Rizana M. Mahroof

Time-Mortality Relationships for Tribolium castaneum (Coleoptera: Tenebrionidae) Life Stages Exposed to Elevated Temperatures

The use of elevated temperatures (> or = 40-60 degrees C) or heat treatments for managing insects in food-processing facilities is a viable alternative to space fumigation with methyl bromide. Quantitative data are lacking on the responses of life stages of the red flour beetle, Tribolium castaneum (Herbst), an important pest of food-processing facilities worldwide, to elevated temperatures used during heat treatments. We determined time-mortality relationships for eggs, young (neonate) larvae, old larvae, pupae, and adults of T. castaneum, exposed to constant temperatures of 42, 46, 50, 54, 58, and 60 degrees C. Generally, mortality of each stage increased with an increase in temperature and exposure time. Young larvae were the most heat-tolerant stage, especially at temperatures > or = 50 degrees C. Exposure for a minimum of 7.2 h at > or = 50 degrees C was required to kill 99% of young larvae, whereas the other stages required < or = 1.8 h. Heat treatments that control young larvae should control all other stages of T. castaneum, and young larvae should be used as test insects to evaluate efficacy against T. castaneum during an actual facility heat treatment. These results provide the basis for successful use of elevated temperatures for management of T. castaneum life stages associated with food-processing facilities.

Changes in Expression of Heat Shock Proteins in Tribolium castaneum (Coleoptera: Tenebrionidae) in Relation to Developmental Stage, Exposure Time, and Temperature

Abstract The use of elevated temperatures or heat treatments for managing insect pests in food-processing facilities is becoming a popular alternative to methyl bromide fumigation. We found that young larvae (first instars) of red flour beetle, Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae), were relatively more tolerant to elevated temperatures than eggs, old larvae, pupae, and adults. Our objective was to determine whether heat shock proteins (HSPs) confer thermotolerance in T. castaneum life stages. Western blot analyses by using HSP 70 antibody showed constitutive expression of HSP 70 in all stages of T. castaneum. However, the expression of HSP 70 in young larvae increased by ≈33%, after the larvae were exposed to 40°C for 1 h. The expression of HSP 70 in other stages did not vary significantly, but for eggs the expression of HSP 70 showed significant reduction at 40°C. Young larvae possessed two distinct HSPs with molecular masses of 70 and 24 kDa, both recognized by a monoclonal anti-bovine brain HSP 70 antibody. Our study suggests that increased thermotolerance in young larvae could be due to increased expression of HSP 70 at higher temperatures. Time- and temperature-dependent expression of HSP 70 showed that the increased thermotolerance in young larvae might last as long as 8 h at 40°C or 30 min at 46°C.

Dispersal of Rhyzopertha dominica (Coleoptera: Bostrichidae) in Different Habitats

ABSTRACT The lesser grain borer, Rhyzopertha dominica (F.) (Coleoptera: Bostrichidae), a serious pest of stored cereal grains, is widely distributed and has been collected in different habitats in North America, such as those from agricultural and nonagricultural settings. Our objective was to study the dispersal distances and direction of dispersal by R. dominica after external marking using fluorescent powder, releasing marked beetles, and recapturing adults using pheromone traps in distinctively different ecological habitats, wooded sites and open grasslands, for 2 consecutive yr. The recapture rate of marked beetles ranged from 6 to 26% in both sites and was generally higher in the wooded site than the open field site for both years. There was a significant difference in dispersal distances between wooded and open sites. Mean dispersal distances in the wooded site ranged from 337 to 375 m, whereas in the open site, they varied from 261 to 333 m. Trap captures for both marked and feral beetles were related to the ambient temperature such that increase in trap captures occurred with increasing temperature. Significant differences were observed for directional movement of R. dominica in both sites and indicated that most beetles dispersed in the northwest direction. Correlation analyses showed that the relationship between numbers of marked-released-recaptured beetles significantly decreased with increasing trap distances. Understanding dispersal distances and directions provide insight to flight behavior of R. dominica and to the relationship between ecologically diverse breeding habitats. Knowledge of R. dominica habitat ecology outside of grain storage facilities may be useful in designing suitable management tactics to minimize the onset of infestations in grain storages.

Orientation of the Cigarette Beetle, Lasioderma serricorne (F.) (Coleoptera: Anobiidae) to Plant-Derived Volatiles

Experiments were conducted to study the orientation of adult cigarette beetles,Lasioderma serricorne (F.), to plant volatiles in a walking bioassay. Seven out of sixteen test materials that displayed attractive responses were further studied for (1) responses to whole extracts from three types of solvents and (2) the effects of sex and mating status of L. serricorne on responses to plant volatiles. Bioassays with extracts revealed that responses of L. serricorne varied among the type of solvent extract. Volatiles from different Capsicum products attracted significantly more adult beetles than did volatiles from other materials. When virgin males, virgin females and mated females were bioassayed, mated females responded significantly more than the other groups to plant volatiles. Semiochemical-based pest management methods may be developed for L. serricorne with plant volatile-based attractants that may be identified and used alone or combined with a synthetic sex pheromone to manipulate beetle behavior.

Responses of stored‐product Anobiidae to pheromone lures and plant‐derived volatiles

Experiments were conducted in different locations to investigate responses of adult Stegobium paniceum and Lasioderma serricorne (Col., Anobiidae) to different commercially available or prototype fabrications of their female‐produced sex pheromones. The results showed that the number of S. paniceum captured in traps baited with the commercially available lures was significantly higher than those captured in traps baited with the prototype stegobinone lures. The three commercially available brands of serricornin lures investigated were equally effective in capturing L. serricorne. In a related study, we conducted a 9‐week trapping experiment to determine if responses of L. serricorne to serricornin can be enhanced by the presence of host plant odours. Traps were baited with serricornin alone, serricornin plus dried red chilli (Capsicum frutescens L.) or red chilli alone. The results showed that the number of beetles captured in traps baited with a combination of serricornin and chilli volatiles were significantly higher than in traps baited with pheromone or chilli volatiles alone, indicating that potential exist for improved monitoring or mass trapping of L. serricorne by combining pheromone with plant‐derived volatiles present in Capsicum spp.

Stable isotopes as markers to investigate host use by Rhyzopertha dominica

Rhyzopertha dominica (F.) (Coleoptera: Bostrichidae) is a serious worldwide pest of stored cereal grains that also has the ability to breed in non‐agricultural host plant material. Stable isotope signatures (concentrations of isotopes) were used as internal tissue markers to determine dietary differences among adult R. dominica and to make inferences about source habitats of field‐trapped insects. Adult R. dominica collected near granaries or from non‐agricultural forested sites near Stillwater, OK, USA, and insects reared on selected hosts under laboratory conditions were studied to determine the carbon and nitrogen isotope signatures. Laboratory‐reared R. dominica showed δ13C (stable isotope ratio of carbon) values similar to the host on which they developed with an enrichment of about 1 in the insect body. Insects reared on seeds of wheat and oak, which have C3 photosynthetic pathways, showed much depleted δ13C values (–23.7 and –26.2, respectively) in comparison to insects reared on seeds of corn, a C4 photosynthetic plant (–11.3). A majority of the field‐collected R. dominica showed δ13C values similar to expectations for a C3 host. However, a few field‐collected insects had δ13C signatures similar to the C4 plant‐reared insects in the laboratory experiment. Stored grain of C4 crops were lacking at many of the sample field sites. These results suggest that R. dominica occurs on either C3‐ or C4‐based hosts in the field, and point to utilization of non‐grain C4 plants as hosts. Our studies indicated that 13C isotope is a reliable marker to infer types of hosts used in the feeding history of R. dominica.

Mating disruption of Lasioderma serricorne (Coleoptera: Anobiidae) in stored product habitats using the synthetic pheromone serricornin

Cigarette beetles, Lasioderma serricorne (F.) (Coleoptera: Anobiidae), cause significant damage to the multibillion dollar food and tobacco industries worldwide each year. A non‐insecticidal alternative to manage L. serricorne is the application of mating disruption, in which high levels of synthetic sex pheromone are released to create an atmosphere that results in males failing to mate females, thereby causing population suppression or extinction. The reported work used synthetic serricornin, the predominant sex pheromone of L. serricorne, in mating disruption trials conducted in selected food‐ and feed‐processing facilities in South Carolina during 2010 and 2011. Mills subjected to mating disruption trials were monitored using oviposition cups filled with larval food and pheromone traps for males that contained monitoring lures. Immediately after deployment of mating disruption dispensers, trap captures declined significantly and indicated a reduction in population levels, that is, there was ‘trap shutdown’. A significant reduction was observed in numbers of adult beetles caught in the traps 8 weeks before and 8 weeks after treatment in both years. Beetle numbers from pheromone traps in untreated buildings remained at similar levels or increased after the time of mating disruption deployment in treated buildings. The numbers of adults that emerged from oviposition food cups were generally low and varied irregularly in treated and untreated buildings and were determined to be of little value for assessing treatment effects on reproduction. These initial field studies in the USA suggest that release of the synthetic sex pheromone of L. serricorne for mating disruption can significantly inhibit proper orientation behaviour of male L. serricorne to females and may lead to pest population decline from mating disruption.

Response of Bemisia tabaci (Hemiptera: Aleyrodidae) to Vapor Pressure Deficit: Oviposition, Immature Survival, and Body Size

ABSTRACT Whiteflies cause major agricultural problems in environments ranging from arid to humid climates on a global scale. A study was conducted on the effects of vapor pressure deficit (VPD) on oviposition, hatching, body size, and survival of immature B-biotype sweetpotato whitefly, Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae). Experiments were conducted at VPD conditions of 0.5, 1.7, and 2.7 kPa to represent low, medium, and high VPD environments, respectively. The study was conducted at 26°C with insects reared on collard, Brassica oleracea ssp. acephala de Condolle. The rate of oviposition was decreased at the highest VPD treatment. However, percentage egg hatch was not significantly affected by the treatments. More time was required for eggs to hatch at a high (2.7 kPa) compared with a low (0.3 kPa) VPD in a separate experiment. Overall survival to the adult stage was decreased at the highest VPD (≈50%) compared with the other two VPD environments (≈75%). Sizes of males and females were different, as is well known, but VPD had little significant effect on adult body size (length and width). The size effect was erased when the F2 generations from the different treatments were reared under a common environment. Insect population models that include the most relevant environmental parameters can offer the best estimation of life-history events. These results help elucidate the ecology of B. tabaci and indicate that extremes in ambient moisture can have an impact on populations.

Efficacy of Ozone Against the Life Stages of Oryzaephilus mercator (Coleoptera: Silvanidae)

Abstract Ozone is a highly oxidizing gas with insecticidal activity and it is a potential alternative to conventional fumigants, such as phosphine and methyl bromide, for managing stored product insects. Susceptibility of the merchant grain beetle, Oryzaephilus mercator (Fauvel; Coleoptera: Silvanidae), an important pest of stored products, to ozone treatments is unknown. In this study, we investigated the efficacy of ozone for controlling O. mercator. We determined concentration-mortality relationships for all stages of O. mercator exposed to 100–400 ppm for 1 h (1 g/ m3 = 467 ppm). We also determined time-mortality relationships for adults exposed to 100 ppm for 1–6 h. Mortality was recorded as percentages of eggs that failed to hatch 10 days after treatment (DAT), larvae or pupae that failed to develop into adults 20 or 15 DAT, respectively, and adults that died 2 DAT. Generally, mortality increased with an increase in ozone concentration. Mortality was higher when insects were treated without food. When food was not provided, a minimum of 11030 ppm for 1 h is required to kill 99% of eggs, the most tolerant stage, whereas 500 ppm for 1 h is required to kill 99% of larvae, the least tolerant. When provided with food, adults were the most tolerant and larvae the least tolerant. Adults require exposure time of 7.7 h of 100 ppm ozone to kill 99% of insects in the absence of food. The work reported suggests that ozone could be an alternative fumigant for the management of all O. mercator life stages.

Effect of Yellow Flowers on Abundance of Bemisia tabaci (Hemiptera: Aleyrodidae) on Plants

The B-biotype sweetpotato whitefly, Bemisia tabaci (Gennadius), is a serious agricultural pest in field and greenhouse productions on a global scale. There have been several compilations of host plants for B. tabaci arid, collectively, over 1000 host plants have been recorded for this pest (Abd-Rabou and Simmons 2010, Entomol. News 121: 456 465). The problem from feeding by this pest is amplified because it transmits over 100 plant diseases (Jones 2002, European J. Plant Path. 109: 197 221). Many factors are known to affect the population dynamics of whiteflies (Gerling 1984, Phytoparasitica 12: 109 118; Simmons and Mahroof 2011, Ann. Entomol. Soc. Am. 104: 928 934). Understanding the population ecology of this insect is important for its management. Whiteflies have been known to be attracted to yellow color since their orientation to this color was demonstrated nearly a hundred years ago (Lloyd 1921, Bull. Entomol. Res. 12: 355 359). Subsequently, yellow sticky traps have been devised and are widely used in greenhouses and fields to monitor for the presence of whiteflies or to reduce their numbers (Gerling and Horowitz 1984, Ann. Entomol. Soc. Am. 77:753 759; Bi et al. 2002, J. Econ. Entomol. 95:1179 1184; Slosser et al. 2002, J. Econ. Entomol. 95:299 306). In addition to B. tabaci (Mound 1962, Ent. Exp. Appl. 5: 99 104), several natural enemies of B. tabaci are also attracted to yellow; namely, parasitoids in the genera Encarsia and Eretmocerus (Hoelmer and Simmons 2008, Environ. Entomol. 37: 391 399) and a coccinelid predator, Delphastus catalinae (LeConte) (Simmons 2003, J. Entomol. Sci. 38: 481 484). Moreover, aphids (Fereres et al. 1999, Ann. Entomol. Soc. Am.) and several other insects (Adams and Loss 1986, Environ. Entomol. 15: 867 873; Udayagiri et al. 1997, Environ. Entomol. 26: 983 988) are known to be attracted to the color yellow. We are not aware of any report concerning what impact that the color of flowers may have on the population of whiteflies on plants. Because