Laboratory evaluation of three novel insecticides inhibiting cuticle formation against some susceptible and resistant stored products beetles

The insecticidal activity of three 1-(2.6-disubstituted-benzoyl)-3-phenylureas was evaluated against a number of susceptible and resistant stored products beetles. The compounds were DU 19111 (1-(2,6-dichlorobenzoyl)-3-(3,4-dichlorophenyl)-urea), PH60-38 (1-(2,6-dichlorobenzoyl)-3-(4-chlorophenyl)-urea), and PH60-40 (1-chlorophenyl)-3-(2,6-difluorobenzoyl)-urea).

PH60-40 was found to be the most effective compound against susceptible strains of Sitophilus granarius, Sitophilus oryzae, Tribolium castaneum and Lasioderma serricorne. All three compounds were ineffective against Stegobium paniceum. A strain of T. castaneum (Kuala Lumpur strain) showing malathion-specific resistance was found to be more susceptible to PH60-40 than its “susceptible” strain. A non-specific resistant strain of T. castaneum (CTC12 strain) showed approximately two times tolerance to PH60-40 compared with the “susceptible” strain.

PH60-40 was shown to have ovicidal properties and also killed young larvae of T. castaneum after short exposure periods. Oviposition was not affected.

Wheat sprayed with an emulsifiable formulation of PH60-40 at 2, 5 or 10 ppm was found to be protected against susceptible T. castaneum, S. granarius and Oryzaephilus surinamensis and against resistant S. oryzae and T. castaneum (Kuala Lumpur strain) following 40 weeks storage at 20°C and 44 weeks storage at 35°C.

Preliminary toxicological data indicates that PH60-40 is of a sufficient order of safety for consideration for grain admixture. The compound is therefore of potential interest as a replacement for the more conventional grain protectants especially in situations where resistance is producing increasing control problems.     

Effectiveness of spinosad as a grain protectant against resistant beetle and psocid pests of stored grain in Australia

Effectiveness of the bacterium-derived insecticide, spinosad, was determined against eight storage pests of Australia. Laboratory experiments were carried out on relevant resistant strains of four beetle and four psocid species, with the aim of determining the potential of spinosad as a new grain protectant. To explore the possibility that spinosad could have delayed effects, we exposed all insects for 14 d initially and then a further 14 and 28 d for psocids and beetles, respectively. Adult insects of each strain were exposed to untreated wheat (control) and wheat treated with spinosad at 0.1, 0.5 and 1 mg [a.i.]/kg of grain, and adult mortality and reduction of progeny were determined. Among beetles, spinosad was most effective against Rhyzopertha dominica (F.), with 100% adult mortality and progeny reduction after 14 d exposure at 1 mg [a.i.]/kg. Efficacy of spinosad was less with Sitophilus oryzae (L.), and least with Tribolium castaneum (Herbst) and Oryzaephilus surinamensis (L.). Against the psocids, spinosad was most effective against Liposcelis entomophila (Enderlein), with 100% adult mortality after 28 d exposure at 1 mg [a.i.]/kg and 92% progeny reduction after 14 d exposure and 100% subsequently. Spinosad was only moderately effective against Liposcelis bostrychophila Badonnel, L. decolor (Pearman) and L. paeta Pearman. Our findings suggest spinosad to be a potential protectant against R. dominica and L. entomophila in stored grain in Australia. This potential use would be in combination with another protectant capable of controlling other members of the pest complex.     

Comparative observations on the activity of purethroids against some susceptible and resistant stored products beetles

The activity of six synthetic pyrethroids, allethrin, bioallethrin, resmethrin, bioresmethrin, cismethrin, tetramethrin and also natural pyrethrins, fenitrothion and malathion was examined against susceptible and resistant adult beetles infesting stored products. Cismethrin applied topically was the most active material, alone or synergized, against susceptible Tribolium castaneum, Lasioderma serricorne or Stegobium paniceum.

Solutions in odourless kerosene applied as direct sprays were an average of 6·9 times more active against susceptible T. castaneum than solutions in mineral oil of pyrethrins, bioresmethrin or cismethrin with or without piperonyl butoxide. The factor of synergism was greater when using mineral oil solutions than when using kerosene solutions. It was thought that the more viscous oil slowed penetration of the insecticide giving longer for detoxification, this being inhibited when the synergist was present.

Applied as a dust on wheat, bioresmethrin plus piperonyl butoxide was more active than malathion and less active than fenitrothion against Oryzaephilus surinamensis or susceptible and malathion resistant T. castaneum. Against Sitophilus granarius and susceptible or malathion resistant S. oryzae, synergized bioresmethrin and cismethrin were more active than either malathion or fenitrothion. Malathion resistant S. oryzae was more easily killed by pyrethroids than the susceptible strain. Synergized bioresmethrin was concluded to be the most suitable pyrethroid for controlling stored products beetles, except Lasioderma serricorne and Stegobium paniceum, and was of value against organophosphorus-resistant strains.     

The early dispersal of insect pests of stored products as indicated by archaeological records

Fossil records of insect pests of stored products, principally Coleoptera, from archaeological sites are discussed with particular reference to the dispersal of pest species by man. Available evidence is biased being largely from Egypt and Roman Britain, and the examination of other samples is much needed. Some taxa e.g. Ptinus fur, Mycetaea hirta and Tenebrio spp. occur in natural habitats in northern and central Europe, and others such as Oryzaephilus surinamensis, Cryptolestes ferrugineus and Tenebroides mauritanicus may have colonised synanthropic situations from natural habitats in Southern Europe. Whether species in the latter group were indigenous to Britain or are Roman or earlier introductions is uncertain. Tribolium confusum and T. castaneum probably originated in the southern hemisphere though the latter species is known from an Egyptian tomb of 1345 B.C. Sitophilus granarius is known from grain of the 9th to 7th centuries B.C. in Israel but there are as yet no records from pre-Roman Europe. Calculations of grain production and the requirements of armies in ancient times should take cognisance of losses during storage which are likely to have exceeded 10%.     

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.     

Bioactivity of Jatropha curcas L. to insect pests of stored products

The objective of this research was to assess insecticidal activity of seeds and derivatives of Jatropha curcas to insect pests of stored grains. Lethal exposure times were estimated for 50 and 95% (LT₅₀ and LT₉₅) of the adults of Sitophilus zeamais and Rhyzorpertha dominica to seeds of four genotypes of J. curcas: Gonçalo, Paraguaçu, Filomena and Bento. Toxicity of powders and aqueous extracts from seeds and pericarps of J. curcas were tested on S. zeamais, R. dominica, Tribolium castaneum and Oryzaephilus surimanensis. A uniform toxic response was observed among the four genotypes for S. zeamais and R. dominica. The powders and aqueous extracts from seeds and pericarps were lethal to S. zeamais, R. dominica, T. castaneum and O. surimanensis. However, insect mortality was higher in the treatments from seeds, compared to the treatments from pericarps.     

Ozone as a management alternative against phosphine-resistant insect pests of stored products

This study was carried out to assess ozone toxicity to 16 populations of Tribolium castaneum (Herbst), 11 populations of Rhyzopertha dominica (F.) and nine populations of Oryzaephilus surinamensis (L.) collected from six regions of Brazil. These populations were also used to test if there is cross-resistance to ozone and phosphine. The relationship between susceptibility to ozone and respiration rate, and associated fitness costs were also evaluated. The instantaneous population growth rate (r_i), CO₂ production and mean insect body mass of each population were measured. Ozone toxicity was determined using time-response bioassays at the dosage rate of 150 ppm ozone in a continuous flow of 2 L min⁻¹. All of the populations were susceptible to ozone and there was no cross-resistance to ozone and phosphine. The populations of each species differed in respiration rate and body mass, but there was no significant association between respiration rate or body mass and susceptibility to ozone, as was also the case for the instantaneous rate of population increase (r_i). As none of the populations showed resistance to ozone, regardless of their susceptibility to phosphine, ozone is a potential alternative for phosphine resistance management in the insect species evaluated in this study.     

Effects of temperature and humidity on development of four pyralid moth pests of stored products

The development of Plodia interpunctella, Ephestia cautella, E. kuehniella and E. elutella was followed carefully at selected temperatures. Infertility prevented successful breeding of the latter two species at 30°C. The first two species bred successfully at 30°C, failed to complete development at 15°C, and, at 20–30°C, completed development more quickly than the other two. All species took longer to develop and survived less well at 25% r.h. than at 70% r.h., and their pupal stages lasted about twice as long as the egg stages at temperatures allowing development of both. At 25°C, the pupal stage lasted about 9 days in P. interpunctella and E. cautella, 11–12 days in E. kuehniella and about 13 days in E. elutella.

In all species other than E. elutella, eggs held at 25°C became more tolerant of cold when aged over 1 day. Younger eggs of P. interpunctella were less tolerant of cold than any eggs of the other species, and were killed outright by holding for 19 days at 15°C.

Stocks of all four species recently collected from the field generally tolerated low r.h. and low temperature a little better than laboratory stocks, but at higher temperatures developed from egg to adult a little more slowly.     

The effect of gamma and microwave irradiation of wheat grain on development parameters of some stored grain pests

Wheat grain was treated with different doses of gamma irradiation or different times of microwaves. Gamma rays (0.05-10 kGy) caused statistically significant differences in soluble protein contents and kernel hardness. Microwave treatment (15-180 s) resulted in some statistically significant changes in moisture and soluble protein contents. Mortality, intensity of feeding, fertility of adults, progeny number and development time of larvae of the granary weevil (Sitophilus granarius L.) on treated grain were observed. On the basis of progeny number and larval development time the coefficient of food value (CFV) was calculated. Some statistical differences were stated in studied parameters, however no one in all calculated coefficients of food values. The same treated grain was also used as a food for larvae of the confused flour beetle (Tribolium confusum Duv.) and Mediterranean flour moth (Ephestia kuehniella Zell.). Mortality of larvae and their development time were studied. Only gamma irradiated wheat grain at the dose 0.1 kGy used as a food for larvae of T. confusum Duv. caused statistically significant extension of development time by 7 days, when comparing to the control food. On the other hand, microwave treatment of wheat grain used as food significantly shorten the development time of larvae in both species.     

Additivity of action of three organophosphorus insecticides to some pests of stored grain, and the use of linear programming to identify minimum cost mixtures

Dust formulations of malathion, pirimiphos methyl and etrimfos and their 1:1 w/w mixtures were bioassayed against six species of stored product beetle pests, including a specifically malathion resistant strain of Tribolium castaneum. The bioassay data was consistent with the hypothesis of additive action of the mixtures against the species tested. The use of linear programming to identify minimum cost insecticide mixtures in cases where the components act additively against a number of target pest species is illustrated     

The effect of grain stability on damage caused by Prostephanus truncatus (Horn) and three other beetle pests of stored maize

In an experiment where grain was presented to Prostephanus truncatus (Horn), Rhyzopertha dominica (F), Sitophilus zeamais Motsch, and Tribolium castaneum (Herbst) in four different ways, it was found that on simulated maize cobs P. truncatus caused much more damage than on loose maize, whereas the reverse was true for the other species. Damage was measured as percentage weight loss over a 6 week period, starting with adult beetles. It is suggested that such differences in the biology of the pests should be taken into account when investigating the inherent susceptibility to infestation of different maize varieties.     

Factors affecting the behaviour of beetle pests in stored grain, with particular reference to the development of lures

This review summarises the published information on the behaviour of beetles in grain bulks that could lead to the identification of additional factors with the potential for enhancing existing lures or developing new ones. The review concentrates mainly on the adult stage of the five beetle pest species Oryzaephilus surinamensis (L.), Sitophilus granarius (L.), Cryptolestes ferrugineus (Stephens), Typhaea stercorea (L.) and Ahasverus advena (Waltl). After an analysis of the grain store environment and the origins of storage pests, particular attention is paid to behaviour associated with beetle movement and distribution within grain bulks, and their response to food and other multi-species attractants. Potential sources of new semiochemicals are identified; as well as the grains themselves, these include attractive volatiles associated with hot spots in grain, mouldy grain, and alternative insect pest habitats such as mammals’ and birds’ nests. It might also be worth looking for new semiochemicals produced during the mass upward movements of beetles from grain often seen following disturbance, although these could be repellents rather than attractants. Other sources of repellent semiochemicals with potential as grain protectants could be predatory and parasitic species of insects. Consideration is given to behavioural influences that may conflict with the intended response to attractive lures; for example, the presence of damaged grains, moisture and temperature gradients in the grain bulk may act as rival attractants, while many species prefer to hide away from bright light. As population densities rise, inter- and intra-specific competition becomes increasingly important. Human activities associated with grain handling, drying, cooling and pest control, as well as the presence of natural enemies and pathogens, all have the potential to affect insect response to a lure. Opportunities for the development of more effective lures are highlighted.     

Laboratory assessment of insecticidal effectiveness of natural zeolite and diatomaceous earth formulations against three stored-product beetle pests

The insecticidal effectiveness of two natural zeolite formulations (Minazel plus and Minazel), applied to wheat at selected rates of 0.25, 0.50 and 0.75 g/kg, and a diatomaceous earth formulation (DE) (Protect-It™), applied at the recommended rates of 0.15 g/kg for Sitophilus oryzae, 0.20 g/kg for Rhyzopertha dominica and 0.30 g/kg for Tribolium castaneum, were tested under laboratory conditions (24 ± 1 °C temperature and 45 ± 5% relative humidity). The highest adult mortality was observed after the longest exposure period of 21 days and 7 days of recovery, when all three zeolite dosage rates and the recommended DE dosage caused 97-100% mortality of S. oryzae and 94-100% of T. castaneum. On the other hand, 100% mortality was not achieved in any test variant involving R. dominica; the highest (about 92%) was detected for DE, while 52% and 79% mortality was achieved with the zeolites at the highest rate of 0.75 g/kg. Progeny reduction by >90% was achieved after 21 days of contact of all three beetle pests with DE-treated wheat, while the same level of reduction was achieved for S. oryzae and T. castaenum only after contact with the highest rate of the zeolite product, Minazel. Thus the two zeolite formulations are comparable to diatomaceous earth in controlling adult S. oryzae, R. dominica and T. castaneum, but only the Minazel formulation could effectively protect wheat from attack by S. oryzae or T. castaneum, and only with a higher rate of application than for the DE formulation.     

A simple curve describing the development pattern of some beetles breeding on stored products

The curve representing the emergence pattern of a generation of Sitophilus zeamais Motsch. developing upon maize was investigated, and it was found that the relationship between the cumulative number of emerged insects (y) and time (t) could be described by the asymptotic model log_ey = a ? bp^t. The model also satisfactorily fitted data for the emergence of S. zeamais breeding on triticale and on barley, Callosobruchus maculatus (F.) breeding on cowpeas and Prostephanus truncatus (Horn) breeding on maize.     

Observations on the pre-harvest infestation of paddy by stored grain pests in Bangladesh

Investigations on the pre-harvest infestation of paddy by stored grain pests were carried out in the Dhaka district of Bangladesh. Paddy heads were drawn from fields located at various distances from rice and paddy stores at different times before harvest, and only Sitotroga cerealella Olivier emerged. No insects emerged from samples collected 12 days before harvest but numbers increased to around one per spikelet the day before harvest. Numbers decreased as the distance from the store increased from 10 to 1440 m.     

Functional properties of protein isolates from soybeans stored under various conditions

Soybeans were stored under 88% relative humidity at 30 °C (adverse condition) for 8 months, under 55% relative humidity at 20 °C (mild condition), cold condition (4 °C), and an uncontrolled ambient garage for 12 months, respectively. Protein isolates were prepared from the soybeans stored under various conditions and periods, and their functional properties were characterized. The protein subunits of the isolates prepared under the adverse conditions were degraded slightly after 3 months, degraded significantly after 6 months, and almost all subunits were degraded completely after 8 months; the relative contents of the protein subunits markedly decreased at the 7th or 8th month and some even approached zero. The relative contents of the 7S and 11S fractions began to decrease markedly at the 5th or 6th month, and the 11S/7S ratios seemed to decrease after the initial 6 months, and then increased at the 7th and 8th month. The nitrogen solubility index (NSI), protein disperse index (PDI), emulsifying activity, emulsifying stability, texture index and thermal stability of soybean protein isolates decreased following the degradation of subunits. The functional properties of protein isolates prepared from the other three conditions (mild, cold and ambient) showed almost no significant changes for 12 months of storage when compared with those of the control.     

华中储粮区浅圆仓储粮害虫防治技术研究

研究了在华中储粮区利用磷化氢防治浅圆仓小麦储粮害虫的效果、磷化氢气体浓度变化规律等,总结了浅圆仓储粮害虫防治的技术要点,为指导浅圆仓储粮害虫防治工作提供技术支撑。     

Bioactivity of Ocimum gratissimum L. oil and two of its constituents against five insect pests attacking stored food products

The fumigant and repellent effects of Ocimum gratissimum L. oil and its constituents, β-(Z)-ocimene and eugenol, were evaluated against adults of Sitophilus oryzae (L.), Tribolium castaneum (Herbst), Oryzaephilus surinamensis (L.), Rhyzopertha dominica (F.) and Callosobruchus chinensis (L.). The fumigant toxicities of the oil and two of its constituents were assessed at four rates (0, 1, 5 and10 μL/L air) in space fumigation, whereas repellence of the oil and eugenol in acetone was evaluated in choice bioassays at five rates (0, 1.0, 2.0, 3.0 and 4.0 μL oil/2 g grain). Results showed that fumigant toxicity and repellence of the oil and its constituents were significantly (P<0.0001) influenced by concentration and time after treatment. At 1 μL/L air, the oil caused 98%, 99% and 100% mortality of R. dominica, O. surinamensis and C. chinensis, respectively, 24 h after treatment, whereas eugenol achieved 79%, 61% and 100% kill of the same insects. β-(Z)-ocimene produced a weaker toxicity with 8%, 11% and 59% mortality of R. dominica, O. surinamensis and C. chinensis, respectively. Except for T. castaneum which was more tolerant, LC₅₀ values for tested insects ranged from 0.20 to 14, 0.01 to 17 and 0.80 to 23 μL/L air 24 h after treatment for O. gratissimum oil, eugenol and β-(Z)-ocimene, respectively. All test insects had percentage repellence (PR) values which ranged from 37.5% to 100% and 45% to 100% for the oil and eugenol, respectively. However, C. chinensis showed a dose-dependent decrease in PR values in the eugenol bioassay with a corresponding dose-dependent mortality on treated grains. Ocimum gratissimum oil and its constituents are potential alternatives to synthetic fumigants in the treatment of durable agricultural products. Successful adoption of plant oils in the protection of food commodities promises an eco-friendly option compatible with international biosafety regulations.     

Evaluation of extracts of neem (Azadirachta indica A. Juss) for the control of some stored product pests

Laboratory investigations on the activity of neem leaf and seed extracts in water or methylated spirit on Callosobruchus maculatus, Sitophilus oryzae and Cylas puncticollis were made at 27 ± 2°C and 65 ± 5% r.h.. Field trials were conducted to determine their effectiveness as protectants of cowpeas and maize in storage at 28 ± 4°C and 82 ± 7% r.h for 5 months.

The results showed that the effectiveness of neem is affected by differences in insect behaviour. The extracts were more active as suppressants of C. maculatus than Sitophilus spp; there was no effect on C. puncticollis. All of the extracts tested resulted in a significant reduction in oviposition, % egg hatch and % adult emergence in C. maculatus and in adult emergence of Sitophilus.

Field trials showed that the extracts mostly gave good protection to cowpea against C. maculatus for 5 months, but only moderate protection to maize against S. zeamais. Seed extracts were more effective than leaf extracts.