Influence of age, mating status, sex, quantity of food, and long-term food deprivation on red flour beetle (Coleoptera: Tenebrionidae) flight initiation.

Effects of age, sex, presence or absence of food, mating status, quantity of food, and food deprivation on rate of and time of flight initiation of the red flour beetle, Tribolium castaneum (Herbst), were determined. Flight initiation declined with increasing age in both presence and absence of food. However, flight initiation was lower when food was present in the flight chambers than in the absence of food. In the presence of food, both mated and virgin beetles were equally likely to disperse by flight. However, in the absence of food, mated beetles initiated flight more readily that virgin individuals. Flight initiation was greatest when little or no food was present. The presence of varying quantities of food inside the flight chambers impacted the number of progeny produced by females before flight, but not the timing of flight. Rate of flight initiation was higher for beetles deprived of food for short periods of time compared with flight initiation of beetles with food in the flight chamber. Flight initiation decreased with increasing time without food. There were no differences in flight tendencies between males and females in the experiments reported here. Our results suggest that T. castaneum uses flight as a mechanism to disperse to new environments during almost any part of their life span and that this type of dispersion does not fit with the model of the so-called true migratory species that involves an "oogenesis-flight syndrome.

Reproductive parameters of the parthenogenetic psocid Lepinotus reticulatus (Psocoptera: Trogiidae) at constant temperatures.

We investigated effects of temperature, at 70% RH, on the reproductive parameters of the parthenogenetic psocid Lepinotus reticulatus Enderlein (Psocoptera: Trogiidae). The lowest fecundity (21) was at 35 degrees C and the highest (41) at 27.5 degrees C. At 22.5, 25, and 27.5 degrees C, peak oviposition rates (eggs/female/week) occurred in week 3 and were 4.7, 6.6, and 7.8, respectively; also 51, 57, and 62%, respectively, of all eggs were laid in the first 4 wk. At 30, 32.5, and 35 degrees C, peak oviposition rates occurred in week 2 and were 8.2, 9.0, and 7.4, respectively; 80, 85, and 98%, respectively, of all eggs were laid in the first 4 wk. The longest preoviposition period (4.4 d) was at 22.5 and 25 degrees C, and the longest postoviposition period (13.1 d) was at 22.5 degrees C. Oviposition period and longevity decreased with increasing temperature; at 22.5 degrees C, these parameters were 66 and 83 d, respectively, and at 35 degrees C, they were 18 and 24 d, respectively. Mean weekly oviposition rate increased with temperature and was highest at 32.5 degrees C (5.8 eggs/female/week). At 22.5, 25, 27.5, 30, 32.5, and 35 degrees C, it took 29, 20, 12, 11, 8, and 6 wk, respectively, for all females to die. Intrinsic rate of population increase increased with temperature until 32.5 degrees C (0.128) and then declined. We have developed temperature-dependent equations for preoviposition period, postoviposition period, oviposition period, oviposition rate, and longevity. Reproductive parameters affect population dynamics, and information on these parameters can be used in simulation models to predict L. reticulatus population dynamics to aid in developing effective management strategies.

Molecular techniques for detection of Tribolium confusum infestations in stored products.

The confused flour beetle, Tribolium confusum Jacquelin du Val (Coleoptera: Tenebrionidae) is a stored-product pest that contaminates a wide range of food products, from flour and cereals to spices. The insect reduces food quality and is responsible for large economic losses every year. Although several methods for detection of stored-product pests are common and widely used, they are time-consuming and expensive. Therefore, establishing molecular methods of detection of stored-product pests could provide a useful alternative method. We have undertaken attempts to establish methods of detection of T. confusum based on molecular biology techniques of standard and real-time polymerase chain reaction (PCR). Total DNA of T. confusum and red flour beetle, Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae), used as a negative control, was isolated from insects and used as a template in standard and real-time PCR reactions. Specific primers have been designed on the basis of sequences of internal transcribed spacer (ITS) fragment of rDNA and subunit I of mitochondrial cytochrome oxidase of T. confusum available in the GenBank database. Standard PCR reactions with primers specific to the ITS fragment proved to be reliable and sensitive. Real-time PCR reactions with primers specific for mitochondrial DNA are considered to serve as a supplemental detection method for quantitative assessment of the infestation level.

Predicting stored grain insect population densities using an electronic probe trap.

Manual sampling of insects in stored grain is a laborious and time-consuming process. Automation of grain sampling should help to increase the adoption of stored grain integrated pest management. A new commercial electronic grain probe trap (OPI Insector) has recently been marketed. We field tested OPI Insector electronic grain probes in two bins, each containing 32.6 tonnes of wheat, Triticum aestivum L., over a 2-yr period. We developed new statistical models to convert Insector catch into insects per kilogram. We compared grain sample estimates of insect density (insects per kilogram of wheat) taken near each Insector to the model-predicted insect density by using Insector counts. An existing expert system, Stored Grain Advisor Pro, was modified to automatically read the Insector database and use the appropriate model to estimate Cryptolestes ferrugineus (Stephens), Rhyzopertha dominica (F.), and Tribolium castaneum (Herbst) density from trap catch counts. Management decisions using Insector trap-catch estimates for insect density were similar to those made using grain sample estimates of insect density for most sampling dates. However, because of the similarity in size of R. dominica and T. castaneum, the software was unable to differentiate counts between these two species. In the central and southern portions of the United States, where both species frequently occur, it may be necessary to determine the proportion of each species present in the grain by manual inspection of trap catch. The combination of SGA Pro with the OPI Insector system should prove to be a useful tool for automatic monitoring of insect pests in stored grain.

Sampling plans for the psocids Liposcelis entomophila and Liposcelis decolor (Psocoptera: Liposcelididae) in steel bins containing wheat.

Psocids are an emerging problem in grain storage, handling, and processing facilities in the United States. We used data from two steel bins each containing 32.6 metric tonnes of wheat, Triticum aestivum L., to develop sampling plans for Liposcelis entomophila (Enderlein), Liposcelis decolor (Pearman) (both Psocoptera: Liposcelididae), and a mixture of the two species. Taylor's coefficients a (a sampling factor) and b (an index of aggregation) for these pests were calculated and incorporated into sampling protocols to improve accuracy. The optimal binomial sample sizes for estimating populations of these psocids at densities of < 25 psocids per refuge were large; therefore, we recommend the use of numerical sampling within this range of densities. Numerical sampling of L. entomophila and L. decolor at densities of < 25 psocids per refuge should not be too laborious given the low psocid numbers involved; we recommend using 10 refuges per bin. For presence-absence sampling of L. entomophila or L. decolor, 20 refuges per bin should be used at densities of 25-100 psocids per refuge. The sampling plans we have developed based on the use of cardboard refuges are convenient for use in steel bins containing wheat because they are inexpensive, provide a rapid assessment of psocid population incidence, and are easy to implement. These sampling plans can be used to monitor populations of and the efficacy of management strategies used against L. entomophila and L. decolor.

Population growth and development of the psocid Liposcelis brunnea (Psocoptera: Liposcelididae) at constant temperatures and relative humidities.

We studied the effects of temperature and relative humidity on population growth and development of the psocid Liposcelis brunnea Motschulsky. L. brunnea did not survive at 43% RH, but populations increased from 22.5 to 32.5 degrees C and 55-75% RH. Interestingly, we found population growth was higher at 63% RH than at 75% RH, and the greatest population growth was recorded at 32.5 degrees C and 63% RH. At 35 degrees C, L. brunnea nymphal survivorship was 33%, and populations declined or barely grew. L. brunnea males have two to four nymphal instars, and the percentages of males with two, three, and four instars were 13, 82, and 5%, respectively. Female L. brunnea have three to five instars, and the percentages of females with three, four, and five instars were 18, 78, and 4%, respectively. The life cycle was shorter for males than females. We developed temperature-dependent development equations for male and female eggs, individual nymphal, combined nymphal, and combined immature stages and nymphal survivorship. The ability of L. brunnea to multiply rather rapidly at 55% RH may allow it to thrive under conditions of low relative humidity where other Liposcelis species may not. These data give us a better understanding of L. brunnea population dynamics and can be used to help develop effective management strategies for this psocid.

Temporospatial distribution of the psocids Liposcelis entomophila and L. decolor (Psocoptera: Liposcelididae) in steel bins containing wheat.

We studied the temporospatial distribution of psocids in steel bins containing 32.6 tonnes of wheat in 2005 and 2006 in Manhattan, KS. Psocids were sampled in the top 0.9 m of wheat using a 1.2-m open-ended trier; samples were taken from the bin center and in the four cardinal directions at 0.15 and 0.76 m from the bin wall. In addition, a 2.4-m partitioned grain trier with 16 compartments was used to sample psocids from a 2-m-diameter circle in the center of the bins and to a depth of 1.96 m. Only two species of psocids were identified in the study: Liposcelis entomophila in 2005 and L. decolor in 2006. Densities of psocids were low immediately after bins were filled in July 2005, peaked in October, dropped to almost zero in December as temperatures decreased, and remained at low levels until the study was ended in March. In 2006, densities of psocids increased gradually from August to mid-October and declined until the study was ended in early November. During the fall, psocids were more abundant at the center of the bin and at lower depths. In October to November of both years, the temperatures and moisture contents of grain in the center also were higher than that in other locations. This is the first report of temporospatial distribution of psocids in steel bins of wheat.

Evaluation of five sampling methods for the psocids Liposcelis entomophila and L. decolor (Psocoptera: Liposcelididae) in steel bins containing wheat.

An evaluation of five sampling methods for studying psocid population levels was conducted in two steel bins containing 32.6 tonnes of wheat in Manhattan, KS. Psocids were sampled using a 1.2-m open-ended trier, corrugated cardboard refuges placed on the underside of the bin hatch or the surface of the grain, and manual or automated electronic counts from Insector probe traps. Only two species were identified in this study: Liposcelis entomophila (Enderlein) in 2005 and L. decolor (Pearman) in 2006. In both years, psocid numbers started to increase in early September, peaked earliest in surface refuges, and peaked at nearly the same time in grain samples and manual and electronic Insector counts. No psocids were found in hatch refuges in December to February, although psocids were detected by the other sampling methods during this time. Numbers of psocids in the grain samples could be estimated from the numbers of psocids obtained using the cardboard refuges and Insector probe traps in both years. The results indicate that cardboard refuges or Insectors may provide an effective method for sampling psocids in bins of wheat.

Population growth and development of psocid Lepinotus reticulatus at constant temperatures and relative humidities.

We investigated the effects of temperature and relative humidity on population growth and development of the psocid Lepinotus reticulatus Enderlein. Part of this study assessed the effects of marking psocids by using methylene blue, chalk powder, and fluorescent powder to differentiate nymphal stages during development. We found that marking psocids by using methylene blue increased mortality and took twice as long to accomplish compared with marking by using fluorescent powder. Using chalk powder shortened the duration of third and fourth nymphal instars. Marking psocids by using fluorescent powder had no effect on mortality or duration of nymphal instars. Therefore, we recommend using fluorescent powder for marking psocids. L. reticulatus did not survive at 32, 43, and 55% RH, whereas populations increased from 22.5 to 32.5 degrees C at 75% RH. The largest population growth was recorded at 30 and 32.5 degrees C, whereas only 9% of nymphs developed to adults and populations declined at 35 degrees C. We developed temperature-dependent developmental equations for eggs, individual nymphal, combined nymphal, and combined immature stages. These equations showed predicted optimal temperatures for the development of eggs, combined nymphal, and combined immature stages to be 32.3, 34.5, and 34.4 degrees C, respectively; development at these temperatures was completed in 6.3, 16.7, and 23.3 d, respectively. Our study shows that psocids that consume their exuviae develop faster than those that do not, and this effect is more pronounced at lower temperatures. These data give us better understanding of L. reticulatus population dynamics, and they can be used to develop effective management strategies for this psocid.

Effects of diet on population growth of psocids Lepinotus reticulatus and Liposcelis entomophila.

We investigated the suitability of 11 diets as culture media for the psocids Lepinotus reticulatus Enderlein (Psocoptera: Trogiidae) and Liposcelis entomophila (Enderlein) (Psocoptera: Liposcelididae). The culture media comprised six diets made of plain cereals, namely, wheat (Triticum aestivum L.), corn (Zea mays L.), milo Sorghum bicolor (L.), barley (Hordeum vulgare L.), oats (Avena sativa L.), and rice (Oryza sativa L.), and five artificial diets. We found that, with the exception of corn, L. reticulatus population increase was greater on plain cereal diets than on artificial diets, and the greatest population growth was on oats. There was an inverse relationship between L. reticulatus population growth and diet compactness. L. entomophila populations grew fastest on wheat, barley, and a mixture of cracked wheat, rice krispies, and brewer's yeast (97:2:1, wt:wt). The proportion of females was greater in diets that were less suitable for L. entomophila population growth compared with that in the more suitable diets. Diet compactness had a weak effect on L. entomophila population growth. This study also has established the relative level of suitability of damaged wheat, corn, milo, barley, oats, and rice to L. reticulatus and L. entomophila.

Differential heat shock tolerance and expression of heat-inducible proteins in two stored-product psocids.

The recent recognition of psocids as a major concern in stored products and also the reemergence of heat treatment as a control tactic of stored-product insects led to the present investigation. The objectives of this study were to determine whether there are differences in heat shock tolerance of two species of stored-product psocids--Lepinotus reticulatus Enderlein (Trogiidae) and Liposcelis entomophila (Enderlein) (Liposcelididae)--and to determine whether heat shock proteins (HSPs) underlay such tolerance. Time-response bioassays were therefore carried out at increasing temperatures for both psocids. The lethal time (LT)50 and LT95 estimates were correlated with the expression of heat shock proteins after exposure at the same range of temperatures for 30 min. The expression of HSP was determined through Western blot analyses using HSP 70 antibody. Liposcelis entomophila was more than two-fold more tolerant than L. reticulatus for nearly all of the range of temperatures (> or = 40.0 degrees C). Expression of HSP 70 was not observed for either of the psocid species, but the expression of two low-molecular-mass heat-inducible proteins (HIPs; 23 and 27 kDa) was observed in L. entomophila. The expression of these small proteins was induced by exposure to higher temperatures, and the trend was particularly strong for HIP 27. In contrast, no expression of small heat-inducible proteins was detected in L. reticulatus, reflecting its higher susceptibility to heat treatments. The relatively high heat tolerance of L. entomophila might help explain its more common occurrence in grain stored in warmer regions of the world.

Susceptibility of eggs and adult fecundity of the lesser grain borer, Rhyzopertha dominca, exposed to methoprene.

A series of tests were conducted to determine the susceptibility of eggs and neonates of the lesser grain borer Rhyzopertha dominica (F.) (Coleoptera: Bostrichidae = Bostrychidae), exposed to the insect growth regulator, methoprene, on filter paper and on rough rice. In the first test, the hatch rate of eggs exposed on filter paper treated with methoprene at the label rate of 0.003 mg [AI]/cm(2) when used as a surface treatment in structures was 52.0 +/- 7.3% compared to 93.0 +/- 3.3% on untreated controls. In the second test, eggs were exposed to a dose-response series of 0.00003 to 0.03 mg[AI]/cm(2). Egg hatch was directly proportional to concentration and ranged from 85.0 +/- 2.0% on untreated controls to 26.7 +/- 8.3% at the highest concentration tested. In the third test, 1 ppm of methoprene was sprayed on long grain rough rice (paddy) (Cocodrie variety), and then individual kernels were cracked and an egg of R. dominica was placed directly on the kernel. On untreated rice kernels, 67.5 +/- 11.6% of the eggs hatched and were able to bore inside, and all of these larvae emerged as adults. In contrast, 40.0 +/- 5.3% of the eggs placed on treated cracked kernels were able to develop to where the larvae were visible through X-ray detection, but none emerged as adults. In the final test, newly-emerged adults were exposed on rough rice treated with 1 ppm methoprene. The number of eggs from adults on untreated rice was 52.1 +/- 4.3 eggs per female, and on treated rice the average egg production was 12.5 +/- 1.1 eggs per female. Methoprene applied on a surface or on rough rice affected development of egg hatch also reduced fecundity of parent adults exposed on the treated rough rice.

Methodology for assessing rice varieties for resistance to the lesser grain borer, Rhyzopertha dominica.

Several physical and chemical attributes of rice were evaluated to determine which character would be best to use to assess multiple rice varieties for resistance to the lesser grain borer, Rhyzopertha dominica (F.). Laboratory tests were conducted on single varieties of long-, short-, and medium grain-rice to develop procedures and methodologies that could be used for large-scale screening studies. Progeny production of R. dominica was positively correlated with the percentage of broken hulls. Although kernel hardness, amylose content, neonate preference for brown rice, and adult emergence from neonates varied among the three rice varieties tested they did not appear to be valid indicators of eventual progeny production, and may not be useful predictors of resistance or susceptibility. Soundness and integrity seem to be the best characters to use for varietal screening studies with R. dominica.

Influence of maternal age on the fitness of progeny in the rice weevil, Sitophilus oryzae (Coleoptera: Curculionidae).

We studied the effects of maternal age on fitness of progeny in the rice weevil, Sitophilus oryzae L. (Coleoptera: Curculionidae). Five-, 20-, and 50-d-old female rice weevils were used to study the effects of maternal age on the lifetime fecundity and longevity of their daughters. In addition, we determined the effects of maternal age on the weight and survivorship of daughters' progeny. Daughters of 5- and 20-d-old weevils lived longer, and the numbers and weights of the progeny of these daughters were higher than for daughters of 50-d-old weevils. Survivorship of immature grand-offspring of 5-, 20-, and 50-d-old female weevils was similar. None of the fitness characteristics of the daughters and grand-offspring of 5- and 20-d-old weevils that were measured differed significantly. We believe maternal age effects on rice weevil progeny fitness may at least partly be acting through maternal age effect on egg size. Individuals that developed from younger 5- and 20-d-old weevils had a greater fitness than those produced by older 50-d-old females. Our study shows maternal age is impacting life history parameters that influence population dynamics across generations. Therefore, maternal age could significantly affect population development and have far reaching implications for pest management and simulation modeling of rice weevil populations.

Hydroprene prolongs developmental time and increases mortality in wandering-phase Indianmeal moth (Lepidoptera: Pyralidae) larvae.

Wandering phase Indianmeal moth, Plodia interpunctella (Hübner), larvae were exposed to the label rate of hydroprene (1.9 x 10(-3) mg [AI] /cm2) sprayed on concreted petri dishes. Larvae were exposed for 1, 3, 6, 12, 18, 24, and 30 h and maintained at 16, 20, 24, 28, and 32 degrees C and 57% RH until adult emergence. Larval developmental time and mortality were significantly influenced by temperature and exposure intervals. Maximum developmental time (47.2 +/- 1.3 d) occurred at 16 degrees C, and the minimum developmental time (7.0 +/- 0.5 d) occurred at 32 degrees C. Larval mortality generally increased at all of the five tested temperatures as exposure period increased. The greatest mortality (82.0 +/- 0.1%) occurred when larvae were exposed for 30 h at 28 degrees C, and minimum mortality (0.0 +/- 0.5%) occurred at 16 degrees C when larvae were exposed for 1 h. The relationships between temperature, exposure period, and developmental time were described by polynomial models, based on lack-of-fit tests. Hydroprene has potential to be an effective alternative to conventional insecticides in surface treatments for Indianmeal moth management. Response-surface models derived from this study can be used in simulation models to estimate the potential consequences of hydroprene on Indianmeal moth population dynamics.

Hydroprene prolongs developmental time and increases mortality of Indianmeal moth (Lepidoptera: Pyralidae) eggs.

Eggs of the Indianmeal moth, Plodia interpunctella (Hübner), were exposed to the labeled rate of hydroprene (1.9 x 10(-3) mg [AI]/cm2) sprayed on concreted petri dishes. These eggs were exposed for 1, 3, 6, 12, and 18 h and until hatching (continuous exposure) at temperatures of 16, 20, 24, 28, and 32 degrees C and 57% RH until the emergence of first instars. The developmental time and egg mortality were significantly influenced by temperature and exposure periods. At 16 degrees C, hydroprene did not cause differences in developmental time when eggs were exposed for different periods. At temperatures >16 degrees C, both exposure period and temperature influenced developmental time. The maximum developmental time (15.0 +/- 0.2 d) occurred at 16 degrees C, and the minimum developmental time (3.2 +/- 0.3 d) occurred at 32 degrees C. Mortality increased when eggs were exposed to hydroprene for longer periods at all of the five tested temperatures. The greatest mortality (81.6 +/- 2.1%) occurred when eggs were continuously exposed on treated surfaces at 32 degrees C. We used developmental time instead of rate (1/ developmental time) to fit simple linear or polynomial regression models to the development data. Appropriate models for developmental time and mortality were chosen based upon lack-of-fit tests. The regression models can be used in predictive simulation models for the population dynamics of Indianmeal moth to aid in optimizing use of hydroprene for insect management.

Transgenic avidin maize is resistant to storage insect pests.

Avidin is a glycoprotein found in chicken egg white, that sequesters the vitamin biotin. Here we show that when present in maize at levels of > or =100 p.p.m., avidin is toxic to and prevents development of insects that damage grains during storage. Insect toxicity is caused by a biotin deficiency, as shown by prevention of toxicity with biotin supplementation. The avidin maize is not, however, toxic to mice when administered as the sole component of their diet for 21 days. These dates suggest that avidin expression in food or feed grain crops can be used as a biopesticide against a spectrum of stored-produce insect pests.

Emergence, survival, and fecundity of adult cat fleas (Siphonaptera: Pulicidae) exposed as pupae to juvenile hormone mimics.

Cat flea, Ctenocephalides felis felis (Bouché), adults exposed to sprays of methoprene, pyriproxyfen, or fenoxycarb as cocooned pupae emerged approximately 1 d earlier than adults from water-treated control pupae. Mortality of adult fleas, after exposure to juvenile hormone mimics as pupae, was increased over that of controls. Females had higher mortality than males within the first 48 h of feeding. Fecundity of females exposed as pupae to juvenile hormone mimics was not different from that of controls. Early emergence of preemerged adults from treated cocoons is discussed along with reasons for higher female susceptibility to juvenile hormone mimics.