The tolerance of immature stages of four stored product moths to methyl bromide

Eggs, last instar larvae, and pupae of the Pyralid moths, Ephestia elutella (Hübner). E. kuehniella Zeller, E. cautella (Walker) and Plodia interpunctella (Hübner) reared at 25°C were exposed to methyl bromide over a wide range of concentrations and times at 10–30°C. One laboratory stock, and one field stock of each species were tested, but differences between stocks of the same species were small.P. interpunctella required lower CT products than the other species for complete kill of each stage. At 10°C, larvae of the field stock of E. cautella required a CT product of 110 mg h/l. for complete control. All stages of all species succumbed to a CT product of 64 mg h/l. at 15°C. When exposed at 20°C or above, pupae aged 0–3 days were more tolerant than other stages. Eggs aged 2 days or over were more tolerant than younger ones.The fertility of survivors from fumigated eggs resembled that of controls, but that of some individuals fumigated as pupae was depressed. For fumigated eggs of E. elutella and P. interpunctella at 15°C, the CT relationship held over concentrations from 4·2 to 10·8 mg/l. and exposure periods from 1 to 16 h.     

The toxicity of phosphine to all developmental stages of thirteen species of stored product beetles

The toxicity of phosphine to all stages of 13 species of stored product beetles was determined using large numbers of test insects which made possible more accurate assessments of mortality. Species tested were Acanthoscelides obtectus, Caryedon serratus, Cryptolestes ferrugineus, C. pusillus, Lasioderma serricorne, Oryzaephilus surinamensis, Ptinus tectus, Rhyzopertha dominica, Sitophilus granarius, S. oryzae, S. zeamais, Tribolium castaneum and Trogoderma granarium. Tests were conducted as appropriate at 10, 15, 25 and 30°C, all at 70% r.h., with concentrations ranging from 0.013 to 2.96 mg/l and exposure times from 1 to 16 days. Sitophilus spp. proved the most tolerant, and in all species other than T. granarium, in which diapausing larvae were the more tolerant in longer exposures, eggs and pupae were the most tolerant stages. Phosphine was most effective at the higher temperatures, whilst long exposures at low concentrations were far more effective than short exposures at high concentrations. The use of phosphine to control these species of stored-product insects will only be effective at 15°C or below if long exposures can be guaranteed.     

Problems in the laboratory investigation of the toxicity of phosphine to stored product insects

The principles to be observed in determining the toxicity of fumigants to stored product insects by means of laboratory experiments, and the circumstances in which these must be modified for phosphine are discussed. After assessing the published literature two kinds of experiment are recommended, to imitate the levels of concentration and exposures used in practice and to limit the exposure period to 8 or 24 hr. For the latter exposures higher concentrations than are used in practice would be required and it might not be possible to achieve complete mortality of test samples. However, this technique should separate the tolerant and susceptible stages of the life cycle and reveal any stages of intermediate susceptibility. The maximum duration of the developmental period of the tolerant stages would represent the minimum exposure period for phosphine desirable in practice provided all the individuals in a tolerant stage developed and reached a susceptible one.     

Insecticidal effect of contact insecticides against stored product beetle populations with different susceptibility to phosphine

In the present work we evaluated the effect of alpha-cypermethrin, pirimiphos-methyl and spinetoram on field and laboratory strains of Sitophilus oryzae (L.) and Oryzaephilus surinamensis (L.) with different susceptibility levels to phosphine. The field populations were collected from storage facilities in Greece and were characterized as resistant by using the Food and Agriculture Organization (FAO) protocol, based on the same protocol, populations were characterized as susceptible to phosphine. The insecticides were applied at three dose rates (0.1, 1 and 10 ppm) on wheat and adult mortality was measured after 7, 14 and 21 days of exposure, while progeny production was assessed 65 days later. For S. oryzae populations, complete control was noted at the highest dose on pirimiphos-methyl and spinetoram, while mortality caused by alpha-cypermethrin was 62 and 100% for the field and laboratory populations, respectively. For O. surinamensis, complete control was recorded at the highest dose only on alpha-cypermethrin for the laboratory population, in contrast with the field population, where mortality was only 32% after 21 days of exposure. In general, the variations among populations were negligible for spinetoram, probably due to the fact that the populations tested were not previously exposed to this active ingredient. In contrast, the lowest susceptibility of the field populations to the other two insecticides can be attributed to the fact that these populations might have been exposed to these active ingredients, while any hypothesis for cross-resistance with phosphine has to be examined more thoroughly.     

Efficacy of heat treatment on phosphine resistant and susceptible populations of stored product insects

In this study we evaluated the efficacy of heat treatment on phosphine resistant and susceptible populations of stored product insects at twenty three different commercial facilities in Greece. Heat treatments were carried out by using special equipment, such as Therminate, TempAir and ThermoNox, applied alone or in combination. The overall temperature range was between 33 and 55 °C and the duration of the heat treatments was between 20 and 39 h. Adults of the lesser grain borer, Rhyzopertha dominica (F.) (Coleoptera: Bostrychidae), and the sawtoothed grain beetle, Oryzaephilus surinamensis (L.) (Coleoptera: Silvanidae), were used in the experiments. The field populations were collected from different storage facilities in Greece and were characterized as resistant populations by using the Detia Degesch Phosphine Tolerance Test Kit. Insect mortality was measured at the termination of each trial. Then, the vials were kept in incubator chambers at 25 °C and 65% relative humidity and 65 d later the progeny production was measured in the treated substrate. In light of our findings, in the vast majority of the cases, complete control was observed for both resistant and susceptible populations at all facilities. In general, in the few cases where survival and progeny production was recorded, there was no specific trend towards specific species or population. Overall, based on the current results, heat treatment can be used by the industry as an alternative method for the control of phosphine-resistant adults of R. dominica and O. surinamensis.     

The toxicity of methyl chloroform to stored product insects

The susceptibility to methyl chloroform of all developmental stages of Cryptolestes ferrugineus, Ephestia kuehniella, Oryzaephilus surinamensis, Rhyzopertha dominica, Sitotroga cerealella, Sitophilus granarius, S. oryzae and Tribolium confusum, diapausing larvae of Ephestia elutella, E. cautella, Plodia interpunctella and Trogoderma granarium and adults of Tribolium castaneum, was studied. Tests were conducted at 15, 20 and 25°C, 55–75% r.h. with concentrations ranging from 25 to 200 mg/l and exposure times from 8 h to 16 days. The toxicity of methyl chloroform was in general similar to that of carbon tetrachloride. Immature stages of R. dominica, S. cerealella and Sitophilus spp, and diapausing larvae of T. granarium, showed the highest levels of tolerance. Methyl chloroform was more effective at the higher temperatures but a concentration of 50 mg/l was below the threshold level for full toxicity against 5 species at 25°C. Depending on the species concerned, the concentration × time (CT) product required for control varied from 3,700 mgh/l at 25°C to 60,000 mgh/l or more at 20°C. At 15°C fewer species were tested but five out of nine survived CT products in the region of 30,000 mgh/l. There was no appreciable difference between the susceptibility of the immature stages of malathion-resistant and susceptible strains of O. surinamensis. Neither were any consistent differences observed between adults of normal susceptibility and those resistant to methyl bromide or phosphine.     

Assessment of Australian Trichogramma species (Hymenoptera: Trichogrammatidae) as control agents of stored product moths

Trichogramma species (T. brassicae, T. pretiosum and T. carverae) were assessed for their suitability as bio-control agents against Ephestia cautella and E. kuehniella which are important pests in food manufacturing and processing facilities in Australia. Parameters examined were longevity, fecundity on eggs of E. kuehniella, walking speed of adult wasps, reaction to moth scales, and host acceptance and host suitability of eggs of E. cautella and E. kuehniella. T. pretiosum and T. carverae performed better than T. brassicae in all traits examined apart from fecundity. T. pretiosum and T. carverae differ mainly in higher fecundity and host acceptance in T. pretiosum, and a better host-finding ability (walking speed, reaction to moth scales) in T. carverae. The suitability of the Trichogramma species for use as control agents is discussed with respect to these results.     

The efficacy and persistence of diatomaceous earths admixed with commodity against four tropical stored product beetle pests

The efficacy and persistence of two commercially available enhanced diatomaceous earth (DE) products (Dryacide^® and Protect-It^®) against four common tropical storage pests (Prostephanus truncatus, Sitophilus zeamais, Callosobruchus maculatus and Acanthoscelides obtectus) were studied when admixed with typical host commodities at different application rates and relative humidities. Persistence of the enhanced DE treatments was considered after 3 and 6 months storage by assessment of both adult mortality and F1 progeny emergence. Both DEs usually increased parental mortality and reduced progeny emergence of all four insect species in comparison with the untreated control at both 50% and 60% r.h., and at all storage periods. However, efficacy was inversely related to duration of storage and over time the host commodity also became less suitable for insect development. Each insect species differed in its susceptibility to the DE treatments, highlighting the need for field application rates to be based upon the entire spectrum of pest species likely to be present during storage.     

Modeling post-fumigation desorption of phosphine in bulk stored grain

Phosphine is a dangerous gas commonly used in fumigations of stored grains throughout the world. Grain that has not fully released the phosphine it absorbed during fumigation may continue to desorb phosphine into the headspace of a shipping container or storage. USOSHA standards for handling phosphine state the acceptable Threshold Limit Value (TLV) of 0.3 ppm. In many cases, during grain transport and handling, the level of phosphine in work environments can exceed the 0.3 ppm TLV which resulted from desorption of phosphine from fumigated grains. It is also important to note that desorbing grain, with low concentrations of phosphine, can facilitate insect resistance. Therefore, it is important to understand the process of phosphine venting and desorption in order to ensure safe handling of fumigated grain. In order to achieve this, the venting and release of phosphine was studied on location in a well-sealed grain silo in Lake Grace, Western Australia. The data set served for verification of a 3D finite element ecosystem model and were compared to the predicted results. Results were calculated using two different fumigant desorption models based on previous literature, i.e., a reversed sorption model and an air-grain equilibrium model. Simulations reproduced accurate trends of desorption but did not accurately reproduce the quantity of fumigant, with 55.5% error for the model based on reversed sorption equations, and 86.3% error for the air-grain equilibrium based model. For both models, additional simulations were conducted to compare the effectiveness of existing grain venting regulations at producing grain that is within post-fumigation safe handling limits. Results revealed that current U.S. standards may be insufficient to guarantee safety based on minimum venting times needed. These results highlight the necessity for continued research into phosphine desorption and the importance for establishing realistic post-fumigation venting guidelines.     

Fumigation toxicity of monoterpenoids to several stored product insects

Twenty naturally occurring monoterpenoids were evaluated in a preliminary fumigation screening test on some important stored-product pest insects, including the rice weevil, Sitophilus oryzae, the red flour beetle, Tribolium castaneum, the sawtoothed grain beetle, Oryzaephilus surinamensis, the house fly, Musca domestica, and the German cockroach, Blattella germanica. Cineole, l-fenchone, and pulegone at 50 μg/ml air caused 100% mortality in all five species tested. Ketone compounds were generally more toxic than other monoterpenoids. Three monoterpenoids, the ketones pulegone, l-fenchone, and the aldehyde perillaldehyde, were selected for further study. They were effective against T. castaneum in the fumigation assay; however the toxicity was relatively low in comparison to dichlorvos. LC₅₀ values of these three monoterpenoids tended to decrease at longer exposure times and higher temperatures. Inclusion of either maize kernels or house fly medium (HFM) increased LC₅₀ values, HFM more so than maize kernels. Monoterpenoids may be suitable as fumigants or vapor-phase insecticides because of their high volatility, fumigation efficacy, and their safety.     

The susceptibility of the immature and adult stages of Sitophilus granarius to phosphine

A concentration of 4 mg/l. of phosphine applied for 8 hr at 25°C permitted a considerable survival of the developmental stages of Sitophilus granarius (L.). Eggs of 3–4 days old were very tolerant and pupae even more so but larvae were very susceptible. A concentration of 1 mg/l. applied for 32 hr completely killed all stages except pupae. The most tolerant eggs were 2–4 days old. At 0·5 mg/l., pupae were again the most tolerant stage and eggs were most tolerant at 1–2 days old. At 0·3 mg/l. or less the majority of eggs were killed during the fifth day of development irrespective of their age at the start of fumigation, but over half were dead by 4 days old at 0·4 mg/l. and about a third survived beyond the sixth day at 0·05 mg/l. It is only at these latter concentrations at these ages that mortality of eggs was clearly related to dosage.

The physiological age range of pupae in samples was more dispersed. Pupae were most tolerant to phosphine at about 32 days old. From 5 to 7 days were needed for complete mortality at concentrations of 0·1–0·05 mg/l.

Adults were very susceptible to phosphine, all being killed by 8 hr at 1 mg/l. which permitted survival of some larvae. Freshly emerged adults were the most tolerant; older adults were very susceptible, at 1 month old being killed by 4 hr at 1 mg/l. and 3 days at 0·01 mg/l. Insects surviving fumigation as larvae or pupae usually laid fewer eggs than controls though their longevity was unaffected. Those surviving fumigation as eggs were not adversely affected. There is a possibility that some individuals surviving, as eggs or pupae, a fumigation causing very high mortality may lay more rapidly than controls.     

Host-preference and parasitic capacity of new candidates of Trichogramma species (Hym.:Trichogrammatidae) against some stored product moths

The host-preference and parasitic capacity of some local Trichogramma spp. (T. bourarachae, T. cordubensis, T. euproctidis and T. cacociae) towards four species of stored product moth eggs were investigated in order to select new candidate species for use in mass rearing and biological control against moths in storages. The efficacy of the Trichogramma spp. was compared with T. evanescens, the common wasp used commercially for biological control. Experiments were carried out by offering a single parasitoid female to eggs of the Indianmeal moth Plodia interpunctella (Hubner), the Mediterranean flour moth Ephestia kuehniella Zeller, the warehouse moth E. elutella (Hubner), and the almond moth, Cadra cautella (Walker) in choice and no-choice assays. Two different choice experiments were used to certify the same conclusion in both methods. The bioassay for host-preference of Trichogramma was carried out by offering a single early female wasp the choice between equal numbers of host eggs on square cards “Petri dish tests “and/or strip cards “strip card tests”. In Petri dish tests, E.kuehniella was a highly acceptable host species for T. bourarachae, T. euproctidis, and T. cacociae wasps while E.elutella and C.cautella eggs were more acceptable for T. evanescens and T.cordubensis, respectively. In strip card tests, E.kuehniella eggs were highly acceptable for T.bourarachae, T.cacociae and T.evanescens. Eggs of E.elutella and C.cautella were more acceptable for T.euproctidis andT. cordubensis, respectively. Significant differences were found among the parasitic capacity of the tested Trichogramma spp.: T. borarachae showed a good parasitic potential against S.cerealella and E. kuehniella; T.evanescens and T. cacociae against S.cerealella; T. cordubensis against S.cerealella and P. interpunctella and T. euproctidis against P. interpunctella. All tested wasps had a propensity to superparasitize the host eggs. T. cordubensis, T. euproctidis and T. borarachae showed promise for further investigation into selecting new biological control agents against some stored product lepidopterous pests.     

Chlorine dioxide fumigation to control stored product insects in rice stored in a room

Gaseous chlorine dioxide (ClO₂) was applied to fumigate larvae and adult stages of Plodia interpunctella (Hübner) (Lepidoptera: Pyralidae) and Sitophilus zeamais (Motschulsky) in rice grain bags stored in a grain storage room. It was confirmed that the fumigation efficiency varied depending on the storage position and insect life stage and species. The fumigation effect was the highest on the surface of the grain bag and lowest on the middle of the outer position on the grain storage bag. The mortality of adult P. interpunctella, 5 days after ClO₂ fumigation, reached 100% regardless of their position, whereas that of the larva P. interpunctella and adult S. zeamais varied depending on their positions. The mortalities in the outer portions of the grain bag were the highest, followed by that at the top of the grain bag. The ClO₂ residue of treated rice were lower than that accepted by international standards. To achieve fumigation effectiveness which similar with lab scale experiment, more researches which are related to infiltration or circulation of gaseous ClO₂ are needed.     

磷化氢对六种甲虫的抗性品系和敏感品系的发育未成熟的毒力与防治关系

<正> 试验用谷象、米象、谷蠹、锈赤扁谷盗、锯谷盗和赤拟谷盗6个品种甲虫的13个品系(有的叫小种)的各个发育期,在15℃和25℃温度下,置于密闭的熏蒸箱内熏蒸。其中已知7个品系的成虫对磷化氢抗性。结果发现除抗品系的成虫具有抗性外,其发育未成熟期即卵、幼虫、和蛹也具有抗性,在抗性品系甲虫的整个生活史中,抗性最大的是蛹。锯谷盗、赤拟谷盗、锈赤扁谷盗和谷蠹的敏感品系各发育期,在15℃和25℃温度下,密闭4天,可以控制,虽然其中后两者在15℃时的磷化氢剂量要高达2克/米~3,但相     

Control of stored product pests by ionizing radiation

Food irradiation for prevention of food-borne illness and disinfestation of commodities of pests is increasing in a number of countries. The goal of this review is to analyze the literature and current use of irradiation to control stored product pests and suggest research to optimize its potential. Doses to prevent reproduction of stored product pests range from 0.05 kGy for Tenebrio molitor L. to 0.45 kGy for Sitotroga cereallela (Olivier). Small but increasing amounts of grains and pulses are being irradiated in the world today especially in Asia. At least 33 countries permit irradiation of some stored products with 14 countries permitting it for all stored products. Ways in which stored product irradiation research and application may influence other uses of irradiation technology are also discussed. Deactivation of weed seeds might be an area of stored product phytosanitation where irradiation would have an advantage over other measures.     

辽宁地区储粮害虫对磷化氢抗性测定及对策研究

运用联合国粮农组织(FAO)1975年推荐的测定储粮害虫磷化氢抗性的方法,对采自辽宁大连地区的玉米象和赤拟谷盗等2个品种7个品系的储粮害虫进行了抗性测定.试验结果表明,大连地区玉米象和赤拟谷盗均为低抗品系.通过对试验结果进行分析,提出延缓害虫对磷化氢抗性发展的相应对策,为今后科学防治储粮害虫提供了一定的参考依据.     

Effect of cultural factors on the development of four stored-product moths

Survival and developmental rate of Ephestia cautella, E. kuehniella, E. elutella and Plodia interpunctella in a constant food volume were improved by rearing in cultures of greater cross-sectional area, but not by increasing the depth of the food bulk in cultures of constant cross-sectional area. In cultures of similar shape and size, increase of the population density decreased percentage survival, at first gradually and then more sharply. Ephestia cautella was more sensitive than other species to crowding, and produced fewer moths in each type of culture. Development was delayed at population densities depressing percentage survival to 75% or below. In cultures of E. cautella reared at population densities of 4 or more larvae per cm², two peaks of emergence were observed, the second following the first by about 3 weeks and comprising up to 20% of the total population.Metabolic heating which was observed in densely populated 14 cm diameter cultures of all 4 species, raised the temperature by 4° to 7°C above ambient during the latter half of larval development. The highest temperatures were recorded near the centre of the culture at the food surface. Two temperature peaks were observed in cultures of E. kuehniella, the second corresponding with a downward movement of larvae. Adults emerging from cultures of E. kuehniella, in which maximum temperatures exceeded 30°C, proved fertile. The rapid temperature changes in cultures influenced humidity at the food surface.The temperature rise measured in cultures was proportional over a limited range to the logarithm of the initial number of insects added.When a thousand or more insects were present in cultures 14 cm in diameter, E. cautella produced a greater temperature rise than other species.     

Susceptibility of thirteen stored product beetles to entanglement by Trogoderma hastisetae

Factors affecting the susceptibility of adults of 13 and larvae of 2 species of stored product beetles to entanglement by Trogoderma larval hastisetae were studied. The length, diameter, shape, density, and angle of the test insects' setae probably affected susceptibility. The setae on the hindwings of Trogoderma adults were susceptible to permanent hastisetal attachment which prevented normal closure of elytra over the hindwings. Sitophilus oryzae (L) and Cryptolestes pusillus (Schönherr) were susceptible, with 93 and 83% mortality, respectively, at the end of 72 hr exposure. Tribolium castaneum (Herbst), T. confusum (duVal), Gibbium psylloides (Czenpinski), and Tenebroides mauritanicus (L.) resisted hastisetal attachment. Scanning electron micrographs revealed the attachments of heads of hastisetae to setae of several beetles exposed to larval Trogoderma.