Assessing repellency,movement, and mortality of three species of stored product insects after exposure to deltamethrin-incorporated long-lasting polyethylene netting

Long-lasting insecticide-treated netting (LLIN) has begun to be used in agricultural product protection. We investigated the effect of a deltamethrin-incorporated LLIN on three stored product insects, red flour beetle, Tribolium castaneum (Herbst), lesser grain borer, Rhyzopertha dominica (F.), and rice weevil, Sitophilus oryzae (L.). Long-distance repellency was assessed in a wind tunnel for adults of each species, but no repellency was observed. Insect movement and behavior was assessed by observing the movement of adult beetles on treated and untreated netting during a 5 min period for distance traveled, velocity, mobility, and time on each netting type. Among all netting combinations, T. castaneum spent the most time highly mobile, higher velocity, and traveled a greater distance. Sitophilus oryzae and R. dominica spent significantly more time immobile and lower velocity. Efficacy of LLIN was tested by exposing adults for 60 min, removing, and holding with or without food, and monitoring for mortality up to 7 d. All S. oryzae and R. dominica were either affected or dead at all post-exposure times. The number of affected and dead adult T. castaneum combined 7 d after exposure was 42% and 95%, with or without food, respectively, and 52% of affected adults were able to recover when food was present. Overall, LLIN had no repellency or negative effect on insect movement, which increases the probability of lethal exposures of adults from walking on the netting. LLIN can be adopted in existing integrated pest management (IPM) programs for food processing facilities to prevent stored product insect infestations.

     

Insecticidal properties of <Emphasis Type="Italic">Thymus persicus</Emphasis> essential oil against <Emphasis Type="Italic">Tribolium castaneum</Emphasis> and <Emphasis Type="Italic">Sitophilus oryzae</Emphasis>

Red flour beetle Tribolium castaneum (Herbst) and rice weevil Sitophilus oryzae (L.) are considered to be the major insect pests in storage. Essential oils from aromatic plants are recognized as proper alternatives to fumigants. Thymus persicus (Ronniger ex Rech. f.) is one of these plants that have medicinal properties and is indigenous to Iran. The essential oil was obtained from aerial parts of the plant and analyzed by GC and GC–MS. Carvacrol (44.69%) and thymol (11.05%) were the major constituents of the oil extracted. In this experiment, fumigant toxicity of the essential oil was studied against T. castaneum, S. oryzae at 27 ± 1°C and 60 ± 5% RH in dark condition. The adult insects were exposed to the concentrations of 51.9, 111.1, 207.4 and 370.4 μl/l air to estimate median lethal time (LT₅₀) values. The fumigant toxicity was increased in response to increased essential oil concentrations. The LT₅₀ values at the lowest and the highest concentrations tested were ranged from 28.09 to 13.47 h for T. castaneum, and 3.86 to 2.30 h for S. oryzae. It was found that S. oryzae adults were much more susceptible to the oil than T. castaneum. After 24 h of exposure, the LC₅₀ values (95% fiducial limit) for T. castaneum and S. oryzae were estimated to be 236.9 (186.27–292.81) and 3.34 (2.62–4.28) μl/l air, respectively. These results suggest that T. persicus essential oil merits further study as potential fumigant for the management of these stored-product insects.     

The activity of some compounds extracts byAllium on stored-product insectsOryzaephilus surinamensis (L.),Sitophilus oryzae (L.) andTribolium castaneum (Herbst)

The bioactive metabolites of someAllium plants, all exhibiting interesting pharmacological activities, were tested for their attractive/repellent activity against saw-toothed grain beetle,Oryzaephilus surinamensis (L.), rice weevil,Sitophilus oryzae (L.), and rust-red flour beetle,Tribolium castaneum (Herbst), insects infesting the stored-products. The data obtained showed significant repellent effect of the thiosulfinates againstS. oryzae. Part 6 in the series “Chemistry of the genus Allium”.     

Insecticidal activity of (2<Emphasis Type="Italic">n</Emphasis>-octyl<Emphasis Type="Italic">cyclo</Emphasis>prop-1-enyl)-octanoic acid (I) against three Coleopteran stored product insects from <Emphasis Type="Italic">Sterculia foetida</Emphasis> (L.)

The insecticidal activities of the extracts, fractions, and pure compound of Sterculia foetida (L.) seeds were investigated against three major stored product pests, namely, Sitophilus oryzae (L.), Callosobruchus chinensis (L.), and Tribolium castaneum (H.), through contact and fumigation bioassay. Responses varied with test chemicals, insect species, exposure times, and doses individually. The biologically active constituent of the S. foetida seeds was characterized as a cyclopropene fatty acid structurally elucidated as (2n-octylcycloprop-1-enyl)-octanoic acid (I) by spectroscopic analysis. The filter paper application of, (2n-octylcycloprop-1-enyl)-octanoic acid (I) at 0.2 mg/cm² caused 100% mortality to all test insects 2 days after treatment (2 DAT). Among the chromatographic fractions, only the pure hexane-eluted fraction caused 100% mortality at 0.3 mg/cm² to S. oryzae and C. chinensis 2 DAT, while the dose required to obtain the same percentage of mortality with the crude seed extract was 0.6 mg/cm². Under all treatment conditions, T. castaneum exhibited less susceptibility, taking longer than the other insects to show symptoms of toxicity. In terms of fumigant activity, the compounds appeared to be more effective in a vapor form against all the three insects in closed containers compared with open containers. These results suggest that the insecticidal activities of the test compounds were attributable to contact mode of action, although there was also significant fumigant toxicity. The results indicate that the bioactive compound isolated from S. foetida could act as a potent insecticide against S. oryzae, C. chinensis, and T. castaneum populations.     

Occurrence of Arthropods in a Central Italy feed-mill

This paper deals with the Arthropods fauna collected by bait and pheromone traps and categorized during one-year study in a Central Italy feed-mill. A total of 17,919 Arthropods were collected: Arachnida, Isopoda and Insecta. In the Arachnida we found mites, pseudoscorpions and mostly spiders; while in the Isopoda the only species noted wasPorcellio scaber (Latreille); in the Insecta 9 orders and 33 determined species were associated with the feed-mill: Collembola, Thysanura, Dermaptera, Psocoptera, Rhynchota, Lepidoptera, Coleoptera, Diptera and Hymenoptera. In the order Lepidoptera about 55% of the insects were collected. Eight species of stored product Lepidoptera were cuaght:Ephestia kuehniella. Zeller, was the most abundant and wide-spread in the feed-mill (with 8,230 males, 83.53% of Lepidoptera trapped) followed byPlodia interpunctella (Hübner), (1,415 males) andEphestia elutella, (Hübner), (161 males). Coleopterans made up 40.43% of the insects collected.Tribolium confusum J. Du Val, was the most abundant and widespread in the feed-mill (with 5,451 specimens, 75.23% of Coleoptera trapped); less abundant wereOryzaephilus surinamensis (L.) (752 specimens),Tribolium castaneum (Herbst) (359 specimens),Attagenus brunneus Fald. (223 specimens),Stegobium paniceum (L.) (156 specimens) andSitophilus oryzae (L.) (118 specimens). Arthropods infestation level found during this survey were probably directly proportional to the amount of debris present in the departments. Because of these and other peculiarities, the feed-mill staff have to be continually alert to prevent, detect, and control pest problems within their work environment.     

Untersuchungen über die Invasion von Eilarven von vorratsschädlichen Insekten durch verschieden große Poren des Verpackungsmaterials

The diameter of head capsules of egg-larvae of the stored product insect species was measured with an ocular micrometer. The average diameter of head capsules of the egg-larvae in μm:Lasioderma serricorne=142±8,Oryzaephilus surinamensis=257±9,Rhizopertha dominica=126±3,Stegobium paniceum=141±7,Tenebroides mauritanicus=232±9,Tribolium castaneum=151±2,Tribolium confusum=177±4,Plodia interpunctella=177±4. Moreover, the invasion of the egg-larvae ofL. serricorne, O. surinamensis, Rh. dominica, T. castaneum andP. interpunctella through the different sizes of Pores of a cellophane foil (40 μm) was investigated: 100, 125, 150, 175, 275, 200, 225, 250, 275 and 300 μm. These results revealed that the egg-larvae were not able to invade through the pores which were smaller than the diameter of head capsules of the larvae.     

Effects of accumulate dead and alive insects in trap on the capture ofTribolium castaneum (herbst)

In the trapping ofTribolium castaneum (Herbst), the activity of traps baited or not baited with aggregation pheromone 4,8-dimethyldecanal is influenced by the presence in the traps of accumulate specimens trapped. This fact has been observed both in trap containing alive or dead specimens. Interactions in the different substances produced by adults of Red Flour Beetle during their communication relationship are involved in this behaviour.The results obtained in the trials suggests that the presence of alive insects in traps is attractive for other free specimens, but under conditions of overcrowding quinone produced by them regulate population density by counteracting the effect of the aggregation pheromone, causing the insects to disperse or suppressing aggregation behaviour.The presence of dead insects in the traps, baited or not baited with pheromone, can be repellent for other free specimens ofT. castaneum, probably related to the presence of a residual alarm pheromone produced by the specimens before of death.With 10 figures and 3 tables     

A comparative study of monoterpenoids and phenylpropanoids from essential oils against stored grain insects: acute toxins or feeding deterrents

The relationship between the acute toxicity and feeding deterrent activity of ten compounds occurring commonly in essential oils was explored in order to determine whether they are acute toxins or antifeedants against stored-grain pests. Simultaneously, the objective was also to demonstrate the comparative efficacy against three post-harvest stored-grain pests. Thymol, carvacrol, eugenol and trans-anethole were specifically toxic, and linalool was a generalist feeding deterrent against all three species studied. Thymol was most toxic to Tribolium castaneum and Rhyzopertha dominica compared to carvacrol and eugenol but was least toxic to Sitophilus oryzae. Similarly, linalool deterred feeding of S. oryzae (FI₅₀ = 0.025 mg/g of the wafer diet), T. castaneum (FI₅₀ = 0.207 mg/g of the wafer diet) and R. dominica (FI₅₀ = 0.482 mg/g of the wafer diet) at different concentrations; R. dominica beetles required about 20 times the concentration to deter feeding compared to S. oryzae and more than twice compared to T. castaneum. Comparison of toxicity and deterrent activity with respective artificial blends as binary mixtures revealed that synergism was not a generalized phenomenon, and the variations were both species as well as blend specific. Individual compound efficacy correlations were not ascertained, which suggests that artificial blends could be prepared to obtain potential mixtures for substantial control of stored-grain insect pests. The present study also implies that the compounds are mostly acute toxins, and whatever inhibition in feeding was obtained could be due to physiological toxicity rather than any interaction with gustatory receptors.     

Intraspezifische Konkurrenz und Nachkommenproduktion beiSitophilus oryzae (L.) (Coleopt.) undSitotroga cerealella (Oliv.) (Lepid.) in Sorghum-Körnern

Zusammenfassung Die Nachkommenzahl von einem Weibchen vonSitophilus oryzae oderSitotroga cerealella in Sorghum-Körnern nahm mit dem Ansteigen der ursprünglichen Elterndichte ab. Jedoch nahm die Gesamtzahl an Nachkommen beiS. oryzae bis zu einem Maximalwert zu und danach bei weiterem Anstieg der Elterndichte wieder ab (Crowding-Konkurrenz). BeiS. cerealella dagegen tendierte die Nachkommenzahl dazu, von einem Grenzwert ab—unabhängig von der Elterndichte—konstant zu bleiben (Wettkampf-Konkurrenz).

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Intraspezific competition and progeny production inSitophilus oryzae (L.) (Coleopt.) andSitotroga cerealella (Oliv.) (Lepid.) in Sorghum grain

The number of progeny produced per femaleSitophilus oryzae (L.) orSitotroga cerealella (Oliv.), on sorghum grain, decreased as the initial parental density increased. However, the total number of progeny (off-springs) produced inS. oryzae increased to a peak then declined with further increases in parental density (Scramble competition). InS. cerealella the progeny produced tended to be fairly constant once a certain parental density was passed (Contest competition).

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Mit einer Tabelle     

Aus der Vorratsschutz-Arbeit des Pflanzenschutzamtes Berlin. Die Beschau von Pflanzenerzeugnissen bei der Einfuhr in den Jahren 1980 bis 1985

Zusammenfassung Nach einem kurzen Überblick über die gesetzlichen Grundlagen für die Durchführung der Pflanzenbeschau wird über die Ergebnisse der Kontrollmaßnahmen bei der Einfuhr von Pflanzenerzeugnissen (Getreide) nach Berlin (West) berichtet. Von 1980 bis 1985 wurden insgesamt mehr als 700 000 Tonnen Weizen, Braugerste, Roggen, Hafer, Sonnenblumenkerne, Hirse und Erdnüsse aus 12 europäischen, amerikanischen und afrikanischen Ländern eingeführt, davon mehr als 99% allein aus der DDR.Die Importe aus der DDR waren im Durchschnitt zu knapp 1% mit Vorratsschädlingen befallen, und zwar mit dem Reiskäfer (Sitophilus oryzae L.), dem Gemeinen Kornkäfer (Sitophilus granarius L.), Leistenkopfplattkäfern (Cryptolestes spp.), dem Amerikanischen Reismehlkäfer (Tribolium confusum Duv.) und dem Rotbraunen Reismehlkäfer (Tribolium castaneum Hbst.).

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Stored products activities of the plant protection office Berlin. The inspection of imported stored products from 1980 to 1985

A brief survey is given about the legal basis for the inspection of stored products (cereals) imported to Berlin (West). This follows a report about the results of those controls. From 1980 to 1985 more than 700,000 tons of wheat, barley, reye, oats, sunflower seeds, millet and peanuts were imported from 12 European, American and African countries, more than 99% of them from the GDR.On average about 1% of the imports from the GDR were infested by stored product pests; there were rice weevil (Sitophilus oryzae L.), grain weevil (Sitophilus granarius L.), grain beetles (Cryptolestes spp.), confused flour beetle (Tribolium confusum Duv.) and red flour beetle (Tribolium castaneum Hbst.).

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Mit 2 Abbildungen und 3 Tabellen     

Individual and synergistic toxicity of solanaceous glycoalkaloids against two coleopteran stored-product insects

Toxicity of solanaceous glycoalkaloids against stored-grain insects was investigated under laboratory conditions. The total glycoalkaloids (TGAs), α-chaconine and α-solanine from potatoes, Solanum tuberosum L. and α-tomatine from tomatoes, Lycopersicon esculentum Mill. were isolated and tested in this bioassay. Their acute and residual toxicity were assessed against the rust red flour beetle, Tribolium castaneum Herbst (Coleoptera: Tenebrionidae), and the rice weevil, Sitophilus oryzae L. (Coleoptera: Curculionidae). All compounds were tested either individually or as binary mixtures. Results revealed considerable toxicity of the tested glycoalkaloids against the target insects. When adults of S. oryzae were exposed to a dry-film residue of these phytochemicals, the total glycoalkaloids (TGAs) fraction was the most toxic, followed by α-solanine, α-chaconine, and α-tomatine with LC_50s of (38.6 and 22.1), (48.2 and 38.9), (52.00 and 41.6), and (82.3 and 67.00) μg/cm² at 24 and 48 h post-treatment, respectively. The order of toxicity against T. castaneum in a descending order was TGAs > α-chaconine > α-solanine > α-tomatine. All compounds were more toxic when insects were fed grains treated with these phytochemicals (LC_50s of TGAs were 7.4 and 16.2 mg/kg grains at 48 h post-treatment against S. oryzae and T. castaneum, respectively. All compounds, particularly the TGAs, exhibited promising residual toxicity effects. Toxicity of glycoalkaloids was exceeded when tested as binary mixtures indicating their synergistic interaction. The study recommends the use of glycoalkaloids of Solanaceae as biorationals and natural leads to protect stored grains from insect infestation.     

Methodology for determining susceptibility of rough rice to Rhyzopertha dominica and Sitotroga cerealella

Varieties of rough rice, Oryzae sativa (L.), were obtained from different sources in the south-central United States and evaluated for susceptibility to the lesser grain borer, Rhyzopertha dominica (Fab.), and the Angoumois grain moth, Sitotroga cerealella (Olivier), in laboratory studies. Adult R. dominica were fed on the rice varieties for 2 weeks, removed, and assessed for progeny production after an additional 6 weeks. Sitotroga cerealella susceptibility was evaluated by exposing two mating pairs of moths on a particular variety until the adults died. Rhyzopertha dominica parental survival, progeny production, and feeding damage by parental and progeny adults were variable, with survival ranging from 19.4 to 95 %. Rhyzopertha dominica parental feeding damage, progeny production, and progeny feeding damage were all correlated (r = 0.35–0.97, P < 0.001). Parental feeding of R. dominica provided access for neonate larvae to infest the rice hull. All rice varieties supported development of S. cerealella, and the variety Vista, which did not support growth of R. dominica, was one of the most susceptible varieties to S. cerealella. Progeny production of both species was generally correlated, but we observed only two instances of specific correlation for any rice variety. Results show that differences in variety susceptibility to stored product insects and differential susceptibility among species are important factors to consider when developing insect pest management programs for stored rice.     

Bioactivities of <Emphasis Type="Italic">Cocos nucifera</Emphasis> L. (Arecales: Arecaceae) and <Emphasis Type="Italic">Terminalia catappa</Emphasis> L. (Myrtales: Combretaceae) leaf extracts as post-harvest grain protectants against four major stored product pests

Compounds extracted from the leaves of coconut palm, Cocos nucifera L. (Arecales: Arecaceae) and the Indian almond, Terminalia catappa L. (Myrtales: Combretaceae) were assessed as potential grain protectants against four major pests of stored grains, Sitophilus oryzae (L.) (Coleoptera: Curculionidae), Rhyzopertha dominica (F.) (Coleoptera: Bostrychidae), Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae), and Callosobruchus chinensis (L.) (Coleoptera: Bruchidae). The crude leaf extracts and their fractions were obtained by solvent elution and bioassayed in the laboratory, focusing on (a) the duration of protection and (b) their effects on progeny production. Results showed that adults of C. chinensis, S. oryzae, and T. castaneum were equally susceptible to the fumigant toxicity of C. nucifera and T. catappa crude extracts as well as their column eluted fractions. On the contrary, adults of R. dominica showed tolerance to all the extracts tested in both fumigation and contact mode bioassays. Cocos nucifera crude extracts were highly effective in offering long-term protection in residual toxicity trials and along with the crude extracts of T. catappa showed strong repellent properties against the tested species except for R. dominica in a Y-tube olfactometer. Generally, the chromatographic fractions of crude leaf extracts eluted with ethyl acetate were significantly more effective than methanol, chloroform or hexane-eluted fractions. Further, all the tested plant extracts demonstrated a negative impact on several biological parameters such as feeding activity and progeny production of the tested species. These results highlight the potential of C. nucifera and T. catapa extracts as potent insecticides, feeding deterrents and progeny production inhibitors and consequently are suitable for the control of pests in stored commodities.     

Wirkung der Glasur von Reis auf die Vermehrungsfähigkeit von Vorratsschädlingen

The glazing of rice kernels with a coating of glucose and talc has a limited effect against infestation by some stored product insects. In the case of long kernel rice the development of te offspring ofTribolium castaneum, Tribolium confusum, Sitotroga cereallella andOryzaephilus surinamensis is significantly inhibited. In case of round kernel rice, a protecting effect againstTribolium castaneum, Tribolium confusum andOryzaephilus surinamensis is observable; whereasSitophilus granarius, Sitophilus oryzae andRhizopertha dominica have a greater number of progeny on glazed than on unglazed round kernel rice.     

Insektenschäden an Souvenirs aus fernen Ländern

Summary There is reported on insects imported to Hamburg in souvenirs and on insect damages on souvenirs from subtropical and tropical countries:Lyctus brunneus (Steph.) in a North-African stringed instrument, pupal chambers ofDermestes maculatus De Geer andfrischii Kugel. in Indian teatable attacked byLyctus sp., bonboo insects especiallyChlorophorus annularis (F.),Niphonoclea furcata (Bates), andDinoderus minutus (F.),Dinoderus brevis Horn in boxes for Japanese okimono-figures,Bostrychoplites cornutus (0l.) in Southwest-African native carved work and drum,Stegobium paniceum (L.) in a leather cushion,Ceratophaga vastella (Zell.) on Angolan hunting trophy, gnawing at goats skin of native drums from Mombassa by young larves ofD. maculatus, damages on Indian tea table by termites, andPachymerus nucleorum (F.) in a Brasilian palmseed-neckchain. The ability to acclimatization of these insects is discused.     

Rasterelektronenmikroskopische Untersuchungen an von Vorratsschädlingen angegriffenen Verpackungsfolien aus synthetischen Kunststoffen und abgewandelten Naturstoffen

Packaging foils made of cellulose actetate, cellophane, polyethylene, polypropylene, polystyrene, polyester, polyvinyl chloride, attacked byRhizopertha dominica F.,Stegobium paniceum L.,Tribolium castaneum Hbst. and larvae ofPlodia interpunctella Hbn. were examined with the scanning electron microscope (SEM). Because of the destruction marks made by the insects, it is possible to determine with the SEM the side of packaging material which has been attacked by the pests. Due to the shape and position of the mouthparts of the insects the gnawing marks are rather typical for the different species. By means of a standard of comparison it might be possible to determine the family and perhaps the genus or species of the insects involved. The influence of shape and size of the mouthparts as well as the position of the mandibles in relation to the anatomy and to the axis of the body on the gnawing ability of stored-product pests is discussed. The reasons for the insect resistance of packaging materials are discussed (smoothness of the surface, rigidity, thickness).     

Field evidence for the large pine weevil,Hylobius abietis as a vector of Heterobasidion annosum

Mycological analysis of the excrements of adult weevils (Hylobius abietis L.), trapped in the baited pitfall traps in South Bohemia, Czechosovakia, demonstrated the presence of viable spores which suggest a positive role of the weevils as vectors of H. annosum.     

Efficacy of spinosad and methoprene,applied alone or in combination,against six stored-product insect species

Efficacy of the insecticides spinosad and methoprene, applied alone or in combination to wheat, was evaluated against six stored-product insect species, Rhyzopertha dominica, Sitophilus oryzae, S. granarius, Cryptolestes ferrugineus, Oryzaephilus surinamensis, and Liposcelis bostrychophila. The concentrations of the insecticides were 0.1 and 0.5 ppm for spinosad and 1 and 5 ppm for methoprene. Parental mortality of R. dominica was 100% on wheat treated with either rate of spinosad, with no progeny production in any combination treatment. Parental mortality of S. oryzae did not exceed 62%, and progeny production was not reduced by any insecticide treatment. All S. granarius adults exposed on wheat treated with spinosad alone at 0.5 ppm were killed, but parental mortality was reduced when methoprene was added. Progeny production was reduced in treatments containing spinosad. Mortality of adult C. ferrugineus was 97% or greater in treatments containing spinosad, but adult mortality of O. surinamensis and L. bostrychophila was not reduced by insecticide treatments. The specific combinations of spinosad and methoprene evaluated in our study would have no benefit over spinosad used alone for control of any of the six species tested.     

Eine einfache Lichtfalle mit Intervallschaltung zur automatischen Erfassung der Tagesrhythmik des Insektenfluges

Zusammenfassung Es wird eine Lichtfalle mit Zeitintervallschaltung beschrieben. Sie kann automatisch die täglichen Flugzeiten nacht- und dämmerungsaktiver Insekten bestimmen und mit Strom oder Batterie betrieben werden. Jeder Tagesfang kann in 25 Sektionen separiert werden, in denen die gefangenen Insekten sich in einem für die Bestimmung guten Zustand befinden. Der Apparat wurde zur Erfassung der nächtlichen Flugphasen von 9 Apfel-Tortriciden verwendet. Vorliegend wird ein Teil der Ergebnisse fürAdoxophycs orana (Fisch. v. Roesl.),Archips rosanus (L.) undPandemis heparana (Schiff.) mitgeteilt.

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A simple time-controlled light trap for determining the diurnal flight periodicity of insects

A light trap fitted with a time-control device is described. The apparatus can automatically determine the diurnal flight periodicity of night- and dawn-active insects. It can be operated from mains or battery. Each day's catch can be separated into 25 distinct sections, and insects trapped in each of these sections are generally in excellent condition for identification. The apparatus has been used to determine the diurnal flight patterns of nine apple tortricids and initial results are given forAdoxophyes orana (Fisch. v. Roesl.),Archips rosanus (L.) andPandemis heparana (Schiff.).

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Mit 4 Abbildungen     

From lethality to mortality: exploring the “grey area” of knockdown as an efficacy indicator of different insecticides against major storage insects using a lethality index

In the present work, a lethality index was applied for the evaluation of three insecticides with different modes of action, i.e., thiamethoxam, chlorfenapyr and lambda-cyhalothrin, as surface treatment against adults of Sitophilus oryzae (L.), Oryzaephilus surinamensis (L.) and Tribolium confusum Jacquelin du Val, in laboratory bioassays. The insecticides were applied at their highest label dose, while insect knockdown and mortality were evaluated after 1, 3, 5 and 7 days of exposure to the treated surfaces according to the Standardized Lethality Index, by ranking each insect from “0” to “4,” with “0” corresponding to insects moving normally and “4” corresponding to dead individuals. After the end of the exposure, the surviving insects were transferred to clean, untreated dishes and delayed mortality was assessed after an additional period of 1, 3, 5 and 7 days. Based on the results, initial knockdown was high for S. oryzae after exposure to thiamethoxam and lambda-cyhalothrin even after 1 day of exposure, whereas for longer exposures high mortality levels were recorded. In contrast, in the case of chlorfenapyr knockdown was low after 1 day of exposure; however, high mortality levels were noted after 3 and 5 days of exposure. Similar results were noted for O. surinamensis, which was highly susceptible to all three insecticides tested. The most tolerant insect species to the tested insecticides was T. confusum, since a noticeable number of T. confusum adults were still active at the end of the exposure (7 days). Our results indicate that knockdown is most likely to lead to mortality than to recovery, but there were important differences among the three insecticides tested.