Michael A. Mullen

The Impact of Spatial Structure on the Accuracy of Contour Maps of Small Data Sets

Spatial analysis of insect counts provides important information about how insect species respond to the heterogeneity of a given sampling space. Contour mapping is widely used to visualize spatial pest distribution patterns in anthropogenic environments, and in this study we outlined recommendations regarding semivariogram analysis of small data sets (N < 50). Second, we examined how contour maps based upon linear kriging were affected by the spatial structure of the given data set, as error estimation of contour maps appears to have received little attention in the entomological domain. We used weekly trap catches of the warehouse beetle, Trogoderma variabile, and the accuracy assessment was based upon data sets that had either a random spatial structure or were characterized by asymptotic spatial dependence. Asymptotic spatial dependence (typically described with a semivariogram analysis) means that trap catches at locations close to each other are more similar than trap catches at locations further apart. Trap catches were poorly predicted for data sets with a random spatial structure, while there was a significant correlation between observed and predicted trap catches for the spatially rearranged data sets. Therefore, for data sets with a random spatial structure we recommend visualization of the insect counts as scale-sized dots rather than as contour maps.

Development of a pheromone trap for monitoring Tribolium castaneum

Abstract Several commercially available pheromone traps were compared for their efficiency in capturing adult Tribolium castaneum under simulated warehouse conditions. The traps compared were the Storgard®, the PT 6 Allure®, and the Trappit®. Traps differed significantly in their effectiveness. Several new designs were tested and the Savannah trap, developed from a tennis ball canister, was found to be the most effective. This design has been refined and patented as U.S. Patent number 5,090,153.

Rapid determination of the effectiveness of insect resistant packaging

A technique was developed to evaluate the usefulness of odour barriers and to determine the effect of package content in consumer size packages on resistance to infestation by insects. Female Plodia interpunctella (Hubner) could distinguish sealed packets containing food from non-food items as a suitable site for oviposition. Utilization ofthis technique will reduce the time needed to evaluate new materials for use in insect resistant packaging.

Effects of Xylocoris flavipes (Hemiptera: Anthocoridae) Releases on Moth Populations in Experimental Peanut Storages

A biological control test in experimental peanut storages indicated that release of large numbers of the warehouse pirate bug, Xylocoris flavipes (Reuter) (Hemiptera: Anthocoridae), a generalist predator of stored-product insects, has considerable potential for suppression of stored-product moth populations. Suppression of the almond moth, Cadra cautella (Walker), and the Indianmeal moth, Plodia interpunctella (Hubner) (Lepidoptera: Pyralidae), was dependent on both the prey species and environmental conditions. Release of X. flavipes suppressed small populations of almond and Indianmeal moths by as much as 78.8% and 71.4%, respectively, before cold weather and a severe freeze eliminated the almond moth population in January. Suppression of the Indianmeal moth lasted through the 7-month test period. X. flavipes may be useful as one component of an integrated peanut control program based on release of biological agents

RESISTANCE IN SWEET POTATOES TO THE SWEETPOTATO WEEVIL, CYLAS FORMICARIUS ELEGANTULUS (SUMMERS)

Fourteen sweet potato [Ipomoea batatas (L.) Lam] cultivars and varieties were examined for resistance to the sweetpotato weevil [Cylas formicarius elegantulus (Summers)] in artificially infested fields in Yoakum, TX. One cultivar W-226, appeared to have a greater level of resistance than the other cultivars examined. The data are compared to earlier resistance trials to show that the germplasm presently available has greater levels of resistance than that in previous years. The resistance levels of “Resisto” and “Regal” for the past 4 years are discussed.

Dynamics ofSitotroga cerealella (olivier) (lepidoptera: gelechiidae) andSitophilus zeamais motschulsky (Coleoptera: Curculionidae) populations in a small bulk of stored corn

The dynamics of Angoumois grain moth,Sitotroga cerealella (Olivier), and maize weevil,Sitophilus zeamais Motschulsky, populations breeding in a small bulk (initially 5.36 t) of shelled corn were studied over an 8-year period by monthly sampling. The weevil population showed wide fluctuations in density superimposed on a general decline with time. The moth population showed no upward or downward trend for the first 60 months, although it fluctuated widely. Following a decline that occurred between 56 and 60 months, the moth population fluctuated within a much narrower range, and there was a general decrease in density with time. The decline of the weevil population paralleled deterioration of the corn as did that of the moth population after ca 60 months, and the decline of both species probably resulted from increasing scarcity of suitable breeding sites. Both populations exhibited seasonal variation in density with minima in late summer and early fall, following periods of adversely high temperatures in the storage shed. The populations increased during the fall, leveled off or declined slightly during the winter months, and then increased to maximum levels in late spring or early summer. It thus appears that high temperatures had a greater adverse effect on the populations than low temperatures. The grain moth and the maize weevil both tended to be randomly dispersed at low population levels and moderately aggregated at intermediate and high levels, although the degree of aggregation was not correlated with population density when low population levels were considered separately, and the maize weevil showed a greater tendency for aggregation than did the grain moth. Analysis of individual samples at fixed points in time showed a conspicuous bias for negative correlation between numbers of the two species within sampling quadrats, suggesting a tendency for the two species to segregate within the grain mass. This process could have resulted from behavioral differences or from the destruction of one species by the other. Competitive displacement of the grain moth by the maize weevil has been demonstrated in laboratory experiments but has rarely been observed under natural conditions, and in our study the two species coexisted for 8 years in a relatively small grain bulk.

Efficiency and Longevity of Two Commercial Sex Pheromone Lures for Indianmeal Moth and Almond Moth (Lepidoptera: Pyralidae)

Two commercially available sex pheromone lures, a rubber septum and a controlled release membrane, that were impregnated with (Z,E)-9-12-tetradecadien-1-yl-acetate, were tested for efficiency and l...

Spatial distribution of eggs by ovipositing Indian meal moths,Plodia interpunctella (Hübner) (Lepidoptera: Pyralidae)

A series of increasing egg densities was obtained by releasing various numbers of femalePlodia interpunctella (Hübner) in rooms where dishes of moth rearing medium were evenly spaced on the floor. The number of larvae produced in each dish was taken as an indication of the number of eggs that had been laid. At all egg densities, the eggs were aggregated, and most of the distributions conformed quite well with the negative binormial, but the degree of aggregation denreased as mean egg density increased. The implications of the results for the development of ware-house sampling strategies are discussed.

Response of Cadra cautella and Plodia interpunctella (Lepidoptera: Pyralidae) to Pheromone Baited Traps

The effect of the presence of the Indianmeal moth, Plodia interpunctella (Hubner), on the capture of the almond moth, Cadra cautella (Walker), in pheromone-baited traps was evaluated. It was found that when both sexes of each species were released into a large warehouse simultaneously, the capture of male C. cautella was reduced to 5.5 ± 0.8 in traps baited with a two-component lure as compared to 11.4 ± 2.2 when only C. cautella were released. This decrease in response may have been caused by an inhibitory substance produced by the female P. interpunctella that affects the response of male C. cautella to the pheromone or confusion caused by an increase in the amount of pheromone present. This reduced response of C. cautella must be considered when using pheromone-baited traps to estimate population levels when both species are present.

Development of six species of stored-product insects on multi-grain blend supplement.

A multi-grain blend intended as a flour supplement to fill the void between brown and white bread and provide an economical source of protein and fiber was tested to determine the potential for inf...