Sorption of carbon dioxide by chickpeas packaged in modified atmospheres

Modified atmospheres (MAs) with high CO2 concentrations are used for packaging several commodities with different purposes, including as an alternative method for pest control. When used in gas-tight flexible packages, sorption by the commodity produces a vacuum effect that causes the package to adopt a random shape and makes it impossible to reshape it without opening the package. Other than storage problems in retail storehouses, sorption can affect the amount of gas inside the packages needed for pest control. This study reports the amount of CO2 sorption by chickpeas packaged with different MAs and the negative pressure produced due to the decrease in the partial pressure of the gas. Trials were conducted in 710 mL semi-rigid plastic containers filled up to 24%, 48% and 96% of their capacity (filling ratios). Three MAs (90%, 70% and 50% CO2 with a residual of 3%, 6% and 10% O2, respectively, and balanced by N2) were used during 24 h, 48 h, 240 h and 384 h of exposure at 20 °C. The maximum sorption (1.28 g CO2/kg of chickpea) was obtained with the lower filling ratio (24%) and with an initial concentration of 90%. Sorption decreased with the decline in the initial CO2 concentration and with the rise in the filling ratio. The time needed to reach the equilibrium sorption varied between 141 h and 27 h, depending on the initial CO2 concentration and the filling ratio of chickpeas. The vacuum effect produced inside the containers by sorption produced a negative pressure that increased with the increase in the filling ratio and the initial CO2 concentration. Whether the amount of CO2 available in packages after gas sorption is still effective for controlling chickpea pests remains to be tested.info:eu-repo/semantics/acceptedVersio

Biological control of Acanthoscelides obtectus and Zabrotes subfasciatus in stored dried beans

This study assesses the feasibility of using natural enemies for the control of Acanthoscelides obtectus Say and Zabrotes subfasciatus Boheman (Coleoptera: Chrysomelidae), key pests of stored dried beans, Phaseolus vulgaris L. (Fabales: Fabaceae). The predatory mites Blattisocius tarsalis Berlese (Acari: Ascidae) and Amblyseius swirskii Athias-Henriot (Acari: Phytoseiidae) were able to prey on A. obtectus eggs, reducing the bruchid population by more than 60% under both controlled and warehouse conditions. Therefore, they show good potential as biological agents for controlling this pest. The larval parasitoids Anisopteromalus calandrae Howard and Lariophagus distinguendus Förster (Hymenoptera: Pteromalidae) were both moderately effective (34–38% reduction) at suppressing A. obtectus populations, but when A. calandrae was combined with B. tarsalis, a significant improvement in control efficacy (81% reduction in emergence) was observed. Therefore, the release of A. calandrae combined with B. tarsalis seems to be a promising strategy for controlling A. obtectus. Neither B. tarsalis nor A. swirskii were able to prey on Z. subfasciatus eggs. Only the parasitoid A. calandrae was moderately effective (39% reduction) at supressing Z. subfasciatus populations. Further testing is needed to identify other natural enemies that can complement the action of A. calandrae in reducing Z. subfasciatus populations.info:eu-repo/semantics/acceptedVersio

Susceptibility of Rhyzopertha dominica to high CO2 modified atmospheres in packaged chickpeas

Three MAs with 50%, 70% and 90% CO2 in air was tested at different exposure times on all the developmental stages of R. dominica using chickpeas packed with 4% and 96% filling ratio in which there was excess of CO2. At 4% filling ratio the loss of the gas was negligible. The exposure time to reach 50% mortality (LT50) was estimated for each developmental stage and CO2 concentration, ranging from 7 h for larvae with 90% to 2 days for pupae with 50% CO2. At 96% filling ratio and for the intervals of the estimated exposure times (LT50) from the 4% filling ratio, mortality decreased significantly for eggs and adults at the three MAs tested, while for the internal developmental stages, larvae at 50% and 70% CO2 and pupae in all concentrations of CO2, the susceptibility remained the same as with a 4% filling ratio. This decline in mortality of the external developmental stages was possible due to the sorption of CO2 by the chickpeas, which caused a loss of intergranular levels of CO2 between 17% and 29%. This sorption ranged from 0.1955 to 0.3285 g of CO2 per kg of chickpeas and produced a negative pressure of 77.12 to 60.65 kPa. In conclusion, when chickpeas are packed with high CO2 MAs, a decrease in the mortality of eggs and adults of R. dominica could be expected due to pulse sorption.info:eu-repo/semantics/acceptedVersio

Efficacy of Modified Atmospheres on Trogoderma granarium (Coleoptera: Dermestidae) and Sitophilus zeamais (Coleoptera: Curculionidae)

We investigated the efficacy of two types of modified atmospheres (MA) against adults of the khapra beetle, Trogoderma granarium Everts, and the maize weevil, Sitophilus zeamais Motschulsky, under laboratory conditions. Adults of the above species on wheat were exposed to a carbon dioxide (CO2) concentration of 70% or a low oxygen (O2) concentration of 0.1% for durations of 0.67 (16 h), 1, 2, 4, and 6 d and stored in an environmental chamber set at 28 ± 2°C, 70 ± 5% RH, and a photoperiod of 16:8 (L:D) h. After each exposure interval, immediate mortality and knockdown were recorded, and the surviving or knocked down individuals were transferred to normal atmospheres and returned to the environmental chamber, where survival was recorded 7 d later. In addition, after the immediate and delayed mortality counts, all adults were removed from the substrate, and the number of progeny produced was recorded 60 d later. Both MA conditions totally controlled (100% mortality) the adults of T. granarium and S. zeamais immediately after a 6-d exposure or after a 4-d exposure when delayed mortality was taken into account, showing the postexposure effect of the MA. Moreover, high CO2 was more effective than low O2 for S. zeamais, whereas the reverse was true for T. granarium. The 4-d exposure period was crucial for the production of progeny of both species because after that period surviving insects did not produce offspring. Our results show that both MA conditions can be used with success to control these species.info:eu-repo/semantics/acceptedVersio

Biological control of Callosobruchus chinensis (Coleoptera: Chrysomelidae) in stored chickpeas through the release of natural enemies

In this study, two predatory mites and two parasitoid wasps were evaluated for their effectiveness in controlling Callosobruchus chinensis (Coleoptera: Chrysomelidae), a common pest in stored chickpeas. The predatory mite Amblyseius swirskii (Acari: Phytoseiidae) preyed on the bruchid’s eggs but did not consume a large amount; the mite Blattisocius tarsalis (Acari: Ascidae) did not consume C. chinensis eggs. However, the larval parasitoids Anisopteromalus calandrae and Lariophagus distinguendus (Hymenoptera: Pteromalidae) were effective at reducing the bruchid’s larval population, producing mortality rates above 90% in controlled conditions (28 ± 2°C, 75 ± 5% relative humidity [RH]). In tubes of 20-cm diameter filled with 9 to 35 kg of chickpeas, both parasitoids were able to parasitize the host at depths of 40, 100, and 150 cm, even when larvae were offered simultaneously at all depths. This indicates that parasitoids will probably be able to locate hosts at least at 150 cm of distance in a storage facility. A. calandrae was similarly effective at reducing the bruchid population at different parasitoid-to-host ratios (1:7, 1:15, 1:30, and 1:60). Moreover, A. calandrae efficiently reduced C. chinensis populations when released in 25-kg commercial polypropylene bags of chickpeas in simulated warehouse conditions (27 ± 2°C and 65 ± 4% RH). This is the first time that A. calandrae and L. distinguendus are shown to be effective biological control agents for the integrated management of C. chinensis in stored chickpeas and can be an alternative to the application of pesticides for maintaining low bruchid population levels.info:eu-repo/semantics/acceptedVersio

Effect of packaging chickpeas with CO2 modified atmospheres on mortality of Callosobruchus chinensis (Coleoptera: Chrysomelidae)

High CO2 modified atmosphere packaging (MAP) is a sustainable alternative for pest control in stored products. The effectiveness of this method varies depending on the CO2 concentration used, insect exposure time, temperature, humidity, the tested insect species, and the insect's stage of development. One factor that substantially influences the concentration of CO2 available inside the packages, and therefore the effectiveness of the treatment, is the sorption of gas in the commodity. This study evaluated the impacts of packaging chickpeas in modified atmospheres of 50% and 90% CO2 with filling ratios (proportion of grain relative to the volume of the package) of 1% and 96% grain on the mortality of C. chinensis eggs and pupae and on the fecundity of the females emerging from the surviving individuals. In packages with a 96% filling ratio, CO2 concentration in the headspace of packages reduced to 60% and 30% from initial concentrations of 90% and 50% (respectively) in the first 24 h of exposure. Despite this reduction in CO2 concentrations, no differences in the mortality of C. chinensis eggs and pupae were observed between these packages and those with a 1% filling ratio. The estimated exposure time to achieve 95% mortality (LT95) of the eggs ranged from 38 to 68 h; for pupae, it ranged from 142 to 248 h. The fecundity of females that emerged from the surviving pupae decreased after 48 h of exposure to CO2, but the fecundity of females that emerged from surviving eggs was not affected by exposure time, MAPs, or filling ratio. Therefore, effective pest control can be accomplished with the use of sufficient treatment times to eradicate the most tolerant developmental stages, regardless of whether the packages are full or not.info:eu-repo/semantics/acceptedVersio

Comparative kinetic characterization of the activity of glycosylated and non-glycosylated trypsin-like serine protease isolated from adults of Rhyzopertha dominica (Coleoptera: Bostrichidae) reared on the grain of three different cultivars of wheat

Rhyzopertha dominica is a pest that uses trypsin-like serine protease enzymes to hydrolyse the proteins in the cereal grains on which it feeds. The present study reveals for the first time that that there are both glycosylated and non-glycosylated serine proteases. The progeny of R. dominica reared on the grain three varieties of wheat were used to fractionate their trypsin-like serine proteases using Concanavalin A affinity chromatography. The albumin fractions from the wheat cultivars used in this study were subjected to size exclusion chromatography to fractionate the albumin inhibitors that are highly specific for the serine protease activity of R. dominica. Kinetic and thermodynamic assays were used to differentiate both types of enzymes. In general, the catalytic efficiency values Vmax/Km for glycosylated proteases were higher, indicating that glycosylation increases the affinity for the substrate. Inhibition assays using wheat albumins revealed that the glycosylated enzymes had higher Ki values, indicating a low affinity for the inhibitors than the non-glycosylated enzymes. Thermodynamic analysis indicates that glycosylation increases the activation energy Ea improving the serine proteases' catalysis. Thus it is likely that R. dominica uses glycosylated proteases in order to optimize the hydrolysis of cereal proteins and nullify the action of wheat grain protease inhibitors and increase its chances of survival