinon. There was little loss of insecticide ( < 10%) from the blocks treated with chlorfenvinphos or chlorpyrifos, and the stability of the insecticides was unaffected by seasonal temperature changes, but the rate of loss of diazinon increased markedly from January to July. The rate of oxidation of phorate to its sulphoxide and sulphone analogues increased gradually from January to May but was much slower than in the field after a bow-wave application. With all insecticides, there was no significant difference in loss rates at 25 and 10 mg a.i. per block. After incorporation into three moss peats and two proprietary blocking composts, there was no consistent difference in the rates of loss of either diazinon or of total phorate residues, although the rates of oxidation of phorate and its sulphoxide were not similar in all the peats and composts. It was concluded that, despite the substantial water content and high insecticide concentrations, the principal factor determining insecticide behaviour in the blocks was the adsorptive capacity of the peat.     

Some experiments with different formulations of organophosphorus insecticides as seed dressings to control wheat bulb fly (Leptohylemyia coarctata)

Experiments on the control of wheat bulb fly larvae by seed dressings compared four organophosphorus compounds in standard siliceous earth formulations with special formulations of the same compounds in polyvinyl acetate, polypropylene or wax. The special formulations allowed more insecticide to be placed on the seeds without affecting germination. Counting shoots damaged by wheat bulb fly larvae showed that: siliceous earth formulations of diazinon gave good control which was not improved by special formulations; control with siliceous earth formulations of dimethoate was poor and was improved only little by the special formulations; and control with siliceous earth formulations of parathion and dichlofenthion was moderate and was improved by special formulations, especially polyvinyl acetate and polypropylene. The results suggest that special formulations are of most value with compounds that are moderately effective but where the amount of insecticide in standard seed dressings cannot be increased without damaging the plants.     

The persistence of insecticide spray deposits on woven polypropylene and jute sacking

In a trial, simulating the spray treatment of bags, the persistence and biological activity of insecticide spray deposits on jute and woven polypropylene sheets have been compared; in addition, the build-up of residues in thin layers of maize under the sprayed sheets has been measured. The insecticides were found to have a much shorter persistence on polypropylene than on jute and this was coupled with higher residues on the grain. However, the deposits on polypropylene retained equal or greater activity against Sitophilus zeamais Motsch. and Tribolium castaneum (Herbst) than the deposits on jute, despite the loss of surface deposit. Wettable powder formulations had a slightly greater surface persistence than emulsifiable concentrates and resulted in smaller residues in the grain. There would seem to be more usefulness in using insecticide sprays on woven polypropylene than on jute bags, and a wettable powder formulation of a non-volatile insecticide of low mammalian toxicity would be the best choice. Of the insecticides tested, the pyrethroid permethrin (cis: trans ratio= 25:75) was the most effective and gave the least residue in the grain.     

Influence of particle size and type of formulation on phytotoxicity and persistence of atrazine

The initial and residual activities of wettable powder formulations of atrazine comprising different particle sizes were investigated in field and glasshouse experiments. A flowable formulation was also compared with these. Oats were used as the test species for the glasshouse studies while in field trials effects on control of broadleaf weeds in maize were studied. No marked differences were noted in the activity of wettable powders of different particle sizes in the glasshouse as pre-emergence applications. As a post-emergence treatment the fine particle size was more phytotoxic than the coarse material, especially when a wetting agent was added to the spray solution. In the field trials, no appreciable differences in weed control or crop tolerance could be established regardless of the time or rate of application. The flowable formulation was less active than the wettable powders in some glasshouse experiments but no such trend was apparent in field trials. Bioassays showed that the residual activity of the flowable formulation was lower than wettable powder formulations in both glasshouse and field studies but no consistent differences were noted in the persistence of the three forms of wettable powders.     

Control of seed-borne Sclerotinia sclerotiorum by fungicidal treatment of sunflower seed

Treatment of sunflower seeds with benomyl, vinclozolin, iprodione or procymidone virtually eliminated seed-borne Sclerotinia sclerotiorum. Applications of fungicides increased the number of surviving seedlings when seeds were sown in vermiculite or in steam-sterilized soil. With the exception of benomyl, fungicides were significantly more effective when applied in acetone solutions than when 100 g a.i./100 kg of seed was applied as conventional dry dressings. There was no difference in effectiveness between the two application methods when the dry dressings were applied at 200 g a.i/100 kg of seed. The acetone infusion method had no deleterious effects on germination of disease-free seed nor on seedling vigour. For a comparable level of control, less fungicide was needed in the infusion treatment than in the dust treatment. If fungicidal treatment of sunflower seeds is used routinely then the introduction of S. sclerotiorum into uninfested land could be controlled.     

Brief exposure of Blattella germanica (Blattodea) to insecticides formulated in various microcapsule sizes and applied on porous and non-porous surfaces

BACKGROUND: The authors explored how microcapsule size and brief exposure affected the bioavailability of five microencapsulated insecticide formulations, chlorpyrifos 23.1 g L(-1) CS (Detmol-PRO), chlorpyrifos 20 g L(-1) CS (Empire 20), fenitrothion 20 g L(-1) CS (Detmol-Mic), cyphenothrin 10 g L(-1) CS (Detmol-CAP) and diazinon 30 g L(-1) CS (Diacap), to Blattella germanica L. on porous and non-porous surfaces. The hypothesis was tested that microencapsulated (CS) insecticides comprising larger microcapsules show higher efficacy on porous surfaces than formulations with smaller microcapsules. RESULTS: Brief exposure was accomplished by allowing B. germanica to cross a 0.3 m insecticide barrier in 30 s (1.01 cm s(-1)). Such short exposure did not lead to 100% mortality in any formulation or surface tested. Significant differences in bioavailability on the porous and the non-porous surfaces were found: the largest difference was observed in Empire 20 and Detmol CAP, while bioavailability of Detmol MIC did not differ on porous and non-porous surfaces. Comparison of their microcapsule size spectra revealed that formulations containing larger microcapsules had higher efficacy on porous surfaces than formulations with smaller microcapsules. In order to explain the difference in efficacy, the variance of microcapsule sizes was regressed on the efficacy ratio on porous versus non-porous surfaces. Although negative correlation was evident between size of capsules and the efficacy ratio on porous and non-porous surfaces, the difference in the slope parameter was not statistically significant. CONCLUSION: Brief contact of B. germanica with insecticide spray residues, which is common in barrier treatment, may lead to low efficacy, especially on porous surfaces. The latter should be preferably treated with CS insecticides containing a fraction with large capsules. In addition to the size of the microcapsules, the role of other factors, such as wall capsule thickness and chemical composition, on CS insecticide activity on various surfaces should be examined in future work.     

Evaluation of chlorfenapyr for control of the bed bug,Cimex lectularius L.

BACKGROUND: The presence of bed bug populations resistant to pyrethroids demands the development of new control tactics, including the use of insecticides with new modes of action. Insecticides that disrupt oxidative phosphorylation in insect mitochondria can be an option. Laboratory assays were used to measure the toxicity of chlorfenapyr to susceptible strains and two strains highly resistant to pyrethroids. The effectiveness of two chlorfenapyr‐based formulations was compared, and behavioral responses of bed bugs to dry residues of aerosol sprays were evaluated. RESULTS: Chlorfenapyr was effective against all bed bug strains, killing them at a similar rate, regardless of their susceptibility status to pyrethroids. Dry residues aged for 4 months were as toxic as fresh dry residues. The aerosol formulation had contact activity and caused faster mortality than a water‐based formulation. Bed bugs did not avoid resting on surfaces treated with aerosol. CONCLUSION: Chlorfenapyr is an option for controlling pyrethroid‐resistant bed bugs. While it does not cause quick knockdown, its long residual activity and no avoidance behavior of bed bugs to dry residues appear to make this insecticide suitable for bed bug control. A faster insecticidal effect is obtained with the aerosol formulation, suggesting greater bioavailablity of the toxicant. Copyright © 2010 Society of Chemical Industry     

解淀粉芽胞杆菌干悬浮剂对稻瘟病的防治效果及安全性评价

目前芽胞杆菌微生物杀菌剂的剂型主要以水剂和可湿性粉剂为主,芽胞杆菌干悬浮剂作为芽胞杆菌类杀菌剂的新剂型,其安全性及特性需要研究。本文分析了解淀粉芽胞杆菌T429、JT84、Lx-11、B-916干悬浮剂对稻瘟病菌的抑菌活性,平板对峙试验结果表明,抑菌带宽分别为12.00、10.33、7.67和7.50 mm;使用20 mL甲醇萃取2 g干悬浮剂,发现其对稻瘟病菌抑菌带宽分别为7.00、6.33、5.50和5.00 mm。显微观察后发现稻瘟病菌菌丝明显膨大,表明在解淀粉芽胞杆菌干悬浮剂中存在脂肽类物质;在水稻破口期喷施解淀粉芽胞杆菌T429、JT84、Lx-11、B-916干悬浮剂75 g/667 m~2,对水稻穗颈瘟的防治效果分别为85.2%、79.3%、79.6%、78.9%;使用4株解淀粉芽胞杆菌干悬浮剂对水稻种子进行浸种处理,当稀释500倍时,对水稻种子安全,且具有不同程度的促生作用;上述4株菌株干悬浮剂室内稳定性测定结果表明,存放90 d时活菌数减少不显著,存放180 d时T429与B-916变化不显著,Lx-11与JT84下降30%左右,存放360 d时4株解淀粉芽胞杆菌干悬浮剂活菌数不低于1×10~9 cfu/mL。     

Susceptibility of house flies (Diptera: Muscidae) exposed to commercial insecticides on painted and unpainted plywood panels

House flies were collected from dairies in New York state and the levels of resistance to commercially available insecticide formulations were measured on painted and unpainted plywood panels. Dimethoate was ineffective on all surfaces. The wettable powder permethrin formulation was more toxic than the emulsifiable concentrate formulation. The wettable powder cyfluthrin formulation was also more toxic than the recently developed liquid formulation. In general, the best house fly control was obtained on flat latex painted plywood panels and the poorest control on gloss latex painted panels. It is highly unlikely that producers obtain adequate control with dimethoate and permethrin.     

Is attract‐and‐kill technology potent against insecticide‐resistant Lepidoptera?

Attract-and-kill techniques, associating an attractant and a contact insecticide in a sticky formulation, are a new way of controlling Lepidopteran pests. Insecticide resistance may, however, limit the effectiveness and even the attractiveness of such formulations where resistance pleiotropic effects influence pheromone perception. We have tested this hypothesis on resistant codling moths Cydia pomonella (L) using a commercial formulation containing (E,E)-8,10-dodecadien-1-ol (codlemone), the major component of the sex pheromone, as an attractant and permethrin as toxicant. We first compared the attractiveness of codlemone in a wind tunnel and the contact toxicity of pyrethroids on males of one susceptible and of three strains selected for resistance to diflubenzuron, deltamethrin and azinphos-methyl. The dose-response relationships of males of susceptible and resistant strains to codlemone did not differ significantly. The deltamethrin-selected strain was the most resistant to pyrethroids, exhibiting 138-, 25- and 18-fold resistance ratios to deltamethrin, cypermethrin and permethrin, respectively. The efficiency of the attracticide formulation, applied successively on filter paper support, glass support and wood support, was estimated by recording the mortality delay of males after natural contact with the formulation in the wind tunnel. The deltamethrin- and diflubenzuron-resistant strains were significantly less affected than the susceptible strain by contact with the attracticide on the wooden support, exhibiting 58- and 2.3-fold greater LT50 ratios, respectively. Mortality of deltamethrin-resistant moths did not exceed 40% after 48 h. The LT50 value was significantly greater on filter paper support than on the two other supports. Surprisingly, the LT50 ratio of the deltamethrin-resistant strain was markedly higher on filter paper support (1021-fold), which was more absorbent, than on the glass support (31-fold). No sublethal effects in terms of pheromone response, mating or fecundity occurred in moths surviving contact with the attracticide. Choice of insecticides in attracticide formulations will be influenced by the resistance background of the target pests. Principles of insecticide resistance management may also be applied to attract-and-kill technology by alternating with other insecticides or control methods.     

Surfaces and other factors modifying the effectiveness of pyrethroids against insects in public health

Features of the evolution of synthetic pyrethroid insecticides are reviewed and related to the target function in control. The factors affecting residual activity are discussed and related to the surfaces to which different formulations are applied. Many insecticide/formulation/surface combinations lose effectiveness rapidly. The consequence of this in relation to the recovery of cockroach populations are discussed using mathematical models and field observations.     

Systemic insecticides for control of Delphacodes kuscheli and the Mal de Río Cuarto virus on maize

Control of the Mal de Río Cuarto virus (MRCV) and its planthopper vector Delphacodes kuscheli was studied on maize hybrids whose seeds had been treated with systemic insecticides. Laboratory tests were performed to determine the effects of seed treatments with insecticides (acephate, carbofuran, imidacloprid) on the survival of the planthopper. Field experiments using four maize hybrids whose seeds had been treated with the insecticides were performed to establish the effect of the latter on MRCV incidence and severity, and on grain yield. MRCV infection was confirmed by DAS-ELISA. Carbofuran was the most effective insecticide in laboratory tests, independently of the hybrid tested, followed by imidacloprid and acephate. MRCV incidences were high in all treatments in the field test under natural planthopper infestations. Disease severity data analysis indicated that the insecticide - hybrid interaction was not significant. Maize hybrid Dekalb 664 and the imidacloprid treatments had the lowest severity means among the four hybrids and three insecticide treatments, respectively. Data for grain yield showed that the insecticide - hybrid interaction was significant and imidacloprid was generally the most effective in the field experiments. A negative correlation was observed between the mean disease severity index and mean grain yield. The results suggest that if an effective systemic insecticide is applied as a seed coating, it may be possible to obtain good control of D. kuscheli, decrease MRCV severity and increase grain yield under field conditions in areas at risk for MRCV.     

Effects of particle size and active ingredient content on residual activity of chlorpyrifos wettable powder formulations against codling moth,Cydia pomonella (L.)

In a laboratory experiment Cydia pomonella (L.) eggs, two days from eclosion, were placed on apples which had been sprayed five weeks previously with chlorpyrifos (125 mg/litre) from five formulations. Four were wettable powders (250 g a.i./kg) with particles ca 4, 5, 9 and 10 μm in diameter and one (500 g a.i./kg) with particles 2 μm in diameter. The treated apples were aged in direct sunlight. The percentage of apples without deep entries by first instar larvae one week after positioning of eggs, was greater the greater the ratio of active ingredient content of a formulation to total wettable powder particle surface area.     

Thermal behaviour and biological activity of pyrethroids in smoke-generating formulations

Smoke-generating insecticide formulations are nowadays very important for the control of Chagas' disease vectors. In this work, the thermal decomposition of different pyrethroid insecticides in smoke-generating formulations has been studied. Their recovery from the smoke has been determined, and the effect on this of the addition of foaming agents such as cyanoguanidine (CNG) or azodicarbonamide (ADC), or antioxidant agents such as butylated hydroxytoluene (BHT) or butylated hydroxyanisole (BHA) has been assessed. In each case the best smoke-generating formulation was established. Calorimetric studies were done to justify the behaviour of the smoke-generating mixtures. The isomerization process for different pyrethroids was also studied, to establish the influence of the foaming agents in inhibiting isomerization to less active pyrethroids. Smoke-generating mixtures containing β-cypermethrin and cis-permethrin as insecticides and CNG or ADC as foaming agents were evaluated for their insecticidal activity against nymphs I of Triatoma infestans, vector of Chagas' disease. The best effect was found with β-cypermethrin formulated with ADC, with LT₅₀ values lower than 5 min. © 1999 Society of Chemical Industry     

Comparative sensitivity of barley (Hordeum vulgare L.) to insecticide and fungicide on different stages of cell cycle

In this study, the comparison of cytogenetic effects of insecticide and fungicide in different phases of cell cycle was investigated in the root tip cells of barley (Hordeum vulgare L.). The seeds of H. vulgare L. Var. Karan 16 were treated with different concentrations (0.05%, 0.1% and 0.5%) of insecticide Profenophos (PF) and fungicide Mancozeb (MZ) for 6 h after presoaking durations of 7, 17 and 27 h.The different presoaking durations were used to bring the cells in various phases of cell cycle. Negative control was run parallel in distilled water. Cytogenetic examinations of root meristems exposed to the PF and MZ showed significant inhibition of mitotic index (MI) as well as significant increase in chromosomal aberrations (CAs). These parameters were dependent on the concentrations of insecticide and fungicide. The present study shows that PF and MZ both caused more damage in S phase of cell cycle which indicates that S phase is more sensitive in comparison to other phases.     

Insecticide-tolerant and plant-growth-promoting Rhizobium improves the growth of lentil (Lens esculentus) in insecticide-stressed soils

BACKGROUND: Application of insecticides in modern agriculture in order to enhance legume production has led to their accumulation in soils to levels that adversely affect soil microflora such as rhizobia and exert a negative impact on the physiological activities associated with them. This study was therefore designed to identify rhizobial strains expressing higher tolerance to insecticides fipronil and pyriproxyfen and synthesising plant growth regulators even amid insecticide stress. RESULTS: The fipronil‐ and pyriproxyfen‐tolerant Rhizobium sp. strain MRL3 produced plant‐growth‐promoting substances in substantial amounts, both in the presence and in the absence of the insecticides. In general, both insecticides at recommended and higher rates reduced plant dry biomass, symbiotic properties, nutrient uptake and seed yield of lentil plants. Interestingly, when applied with any concentration of the two insecticides, Rhizobium sp. strain MRL3 significantly increased the measured parameters compared with plants grown in soils treated solely with the same concentration of each insecticide but without inoculant. CONCLUSION: This study suggests that Rhizobium strain MRL3 may be exploited as a bioinoculant to augment the efficiency of lentil exposed to insecticide‐stressed soils. Copyright © 2010 Society of Chemical Industry     

Comparative sensitivity of barley (Hordeum vulgare L.) to insecticide and fungicide on different stages of cell cycle

In this study, the comparison of cytogenetic effects of insecticide and fungicide in different phases of cell cycle was investigated in the root tip cells of barley (Hordeum vulgare L.). The seeds of H. vulgare L. Var. Karan 16 were treated with different concentrations (0.05%, 0.1% and 0.5%) of insecticide Profenophos (PF) and fungicide Mancozeb (MZ) for 6 h after presoaking durations of 7, 17 and 27 h.The different presoaking durations were used to bring the cells in various phases of cell cycle. Negative control was run parallel in distilled water. Cytogenetic examinations of root meristems exposed to the PF and MZ showed significant inhibition of mitotic index (MI) as well as significant increase in chromosomal aberrations (CAs). These parameters were dependent on the concentrations of insecticide and fungicide. The present study shows that PF and MZ both caused more damage in S phase of cell cycle which indicates that S phase is more sensitive in comparison to other phases.     

Droplet size and efficacy of an adulticide-larvicide ultralow-volume formulation on Aedes aegypti using different solvents and spray application methods

BACKGROUND: When cases of dengue are reported or the density of adult Aedes aegypti (L.) becomes too high, ultralow-volume (ULV) application of insecticides is the recommended control method. The droplet size of an aerosol insecticide influences its efficiency in killing adult mosquitoes. Many studies have been carried out to determine the optimum droplet size that maximises vector control efforts, but only a few have determined droplet-size spectra for specific equipment using different solvents and comparing thermal and non-thermal aerosols. RESULTS: The present study showed that the droplet size for a water-based adulticide–larvicide formulation was larger than for the same formulation diluted in gasoil or biodiesel. No significant differences in adult mortality were observed between sprayers and solvents, but efficacy decreased with distance from the sprayer nozzle. Adult emergence inhibition was more than 90% when using water as a solvent for both thermal and cold foggers, and the efficacy did not decrease with distance from the sprayer nozzle. On the other hand, oil-based solvents became less effective with distance. CONCLUSION: The use of water as a solvent with both thermal and cold foggers improves the efficacy of the studied formulation containing permethrin as adulticide and pyriproxyfen as larvicide in scaled-up assays. Moreover, it reduces the environmental impact and costs of spraying by comparison with formulations using oil solvents. Copyright © 2011 Society of Chemical Industry     

Synergism between EBI fungicides and a pyrethroid insecticide in the honeybee (Apis mellifera)

The synergistic effect of a range of ergosterol-biosynthesis-inhibiting (EBI) fungicides and a pyrethroid insecticide was studied in the honeybee (Apis mellifera L.). Various EBI fungicides were combined separately with the pyrethroid lambda-cyhalothrin at ratios derived from their recommended application rates to represent tank-mixing in the field. The mixture was then applied topically to the thorax of honeybees, and mortality assessed 24 h post-treatment. All the fungicides tested increased the toxicity of lambda-cyhalothrin to honeybees. The fungicide propiconazole was found to have the strongest synergistic effect, decreasing the LD₅₀ of lambda-cyalothrin from 68.0 ng bee^?1 to 4.2 ng, thus having a synergistic ratio of 16.2. Hazard ratios were calculated for lambda-cyhalothrin and fungicide mixtures using a recommended application rate of 7.5 g a.i. ha^?1. The hazard ratio for lambda-cyhalothrin alone was 110, but when mixed with fungicide synergists, the hazard ratio ranged from 366 with flutriafol to 1786 with propiconazole. A blank formulation of a fungicide (without the active ingredient prochloraz) had little effect on the toxicity of lambda-cyhalothrin, indicating that it is primarily the fungicide active ingredient that is responsible for the synergistic effect. The results are discussed in terms of the potential hazard posed by pesticide synergism to honeybees in the field.