Progress 08/15/02 to 08/14/05
Outputs
The effectiveness of spinosad at 1 mg(AI)/kg (1 ppm) in suppressing stored-product insects was evaluated by treating 2002 wheat stored in bins on three Kansas farms, and 2002 corn stored in bisn on three Indiana farms. The effectiveness of spinosad was compared with untreated wheat or corn (control), and wheat treated with chlorpyrifos-methyl [Reldan] at 3 ppm (half the labeled rate) in Kansas or corn treated with pirimiphos-methyl (Actellic) at 4 ppm (half the labeled rate), and wheat treated with 1 ppm spinosad combined with 3 ppm chlorpyrifos-methyl or corn treated with 1 ppm spinosad combined with 4 ppm chlorpyrifos-methyl. Wheat was monitored for 6 months starting July 2002, whereas the corn was monitored for 2 years starting with fall storage in 2002. On wheat the actual deposit at 1 ppm spinosad was 0.7 ppm, whereas on corn it ranged from 0.4 to 0.6 ppm. No live insects were found in wheat treated with spinosad whereas mold feeders were observed in untreated and
spinosad-treated corn. In laboratory bioassays, spinosad-treated wheat completely killed adults of the lesser grain borer, rusty grain beetle but not the red flour beetle, but all three species progeny were effectively. Chlorpyrifos-methyl was also effective against the latter two species. On corn, spinosad effectively controlled maize weevils and Indianmeal moths for a period of two years despite loss of residue over time. Pirimiphos-methyl and spinosad plus pirimiphos-methyl treatments were effective against the lesser grain borer, maize weevil, and red flour beetle during the first year. The grain quality of wheat in bin across all treatments was essentially similar, except with respect to insect-damaged kernels. There were three to five times as many insect damaged kernels in untreated wheat and wheat treated with chlorpyrifos-methyl alone. Trends in insect damaged kernels in corn corresponded well with progeny production of the insect species over the two year test period.
Impacts
Wheat in Kansas is stored for three to six months, and spinosad provided effective protection of stored-wheat from insect infestations during the six months of the study. Spinosad is a viable grain protectant at 1 ppm, as opposed to 6-8 ppm of traditionally used organophosphates. Furthermore, spinosad is highly effective against lesser grain borer-a devastating pest of stored wheat in Kansas and other parts of the world. Corn in Indiana is often stored into the following spring and summer. Spinosad provided effective protection of stored corn from insect infestation during the first and second summer storage seasons. Furthermore, spinosad was effective against two key corn insects, the maize weevil and Indianmeal moth. In January 2005, Spinosad received a full label as a grain protectant and commercial products will be available for use by producers in late 2006 or 2007 pending acceptance of international tolerances.
Publications
- Szabela, D. 2005. Fate and efficacy of spinosad for insect management in farm-stored corn. Unpublished M. S. Thesis, Purdue University, West Lafayette, Indiana.
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Progress 01/01/04 to 12/31/04
Outputs
Spinosad, a reduced-risk bacterial insecticide, was evaluated on hard red winter wheat stored in round metal bins on three Kansas farms during 2002-2003. On each farm, four bins each holding approximately 75 metric tons received different treatments as follows: untreated control, spinosad at 1 mg (AI)/kg, chlorpyrifos-methyl (Reldan) at 3 mg (AI)/kg, and spinosad, 1 mg/kg + chlorpyrifos-methyl, 3 mg/kg. Grain samples were removed with a trier monthly starting July 2002 until May 2003 to determine types and numbers of insects present. Grain samples were equilibrated to 13% moisture in a laboratory chamber and exposed to adults of the lesser grain borer, red flour beetle, and rusty grain beetle. Both the field and laboratory observations showed that spinosad and spinosad + chlorpyrifos-methyl treatments to be effective in completely suppressing insects. In the untreated grain, line insects were observed after the second moth and steadily increased 20 live adults/kg of
grain after 6 months of storage. The chlorpyrifos-methyl treated grain lost effectiveness after 2 months, and after 6 months had 10 live adults/kg. Live insects were not found in samples collected from grain receiving spinosad treatments. The original residue of spinosad in spinosad and spinosad + chlorpyrifos-methyl treatments ranged from 0.68-0.73 mg/kg soon after grain treatment and residues after 6 mointsh of storage were 0.42-0.62 mg/kg. However, this degration over time was not statistically significant. Very few insect-damaged kernels (<1/100 g) were found in spinosad and spinosad + chlorpyrifos-methyl treatments compared with 8.3 insect-damaged kernels in the untreated and chlorpyrifos-methyl treated grain.
Impacts
Spinosad alone, during the 6-months of study, provided effective control of grain insects. Spinosad appears to be a viable grain protectant for organic and non-organic wheat or wheat that is not aerated. The US-EPA recently approved registration of spinosad as a grain protectant for use of wheat and other grains, with an application rate of 1 mg/kg and a tolerance level of 1.5 mg/kg.
Publications
- Flinn, P. W., Bh. Subramanyam, and F. H. Arthur. 2004. Comparison of aeration and spinosad for suppressing insects in stored wheat. Journal of Economic Entomology 97: 1465-1473.
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Progress 01/01/03 to 12/31/03
Outputs
Spinosad was evaluated on hard red winter wheat stored in round metal bins on three Kansas farms during 2002-2003. On each farm, four bins each holding approximately 75 metric tons received different treatments as follows: untreated control, spinosad at 1 mg (AI)/kg, chlorpyrifos-methyl (Reldan) at 3 mg (AI)/kg, and spinosad, 1 mg/kg + chlorpyrifos-methyl, 3 mg/kg. Grain samples were removed with a trier monthly starting July 2002 until May 2003 to determine types and numbers of insects present. Grain samples were equilibrated to 13% moisture in a laboratory chamber and exposed to adults of the lesser grain borer, red flour beetle, and rusty grain beetle. Both the field and laboratory observations showed that spinosad and spinosad + chlorpyrifos-methyl treatments to be effective in completely suppressing insects. The chlorpyrifos-methyl treatment lost effectiveness after 2 months. Large numbers of insects were observed in the untreated control bins. These results
suggest that spinosad could be a potential grain protectant for use on stored wheat in Kansas. Bioassays in the laboratory with three insect species showed that spinosad and spinosad+chlorpyrifos-methyl treated grain were effective in providing complete control of adults of the lesser grain borer and rusty grain beetle, and prevented their progeny production. The red flour beetle adult mortality ranged from 40-60% throughout the study, but both spinosad and spinosad+chlorpyrifos-methyl treatments suppressed progeny production. Chlorpyrifos-methyl treated wheat was only partially effective against the three species after 2 months. The residues of spinosad were stable on the grain during the 11-month study period.
Impacts
A full label petition by the registrant, Dow AgroSciences, has been submitted to EPA in 2003. A label approval is expected in the 3rd or 4th quarter of 2004. Registration of this product on grains will prevent damage to wheat and other grain by the lesser grain borer and other insects, and thereby improve quality of grains stored on farms and at commercial elevators.
Publications
- Toews, M. D., Bh. Subramanyam, and J. Rowan. 2003. Knockdown and mortality of eight stored-product beetles exposed to four surfaces treated with spinosad. J. Econ. Entomol. 96: 1967-1973
- Huang, F., Bh. Subramanyam, and M. D. Toews. Susceptibility of laboratory and field strains of four stored-product insects to spinosad. J. Econ. Entomol. (Submitted in December 2003).
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Progress 01/01/02 to 12/31/02
Outputs
Four round metal bins of 3000-bushel capacity on three separate farms in Kansas were provided by producers to conduct farm-bin trials with spinosad. Spinosad (SpinTor 2SC) was approved by the US-EPA in May 2002 for grain treatment at 1 mg/kg (ppm). On each farm, four different grain treatments were applied to the four different bins. One of the bins was untreated (control), one was treated with spinosad at 1 mg/kg, one was treated with chlorpyrifos-methyl (Reldan) at 3 mg/kg (half the labeled rate), and one was treated with spinosad (1 mg/kg) + Reldan (3 mg/kg). All insecticide treatments were made by diluting the insecticide(s) in water and applying it to the grain stream before bin loading. After bin loading, the grain surface in all bins was leveled. Grain treatments on all three frams occurred in July 2002. Temperatures within each bin were measured using thermocouples placed to a depth of 6 cm from the surface. Grain samples (7500 lb) were removed monthly with a
6 ft grain trier from each bin. Grain samples were sifted to count live insects in samples. A portion of the grain samples (1000 g) collected at months 0, 3, and 6 were submitted to Kansas Grain Inspection Service for an OCIS Grade. After separating insects from the grain, the samples were frozen at -13oC for 1 week and later tempered to 12-13% moisture in an environmental growth chamber set at 28oC and 65% RH. Grain samples were used to conduct bioassays with adults of the lesser grain borer, red flour beetle, and rusty grain beetle. In 200 g of grain sample from each bin, 50 adults of each species were introduced. Each species was tested separately. Beetle mortality after 14 days and progeny production after 8 weeks was determined. Independent samples were used for the 14 day and 8 weeks assessment. There were no significant differences in grain temperatures among bins within a farm. No live insects were found in all bins sampled in July, but in August, live insects were found in
untreated bins. In September, live insects were found in bins treated with Reldan. No insects were found in bins treated with spinosad + Reldan. Live insects were also not found in any spinosad-treated bins. This suggested that spinosad was responsible for the insect suppression observed in the bin receiving the combination treatment. Laboratory bioassays between July and October showed that spinosad was effective in killing all adults of the lesser grain borer and rusty grain beetle exposed for 14 days and prevented their progeny production. However, spinosad, as expected, killed only 50% or less adults of the red flour beetle. However, spinosad suppressed progeny production of the red flour beetle. Untreated grain had less than 10% mortality and more than 70-300 adults after 8 weeks. Grain samples between July and August containing Reldan residues killed adults of all three species and suppressed their progeny. However, the effectiveness of Reldan against the three species started
to decline after August. The combination treatment was as effective as the spinosad treatment in killing and suppressing progeny of all three species.
Impacts
Results from our farm trials are consistent with results obtained on stored wheat in laboratory and pilot bin tests. The excellent activity against the lesser grain borer-a devastating pest of stored wheat in Kansas and the US-at 1 mg/kg and its persistence on grain suggests that spinosad is a viable stored wheat protectant. Reldan at 3 mg/kg degraded within two months and therefore combining spinosad with Reldan is not desirable. Although spinosad was partially effective against the red flour beetle adults in laboratory bioassays, it suppressed progeny production of this species. Furthermore, in farm bins, spinosad bins did not contain any live insects, including the flour beetles, while the untreated bins had several live flour beetles. Spinosad was effective against rusty grain beetles. Spinosad's performance was excellent during the first six months of this study. The farm bin trials will conclude by June 2003.
Publications
- No publications reported this period
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