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United States Department of Agriculture

Agricultural Research Service

March 2014

Temporal Changes in Stored-Product Insect Populations Associated with Boot Pit and Load-out Areas of Grain Elevators and Feed Mills
Stored grain insect infestations in elevator boot pits areas can spread throughout grain storage and processing facilities, reducing grain quality, contaminating the grain, and causing economic losses. The effect of time of year on insect infestations in elevator boot pit areas has not been studied before. We determined the types and numbers of stored-grain insect species found in the boot (pit) area and in grain stored in silos of commercial elevator and feed mill facilities. The number of insects found in residual grain samples was low in the cool winter months and peaked during the warm summer months. These results showed regular boot and pit cleaning is critical in preventing pest population outbreaks during the warm summer months. New facility pest management sanitation guidelines were developed including boot residual grain clean-out every 30 days, removal of grain spillage and floor sweepings from the pit area, and proper disposal of boot and pit residual grain. Grain handling facilities following the frequent clean-out of the boot residual grain and general sanitation of the pit area should reduce the number of insects that are picked-up in the boot area and transferred to other locations of a facility, which will reduce the damage and losses that would occur if insects are allowed to proliferate in the boot area and spread elsewhere.
 • FRank Arthur, 785.776.2783, Frank.Arthur@ars.usda.gov
 
Using RNA-Seq to Understand Insecticide Resistance in the Red Flour Beetle, Tribolium castaneum
Phosphine is the most popular and economical fumigant, but insect resistance to phosphine is increasing. We studied the genetic differences in a phosphine-resistant strain of the red flour beetle from Brazil and compared it to a phosphine-susceptible laboratory strain. We found differences in expression levels of 53 genes in the resistant strain. However, reducing expression of the most highly expressed gene, a cytochrome P450, in the resistant strain did not prevent resistance. We also tried to mimic the resistant strain by reducing expression of another gene in the susceptible strain, but they were still susceptible to phosphine. We studied a known phosphine resistance gene and found mutations associated with phosphine resistance in the resistant strain. The phosphine-resistant strain was cross-resistant to a pyrethroid, suggesting that multiple resistance genes may be accumulating in stored product insects with increased insecticide exposure. These data provide valuable insights into phosphine resistance and how management strategies may need
 • Brenda Oppert, 785.776.2780, Brenda.Oppert@ars.usda.gov
 
 
February 2014

Effect of abiotic factors on initiation of red flour beetle (Coleoptera: Tenebrionidae) flight
The red flour beetle is one of the major pests in stored grain and in grain processing facilities throughout the world. Traps are used to monitor their movement to aid in making pest management decisions, but we don't fully understand the factors that cause their movement. We found that flight initiation was greatest at 86 to 95°F, and no beetles flew at 72 and 113°F. Only 2% of beetles flew in complete darkness, and the photoperiod at which the maximum percentage of beetles flew (41%) was 18 hours of light. Rates of flight initiation did not vary with light intensities from 1,784 to 4,356 lux or relative humidities from 25 to 85%. Thus, temperature and photoperiod are the main abiotic factors tested that impact flight initiation in the red flour beetle, and red flour beetles have broad ranges of temperatures and photoperiods over which they can fly. These results will help to develop better methods for interpreting trap catches from pest monitoring programs.
 • James Campbell, 785.776.2717, James.Campbell@ars.usda.gov
 
 
January 2014

Horizontal Transfer of Methoprene by Tribolium castaneum and T. confusum
In food facilities the majority of an insect population is typically within hidden locations that are difficult to reach with conventional insecticide application methods, but as insects move in and out of these hidden areas they could pick up insecticide on their bodies and transport it back into these hidden areas. If this process results in transfer of insecticide from this individual to another and it causes negative effects on that individual then it is termed horizontal transfer. This process is important in other pest systems, but has not been previously evaluated for stored-product insects in food facilities. In a series of laboratory experiments using red flour beetle and confused flour beetle, we showed that the insect growth regulator methoprene could be transferred from a treated to an untreated individual. When red flour beetle immature stages were exposed to a treated insect normal adult emergence was reduced. The confused flour beetle is less susceptible to methoprene than the red flour beetle, so the effects of horizontal transfer were less apparent although adult emergence was still reduced. However, when immatures were able to survive exposure to methoprene treated individuals and emerge as normal adults, their reproductive ability was not affected. This is the first report indicating that methoprene can be transferred between stored-product insects and highlights a potential mechanism that might increase the effectiveness of insecticide treatments in reducing insect populations in food facilities such as mills, processing plants and warehouses
 • James Campbell, 785.776.2717, James.Campbell@ars.usda.gov
 
 
November 2013

Methods for Assessing Infestations of Sunflower Stem Weevil, Cylindrocopturus adspersus LeConte (Coleoptera: Curculionidae) in Sunflower Stems
Sunflower stem weevils reduce sunflower yields by promoting diseases, damaging vascular tissues, and causing lodging of sunflower plants. To measure weevil populations for host plant resistance or insecticide field trials, usually larvae are dissected out of stems, a process that is slow and expensive. Alternative methods to estimate weevil populations include digital radiographs (X-rays) of stem sections or rearing out overwintering stem weevils. When tested, digital X-rays of small stem pieces (15 cm above soil level) explained most of the variation in numbers of weevil larvae from dissected stem samples (50 cm), but required less than one-fifth the time of manual dissection. Using emergence boxes to estimate weevil populations was similarly time-efficient, but may not be easily related to weevils per plant because of parasitism and death of weevil larvae inside the stems. Results suggest for large field trials with sunflower stem weevils, digital X-rays provide much more cost-efficient larval population estimates, increasing researchers’ ability to detect differences among treatments.
 • James Campbell, 785.776.2717, James.Campbell@ars.usda.gov
 
 
October 2013

Efficacy of Dinotefuran (Alpine® Spray and Dust) on Six Species of Stored Product Insects
Alpine® is a new insecticide that is being used to control urban insect pests, and is available as a pressurized spray or as a dust combined with diatomaceous earth (DE). We conducted tests with both products to determine effectiveness on different stored product insects. The dust formulation was much more effective than the spray on all adult insects tested, but larvae were easily killed by both products. Results show this new insecticide could be adopted for control of stored product insects in milling and processing facilities
 • Frank Arthur, 785.776.2783, Frank.Arthur@ars.usda.gov
 
 
August 2013

Development of Phytosanitary Cold Treatments for Oranges Infested with Bactrocera invadens and B. zonata (Diptera: Tephritidae) by Comparison with Existing Cold Treatment Schedules for Ceratitis capitata] (Diptera: Tephritidae)
A new invasive fruit fly attacking a wide variety of fruits has been described in Africa (Bactrocera invadens Drew, Tsuruta and White). It is rapidly spreading throughout central Africa and threatens other continents. As part of management strategies phytosanitary treatments are needed. Cold treatments were attempted for it and another invasive fruit fly for which treatments are lacking, Bactrocera zonata, by comparison with the Mediterranean fruit fly (Medfly), for which cold treatments exist. Oranges were infested by puncturing holes in the peel and allowing the flies to oviposit there. Results show that B. invadens is less cold tolerant than Medfly and B. zonata at 1.0±0.1°C and lend support to the use of Medfly cold treatments for B. invadens. It cannot be concluded that Medfly cold treatments could be used against B. zonata because B. zonata could be more cold tolerant than Medfly.
 • Guy Hallman, 785.776.2705, Guy.Hallman@ars.usda.gov
 
Phytosanitary Cold Treatment for Oranges Infested with Bactrocera zonata (Diptera: Tephritidae)
The peach fruit fly (PFF) attacks many fruits and occurs from Egypt to Vietnam. Occasionally it is trapped in subtropical US states and may result in costly quarantines until it is declared eradicated. Treatments are required to export fruit hosts of the pest out of quarantined areas to non-infested areas where it could become established. This research describes a cold treatment of 18 days at 1.7°C (35°F) that was developed for infested oranges. The PFF was not found to be less cold tolerant than the Mediterranean fruit fly; therefore, treatments for the latter could not be used for PFF. PFF was found to be more susceptible to cold than the Mexican fruit fly (Mexfly); therefore, treatment schedules for Mexfly could be used for PFF. However, the treatment for Mexfly requires 22 days. A shorter treatment was desired and verified for PFF when a total of 36,820 large larvae reared in oranges were treated at 1.7°C for 18 days with no larvae moving upon examination 24 hours after cold treatment. This information will be useful for developing treatments for fruits exported from quarantine areas.
 • Guy Hallman, 785.776.2705, Guy.Hallman@ars.usda.gov
 
Variation in Susceptibility of Laboratory and Field Strains of Three Stored-Grain Insect Species to beta-Cyfluthrin and Chlorpyrifos-methyl plus Deltamethrin
Residual insecticides are often applied inside grain bins before grains are loaded into the bin or to structural surfaces supporting those bins, and there are questions regarding effectiveness of insecticides on field strains of stored product insects compared to laboratory strains. We exposed different fields strains of some common stored product insects on concrete treated with labeled insecticides, and then placed them on untreated concrete with flour. Insects survived when given food, there was variation among the insecticides regarding effectiveness for control of the field strains, and in general the field strains were harder to kill than comparable laboratory strains. Results show that no single insecticide was completely effective for control of all species and field strains, and application of a specific residual insecticide may depend largely on the intended target species.
 • Frank Arthur, 785.776.2783, Frank.Arthur@ars.usda.gov
 
 
June 2013

Economic Feasibility of Methoprene Applied As a Surface Treatment and As An Aerosol Alone and In Combination with Two Other Insecticides
Insect growth regulators (IGRs) used alone or combined with other insecticides are being evaluated for control of the Indianmeal moth, a common stored product pest, but there is little research regarding economic feasibility of treatments. We used mortality data from laboratory and field studies to conduct an economic risk analysis of different treatments. The optimal insecticide was a combination of methoprene combined with the pyrethroid esfenvalerate, but more frequent treatment is needed to reduce risk when Indianmeal moth developed on an optimal diet compared to a sub-optimal diet. Results show how risk assessments can be developed to help minimize damage caused by the Indianmeal moth.
 • Frank Arthur, 785.776.2783, Frank.Arthur@ars.usda.gov
 
 

Last Modified: 4/21/2014