Pirimiphos-Methyl Degradation and Insect Population Growth in Aerated and Unaerated Com Stored in Southeast Georgia: Small Bin Tests

Lots of 229 kg untreated seed com and com treated with 8 ppm pirimiphosmethyl were stored in unaerated bins and bins modified with a fan blower to provide aeration. The corn was infested artificially with adults of the red flour beetle, Tribolium castaneum (Herbst); the maize weevil, Sitophilus zeamais Motschulsky; and eggs of the Indianmeal moth, Plodia interpunctella (Hiibner), to determine the effects of aeration on insect control in southeastern Georgia. Total temperature units in unaerated and aerated treated corn during the storage period of 15 October through 4 August were 5,729 and 5,196 degree-days, and moisture content was significantly greater in unaerated than in aerated bins. Pirimiphos-methyl degraded more quickly in unaerated than in aerated bins. No live insects were recovered from either unaerated or aerated treated bins. Total temperature units in untreated unaerated and untreated aerated corn were 5,745 and 5,391 degree-days. Percentage moisture content, percentage insect-damaged kernels, and number of beetles were greater in unaerated untreated than in aerated untreated bins. Indianmeal moth populations did not increase with time in untreated unaerated or untreated aerated bins. Aeration potentially can reduce insect pest population levels and subsequent damage in corn stored in southeastern Georgia

Degradation and Biological Efficacy of Chlorpyrifos-Methyl on Wheat Stored at Five Temperatures and Three Moisture Contents

Soft red winter wheat was treated with a calculated dosage of 6 ppm chlorpyrifos-methyl and stored at 15, 20, 25, 30, or 35°C and either 11.2, 12.1, or 13.7% moisture content (15 combinations). Measured residue deposition on the wheat was 4.39 ± 0.57 ppm, a 27.2% reduction from the calculated dosage. Residue degradation was asymptotic at all combinations except 15°C and 11.2 and 12.1% moisture content. Residue loss during the initial months of storage increased with increases in both temperature and moisture content within temperature. Rice weevils, Sitophilus oryzae (L.), did not survive bimonthly bioassays on wheat stored at either 15 or 20°C, but did survive on wheat stored at 20°C and 13.7% moisture content. Above 20° C, survival on treated wheat increased as residues decreased, and residues became either inactivated or diluted by increased moisture content. Numbers of F1 progeny, the percentage of insect-damaged kernels, and the amount of ground wheat flour (dockage) were positively correlated with weevil survival and negatively correlated with residue levels

Chlorpyrifos-Methyl Degradation and Biological Efficacy Toward Maize Weevils (Coleoptera: Curculionidae) on Corn Stored at Four Temperatures and Three Moisture Contents

Corn was treated with 6 ppm chlorpyrifos-methyl and stored for 10 mo at each of four temperatures (15.0, 22.5, 30.0, and 37.5·C) and three moisture contents (11.4, 12.4, and 14.4%). Every 2 mo, samples were removed from storage and analyzed for chlorpyrifos- methyl residue and infested with maize weevils, Sitophilus zeamais Motschulsky. Initial residues on the corn were 4.95 ± 0.67 ppm. Of the residues that were lost, most were lost during the first 2 mo of storage. The loss rate increased as temperature and moisture content increased. No weevils survived on corn stored at 15.0 or 22.5°C,except for 7.2% of the weevils that survived at month 10 on corn stored at 22.5°C. Weevil survival increased as moisture content increased in corn stored at 30.0 and 37.5°C. The threshold for weevil survival was ≈1.22 ppm chlorpyrifos-methyl. Population growth, the percentage of insect-damaged kernels, and dockage weight were all correlated with insect survival

Efficacy of grain protectants against four psocid species onmaize, rice and wheat

BACKGROUND: Psocids are emerging pests in stored products, particularly in amylaceous commodities such as grains. Currently, their control is based on the use of fumigants and contact insecticides; however, newer data indicate that psocids are tolerant to insecticides used to control other stored-grain species. This study evaluated the insecticides registered in the USA for use on stored maize, rice and wheat for control of the psocid species Lepinotus reticulatus, Liposcelis entomophila, L. bostrychophila and L. paeta. Mortality of exposed adult females was recorded after 7 and 14 days of exposure, while progeny production was assessed after 30 days of exposure. RESULTS: On wheat and rice, chlorpyriphos-methyl + deltamethrin was generally more effective against exposed parental adults than spinosad or pyrethrin, while pirimiphos-methyl was more effective on maize than spinosad or pyrethrin. In most cases, progeny production was suppressed in the treated grains. Progeny production was consistently lowest on wheat and rice treated with chlorpyriphos-methyl+ deltamethrin and maize treated with pirimiphos-methyl. CONCLUSIONS: Chlorpyriphos-methyl+deltamethrin and pirimiphos-methyl were the most effective insecticides for all species and commodities. Conversely, efficacy of spinosad or pyrethrum was highly dependent on the psocid species and commodity

Efficacy of layer treatment with methoprene for control of \u3ci\u3eRhyzopertha dominica\u3c/i\u3e (Coleoptera: Bostrychidae) on wheat, rice andmaize

BACKGROUND: Insect growth regulators are promising alternatives to traditional pesticides in stored grain. The efficacy of the juvenile hormone analogue methoprene was evaluated as a layer treatment in a laboratory experiment for control of Rhyzopertha dominica (F.) (Coleoptera: Bostrychidae) in wheat, rice and maize. RESULTS: Adults of R. dominica were placed in vials containing 33, 26 and 29 g (to a depth of 6.5 cm) of wheat, rice and maize, respectively, that was entirely or partially treated with 1, 5 or 10mg kg−1 methoprene. In wheat and rice, the layer treatments were not as effective as the whole-grain treatment, but there was decreased progeny production as the application rate increased. However, on maize the partial treatments were as effective as the whole-grain treatment at 5 and 10 mg kg−1. CONCLUSIONS: The results suggest that partial layer treatments with methoprene can be used to control R. dominica on maize but may not be effective for control of this species on wheat and rice

Effects of Short Exposures to Spinosad-Treated Wheat or Maize on Four Stored-Grain Insects

The effect of short exposures to spinosad-treated wheat, Triticum aestivum L., or maize, Zea mays L., was evaluated against adults of four stored-product insect species: lesser grain borer, Rhyzopertha dominica (F.) (Coleoptera: Bostrichidae); rice weevil, Sitophilus oryzae (L.) (Coleoptera: Curculionidae); red flour beetle, Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae); and the psocid Lepinotus reticulatus (Enderlein) (Psocoptera: Trogiidae). Adult mortality of these species was recorded after 0, 2, 4, 8, 16, and 40 h on commodities treated with 1ppm of spinosad (immediate mortality). Then, the surviving individuals were removed and placed on untreated wheat or maize, and mortality was recorded again 7 d later (delayed mortality). Progeny production then was determined 65 and 35 d later for the beetles and psocids, respectively. Among the four species tested, R. dominica was the most susceptible, and immediate mortality after 40 h reached 78 and 72% on wheat and maize, respectively. Moreover, 7 d later, all adults that had been exposed for \u3e2 h were dead on both commodities. Progeny production was significantly reduced in comparison with the controls, and no progeny were found when parental adults had been exposed for \u3e8 or \u3e4 h on wheat and maize, respectively. For S. oryzae, 40-h exposures significantly increased delayed mortality on both wheat and maize, but progeny production still was high. Generally, no effect of short exposures was noted for T. castaneum. For L. reticulatus, despite the fact that the increase of exposure interval increased mortality on maize,progeny production was not avoided.With the exception of T.castaneum, more progeny were found on wheat than on maize. The results of the current study indicate that R. dominica is very susceptible after short exposures to spinosad-treated substrate, but the other species are able to survive and reproduce at the exposure range examined

Degradation and Biological Efficacy of Chlorpyrifos-Methyl on Wheat Stored at Five Temperatures and Three Moisture Contents

Soft red winter wheat was treated with a calculated dosage of 6 ppm chlorpyrifos-methyl and stored at 15, 20, 25, 30, or 35°C and either 11.2, 12.1, or 13.7% moisture content (15 combinations). Measured residue deposition on the wheat was 4.39 ± 0.57 ppm, a 27.2% reduction from the calculated dosage. Residue degradation was asymptotic at all combinations except 15°C and 11.2 and 12.1% moisture content. Residue loss during the initial months of storage increased with increases in both temperature and moisture content within temperature. Rice weevils, Sitophilus oryzae (L.), did not survive bimonthly bioassays on wheat stored at either 15 or 20°C, but did survive on wheat stored at 20°C and 13.7% moisture content. Above 20° C, survival on treated wheat increased as residues decreased, and residues became either inactivated or diluted by increased moisture content. Numbers of F1 progeny, the percentage of insect-damaged kernels, and the amount of ground wheat flour (dockage) were positively correlated with weevil survival and negatively correlated with residue levels

Efficacy of Methoprene for Control of Five Species of Psocids (\u3ci\u3ePsocoptera\u3c/i\u3e) on Wheat, Rice, and Maize

The insect growth regulator methoprene was evaluated for control of Liposcelis bostrychophila Badonnel, Liposcelis decolor (Pearman), Liposcelis entomophila (Enderlein), Liposcelis paeta Pearman (Psocoptera: Liposcelididae), and Lepinotus reticulatus Enderlein (Trogiidae) at application rates of 1, 5, and 10 ppm on maize, wheat, and rice. Methoprene did not completely suppress progeny production during the 40-day test period, but did cause a significant reduction in adult progeny in all psocid species at the application rates of 5 and 10 ppm. At 1 ppm, numbers of adults were reduced for all species on wheat and maize, but only for L. paeta on rice. Nevertheless, the numbers of nymphs present after 40 days generally were not reduced, relative to the controls. Methoprene applied at rates of 1 to 10 ppm to stored grain would not provide adequate control of psocids

Temporal and spatial patterns in aerosol insecticide droplet distribution: Modifying application strategies to improve coverage and efficacy

With the phase-out of methyl bromide, treatment of food facilities with aerosol insecticides as part of management programs has increased. The physical layout of the structure, the distribution of equipment and other items within the space, and the application method and location may all cause spatial variation in how the insecticide is deposited, which can result in areas with insufficient or excessive amounts of insecticide applied. The impact of aerosol insecticide application position and dispersal method/formulation on the distribution of droplets was evaluated using a series of applications within the same flour mill room. The spatial pattern of droplet distribution and the effect of treatment on bioassay insects (Tribolium confusum Jacquelin DuVal) was evaluated. There was variation in aerosol concentration and droplet size distributions within room and application position had an impact on the spatial pattern of aerosol droplets. The further away and more obstructed by structural features a location was the lower the aerosol concentration, but concentration was also lower to the side and behind the release point. Evaluation of the temporal pattern in droplet deposition shows that most larger droplets settle out of the air relatively quickly, supporting that idea that shorter shutdown times are be possible. Efficacy was correlated with droplet concentration. The overall conclusion is that there can be considerable variation in distribution of aerosol insecticides and as a result considerable potential for improvement in the effectiveness of these applications.With the phase-out of methyl bromide, treatment of food facilities with aerosol insecticides as part of management programs has increased. The physical layout of the structure, the distribution of equipment and other items within the space, and the application method and location may all cause spatial variation in how the insecticide is deposited, which can result in areas with insufficient or excessive amounts of insecticide applied. The impact of aerosol insecticide application position and dispersal method/formulation on the distribution of droplets was evaluated using a series of applications within the same flour mill room. The spatial pattern of droplet distribution and the effect of treatment on bioassay insects (Tribolium confusum Jacquelin DuVal) was evaluated. There was variation in aerosol concentration and droplet size distributions within room and application position had an impact on the spatial pattern of aerosol droplets. The further away and more obstructed by structural features a location was the lower the aerosol concentration, but concentration was also lower to the side and behind the release point. Evaluation of the temporal pattern in droplet deposition shows that most larger droplets settle out of the air relatively quickly, supporting that idea that shorter shutdown times are be possible. Efficacy was correlated with droplet concentration. The overall conclusion is that there can be considerable variation in distribution of aerosol insecticides and as a result considerable potential for improvement in the effectiveness of these applications

Photooxidation of 2-methyl-3-buten-2-ol (MBO) as a potential source of secondary organic aerosol

2-Methyl-3-buten-2-ol (MBO) is an important biogenic hydrocarbon emitted in large quantities by pine forests. Atmospheric photooxidation of MBO is known to lead to oxygenated compounds, such as glycolaldehyde, which is the precursor to glyoxal. Recent studies have shown that the reactive uptake of glyoxal onto aqueous particles can lead to formation of secondary organic aerosol (SOA). In this work, MBO photooxidation under high- and low-NO_x conditions was performed in dual laboratory chambers to quantify the yield of glyoxal and investigate the potential for SOA formation. The yields of glycolaldehyde and 2-hydroxy-2-methylpropanal (HMPR), fragmentation products of MBO photooxidation, were observed to be lower at lower NO_x concentrations. Overall, the glyoxal yield from MBO photooxidation was 25% under high-NO_x and 4% under low-NO_x conditions. In the presence of wet ammonium sulfate seed and under high-NO_x conditions, glyoxal uptake and SOA formation were not observed conclusively, due to relatively low (<30 ppb) glyoxal concentrations. Slight aerosol formation was observed under low-NO_x and dry conditions, with aerosol mass yields on the order of 0.1%. The small amount of SOA was not related to glyoxal uptake, but is likely a result of reactions similar to those that generate isoprene SOA under low-NO_x conditions. The difference in aerosol yields between MBO and isoprene photooxidation under low-NO_x conditions is consistent with the difference in vapor pressures between triols (from MBO) and tetrols (from isoprene). Despite its structural similarity to isoprene, photooxidation of MBO is not expected to make a significant contribution to SOA formation