Persistence and activity towards Sitophilus zeamais (Coleoptera: Curculionidae) of pirimiphos-methyl sprayed at different temperatures on maize

The air temperature in storage units in tropical areas frequently exceeds 50°C during the warmest periods of the day. Since protectant insecticides are sprayed on grains under these conditions, such high temperatures may interfere with the insecticidal activity. To assess this possibility we sprayed maize grains with pirimiphos-methyl 500 EC (0.8 ml c.p./l and 1.5 l/t) at different temperatures (25°C, 30°C, 35°C, 40°C, 45°C, and 50°C) and 55% r.h. The grains were then maintained at 27±1°C and 55±5% r.h. throughout the experiment which lasted 90 days. Residues of pirimiphos-methyl on the sprayed grains were analyzed every 30 days. Grain samples were assessed every 15 days after the insecticide spraying for their effect on the maize weevil, Sitophilus zeamais Motschulsky (Coleoptera: Curculionidae). Insect mortality was evaluated after 24 and 48 h of exposure to the treated grain. The level of pirimiphos-methyl residue on maize grains decreased with an increase in storage period and air temperature during the insecticide spraying (varying from 11.0±0.1 to 1.1±0.1 ppm, corresponding to the residue levels at 25°C on the day of the spraying and after spraying at 50°C and 90 days of storage). The same trend was observed for mortality of the maize weevil, which dropped from 95.4±13.3% to 2.5±2.5% after 90 days storage after insecticide spraying at 50°C. These results indicate that temperature at spraying can affect insecticide persistence and activity during storage.     

Insect infestation in stored animal products

Published information about insect pest infestation in dried or preserved animal products comprising food items like dried fish and milk powder and non-food materials such as hides and skins, silkworm cocoons, wool and woollen materials, honeybee combs, fishmeal and museum collections/exhibits and control measures has been summarised in this review. Beetle and moth pests belonging to the Dermestidae and Tineidae, respectively, attack the animal products, during the processing or manufacturing stage as well as in storage. The insects cause considerable loss or damage to the commodity in terms of quantity, quality and market value. Silk, apiculture and leather industries are particularly affected by the pests. Data on the extent of losses due to insect pests in various preserved animal products are lacking. Insect control measures in these products differ depending on the conditions of storage or processing and the relevant cost factor. Phosphine fumigation plays an important role in insect pest elimination in the majority of the stored animal products. For disinfesting museum objects and honeycombs, freezing (for artefacts) or modified atmosphere application of CO₂ or nitrogen is preferred. Commodities such as woollen materials, dried fish, fishmeal and feeds containing animal products and their storage premises are sometimes treated with residual contact insecticides such as deltamethrin, pirimiphos-methyl, permethrin and synergised pyrethrins. For protecting animal products, especially dried fish, different countries have examined alternatives including plant extracts and vegetable oils.The need for detailed studies on (i) fumigation with alternatives to methyl bromide such as sulphuryl fluoride, ethyl formate and ozone, (ii) disinfestation methods involving the active principles from natural products and (iii) exploitation of insect traps for pest management in museums has been highlighted.     

Potential for using semiochemicals to protect stored products from insect infestation

Methods of using semiochemicals to control insect pests of stored grain are reviewed. The application of semiochemicals for pest control in grain storage is in its infancy, so each method is considered using some key examples of successful use on a commercial scale against pests from other areas of agriculture, followed by a summary of any laboratory and pilot studies in the stored products area. The benefits and disadvantages of each method for protecting stored products are assessed. The review concludes with a list of approaches that are considered to have potential for improving the protection of stored products. These include attractants for mass trapping, repellents as protective bands and flushing agents, synchronised use of attractants and repellents to manoeuvre pests away from stored grain, and semiochemicals to enhance the effectiveness of biocontrol agents such as parasitoids.     

Spinosad: A new natural product for stored grain protection

Spinosad is a reduced-risk insecticide derived by fermentation from the soil actinomycete, Saccharopolyspora spinosa Mertz & Yao. Spinosad is currently registered in several countries as a grain protectant at a maximum labeled use rate of 1 ppm (1 mg a.i./kg of grain) and with the Maximum Residue Level (MRL) or tolerance on grains set at 1 or 1.5 ppm. Global launch of spinosad as a grain protectant is expected in the near future, pending final acceptance of international residue tolerances for spinosad by major grain importing and exporting countries. Spinosad effectively controls economically important beetle and moth pests associated with stored grain and is also effective against certain psocid species. Spinosad provides grain protection through control of adult and/or immature life stages of pest insects. The pest spectrum of spinosad under commercial grain storage conditions is still being defined, but it is clear from available laboratory and field evaluations on various grains that the lesser grain borer, Rhyzopertha dominica (F.); larger grain borer, Prostephanus truncatus (Horn); rusty grain beetle, Cryptolestes ferrugineus (Stephens); flat grain beetle, Cryptolestes pusillus (Schönherr); red flour beetle, Tribolium castaneum (Herbst); confused flour beetle, Tribolium confusum Jacquelin du Val; Indian meal moth, Plodia interpunctella (Hübner); rice moth, Corcyra cephalonica (Stainton); Angoumois grain moth, Sitotroga cerealella (Olivier); almond moth, Cadra cautella Walker; and the psocid species Lepinotus reticulatus Enderlein and Liposcelis entomophila (Enderlein) are susceptible to spinosad and complete control is to be expected. Other pest species such as the maize weevil, Sitophilus zeamais Motchulsky; rice weevil, Sitophilus oryzae (L.); and sawtoothed grain beetle, Oryzaephilus surinamensis (L.) are susceptible to spinosad to varying degrees, but their overall level of control remains to be verified under commercial grain storage conditions. Spinosad residues are highly stable on grains stored in bins, with a length of protection ranging from 6 months to 2 years. Numerous factors have been shown to impact the overall performance of spinosad, including insect pest species, pest life stage, grain type, grain variety, and formulation type. Spinosad possesses a unique mode of action in insects and controls insect strains resistant to other grain protectants. When launched globally, spinosad will represent a valuable new addition to the limited arsenal of grain protectants and can positively impact global food security. Its combination of high efficacy, broad insect pest spectrum, low mammalian toxicity, and sound environmental profile is unique among existing products currently used for stored-grain protection.     

Metals in mandibles of stored product insects: do zinc and manganese enhance the ability of larvae to infest seeds?

Although high concentrations of zinc and manganese were found in mandibles of insect larvae that bore into seeds, these metals were not detected in mandibles of insect larvae that attack previously damaged seeds. Metals were present in the larval mandibles of a lepidopteran, the Angoumois grain moth (Sitotroga cerealella), and eight coleopterans, the lesser grain borer (Rhyzopertha dominica), cigarette beetle (Lasioderma serricorne), drugstore beetle (Stegobium paniceum), spider beetle (Gibbium aequinoctiale), warehouse beetle (Trogoderma variabile), cadelle (Tenebroides mauritanicus), larger black flour beetle (Cynaeus angustus), and cowpea weevil (Callosobruchus maculatus). Larvae of these species can chew into seeds. Larvae of six other coleopterans, the varied carpet beetle (Anthrenus verbasci), sawtoothed grain beetle (Oryzaephilus surinamensis), rusty grain beetle (Cryptolestes ferrugineus), red flour beetle (Tribolium castaneum), longheaded flour beetle (Latheticus oryzae), and granary weevil (Sitophilus granarius) have little if any ability to chew into seeds, and did not have metal in their mandibles. Larvae of the granary weevil hatch and feed within seeds that were penetrated previously during egg deposition by adults. However, newly hatched larvae of the cowpea weevil and the Angoumois grain moth have to bore through the seed coat before they begin feeding, and they have mandibles with high concentrations of zinc. These data support the hypothesis that deposition of zinc and/or manganese in larval mandibles enhances the larva's ability to penetrate seeds.     

唇形科植物在储粮害虫防治中的应用

总结了应用唇形科植物粗提物、活性成分、精油等对储粮害虫进行防治的研究进展,并指明了今后防治储粮害虫的发展方向。     

Olfactory host location in the rusty grain beetle parasitoid Cephalonomia waterstoni (Gahan) (Hymenoptera: Bethylidae)

Parasitoids can suppress populations of their host and thus play a primary role in Integrated Pest Management. The parasitic wasp Cephalonomia waterstoni Gahan (Hymenoptera: Bethylidae) is a natural enemy of the rusty grain beetle Cryptolestes ferrugineus (Stephens) (Coleoptera: Cucujidae). In the stored product environment, stimuli deriving from plant products, damaged plant products and hosts might be important for host location by the parasitoids. We tested the response of female parasitoids to odours deriving from infested and uninfested plant products, the grain dust produced by feeding primary pests, and various life stages of the rusty grain beetle. The olfactory response of C. waterstoni was found to be strongly elicited both by chemicals emitted by the dust, adult C. waterstoni and C. waterstoni third and fourth instar larvae. Our findings may contribute towards biological control of C. ferrugineus and the chemical ecology of olfactory host location by C. waterstoni.     

Laboratory studies on parasitism of Plodia interpunctella (Hübner) (Lepidoptera: Pyralidae) by two species of Trichogramma Westwood (Hymenoptera: Trichogrammatidae) in different grains,and evaluation of traps for their monitoring

The aim of the present study was to evaluate two species of egg parasitoids under laboratory conditions for biological control of the Indian meal moth Plodia interpunctella, an emerging stored product pest in bulk grain. Trichogramma evanescens proved to be a better candidate for biological control compared to T. cacoeciae as it accepted and parasitised a higher percentage of Indian meal moth eggs. Consequently the foraging of T. evanescens was studied in detail. Preferred oviposition sites on individual seeds by P. interpunctella are the germ region and the raphe. Moth eggs were parasitised at both regions. P. interpunctella eggs received higher parasitism at the germ region compared to the raphe. In stored grain and rice, P. interpunctella eggs can be found in the upper 8 cm of the bulk. Foraging parasitoids were shown to enter up to this depth into wheat, oats, and paella and Basmati rice. Wheat and oats were found most suitable for foraging, as larger numbers of T. evanescens were able to reach this depth as compared to the rice varieties. Among different traps, i.e. probe traps, cone traps and wiregauze tubes with adhesive cardboard, cone traps proved best for monitoring T. evanescens. These cone traps as well as the wiregauze tubes were used for the first time to monitor Trichogramma spp. in bulk grain. Cone traps recorded T. evanescens both when placed on the grain surface and in 5 cm depth within the grain irrespective of the release technique of Trichogramma, i.e. release from cardboard cards or sprinkling loose parasitised eggs. The potential for release of Trichogramma spp. within an integrated control strategy for the Indian meal moth in bulk stored grain and rice is discussed.