Orientation of rusty grain beetles,Cryptolestes ferrugineus (Coleoptera: Laemophloeidae), to semiochemicals in field and laboratory experiments

Cryptolestes ferrugineus is a common beetle pest of stored grain for which techniques to monitor dispersing beetles are limited. Early research found several male-produced aggregation pheromones, but there has been little related work since that time. This paper reports experiments on orientation of C. ferrugineus in response to synthetic pheromones and other semiochemicals via flight and walking. Field trapping studies showed that flying beetles were caught on the western sides of grain bins in Kansas compared to the other three cardinal directions. Work with synthetic formulations of the two male-produced aggregation pheromones found that flying beetles were attracted to traps with the pheromone and wheat compared to traps with wheat only. Walking bioassays in the laboratory determined that either of the two aggregation pheromones, known as Cucujolide I and Cucujolide II, were attractive whether deployed singly or in combination. Laboratory bioassays showed that volatiles from grains, other grain-based materials and two commercial food attractants used in traps were attractive to C. ferrugineus. Further laboratory assays demonstrated that C. ferrugineus would orient to synthetic pheromones of three other beetle species and one moth species, all common pests of stored products. These new data on semiochemicals for C. ferrugineus suggest future work that could be done toward developing new tools for detecting and monitoring this serious pest.     

Field monitoring Sitophilus zeamais and Sitophilus oryzae (Coleoptera: Curculionidae) using refuge and flight traps baited with synthetic pheromone and cracked wheat

Flight traps with open vertical baffles and refuge traps in the form of rectangular cardboard boxes were used to catch Sitophilus zeamais and S. oryzae in Kenya. Traps baited with the aggregation pheromone (Sitophilure), and for the first time traps baited with pheromone and food bait (cracked wheat), were field tested. Both traps types were effective in capturing Sitophilus spp and gave higher weevil catch when baited with pheromone and cracked wheat combined than with pheromone or cracked wheat alone. The combination of pheromone and cracked wheat had an additive effect on trap catch and not a synergistic effect as reported in earlier laboratory trials. Different pheromone loadings of 0.5, 1 and 2 mg were tested. The catch of S. zeamais in flight traps rose significantly with increasing dosage. For refuge traps, the same effect was observed although the difference between 1 mg and 2 mg was not statistically significant. The trend was for increasing S. oryzae catch with dosage, although total catches were very much lower than those for S. zeamais, and differences did not prove statistically significant. Traps placed on the floor near infested maize cribs captured significantly more Sitophilus spp than those actually placed in the cribs. Adult Sitophilus captured were sexed and in both flight and refuge traps the sex ratio was biased in favour of females even though the sex ratio of weevils from infested maize cobs, which were the source of the captured weevils, was approximately even.     

Laboratory studies on behavioural interactions of Prostephanus truncatus (Horn) (Coleoptera: Bostrichidae) with conspecifics, synthetic pheromone and the predator Teretriosoma nigrescens (Lewes)(Coleoptera: Histeridae)

A bioassay method was devised to test the responses of adult Prostephanus truncatus (Horn) to conspecific adults or synthetic pheromone and to observe the response of the predator Teretriosoma nigrescens (Lewes) to adult or larval P. truncatus or the synthetic pheromone of this species.

The results confirmed earlier observations that male P. truncatus are the source of a pheromone attractive to both males and females, P. truncatus adults (in this case virgin females) are disinclined to leave food in response to the pheromone and maize itself is relatively unattractive to P. truncatus. For the first time it has been demonstrated that males are not attracted to females, females repel or avoid each other and males are less attracted to the naturally produced pheromone secretion than are females. In view of the fact that unmated females will not leave food to locate a calling male it was concluded that the female response to the pheromone is primarily a means of locating a food source, rather than a sexual partner. In contrast, males release their secretion to attract females.

When adult P. truncatus were tested against grains treated with the synthetic pheromone the response of males and females was apparently identical, in contrast to the lower response of males when tested against conspecific males. It seems probable that the amounts of pheromone used when testing the synthetic mixture are greater than would be produced naturally by a calling male and that this may mask the apparently lower sensitivity of males to the natural pheromone.

The pheromone of P. truncatus is known to be a kairomone for T. nigrescens, but in the bioassay this species was not attracted to synthetic pheromone and responded more strongly to empty maize grains than to adult or larval P. truncatus. It would appear that when walking, adult T. nigrescens are unwilling to approach closely to P. truncatus. The possible significance of this is discussed.     

Aggregation pheromone 4,8-dimethyldecanal and kairomone affect the orientation of Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae) adults

Tribolium castaneum, the red flour beetle, is a major pest of stored products throughout the world. The male T. castaneum adults biosynthesize and release the aggregation pheromone 4,8-dimethyldecanal (4,8 DMD), and the monitoring traps having the synthetic form of this pheromone and kairomone are commercially available. However, certain information available on the response of T. castaneum adults to the strength of pheromone and the nature of air flow is inadequate and thus limits the potential use of this compound. The objectives of this research were to determine if the orientation of adult beetles to the synthetic form of the pheromone 4,8 DMD is affected by the distance from the pheromone, its concentration and air movement. Experimental design was completely randomized design with three replicates. The T. castaneum adults released at different distances from the pheromone placed at varying concentrations tested their orientation to the pheromone with the presence or absence of air flow. The control experiments were conducted without the pheromone. A separate experiment tested if exposure to 4,8 DMD alters the direction of movement in T. castaneum adults. The maximum trap catch (24%) was obtained with 0.5 μL of 4,8 DMD and when the beetles were released at distances up to 60 cm from the pheromone. The percentage of beetles trapped declined when the beetles were released 60–120 cm from the pheromone. The average angles on beetle turning during their orientation were significantly higher in the presence of pheromone than the respective controls. Air movement downstream of the pheromone trap increased the percentage beetles trapped compared to that in the absence of air flow. It is concluded that the orientation of T. castaneum adults is affected by the concentration of 4,8 DMD, distance from the pheromone and the air movement.     

Effects of developmental stage,cold acclimation and diet on the cold tolerance of three species of Cryptolestes (Coleoptera: Laemophloeidae)

Flat grain beetles (Coleoptera: Laemophloeidae) are common stored-product insect pests in Canada, infesting cereals in grain bins, equipment and end products in flour mills. We studied the cold tolerance of the three most common flat grain beetles: Cryptolestes ferrugineus, Cryptolestes turcicus and Cryptolestes pusillus, by measuring the survival at −10 °C and supercooling point (SCP) for different life stages (egg, young larva, old larva, pupa and adult) reared on flour mixed with brewer’s yeast. Probit analysis was used to estimate the lethal time for 50 and 95% mortality. This was done with non-acclimated individuals (only held at 30 °C) or cold-acclimated individuals (held at 18, 10 and 5 °C, for 1 week/temperature). In general, adults were the most cold-hardy stage for each of the species. Acclimated insects were anywhere from no increase in cold tolerance to 14-fold more cold-tolerant than the corresponding non-acclimated stage and species. Cryptolestes ferrugineus was most cold-tolerant species (58 d at −10 °C to reach 95% mortality for acclimated adult), C. turcicus was the next most cold-tolerant, (39 d) and C. pusillus was the least cold-tolerant (11 d). The cold tolerance of adults reared on three diets was measured both for acclimated and non-acclimated insects. The adults reared on grain diet (whole wheat kernels, cracked wheat kernels and wheat germ (90:5:5 mass ratio) were the most cold-tolerant, adults reared on white-wheat flour and brewer’s yeast diet (95:5 mass ratio) had the next highest cold tolerance followed by the adults reared on 100% white-wheat flour. Supercooling point (SCP) of insects ranged from −20.6 to −26.7 °C. In general, acclimated insects had slightly lower SCP than non-acclimated insects.     

Study of the biosynthesis of 1-octen-3-ol using a crude homogenate of Agaricus bisporus in a bioreactor

ABSTRACT:  1-Octen-3-ol and 10-oxo- trans -8-decenoic acid are metabolites of the breakdown of linoleic acid (LA) by mushroom enzymes. These compounds can be produced in a bioreactor using a crude mushroom homogenate and the exogenous addition of LA and oxygen. The factors' duration of blending, mushroom–buffer ratio, effect of a surfactant, whole against partially clarified reaction broths, purity of LA, and utilization of stumps instead of whole mushrooms were studied for their effect on reaction yield using a 1-L bioreactor. The results showed the feasibility of using the more inexpensive 60%-pure LA instead of the 99%-pure LA even when a yield loss was involved. Waste stumps could be used instead of whole mushrooms with a yield decline of 26%.     

Effects of aggregation pheromone concentration and distance on the trapping of Rhyzopertha dominica (F.) (Coleoptera: Bostrychidae) adults

Rhyzopertha dominica male adults produce an aggregation pheromone that attracts both sexes. While many studies have tested the behavioral response of R. dominica adults to its aggregation pheromone, information on the distance of attraction and effective pheromone concentration are lacking. Therefore, the objectives of this study were to determine the recapture rate of R. dominica adults released at different distances from a pheromone-baited and pheromone + kairomone-baited trap, as well as the most effective pheromone concentration for R. dominica. Experiments were arranged as complete randomized design with four replicates. A commercial pitfall trap containing R. dominica pheromone alone or pheromone + kairomone was placed inside an experimental arena. Adult R. dominica were released at different distances from the trap and the adults captured were counted. A separate experiment was conducted using pitfall traps containing different concentrations of the aggregation pheromone placed inside the experimental arena. Adult R. dominica were released 60 cm away from the pitfall trap and the recaptured adults were recorded. The trapping efficiency was higher when the trap contained both the pheromone and kairomone than the pheromone alone. Trap capture was highest when the beetles were released at distances up to 70 cm and at a concentration of 100 μL/1 m². Our findings suggest that food facility managers should take into account the effective pheromone concentration and distance of attraction, while also strongly consider including food kairomones in traps when developing monitoring programs for R. dominica.     

Orientation of Tribolium castaneum (Coleoptera: Tenebrionidae) adults to 4,8-dimethyldecanal,kairomone and botanical oils following ambient,low, or high temperature exposure

The aggregation pheromone 4,8-dimethyldecanal (4,8 DMD) used alone or with kairomone-baited traps generally is used for monitoringTribolium castaneum (Herbst) but low efficiency is reported. Furthermore, insect orientation to pheromones and kairomones following low or high temperature exposure is not yet understood. This research evaluated the orientation of T. castaneum adults to 4,8 DMD and common kairomones following exposure to ambient, low or high temperatures. Fifty adults were introduced to the middle of rectangular glass chamber, and movement to the treatment or control was determined after 1 h. In experiment 1, insects reared at 30°C were used. Experiments 2 and 3 used insects exposed to 10°C for 4 days (cold temperature) and 42°C for 12 h (brief high temperature), respectively at 2–8 h following cold or heat exposure. The highest trapping occurred when 4,8DMD was combined with neem oil whereas the lowest was in coconut oil alone. Neem oil alone demonstrated repellent action. Prior exposure to cold or heat initially reduced taxis of T. castaneum adults to traps. The attraction for adults exposed to cold and heat was restored after 6–8 h when traps contained pheromone + neem or coconut oil. This study marks the first to experimentally test how exposure to high or low temperatures, two key IPM tactics in the post-harvest supply chain, affects the behavioral response of an important stored-product species to pheromone- and kairomones-baited traps.     

The flight activity of Prostephanus truncatus (Horn) (Coleoptera: Bostrichidae) and Teretrius nigrescens Lewis (Coleoptera: Histeridae) in Kenya

The invasive storage pest, the larger grain borer (LGB) Prostephanus truncatus (Horn), was introduced into the maize-deficit, semi-arid areas of the eastern region in Kenya in the early 1980s. In spite of containment efforts and the introduction of the predator Teretrius nigrescens Lewis from Mexico, LGB has spread to the main maize production zone in western Kenya during the past five years. The present work presents results from a 28-month monitoring effort of LGB and its predator, using pheromone traps at five locations along an east-west transect across Kenya. LGB occurred in all regions with highest trap catches in the high potential maize production zones in Western Kenya. T. nigrescens had not spread to western Kenya and trap catches were very low and mostly zero in Eastern Kenya, even in the area where it was released during the 1990s, suggesting that it became locally extinct after initial establishment. LGB flight activity was closely related to relative humidity, temperature and vapour pressure deficit. A model based on climatic factors accurately predicted seasonal trends of LGB flight behaviour in Kakamega and Mombasa but not in Kitale and Thika. It was concluded that models that rely on the direct effect of climate cannot predict LGB flight accurately enough to allow assessment of the impact of T. nigrescens on a regional basis. It is suggested that other factors such as the availability of stored grain and thus the indirect effect of climate via enhanced or reduced crop production play a major role in the flight activity of LGB and T. nigrescens.     

不同温度对氮气气调锈赤扁谷盗各虫态致死时间比较研究

掌握温度对氮气气调中害虫不同虫态致死时间的影响程度对科学控制气调时间和成功杀虫具有重要意义。测定了18℃、23℃和28℃温度时锈赤扁谷盗的卵、幼虫、蛹和成虫在98%氮气气调过程中不同时间的死亡率及完全致死时间。温度18℃时锈赤扁谷盗卵、幼虫、蛹和成虫的完全致死时间分别为28、18、28和14 d,23℃时完全致死时间分别为22、14、24和8 d,28℃时完全致死时间分别为16、9、18和5 d。温度18℃时卵、幼虫、蛹和成虫的完全致死时间比23℃时相应延迟6、4、4和6 d,比28℃时相应延迟12、9、10和9 d。实验温度下98%氮气气调时锈赤扁谷盗耐受力最强的虫为蛹期,其后依次为卵、幼虫和成虫期。锈赤扁谷盗蛹在18、23和28℃温度下的死亡率-时间回归方程分别为y = 3.85x - 3.85、y = 4.01x - 3.53和y = 4.72x - 3.71。温度降低显著延迟98%氮气气调杀虫时间,氮气气调锈赤扁谷盗时应以杀死其耐受力最强的蛹为目标。     

Kinetics of protein physicochemical changes induced by heating in meat using mimetic models: (1) Relative effects of heat and oxidants

Optimizing the nutritional quality of cooked meat needs a better understanding of the mechanisms responsible for protein changes induced by heating. The relative contributions of chemical and thermal effects on protein physicochemical changes were studied using meat models. Two models were tested: a basic model made of an aqueous suspension of myofibrillar proteins, and a complex model, in which oxidants were added in physiological concentrations. Various heating time–temperature combinations were applied to both models in the ranges 45–90 °C and 5–120 min. Protein oxidation was evaluated by carbonyl and free thiol contents. Conformational changes of proteins were assessed by measurements of surface hydrophobicity and aggregation. Carbonyl formation was weakly affected by the thermal process alone but exacerbated by oxidants. A synergistic effect of oxidants and heat treatments on protein oxidation was noted. Changes in protein hydrophobicity and aggregation were dominated by the thermal process.     

Studies of refuge-seeking behaviour and locomotory activity in Cryptolestes ferrugineus (Stephens) (Coleoptera: Cucujidae) using time-lapse video recordings

Refuge-seeking behaviour and locomotory activity of two strains of Cryptolestes ferrugineus (Stephens) were investigated in laboratory arenas with a refuge using time-lapse video recordings. An insectary strain, reared in the laboratory for over 25 years and susceptible to many organo-phosphorus insecticides, exhibited less refuge-seeking behaviour and was slower in its general movements around the arena than another strain which had been collected from the field more recently and was resistant to malathion. There was considerable variation in the amount of time spent in the refuge by individual beetles; however, during each 24 h of a 3 day test period, individuals of the refuge-seeking strain remained in the refuge for a mean of 20 h and only ventured into the arena on 1.3 occasions. Females made fewer exits from the refuge and spent less time in the arena than males.     

Identification and quantification by LC–MS/MS of a new precursor of 3-mercaptohexan-1-ol (3MH) using stable isotope dilution assay: Elements for understanding the 3MH production in wine

The isotopically labelled S-3-(hexan-1-ol)-glutathione d₂/d₃ (G3MHd₂/d₃) was synthesized with a strategy based on acid-labile protecting groups. The natural analogue of this compound could be a precursor of 3-mercaptohexanol, a varietal thiol reminiscent of grape fruit, released during alcoholic fermentation. In a first time, deuterated glutathione conjugate was used to perform identification and quantification by stable isotope dilution assay of G3MH in musts from several varieties: Sauvignon, Riesling and Gewurztraminer.     

Composition of some commercial grappas (grape marc spirit): the anomalous presence of 1,1-diethoxy-3-methylbutane: a case study

A GC-MS study of the composition of nine different grappas (Italian grape marc spirit) was carried out. High-weight alcohols showed the greatest variations, while the lower congener concentrations generally were more uniform. Particularly interesting is the presence of 1,1-diethoxy-3-methylbutane (DMB), never detected before in grappa. DMB was present in all samples, ranging from 0.8 up to 30.6 mg L⁻¹. This latter concentration was the highest detected in an alcoholic beverage so far. A discussion on the other volatile congeners was also reported. Principal component analysis was applied to the data and explained >80% of the whole variability. Most grappas are grouped in a single cluster, while the other samples are completely separated. DMB, ethyl acetate, ethyl lactate, and n-butanol are some examples of constituent able to differentiate the tested products.     

Some effects of a mixture of oxygen, carbon dioxide and nitrogen in the ratio 1:1:8 on the oviposition and development of Sitophilus zeamais Mots. (Coleoptera, Curculionidae)

The emergence pattern of Sitophilus zeamais Mots, adults from whole grain maize was monitored following oviposition in air or the gas mixture with development continuing either in the same or the alternative atmosphere. After exposure to the gas mixture during oviposition only, development only, and during both, the numbers of adult offspring per female were about 40, 50 and 20°_o respectively of those obtained from the controls in air. In addition continuous exposure to the gas mixture during development resulted in a delay of 10–11 days in the mean developmental period. No significant difference was found between the results obtained when the insects were kept in air throughout and when oviposition only took place in pumped air or in air on maize equilibrated in the gas mixture before use.     

Pheromone release by Rhyzopertha dominica (F.) (Coleoptera: Bostrichidae) in the laboratory: daily rhythm, inter-male variation and association with body weight and/or boring activity

Male Rhyzopertha dominica release an aggregation pheromone that is a blend of two components, Dominicalure-1 (D1) and Dominicalure-2 (D2). Factors leading to variation in the output of pheromone were investigated in order to improve the design of future experimental studies. Pheromone output from male R. dominica, during the photophase (08.00-20.00 h), was quantified for six 2-h periods to test for any diurnal rhythms. The amounts of components released were similar during the period 08.00-16.00 h but increased significantly in late afternoon (16.00-20.00 h). Measurements were also made of pheromone release during the whole scotophase and males were found to emit significantly less at this time but the D1:D2 ratio remained relatively constant at 1:1. Mean daily release rates for D1 and D2 were 1.22 and 1.09 μg, respectively for 8-9 day old males. Actual quantities of pheromone components varied 10-fold among individuals, but the blend composition was relatively constant with the mean proportion of D1 in the blend being 51.4% although extremes of 35.1-71.3% were recorded. Both body weight and boring rate were positively correlated with rates of pheromone release, although body weight and boring rate were themselves correlated. The blend ratio did not vary with body weight or boring rate. If experimenting on release of, or behavioural responses to, pheromone, then variation in output can be minimised by choosing males of similar body weight and by restricting study to times of the day when release rates would be expected to be most similar.     

Biochemical changes in phosphorus compounds and in the activity of phytase and α-amylase in the rice (Oryza sativa) grain during germination

Changes in the phytic acid, inorganic phosphorus and ATP contents, and in the activity of phytase and α-amylase in rice (Oryza sativa L) grains were determined during 18 days of germination in a dark room. The effect of phytic acid on α-amylase activity was studied in vitro. Rice grains immersed in sterilised deionised water at 14^°C germinated on the fifth day. Phytase activity, detected in the ripening rice grains, increased linearly until the eighth day and reached a maximum on the tenth day. There was a marked decrease in phytate and an increase in inorganic phosphorus accompanying germination. There was a good inverse correlation between the levels of both phytase activity and inorganic phosphorus, and phytate breakdown. α-Amylase activity was detected on the fourth day and increased markedly from the 12th to the 16th day of germination. ATP level increased from the second to the fourth day and slightly decreased from the fourth to the eighth day; it increased rapidly again from the eighth to the 18th day of germination. α-Amylase activity was influenced by both pH and phytic acid concentration in the assay system. At 75 mM phytic acid, α-amylase activity was lowered by 23%, 93% and 52% at pH 4–0, 5–0 and 6–0 respectively. When the enzyme, phytate and Ca²⁺ were incubated together at pH 5–0, the inhibition of α-amylase by phytic acid was markedly decreased by addition of Ca²⁺. The chemical affinity of Ca²⁺ for phytic acid was higher in the reaction at pH 5–0 than in those at pH 4–0 and pH 6–0, and over 98% of Ca²⁺ in the reaction system was precipitated as Ca-phytate.     

Differences in egg morphology of the stored-grain pests Rhyzopertha dominica and Prostephanus truncatus (Coleoptera: Bostrichidae)

Differences in the egg morphology of the invasive stored-product pests Prostephanus truncatus and Rhyzopertha dominica (Coleoptera: Bostrichidae) based on optical and scanning electron microscope (SEM) micrographs are presented. Diagnostic characteristics and changes in external egg appearance during development of the embryo are described. Significant differences between the eggs of these two species were found in their shape, size, surface structures, colour changes during development, and the thickness and number of eggshell layers.     

Fecundity and ability of the parasitoid Lariophagus distinguendus (Hymenoptera: Pteromalidae) to find larvae of the granary weevil Sitophilus granarius (Coleoptera: Curculionidae) in bulk grain

Fecundity and host finding behavior in the storage environment were examined for the parasitoid Lariophagus distinguendus (Förster), a potential agent for biological control of stored-product pest beetles. Larvae of the granary weevil, Sitophilus granarius (L.), in wheat were used as hosts. The fecundity varied considerably among strains of different geographical origin, from 1.3±2.4 to 92.5±23.6 offspring per female parasitoid. Host finding ability was examined in a small acrylic cylinder (about 42 kg wheat), a silo-bin (20.5 t wheat grain), and the flat storage grain bin in a commercial facility (3000 t rye). Experiments in the cylinder and the silo-bin revealed that the number of hosts found by the parasitoids decreases with increasing depth. Moreover, parasitoids were more likely to find hosts in the cylinder than under field storage conditions in a silo-bin. This indicates that the density of parasitoids per unit volume of the grain might be an important factor in determining how deep they penetrate a grain layer. In the silo-bin and the commercial grain store, parasitoids were able to find and parasitize hosts located up to 4 m vertically and horizontally from the release point. The significance of these results with respect to the suitability of L. distinguendus for biological control of the granary weevil is discussed.