Scott P. Schell

Decreasing Economic and Environmental Costs through Reduced Area and Agent Insecticide Treatments (RAATs) for the Control of Rangeland Grasshoppers: Empirical Results and Their Implications for Pest Management

-Reduced area and agent treatments (RAATs) for management of rangeland grasshopper infestations were compared with blanket applications of 2 standard compounds at traditional rates (100% of infestations treated with carbaryl applied at 16 oz/ac or malathion applied at 8 oz/ac) in southeastern Wyoming during 1995-96. Two RAATs applications of carbaryl (12 oz/ac applied in alternating swaths to 66% of infestations [12-66] and 8 oz/ac applied in alternating swaths to 50% of infestations [8-50]) were essentially indistinguishable from the standard treatment, with 80 to 90% grasshopper mortality. A carbaryl 8-33 treatment resulted in only 40 to 60% control. Mortality following application of 4 oz/ac of malathion in alternating swaths to 80% of an infestation (4-80) was indistinguishable from the standard application, with 75 to 90% control. However, a malathion 4-50 treatment resulted in only 55 to 65% control. Fipronil (14 oz/ac) applied to 25% of an infestation resulted in 80 to 90% control, comparable to the highest rates of mortality with the other RAATs. The greatest benefit: cost ratios (>2.8: 1) were seen with the carbaryl 8-50, malathion 4-80, and fipronil 14-25 treatments. The RAATs strategy appears to depend on movement of grasshoppers from untreated to treated swaths and on the conservation of natural biological control agents. Had RAATs methods been used during the 1986-88 outbreak in the western US, pest managers would have saved

Grasshoppers (Orthoptera: Acrididae) Could Serve as Reservoirs and Vectors of Vesicular Stomatitis Virus

38 million and used 34 million metric tons less insecticide [

Canola oil as a kairomonal attractant of rangeland grasshoppers: an economical liquid bait for insecticide formulation

Abstract Vesicular stomatitis (VS) is an economically devastating disease of livestock in the Americas. Despite strong circumstantial evidence for the role of arthropods in epizootics, no hematophagous vector explains the field evidence. Based on the spatiotemporal association of grasshopper outbreaks and VS epizootics, we investigated the potential role of these insects as vectors and reservoirs of the disease. The critical steps in the grasshopper–bovine transmission cycle were demonstrated, including 1) 62% of grasshoppers [Melanoplus sanguinipes (F.)] fed vesicular stomatitis virus (VSV) from cell culture became infected, with titers reaching 40,000 times the inoculative dose; 2) 40% of grasshoppers that cannibalized VSV-infected grasshopper cadavers became infected, amplifying virus up to 1,000-fold; 3) one of three cattle consuming VSV-infected grasshopper cadavers contracted typical VS and shed virus in saliva; and 4) 15% of grasshoppers became infected when fed saliva from this infected cow. The ecological conditions and biological processes necessary for these transmissions to occur are present throughout much of the Americas. Field studies will be required to show these findings are relevant to the natural epidemiology of VSV.

Reduced agent-area treatments (RAAT) for management of rangeland grasshoppers: efficacy and economics under operational conditions.

Laboratory experiments and field trials demonstrated that canola oil, which is rich in fatty acids that are kairomonal cues in cannibalism, is an effective attractant of rangeland grasshoppers and a suitable oil-based carrier for insecticides. Laboratory-based olfactory tests revealed a significant, positive chemotaxis of Melanoplus sanguinipes in response to canola oil and olive oil mixtures. Small-scale field tests made by airbrush applications of 5 ml of canola oil (equivalent to 500 l/ha) to centres of aluminium rings (0.1 m2

Rangeland Grasshopper Movement as a Function of Wind and Topography: Implications for Pest Management

The Reduced Agent-Area Treatment (RAAT) approach involves applying low rates of insecticides in intermittent swaths to control grasshopper infestations in an effort to achieve a more economically and environmentally sound pest management strategy compared to traditional blanket applications at high rates. Operationalscale (>250 ha) insecticide tests on Wyoming rangeland grasshopper infestations (18-56 grasshoppers/m2) at two sites in 1997 revealed that carbaryl yielded 94% control as a blanket treatment (560 g/ha) and 81% control as a RAAT application (280 g/ha applied to 50% of the infested land). Malathion yielded 90% control as a blanket treatment (683 g/ha) and 91% control as an RAAT application (342 g/ha applied to 80% of the infested land), and fipronil (4 g/ha) yielded 98% control as a blanket treatment and 92% control when applied to 33% of the infested land. One year after treatment, the RAAT and blanket-treated plots had 2-4% (Pollet Ranch) of the densities in untreated plots. Economic analysis showed that the greatest benefit:cost ratio was obtained with the fipronil-RAAT method, followed by carbaryl-RAAT, malathion-RAAT, malathion-blanket, fipronil-blanket, carbaryl-blanket. The worst-case outcome of fipronil and carbaryl with a RAAT approach had a greater economic return than the best-case outcome of no treatment. Following blanket treatments, non-target arthropod abundance was highest in the fipronil plots, followed by carbaryl and malathion; arthropod biomass was higher in the carbaryl plots than fipronil and malathion. In RAAT plots, arthropods were generally less impacted than in the blanket plots, with the least reduction caused by fipronil and carbaryl. Thus, the RAAT tactic appears to be economically and environmentally superior to blanket treatments under large-scale, operational conditions.

Laboratory Bioassays of Vegetable Oils as Kairomonal Phagostimulants for Grasshoppers (Orthoptera: Acrididae)

Monitoring rangeland grasshopper movements with a mark-release/ resight technique demonstrated that these insects have a tendency to move upwind in a native rangeland habitat with flat topography. This directional dispersal was observed with both late instar nymphs (4th and 5th instar) and adult grasshoppers, 60 h after release of marked individuals. Significantly more ofthe marked grasshoppers (34%) were in the northwest quadrant of the plots than in any other quadrant, and the wind was primarily from the northwest. At a native rangeland site with varied topography, where winds were also from the northwest, significantly more grasshoppers moved into the northwest quadrant than the southeast quadrant, 36 and 60 h after release; 35 and 32% of resighted grasshoppers were present in upwind quadrants, respectively. Grasshoppers showed no detectable tendency for movement with respect to topographic aspect in this habitat. An understanding of rangeland grasshopper movement in the context of abiotic factors (wind and topography) is relevant to refining grasshopper control programs that employ Reduced Agent-Area Treatments (RAATs).

Importance of Ecological Scale in Montane Grasshopper (Orthoptera: Acrididae) Species Structure in Similar Habitat between Differing Soil Textures and Dominant Vegetative Canopy Coverage

Vegetable oils have kairomonal attractant properties to grasshoppers primarily due to the presence of linoleic and linolenic fatty acids. These fatty acids are dietary essentials for grasshoppers and, once volatilized, can be detected by the insects’ olfactory receptors. A laboratory bioassay method has been developed to identify vegetable oils that have fatty acid profiles similar to grasshoppers and that induce grasshopper attraction and feeding. Such oils could be useful kairomonal adjuvants and/or carriers for acridicide formulations. Three sets of laboratory bioassays demonstrated that the addition of a standard aliquot of different vegetable oils resulted in varying degrees of grasshopper feeding on otherwise neutral substrates. Addition of olive oil stimulated the greatest feeding in all three sets of assays, regardless of the age of the tested insects. Furthermore, addition of canola or flax oils markedly enhanced grasshopper feeding. These three oils—i.e., olive, canola, and flax oil—proved to be the best performing grasshopper stimulants. A second group of oils included rapeseed-flax mix and rapeseed oils; however, their performance was not as consistent as oils in the first group—especially with regard to nymphal feeding. A third group of oils consisted of soybean, corn, peanut, and sunflower oil. Theoretical expectations regarding these oils varied wildly, suggesting that the results of a single bioassay should be cautiously interpreted as being negative.

CARMA: Assessing Usability through a Non-Biased Online Survey Technique

Abstract Discrepancies in scale dynamics often make cohesive structural conclusions difficult, especially when dealing with ecological variance. We studied presence and abundance of grasshopper species in similar, yet distinct, montane habitat of southeast Wyoming and northern Colorado, USA. By limiting ecological variance, grasshopper species structure at two behavioral scales (grouped species dynamics and individual species interactions) was maximized with regard to soil texture and vegetative canopy coverage. Combining univariate and multivariate statistical methods, we note montane grasshopper species interactions to be scale dependent.

Sustainability of Grasshopper Management and Support through CARMA

CARMA is an advisory and research support tool for grasshopper infestations. Designed with usability as a primary goal, CARMA presents an interface so intuitive that it completely eliminates the need for a user manual. To achieve this goal, CARMA interacts with the user through a goal-oriented, guided style reminiscent of a natural conversation between an advice seeker and an expert. Usability is furthered by its modeling of four important characteristics of human expert problem solving (speed, graceful degradation, explanations, and opportunism). In order to gain non-biased user feedback about CARMAs interface, we surveyed a group of novice users not previously familiar with CARMA. Positive survey results suggest that CARMAs approach to usability is a success. Furthermore, our survey approach illustrates a simple anonymous online technique which elicits candid non-biased feedback from participants about a product, and is particularly applicable to practitioners short on staff or time.

Perceptual, developmental, experiential, and physiological parameters of swimming in Melanopline grasshoppers (Orthoptera: Acrididae)

CARMA is an advisory system for grasshopper infestations that has been successfully used since 1996. During CARMA’s history, grasshopper control has increasingly focused on environmentally friendly and sustainable strategies. In order to keep pace with and support emerging strategies, CARMA’s functionality has been enhanced in a manner which both improves maintainability and which expands CARMA beyond its original role as a grasshopper infestation advisor into that of a grasshopper research support tool. This paper details efforts to develop sustainable grasshopper management strategies and the role that CARMA has played and continues to play in supporting the development and implementation of those strategies.