The inhibition kinetics of dichlorvos on carboxylesterase and acetylcholinesterase (AChE) activity extracted from Liposcelis bostrychophila and L. entomophila (Psocoptera: Liposcelididae) were compared. The results showed that L. entomophila had significantly greater specific activity of carboxylesterase than L. bostrychophila (0.045 versus 0.012 micromoles/mg/min). Moreover, the carboxylexterase of L. entomophila showed higher affinity (i.e. lower Km value) to the substrate 1-naphthyl acetate than L. bostrychophila (0.29 versus 0.67 mM). The specific activity and affinity of AChE of the two species were not significantly different. The carboxylesterase of L. bostrychophila was more sensitive to the insecticide dichlorvos than that of L. entomophila. The I50s values of dichlorvos to carboxylesterase for L. bostrychophila and L. entomophila were 1.43 and 3.28 microM, respectively, and to AChE were 324 and 612 nM, respectively. Inhibition kinetics revealed that AChE from L. bostrychophila was 5.8-fold more sensitive to inhibition than AChE from L. entomophila.

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The effect of the insecticide dichlorvos on esterase activity extracted from the psocids, Liposcelis bostrychophila and L. entomophila

Previously regarded as minor nuisance pests, psocids belonging to the genus Liposcelis now pose a major problem for the effective protection of stored products worldwide. Here we examine the apparent biological and operational reasons behind this phenomenon and why conventional pest management seems to be failing. We investigate what is known about the biology, behavior, and population dynamics of major pest species to ascertain their strengths, and perhaps find weaknesses, as a basis for a rational pest management strategy. We outline the contribution of molecular techniques to clarifying species identification and understanding genetic diversity. We discuss progress in sampling and trapping and our comprehension of spatial distribution of these pests as a foundation for developing management strategies. The effectiveness of various chemical treatments and the availability and potential of nonchemical control methods are critically examined. Finally, we identify research gaps and suggest future directions for research.

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Biology and Management of Psocids Infesting Stored Products

Liposcelis tricolor Badonnel (Psocoptera: Liposcelididae) is worldwide and commonly found in various processed and unprocessed dry foods in households, granaries, and warehouses. The development, survival, and reproduction of L. tricolor were evaluated at eight constant temperatures (20, 22.5, 25, 27.5, 30, 32.5, 35, and 37.5°C). The population reared at 37.5°C failed to develop or reproduce. Between 20 and 35°C, developmental period from egg to adult varied from 56.37 d at 20°C to 30.74 d at 32.5°C. Based on a nonlinear model, the lower temperature developmental thresholds from egg, first through fourth stadia, and combined immature stages were estimated at 9.57, 9.02, 10.04, 13.69, 14.38, and 11.30°C; the upper temperature thresholds were 39.28, 37.55, 37.85, 38.26, 37.37, and 38.98°C, respectively. The survival rate from egg to adult was 67.26% at 27.5°C, 43.62 and 24.22% at 20 and 35°C, respectively. After emergence, the adult had a preoviposition period that ranged from 65.74 d at 20°C to 3.52 d at 30°C. L. tricolor produced the most eggs (53.91) at 27.5°C and the fewest (17.58) at 35°C. The population reared at 30°C had the highest intrinsic rate of increase (0.0367), net reproductive rate (13.55), the shortest populations doubling time (18.89 d), and shorter mean generation time (71.05 d) compared with the populations reared at six other constant temperatures. The populations reared at 30°C had type I survivorship pattern, whereas populations reared at other temperatures had type III survivorship curve as determined by a Weibull frequency distribution. The optimal range of temperature for L. tricolor population growth was 25–30°C.

https://bioone.org/journals/Annals-of-the-Entomological-Society-of-America/volume-100/issue-2/0013-8746(2007)100[228:DAROTP]2.0.CO;2/Development-and-Reproduction-of-the-Psocid-Liposcelis-tricolor-Psocoptera/10.1603/0013-8746(2007)100[228:DAROTP]2.0.CO;2.pdf

Development and Reproduction of the Psocid Liposcelis bostrychophila (Psocoptera: Liposcelididae) as a Function of Temperature

The mortality of three species of Psocoptera, Liposcelis bostrychophila Badonnel, Liposcelis decolor Pearman and Liposcelis paeta Pearman, at moderately elevated temperatures

KUČEROVÁ Z. (2002): Weight losses of wheat grains caused by psocid infestation (Liposcelis bostrychophila: Liposcelididae: Psocoptera). Plant Protect. Sci., 38: 103–107. Psocids are commonly found to be a persistent pest in structures of grain stores. Grain residues are potential pest reservoirs that serve as sources of grain re-infestation. Weight losses caused by psocids on broken wheat kernels were measured. Average weight loss of grain samples was 9.7% after 3 months of Liposcelis bostrychophila infestation. The weight losses were positively correlated with progeny production.

/pdf/weight-losses-of-wheat-grains-caused-by-psocid-infestation-1tifhiuyjo.pdf

Weight losses of wheat grains caused by psocid infestation (Liposcelis bostrychophyla: Liposcelididae: Psocoptera)

Psocids (Liposcelis spp.) are often abundant in tropical storage systems where very large populations can develop relatively soon after fumigation treatments. In order to improve pest management strategies against these pest some factors governing the potential of psocid populations to increase under tropical conditions were investigated in a large‐scale milled rice store and in the laboratory. The factors studied included the success of pest control, rice milling degree, fungal growth and variations in ambient temperature and humidity. Fumigation failure and low milling degree of the rice stock were confirmed as important factors encouraging rapid and substantial psocid population growth while fungal infection rates, routine spraying of store and bag stack and variations in ambient climatic conditions made no obvious contribution to observed fluctuations in psocid numbers. Suggestions are made for improved pest management strategies that need to be tested under operational conditions.

Pest management of psocids in milled rice stores in the humid tropics

Tribolium castaneum is an important insect pest of stored milled rice in Indonesia. The effect of T. castaneum on fungal infection of stored milled rice was investigated together with moisture content and weight loss. Milled rice were placed in glass jars (250 g/jar) and infested with 5, 10, and 20 pairs of T. castaneum . As control, the jars contained only milled rice. Three replications were made for each treatment (including the control). The jars were stored in storage room for 1, 2, and 3 months. Moisture contents (based on wet weight) of milled rice were determined using the oven method. Fungi were isolated and enumerated using dilution plating, followed by pour plate method on Dichloran 18% Glycerol Agar (DG18). Weight loss (based on dry weight) was determined after 3 months of storage.The results showed, that the population of adult T. castaneum increased with the increase in the number of pairs of infested T. castaneum and storage duration. The moisture contents of milled rice were relatively constant during storage. It was assumed, that the moisture contents were more influenced by the environmental conditions rather than the occurrence of T. castaneum . Nineteen fungal species were isolated Aspergillus flavus and Penicillium citrinum were the dominant fungal species. Total fungal population decreased after 2 and 3 months of storage, with the increase in the number of pairs of infested T. castaneum . Weight loss increased with the increase in the number of pairs of infested T. castaneum . Based on weight loss of milled rice, the best storage duration was found when the number of pairs of T. castaneum was five pairs, the duration of storage was 1, 2 or 3 months of storage.

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Serangan Tribolium castaneum pada Beras di Penyimpanan dan Pengaruhnya terhadap Serangan Cendawan dan Susut Bobot

Tribolium castaneum is an important insect pest of stored milled rice in Indonesia The effect of T castaneum on fungal infection of stored milled rice was investigated together with moisture content and weight loss Milled rice were placed in glass jars (250 g/jar) and infested with 5, 10, and 20 pairs of T castaneum As control, the jars contained only milled rice Three replications were made for each treatment (including the control) The jars were stored in storage room for 1, 2, and 3 months Moisture contents (based on wet weight) of milled rice were determined using the oven method Fungi were isolated and enumerated using dilution plating, followed by pour plate method on Dichloran 18% Glycerol Agar (DG18) Weight loss (based on dry weight) was determined after 3 months of storageThe results

Hariyadi Halid

Papers

Pest management of psocids in milled rice stores in the humid tropics

Serangan Tribolium castaneum pada Beras di Penyimpanan dan Pengaruhnya terhadap Serangan Cendawan dan Susut Bobot

on Fungal Infection and Weight Loss