Lethal and sublethal effects of toxic bait formulations on Doryctobracon areolatus (Hymenoptera: Braconidae) and implications for integrated fruit fly management.

The use of toxic baits has become one of the main methods of management of fruit flies in Brazil. The application of toxic baits may cause side effects on the native parasitoid Doryctobracon areolatus (Hymenoptera: Braconidae). Based on the results, formulations made from the food attractants 3% Biofruit, 1.5% Ceratrap, 1.25% Flyral, 3% Isca Samaritá, 3% Isca Samaritá Tradicional, and 7% sugarcane molasses associated with the Malathion 1000 EC and the ready-to-use toxic bait Gelsura (containing the active ingredient alpha-cypermethrin) were classified as harmful (class 4) to D. areolatus (mortality > 85% at 96 HAE). In contrast, for toxic baits formulated with insecticide phosmet, the mortality ranged from 38% to 72%, classified as slightly harmful or moderately harmful. However, when phosmet was added to the 3% Samaritá Tradicional bait, the mortality was only 3.9% (class 1-harmless), similar to the toxicity observed for the Success 0.02 CB ready-to-use bait (0.24 g a.i. spinosad/l) (<5% mortality). Although toxic baits were formulated with spinosyn-based insecticides, all toxic bait formulations were classified as harmless or slightly harmful (<50% mortality) to D. areolatus, with the exception of 1.5% Ceratrap + spinetoram and 7% Sugarcane molasses + spinosad (≈ 60% mortality-moderately harmful). In addition, these formulations did not show sublethal effects in reducing the parasitism and emergence rate of the F1 generation of D. areolatus in A. fraterculus larvae. The results serve as a basis for the correct use of toxic food baits without affecting the biological control.

Persistent prolate polymersomes for enhanced co-delivery of hydrophilic and hydrophobic drugs.

Self-assembled polymersomes encapsulate, protect, and deliver hydrophobic and hydrophilic drugs. Though spherical polymersomes are effective, early studies suggest that non-spherical structures may enhance specificity of delivery and uptake due to similarity to endogenous uptake targets. Here we describe a method to obtain persistent non-spherical shapes, prolates, via osmotic pressure and the effect of prolates on uptake behavior. Polyethylene glycol-b-poly(lactic acid) polymersomes change in diameter from 145 ± 6 nm to 191 ± 1 nm and increase in polydispersity from 0.05 ± 0.02 to 0.12 ± 0.01 nm after addition of 50 mM salt. Transmission and scanning electron microscopy confirm changes from spheres to prolates. Prolate-like polymersomes maintain their shape in 50 mM NaCl for seven days. Nile Red and bovine serum albumin-Fluorescein dyes are taken up in greater amounts by SH-SY5Y neural cells when encapsulated in polymersomes. Prolate polymersomes may be taken up more efficiently in neural cells than spherical polymersomes.

Comparative toxicities and synergism of apple orchard pesticides to Apis mellifera (L.) and Osmia cornifrons (Radoszkowski).

The topical toxicities of five commercial grade pesticides commonly sprayed in apple orchards were estimated on adult worker honey bees, Apis mellifera (L.) (Hymenoptera: Apidae) and Japanese orchard bees, Osmia cornifrons (Radoszkowski) (Hymenoptera: Megachilidae). The pesticides were acetamiprid (Assail 30SG), λ-cyhalothrin (Warrior II), dimethoate (Dimethoate 4EC), phosmet (Imidan 70W), and imidacloprid (Provado 1.6F). At least 5 doses of each chemical, diluted in distilled water, were applied to freshly-eclosed adult bees. Mortality was assessed after 48 hr. Dose-mortality regressions were analyzed by probit analysis to test the hypotheses of parallelism and equality by likelihood ratio tests. For A. mellifera, the decreasing order of toxicity at LD50 was imidacloprid, λ-cyhalothrin, dimethoate, phosmet, and acetamiprid. For O. cornifrons, the decreasing order of toxicity at LD50 was dimethoate, λ-cyhalothrin, imidacloprid, acetamiprid, and phosmet. Interaction of imidacloprid or acetamiprid with the fungicide fenbuconazole (Indar 2F) was also tested in a 1∶1 proportion for each species. Estimates of response parameters for each mixture component applied to each species were compared with dose-response data for each mixture in statistical tests of the hypothesis of independent joint action. For each mixture, the interaction of fenbuconazole (a material non-toxic to both species) was significant and positive along the entire line for the pesticide. Our results clearly show that responses of A. mellifera cannot be extrapolated to responses of O.cornifrons, and that synergism of neonicotinoid insecticides and fungicides occurs using formulated product in mixtures as they are commonly applied in apple orchards.

Field efficacy and application timing of methoxyfenozide, a reduced-risk treatment for control of navel orangeworm (Lepidoptera: Pyralidae) in almond.

Large-scale field efficacy trials of methoxyfenozide (Intrepid), a reduced-risk molting agonist insecticide, were conducted in 2004 and 2005 in an orchard containing 'Nonpareil' and 'Sonora almonds [Prunus dulcis (Mill.) D.A. Webb] located in Kern County, CA. Methoxyfenozide applied one to three times, the organophosphate phosmet (Imidan) alone or in combination with methoxyfenozide, or the pyrethroid permethrin (Perm-Up) were tested for efficacy against the primary lepidopteran pest navel orangeworm, Amyelois transitella (Walker) (Lepidoptera: Pyralidae), and three other lepidopteran pests of almond: oriental fruit moth, Grapholita molesta (Busck); oblique-banded leafroller, Choristoneura rosaceana (Harris); and peach twig borer, Anarsia lineatella Zeller. Two or three applications of methoxyfenozide (bracketing hull split or spring plus bracketing hull split) were more effective than a single hull split application of phosmet, phosmet combined with permethrin, or methoxyfenozide. In these trials, a spring application followed by a posthull split application was as effective as the applications bracketing hull split. Navel orangeworm accounted for > 60% of the total damage, whereas oriental fruit moth and peach twig borer were the dominant secondary pests. In experiments conducted in 2010 to assess the direct toxicity of methoxyfenozide to navel orangeworm eggs under field conditions, exposure to methoxyfenozide reduced survival by 96-99%. We conclude that this reduced-risk insecticide is effective, although its efficacy is maximized with more than one well-timed application.

Field evaluation of reduced insecticide spray programs for managing plum curculio, Conotrachelus nenuphar (Coleoptera: Curculionidae), in Alabama peaches.

BACKGROUND: Plum curculio (PC), Conotrachelus nenuphar (Herbst.), is an important pest of peaches in the southeastern United States. Commercially acceptable control of this insect is typically achieved by weekly or biweekly application of broad-spectrum conventional insecticides, resulting in 6-12 sprays per season. Experiments were conducted in a peach orchard in Alabama during 2007-2009 to compare the conventional calendar-based insecticide spray program involving weekly applications of phosmet with three different reduced spray programs using three targeted (well-timed) insecticide sprays (TIS) of phosmet, permethrin or thiamethoxam applied in an alternated fashion. RESULTS: All three TIS programs significantly reduced PC damage at harvest compared with the untreated control in two of the three years (2008 and 2009). Fruit damage due to stink bugs, which are emerging pests of peaches in the region, was also significantly reduced in the TIS programs in both years. In a separate trial in which one of the TIS programs (three targeted sprays of phosmet) was evaluated in a larger peach block in 2009, percentage fruit damage due to PC increased from < 1% in June to ~4% in late July. CONCLUSION: All the TIS programs evaluated provided effective control of PC and represent potential alternatives to the conventional weekly spray program in peaches with concomitant reduction in insecticide usage and associated costs. However, an additional spray may be necessary for effective control of PC and stink bugs in late-season peach varieties.

Studies on the putative interactions between the organophosphorus insecticide Phosmet and recombinant mouse PrP and its implication in the BSE epidemic.

It has been suggested that exposure of cattle to the ectoparasiticide Phosmet in the 1980s caused a conformational change in the cellular prion protein (PrP(C)) to form the BSE prion (PrP(SC)), which initiated the epidemic of bovine spongiform encephalopathy (BSE). Recombinant mouse cellular prion (r[mouse]PrP(C)) was exposed to the organophosphorus pesticide Phosmet in vitro and the conformation of the prion before and after exposure was monitored using circular dichroism (CD) spectroscopy, utilizing synchrotron radiation at the Council for the Central Laboratory of the Research Councils (CLRC) facilities at Daresbury, UK. Metabolites of Phosmet, generated in situ by rat microsomes, were investigated in the same way, to determine whether they might initiate the conformational change due to their high chemical reactivity. Our studies showed that exposure of r[mouse]PrP(C) to Phosmet or microsomes-generated metabolites of Phosmet did not result in the conformational change in the protein from alpha-helix to beta-pleated sheet that is characteristic of the PrP(C) to PrP(SC) conversion and, therefore, Phosmet is very unlikely to have initiated the BSE epidemic by a simple direct mechanism of conformational change in the prion protein.

Phosmet induces up-regulation of surface levels of the cellular prion protein.

Chronic (2 day) exposure of human neuroblastoma cells to the organophosphate pesticide phosmet induced a marked concentration-dependent increase in the levels of PrP present on the cell surface as assessed by biotin labelling and immunoprecipitation. Levels of both phospholipase C (PIPLC)-releasable and non-releasable forms of PrP were increased on the plasma membrane. These increases appear to be due to post-transcriptional mechanisms, since PrP mRNA levels as assessed by Northern blotting were unaffected by phosmet treatment. These data raise the possibility that phosmet exposure could increase the susceptibility to the prion agent by altering the levels of accessible PrP.

Phosphoinositide phosphorylation and shape changes produced by phosmet-oxon in human erythrocytes.

1. "In vitro" incubation of red blood cells with phosmetoxon induced crenated and invaginated forms. 2. [32P] phosphate incorporation was greater in membranes from erythrocytes exposed to 300 nM phosmetoxon for 10 min than in control cells. 3. The highest incorporation was for phosphatidylinositol (PI), followed by phosphatidylinositol phosphate (PIP) and phosphatidylinositolbiphosphate (PIP2). 4. An activation of phosphatidylinositol (PI) kinase was detected with 150 and 300 nM of the pesticide, while there was no change in poliphosphoinositides (PPI) phosphodiesterase activity. 5. Results suggest an association between changes in PI kinase activity, the phosphorylation cycle of phosphatidylinositols and alterations in erythrocyte morphology induced by phosmetoxon.

A comparative study of guanine N7-alkylation in mice in vivo by the organophosphorus insecticides trichlorphon, dimethoate, phosmet and bromophos.

Following intraperitoneal administration to male mice (strain AB Jena/Halle) of 14C-methyl-labelled trichlorphon, dimethoate, phosmet and bromophos, 10-20 Ci/mol, in dosages of 0.06-0.55 mmol/kg, DNA from liver and kidneys was analyzed for 14C in N-7 methylguanine (7-MeG). The extents of methylation were in the range of 5-10 mumol 7-MeG/mol guanine for trichlorphon and dimethoate and of 0.2-0.4 for phosmet and bromophos, for high doses, respectively Excretion half-lives of 7-MeG were differing between trichlorphon (5 hrs, high dose, and 15-17 hrs, low dose) and dimethoate (23-160 hrs, high dose). The extents of methylation at 0-6 of guanine were estimated to be around 0.01 mumol 0-6 MeG/mol guanine for high doses of organophosphates of sufficient water solubility. Factors associated with the partition of organophosphates in mammalian systems are useful for estimating DNA attack by organophosphates in mammals in vivo.

Experimental study of the effect of a series of phosphoroorganic pesticides (Dipterex and Imidan) on embryogenesis.

Experiments conducted on pregnant Wistar rats show that chlorophos (Dipterex) has embroyotoxic and teratogenic effects after oral introduction in a 80 mg/kg dose during a critical period of embryogenesis. Embryotoxic and teratogenic effects are absent during the introduction of 8 mg/kg of the pesticide. The oral introduction of phthalophos (Imidan) in a 30 mg/kg dose once on day 9 of pregnancy and the introduction of a 1.5 mg/kg dose daily throughout the course of pregnancy caused increased postimplantation mortality of embryos. A dose of 30 mg/kg of phthalophos on day 9 or day 13 of pregnancy causes developmental abnormalities, including hyponathia and hydrocephaly. A 0.06 mg/kg phthalophos dose does not affect the course of embryogenesis in white rats. Thus the organophosphate pesticides Dipterex and Imidan exhibit embryotoxic and teratogenic effects at doses which significantly exceed the acutal amounts of the pesticide that can enter the human organism.