Effectiveness of a Dry Formulation of Spinosad Against Stored-Grain Insects Anna Getchell and Bhadriraju Subramanyam Department of Grain Science and Industry Kansas State University Manhattan, KS Central States Entomological Society April 23, 2005

 Insecticide derived from fermentation products (Spinosyns A and D) of the actinomycete bacterium, A and D) of the actinomycete bacterium, Saccharopolyspora spinosa (Mertz &Yao) Saccharopolyspora spinosa (Mertz &Yao)  Unique mode of action reduces the chances of cross- resistance to traditional insecticides resistance to traditional insecticides  Low mammalian toxicity  Environmentally benign  Registered by US-EPA in January 2005 January 2005  Commercially available in 2007 because of pending international tolerances 2007 because of pending international tolerances Spinosad

Previous Work  Spinosad (marketed as Tracer®, Success® and SpinTor®) has been tested on many crops and targets SpinTor®) has been tested on many crops and targets many pests (Sparks et. al 2001) many pests (Sparks et. al 2001)  All previous work with spinosad on stored-grain insects has been with a liquid formulation (SpinTor 2SC) has been with a liquid formulation (SpinTor 2SC)  At 1 mg/kg (ppm) spinosad killed and prevented population growth of key stored-grain insects under population growth of key stored-grain insects under laboratory and field conditions (Fang et al. 2002a,b; laboratory and field conditions (Fang et al. 2002a,b; Huang and Subramanyam 2003; Flinn et al. 2004) Huang and Subramanyam 2003; Flinn et al. 2004)

Advantages of a Dry Formulation  Does not require  water for dilution  electricity for sprayers  calculations to obtain correct concentration concentration  sprayer calibration

Advantages of Dry Formulation Application  They can be applied at many points within the grain storage process: storage process:  to grain in trucks prior to unloading at elevator unloading at elevator  directly to grain in the hopper or conveyor as it is being loaded into a storage facility or conveyor as it is being loaded into a storage facility  directly to grain surface after loading  Most of the dry dust residues on kernels can be removed from the grain during processing (aspiration) from the grain during processing (aspiration)

Objectives 1.Assessing survival after a 7-day exposure 2.Determining progeny production of the introduced insects after 49 days 3.Counting kernel damage caused by the insects after 49 days Evaluate the effectiveness of a dry formulation of spinosad (0.5% Active Ingredient) at 1 ppm when applied to corn and wheat on four species of stored-grain insects by:

A) Lesser grain borer (LGB), Rhyzopertha dominica (F.) B) Rusty grain beetle (RGB), Cryptolestes ferrugineus (Stephens) (Stephens) C) Red flour beetle (RFB),Tribolium castaneum (Herbst) D) Rice weevil (RW), Sitophilus oryzae (L.) Insects C DA B

Methods - Grain Treatment  Treated samples:1 mg (AI)/kg spinosad Control samples: no application Control samples: no application  100 g of grain/replicate  5 replicates, each sample treated separately  Each sample was infested with 25 unsexed adults of mixed ages mixed ages  Incubated at 28 o C and 65% RH 65% RH  Completely random design

Efficacy Assessment Survival: Survival:  After 7 days, adults were removed from grain  Those that were mobile were considered alive  Surviving insects were counted Progeny production:  After 49 days, all insects were removed from grain removed from grain  All adults and visible larvae (dead or alive) were counted alive) were counted  The original 25 insects were subtracted, to obtain number of progeny produced subtracted, to obtain number of progeny produced

Damaged kernels: Damaged kernels:  After 49 days, the number of kernels damaged by feeding or adult emergence or adult emergence in each sample was in each sample was enumerated enumerated Data analysis: Data analysis:  All data (x) were transformed to log (x + 1) scale and subjected to 3-way ANOVA and two-sample t-tests subjected to 3-way ANOVA and two-sample t-tests  Treatment effects were considered significant at  = 0.05 Efficacy Assessment (continued)

The 7 day adult survival, 49 day progeny production, and 49 day kernel damage were all significant between: Results  the two grain types (F, range = ; df = 1, 64; (F, range = ; df = 1, 64; P, range = <0.0001) P, range = <0.0001)  among insect species (F = ; df = 3, 64; (F = ; df = 3, 64; P < ) P < )  between the two rates (F = ; df = 1, 64; (F = ; df = 1, 64; P < ) P < )

Results - Survival ** * * * * *  Reduction of surviving adults among all species was 6.7 – 100%  Significantly less (P < 0.05) survived on treated grain (denoted by *)  Approx. 100% reduction of lesser grain borer and rusty grain beetles

Results - Progeny Production  Suppression of progeny production among all species: 79.8 – 100%  Significantly (denoted by *) fewer progeny (P < 0.05) were produced on treated grain, except for the RGB on wheat on treated grain, except for the RGB on wheat * * * * * * *

Results - Damaged Kernels * * ** * *  Reduction in damage due to LGB, RFB, and RW: 40.0 – 89.2%  Significantly (denoted by *) fewer damaged kernels (P < 0.05) on treated grain among all species but RGB treated grain among all species but RGB

Conclusions: Effects on Insects  The dry formulation of spinosad at 1 mg/kg effectively controlled lesser grain borer, red flour beetle, and rusty controlled lesser grain borer, red flour beetle, and rusty grain beetle, based on progeny suppression grain beetle, based on progeny suppression  Red flour beetle adults were less susceptible to spinosad than the other species, but spinosad reduced the number than the other species, but spinosad reduced the number of progeny produced by killing neonate larvae of progeny produced by killing neonate larvae  The rice weevil produced more progeny and caused more kernel damage on treated grains than the other species, kernel damage on treated grains than the other species, probably because of the slow action of spinosad on this probably because of the slow action of spinosad on this species species

 Based on adult survival and kernel damage, spinosad performed slightly better on wheat than on corn performed slightly better on wheat than on corn  Progeny production of each species on treated wheat and corn was essentially similar, although more progeny were corn was essentially similar, although more progeny were produced on untreated wheat when compared with produced on untreated wheat when compared with untreated corn untreated corn  The results observed here are consistent with earlier findings using a liquid formulation of spinosad (Fang et al. findings using a liquid formulation of spinosad (Fang et al. 2002a, b) 2002a, b) Conclusions: Effects on Grain

Future Work  Based on the damage caused by the rice weevil (52 wheat kernels/100 g and 134 corn kernels/100 g), spinosad may kernels/100 g and 134 corn kernels/100 g), spinosad may need to be used in conjunction with other grain protectants need to be used in conjunction with other grain protectants to keep the level of damage below the federal Defect to keep the level of damage below the federal Defect Action Level of 32 insect-damaged kernels/100 g Action Level of 32 insect-damaged kernels/100 g  The activity and persistence of the dry formulation of spinosad still needs to be verified under field conditions spinosad still needs to be verified under field conditions  Additional tests on other whole grains and extruded products are currently being investigated products are currently being investigated

Acknowledgements  Bayer (formally Gustafson) and Dow AgroSciences  Daniel Hopper, for technical assistance  Insect photographs, courtesy of Dr. Carl Reed  Research reported here was funded by CSREES-USDA (RAMP) under Agreement No (RAMP) under Agreement No

Questions? Thank you!