James Campbell - Research Summaries     [back]

Evaluation of potential attractants for Liposcelis bostrychophila (Psocoptera: Liposcelididae)

The psocids, also known as booklice, are worldwide insect pests of stored grains that cause significant economic losses by direct feeding and product contamination, and are difficult to control with insecticides. To effectively guide pest management programs it is critical to have a pest- monitoring program, but tools to attract and trap psocids are currently not available. The response of a major stored grain psocid pest species, Liposcelis bostrychophila, to potential attractants (including grains, grain based oils, wheat germ, and brewer's yeast) was studied, and it was determined that brewer's yeast, wheat germ and wheat germ oil had the strongest psocid response. These materials appear promising attractants for incorporation into psocid traps and will be further evaluated for monitoring psocids.
     

Spatial pattern in aerosol insecticide deposition inside a flour mill

Aerosol insecticides are applied as small droplets into the air, which then settle onto surfaces to provide control of stored-product insects inside food facilities such as mills and warehouses. Features inside a room such as mill and processing equipment, bins, columns and pallets of food are predicted to impact how these droplets disperse, creating zones within a room with lower droplet deposition and lower insect mortality. We used a high density grid of dishes containing confused flour beetle as a means to determine the amount of insecticide being deposited at a given location and developed a new efficacy index to show that two pyrethrin aerosols did exhibit zones with high and low efficacy within a flour mill. However, rather than the obvious physical barriers it tended to be along walls and in corners where lower efficacy occurred. The temperature when the aerosol was applied also impacted efficacy. A third insecticide, DDVP, that is an organophosphate and readily vaporizes and can cause mortality in the vapor phase was very consistent in causing insect mortality throughout the flour mill. We also used boxes of different heights and open on only one end to evaluate aerosol dispersal under a horizontal surface. Aerosol dispersal under the box decreased with decreasing box height and distance under the box in a way that could be quantified and used to predict where low efficacy is likely to occur within a food facility. These results show the potential for spatial variation in aerosol efficacy within a food facility and identify locations that are likely to receive lower dosages of insecticide and need supplemental treatment to maximize overall efficacy.
     

Movement of Tribolium castaneum within a flour mill

Understanding the movement patterns of stored-product insect pests within food processing or storage facility is important in terms of identifying and targeting pest management at sources of infestation and determining the potential to avoid pest management tactics. In this case study, we demonstrated using a mark-recapture technique that the red flour beetle, Tribolium castaneum, was able to move among floors within a flour mill, but the majority (86%) of beetles were recovered on the same floor they were marked on. For individuals that moved to a different floor, most moved downward (70%) and typically only to an adjacent floor (87%). Use of heat treatments to disinfest structures is an important pest management tool, but insects have the ability to move away from unfavorable temperatures. During a heat treatment of the mill there was an increase in the number of beetles captured, indicating increased movement, but there was not an increase in movement of marked beetles between floors. These results suggest that the rate of heating was sufficient to not allow the beetles time to move to cooler floors and escape the treatment. Results of this study indicate that red flour beetles are mobile enough that sources on other floors need to be considered in making pest management decisions.
     

How Varying Pest and Trap Densities Affect Tribolium castaneum (Coleoptera: Tenebrionidae) Capture in Pheromone Traps

The red flour beetle is an important insect pest of facilities which process and store grain. Integrated pest management frequently includes monitoring populations using traps that capture walking individuals. However, fundamental questions remain about the most effective way to implement monitoring programs and interpret monitoring data to estimate beetle density. Using experiments conducted in room-sized chambers where beetle density and number of traps could be controlled, we found that the number of individuals captured in traps increased as density of beetles increased, but the percentage of individuals captured remained constant. Applying a mathematical equation to estimate beetle density based on captures in traps, we found that a trap density of 4 traps per chamber (1 trap per 80 square feet) yielded the most accurate estimate of beetle density. The more traps placed in the chamber the greater the captures of beetles, but when trap density increased beyond 3 traps per chamber (1 trap per 108 square feet) the increases in beetle captures with each additional trap diminished to the point where there was little justification for the increased costs. This is the first scientific information available to guide the number of traps needed to monitor red flour beetles effectively and to estimate beetle density based on captures in traps.
     

Distribution, Abundance, and Seasonal Patterns of Plodia interpunctella (Hubner) in a Commercial Food Storage Facility

The Indianmeal moth is a major pest of stored food products, but there are few studies where resident populations have been monitored for more than one year in commercial facilities. We monitored Indianmeal moth populations inside a food warehouse for three years using an attractant for male moths. The focal points of infestation shifted during the storage period, but moths were consistently trapped in certain locations. Also, we caught moths in traps that were in places where no food was stored. In general, more moths were caught during the summer months compared to the remainder of the year. Cost estimates for the monitoring program were calculated using values provided by private industry. We used these values to show how reducing the number of traps could provide information on infestation trends while lowering the costs associated with insect monitoring. Results show the importance of monitoring for Indianmeal moths, but also emphasize the dynamic nature of insect infestations inside an active warehouse.
     

Spatio-Temporal Distribution of Stored-Product Pests around Food Processing and Storage Facilities

Stored-product insects can be found outside of facilities where grain is stored and processed, and these populations can potentially serve as a reservoir and source of food product infestation. Identifying the pattern of distribution of pest species and the factors that determine distribution could help in the targeting of monitoring and pest management programs. Pests were monitored using two types of food-baited traps at three food facilities, and the species captured were a mixture of both important grain and processed food pests and fungal feeding species more commonly associated with degraded grain. Although the types of insects captured were similar between inside and outside locations, more were captured per trap inside and fungal feeding species were proportionally more abundant outside. Features of the landscape around each outside trap were characterized to see which might predict locations with more insect activity. Increased captures in outside traps were primarily associated with proximity to buildings, but surprisingly not associated with presence of food spillage. Overall, there was evidence of considerable movement of insects in the landscape surrounding facilities, resulting in limited spatial pattern other than localized hot spots inside or near structures that varied in location overtime. This study presents a methodology for evaluation of external populations at food facilities, highlights the importance of understanding pest populations over larger spatial scales, and provides insight into where monitoring and pest management tactics need to be focused.
     

Tribolium castaneum (Coleoptera: Tenebrionidae) Associated With Rice Mills: Fumigation Efficacy and Population Rebound

The red flour beetle is the most important insect pest infesting rice milling facilities in the U.S. While this pest has traditionally been managed by fumigation with methyl bromide, this fumigant is currently being phased out under the 1987 Montreal Protocol. The purpose of this study was to evaluate the effectiveness of sulfuryl fluoride (SF), an alternative to methyl bromide, in managing red flour beetle infestations in rice mills. Red flour beetle populations in and around seven rice mills were monitored before and after 25 fumigations with SF. Beetle populations were estimated by the number of adults captured in pheromone traps. The SF fumigations led to an average of 66% reduction in captures of red flour beetle adults. Beetle captures at the rice mills were strongly influenced by seasonal changes in temperature, with more beetles being captured during the warmer months and fewer during the cooler months. In addition, red flour beetle captures in traps located inside mills were positively correlated with captures in traps located outside of the mill. Seasonal temperature fluctuations also strongly impacted the length of time required for captures to return to pre-fumigation levels. Similar studies in wheat flour mills did not share the seasonal patterns or correlation between captures inside and outside the mills. These results highlight the importance of treatment timing in maximizing fumigation efficacy in rice mills and suggest there is a fundamental difference in red flour beetle population dynamics and in the impact of fumigation between wheat and rice mills.