Population Growth and Development of Psocid \u3ci\u3eLepinotus reticulatus\u3c/i\u3e 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°C at 75% RH. The largest population growth was recorded at 30 and 32.5°C, whereas only 9% of nymphs developed to adults and populations declined at 35°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°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 \u3ci\u3eLepinotus reticulatus\u3c/i\u3e and \u3ci\u3eLiposcelis entomophila\u3c/i\u3e

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\u27s 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

Efficacy of dust formulations of spinosad for controlling insects infesting stored wheat

Laboratory experiments were conducted to compare the efficacy of three new dust formulations (B1, C3, and D1) of spinosad as grain protectants on stored wheat. Evaluations were conducted on grain that was held for 1 d and 12, 24, 39, and 52 wk after insecticide treatments were applied. Bioassays for adult mortality and progeny production were conducted at 28°C and about 65% r.h. Dust formulations B1 and C3 effectively controlled adult Rhyzopertha dominica and prevented progeny development for 52 wk while formulation D1 was less effective. Only formulation B1 controlled Sitophilus oryzae adults (> 91% parental mortality) but did not prevent progeny production. None of the dust formulations were effective against Tribolium castaneum adults but progeny production was lower on grain treated with formulations B1 and C3. Egg mortality of Plodia interpunctella was similar for all treatments although overall progeny production was less on grain treated with formulation B1. The type of dust formulation of spinosad is critical in controlling stored grain insects.Keywords: Spinosad dust formulations, Rhyzopertha dominica, Sitophilus oryzae, Tribolium castaneum,Plodia interpunctell

Population Growth and Development of Psocid \u3ci\u3eLepinotus reticulatus\u3c/i\u3e 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°C at 75% RH. The largest population growth was recorded at 30 and 32.5°C, whereas only 9% of nymphs developed to adults and populations declined at 35°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°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

Ecological Studies of the Psocids Liposcelis brunnea, L. rufa, L. pearmani, and Lepinotus reticulatus

Psocids (Psocoptera) are an emerging problem in grain storages, grain processing facilities, and product warehouses in the United States and many other countries. Development of effective pest management programs for psocids is dependent on having sound knowledge of their ecology. Given the limited information available on the ecology of psocids, we conducted ecological studies of four psocid species namely, Liposcelis brunnea (Liposcelididae), Liposcelis rufa, Liposcelis pearmani and Lepinotus reticulatus (Trogiidae). We conducted population growth studies of these four psocid species at different temperatures and relative humidities; development studies of L. brunnea, L. rufa, and L. reticulatus at different temperatures; and investigated the effects of temperature on reproductive parameters of L. reticulatus. Our studies provide important data on life history and reproductive parameters of four storedproduct psocid pests. Because these parameters affect population dynamics, these data can be used in simulation models to predict psocid population dynamics and thereby aid in the development of more effective management strategies

Diagnostic Molecular Markers for Phosphine Resistance in US Populations of Tribolium castaneum and Rhyzopertha dominica

Citation: Chen, Z., Schlipalius, D., Opit, G., Subramanyam, B., & Phillips, T. W. (2015). Diagnostic Molecular Markers for Phosphine Resistance in US Populations of Tribolium castaneum and Rhyzopertha dominica. Plos One, 10(3), 14. doi:10.1371/journal.pone.0121343Stored product beetles that are resistant to the fumigant pesticide phosphine (hydrogen phosphide) gas have been reported for more than 40 years in many places worldwide. Traditionally, determination of phosphine resistance in stored product beetles is based on a discriminating dose bioassay that can take up to two weeks to evaluate. We developed a diagnostic cleaved amplified polymorphic sequence method, CAPS, to detect individuals with alleles for strong resistance to phosphine in populations of the red flour beetle, Tribolium castaneum, and the lesser grain borer, Rhyzopertha dominica, according to a single nucleotide mutation in the dihydrolipoamide dehydrogenase (DLD) gene. We initially isolated and sequenced the DLD genes from susceptible and strongly resistant populations of both species. The corresponding amino acid sequences were then deduced. A single amino acid mutation in DLD in populations of T. castaneum and R. dominica with strong resistance was identified as P45S in T. castaneum and P49S in R. dominica, both collected from northern Oklahoma, USA. PCR products containing these mutations were digested by the restriction enzymes MboI and BstNI, which revealed presence or absence, respectively of the resistant (R) allele and allowed inference of genotypes with that allele. Seven populations of T. castaneum from Kansas were subjected to discriminating dose bioassays for the weak and strong resistance phenotypes. Application of CAPS to these seven populations confirmed the R allele was in high frequency in the strongly resistant populations, and was absent or at a lower frequency in populations with weak resistance, which suggests that these populations with a low frequency of the R allele have the potential for selection of the strong resistance phenotype. CAPS markers for strong phosphine resistance will help to detect and confirm resistant beetles and can facilitate resistance management actions against a given pest population

Insecticidal Effect of Diatomaceous Earth Against Three Species of Stored-Product Psocids on Maize, Rice, and Wheat

We evaluated the efficacy of three diatomaceous earth (DE) formulations, Dryacide, Protect-It, and Insecto, against three Psocoptera species, Liposcelis entomophila (Enderlein) (Liposcelididae), Lepinotus reticulatus Enderlein (Trogiidae), and Liposcelis decolor (Pearman), in the laboratory. Bioassays were conducted in three grain commodities, wheat, rice and maize, at 30°C and 75% RH, and the DEs were applied at the recommended dose rates of 1,000, 400, and 500 ppm for Dryacide, Protect-It, and Insecto, respectively. Differences in adult mortality were found among grains and DEs for L. entomophila and L. reticulatus, but these trends were not consistent for all combinations tested. Type of grain and DE did not affect L. decolor mortality significantly. Moreover, mortality increased with increasing exposure time for L. entomophila and L. reticulatus, but there was no effect of exposure time on L. decolor. After 7 d of exposure, mortalities of L. entomophila, L. reticulatus, and L. decolor were 56, 55, and 40%, respectively, and the respective mortality levels after 14 d were 63, 71, and 42%. Progeny production after 30 d was significantly suppressed for all species in the treated grains. However, progeny production was still high in the treated grains and reached 54, 42, and 76 individuals/10 g of grain for L. entomophila, L. reticulatus, and L. decolor, respectively. Progeny production did not vary with commodity. Our results suggest that DEs, when used alone, will not provide effective control of psocids

Intra and interspecific variation assessment in Psocoptera using near spectoscopy

Several species of Psocoptera are associated with and damage grains and other stored products, books, historical documents, and insect collections. Their small size and lack of expressive morphological variation make it a difficult group for species identification. The spectra of adult males and females of 10 psocid species from the genus Liposcelis were obtained by near infrared spectroscopy (NIRS) and analyzed. Each specimen was placed on a diffuse reflectance accessory of a NIR spectrometer to obtain the respective spectrum, using ten replicates for each species or sex. All spectra were analyzed by combined methods of multivariate analysis using the technique of crossed validation for the multivariate models. The analysis discriminated the species without significant overlapping among the species spectral patterns. The NIRS also revealed variation in the metabolomic profile of males and females; however, it is still possible to distinguish the species using only males or females or even from mixed sex samples. NIRS technique proved to be a powerful tool to discriminate species both at intra and interspecific levels based on dispersion spectral patterns of individual specimens. Keywords: Biological systems, Liposcelididae, stored product pests, Vibrational spectroscopy

Development and Evaluation of a Low-Cost Probe-Type Instrument to Measure the Equilibrium Moisture Content of Grain

Storage of grain in bags is common in Africa, Asia, and many other less developed countries making a bag probing method well-suited for moisture content (MC) measurement. A low-cost meter was developed under a USAID project to reduce post-harvest loss (PHL). The meter, referred to as the PHL meter, measures the MC of maize and other grains based on relative humidity (RH) and temperature (T) measurements obtained by a small digital sensor located in the tip of a tubular probe that can be inserted into bags of grain or other grain bulks. Measurements are used by equilibrium moisture content (EMC) equations programmed into the meter to predict MC. A handheld reader connected to the probe provides a user interface. The PHL moisture meter was evaluated based on laboratory studies in the United States and field studies in Ghana. Meter readings from field studies were compared to two commercial meters, a John Deere Chek-Plus-SW08120 grain moisture tester and a DICKEY-john GAC® 2100 Agri meter. The John Deere portable moisture meter is a low-cost meter by developed country standards (~US$250, 2016 price); the GAC 2100 bench-top moisture meter is an approved moisturetester by the Grain Inspection, Packers and Stockyards Administration (GIPSA) and has been a highly regarded and used electronic meter. Laboratory studies indicated that the PHL meter may require up to 6 min to take a measurement because of the time required by the probe tip and sensor to equilibrate to grain conditions. Methods to reduce the measurement time by measuring temporal equilibration rates were developed. These can be programmed into the reader to shorten measurement time for many conditions. The accuracy of the PHL moisture meter was comparable to the GAC 2100 moisture meter for maize below 15% MCwb. Average differences showed a positive offset of 0.45% for the PHL meter relative to the GAC 2100. The PHL meter provided an effective tool to probe bulk grain and bags

Performance assessment off a commercial scale solar biomass hybrid dryer for quality seed maize production: Presentation

Though several maize varieties have been developed and introduced over the years in Ghana, farmers still face challenges of access to quality seed maize. Among the major constraints is lack of proper drying systems to quarantee quality of seed produced. Peculiar to most parts of Africa, drying of maize in the open, on bare ground along shoulders of roads is still a common practice in Ghana. In this study, a 5-tonne capacity solar biomass hybrid dryer was developed for drying maize for seed and food/feed in Ghana. Effect of drying air temperature in the dryer on the physiological quality and germination of maize kernels was investigated. Maize grains were dried in the open sun simulating farmers practice and using the dryer at 4 varying levels (L1, L2, L3 and L4) with corresponding heights (0.6m, 1.2m, 1.8m and 2.4m) respectively. Harvested maize at 22.8% moisture content was dried at the varying levels until reaching overall mean moisture content of 12.8 ± 0.2% (wb). Results showed that, drying air temperatures in the dryer increased in accordance with height with lowest mean temperature of 44.4 ± 4.6°C recorded at L1 and mean maximum of 52.8 ± 5.4 °C at L4. The increase in drying temperature at L4 increased kernel stress crack index by an average of 14% and reduced germination by 33%. However, drying temperatures at L1-L3 and in the open sun had no significant effect (p > 0.05) on the germination potential of maize grains. This satisfies the dryer’s potential to be used for drying maize grains for high quality seed production on commercial scale.Though several maize varieties have been developed and introduced over the years in Ghana, farmers still face challenges of access to quality seed maize. Among the major constraints is lack of proper drying systems to quarantee quality of seed produced. Peculiar to most parts of Africa, drying of maize in the open, on bare ground along shoulders of roads is still a common practice in Ghana. In this study, a 5-tonne capacity solar biomass hybrid dryer was developed for drying maize for seed and food/feed in Ghana. Effect of drying air temperature in the dryer on the physiological quality and germination of maize kernels was investigated. Maize grains were dried in the open sun simulating farmers practice and using the dryer at 4 varying levels (L1, L2, L3 and L4) with corresponding heights (0.6m, 1.2m, 1.8m and 2.4m) respectively. Harvested maize at 22.8% moisture content was dried at the varying levels until reaching overall mean moisture content of 12.8 ± 0.2% (wb). Results showed that, drying air temperatures in the dryer increased in accordance with height with lowest mean temperature of 44.4 ± 4.6°C recorded at L1 and mean maximum of 52.8 ± 5.4 °C at L4. The increase in drying temperature at L4 increased kernel stress crack index by an average of 14% and reduced germination by 33%. However, drying temperatures at L1-L3 and in the open sun had no significant effect (p > 0.05) on the germination potential of maize grains. This satisfies the dryer’s potential to be used for drying maize grains for high quality seed production on commercial scale