Confusum Larvae Research Articles

Effect of nitrogen in combination with elevated temperatures on insects, microbes and organoleptic characteristics of stored currants

In the present study, the effect of nitrogen, applied as a controlled atmosphere treatment on the microbial and entomological loads, as well as on the organoleptic characteristics of stored dried currants (Corinthian raisins, Vitis vinifera L. var. Apyrena), was investigated. Trials were conducted under “real world” conditions, in the nitrogen chambers of a commercial facility, in which nitrogen was introduced by using an incorporated nitrogen generator. Prior to the initiation of the trial, chambers were filled with pallets carrying dried black currants. Subsequently, currants were artificially infected with all life stages of Tribolium confusum, eggs and larvae of Ephestia elutella and adults of Oryzaephilus surinamensis. Currants were exposed for 3 days in nitrogen (O2 concentration <1 %) at two temperature levels, 25 and 38–43 °C. After treatment, insect mortality was recorded and currant samples were collected and forwarded for microbial analysis and determination of their organoleptic characteristics. When nitrogen was applied at 25 °C, high insect mortality levels were noted; however, in most cases there were a number of insects that survived the nitrogen treatment. In contrast, complete control was achieved at 38–43 °C for all insect species and life stages tested, with the exception of T. confusum larvae. Nitrogen application at 25 °C had no effect on total microbial and yeast and mould counts, while both were reduced at 38–43 °C. Sensory attributes of Corinthian currants remained acceptable after nitrogen fumigation, although taste, odour, aroma and overall acceptance were affected by the treatments. Total phenolic as well as 5-hydroxymethylfurfural content increased after nitrogen application at 38–43 °C, while the lower temperature applied had no effect. The results of the present study suggest that nitrogen-based controlled atmosphere at elevated temperature could be a valuable tool for ensuring clean, pest-free, hygienic standards in dried Corinthian currants.

Insecticidal effect of two novel pyrrole derivatives against two major stored product insect species

Several pyrrole compounds exhibit insecticidal properties against a wide range of insect pest species. In the present work, the insecticidal effect of the two new pyrrole derivatives, ethyl 3-(benzylthio)-4,6-dioxo-5-phenyl-2,4,5,6-tetrahydropyrrolo[3,4-c]pyrrole-carboxylate (3i) and isopropyl 3-(benzylthio)-4,6-dioxo-5-phenyl-2,4,5,6-tetrahydropyrrolo[3,4-c]pyrrole-carboxylate (3k) were studied as stored-grain protectants (maize and barley) against two major stored-product insect species, the confused flour beetle, Tribolium confusum Jaquelin du Val (Coleoptera: Tenebrionidae) adults and larvae and the Mediterranean flour moth, Ephestia kuehniella Zeller (Lepidoptera: Pyralidae) larvae at three doses (0.1, 1 and 10 ppm) and five exposure intervals (1, 2, 7, 14 and 21d). All T. confusum adults were dead at all doses on barley treated with 3i after 21d of exposure, while for 3k mortality was >92%. Progeny production was very low (≤1 individual per vial) at all doses for both pyrrole derivatives. Mortality of T. confusum larvae was not complete with any dose of both pyrrole derivatives but it exceeded 96% with 3k at 10 ppm after 21d of exposure on maize. For barley, all exposed larvae were found dead at all doses of both pyrrole derivates after 7d of exposure. Mortality of E. kuehniella larvae was complete at 1 and 10 ppm of 3i and all doses of 3k at 7d of exposure. After 14d of exposure, all E. kuehniella larvae were dead at 0.1 ppm of 3i. The results of the present study indicate that the tested compounds have elevated insecticidal effect against both species tested on certain combinations of dose, exposure interval and type of commodity.

Evaluation of spinetoram and spinosad for control of Prostephanus truncatus, Rhyzopertha dominica, Sitophilus oryzae, and Tribolium confusum on stored grains under laboratory tests

Spinetoram and spinosad have been evaluated against certain stored-product insect pests with success but there are no data available on the comparison of the efficacy of these two novel compounds in stored grains. Thus, laboratory bioassays were conducted to compare spinetoram and spinosad as grain protectants against Prostephanus truncatus (Horn) (Coleoptera: Bostrychidae) adults, Rhyzopertha dominica (F.) (Coleoptera: Bostrychidae) adults, Sitophilus oryzae (L.) (Coleoptera: Curculionidae) adults, and Tribolium confusum Jacquelin du Val (Coleoptera: Tenebrionidae) adults and larvae. Factors such as treatment (1 ppm spinetoram, 1 ppm spinosad, 0.1 ppm spinetoram + 0.9 ppm spinosad, 0.5 ppm spinetoram + 0.5 ppm spinosad, and 0.9 ppm spinetoram + 0.1 ppm spinosad), exposure interval (1, 2, 7, and 14 days), temperature (20, 25, and 30 °C), and commodity (barley, maize, rye, and wheat) were evaluated. Progeny production was assessed after 60 days of exposure. Concerning temperatures, for P. truncatus adults, after 14 days of exposure, all adults were dead in treatments except of the case of spinosad alone at 20 °C. Offspring emergence was completely suppressed in all treatments at 20 and 25 °C. For R. dominica adults, after 7 days of exposure, the overall mortality ranged from 92.8 to 100 %. After 14 days of exposure, all adults were dead in all treatments of the combined use of spinetoram and spinosad at 25 and 30 °C. Progeny production was completely suppressed in all treatments at 30 °C. For S. oryzae adults, after 7 days of exposure, all S. oryzae were died at 25 and 30 °C in all treatments except in the case of spinosad alone. Offspring emergence was very low in all treatments and temperatures except in the case of spinosad alone at 30 °C. For T. confusum adults, after 1, 2, and 7 days of exposure, the overall mortality was low in all treatments and temperatures. Concerning commodities, for R. dominica adults, after 7 and 14 days of exposure, the overall mortality was >97 %. Offspring emergence was very low in all commodities. For S. oryzae adults, after 7 and 14 days of exposure, the overall mortality was increased exceeding 91 % except in the case of spinosad alone 7 days after exposure in barley. Progeny production was high in barley and rye in all treatments. For T. confusum adults, after 7 and 14 days, the overall mortality was low in barley, rye, and wheat. No offspring emergence was recorded in all treatments and commodities. For T. confusum larvae, after 14 days of exposure mortality was further increased, but did not reach 100 % for any of the combinations tested. The results of the present study suggest that the simultaneous application of spinetoram and spinosad was generally equally effective with the use of either spinosad or spinetoram alone. Furthermore, the increase of dose of either compound resulted in the same mortality levels. Thus, no benefits were achieved when spinetoram and spinosad were used simultaneously on grains, regardless of the proportion of each ingredient. These issues should be seriously considered when control measures against stored-product insects are designed.

Insecticidal effect of chlorantraniliprole against major stored-product insect pests in different grain commodities under laboratory tests

Chlorantraniliprole belongs to the chemical group of anthranilic diamides. It has selectivity to beneficial arthropods and low mammalian toxicity. Laboratory bioassays were conducted to assess chlorantraniliprole as a potential grain protectant against Ephestia kuehniella Zeller larvae, Liposcelis bostrychophila Badonnel adults, Rhyzopertha dominica (F.) adults, Sitophilus oryzae (L.) adults and Tribolium confusum Jacquelin du Val adults and larvae. Factors such as dose (0.01, 0.1, 1 and 10 mg chlorantraniliprole kg(-1) grain), exposure interval (7 and 14 days), formulation (chlorantraniliprole WG and chlorantraniliprole SC) and commodity (barley, maize, oats, peeled rice, whole rice and wheat) were evaluated for their impact on the insecticidal activity of chlorantraniliprole. Progeny production was assessed after 45 days of exposure in the case of L. bostrychophila adults and after 60 days of exposure in the case of R. dominica, S. oryzae and T. confusum adults. For L. bostrychophila adults, after 7 days of exposure, mortality was lower in maize and whole rice in comparison with the other commodities. Increase in dose generally increased mortality. Similar trends were also noted after 14 days of exposure. Offspring emergence was higher in maize and whole rice in comparison with the other commodities. For E. kuehniella larvae, after 7 days of exposure, significant differences were noted among the tested commodities. Increase in dose only slightly increased mortality in all commodities. After 14 days of exposure, mortality was further increased, but did not reach 100%. For R. dominica adults, after 7 days of exposure, increase in dose increased mortality significantly. After 14 days of exposure, mortality in barley, maize, whole rice and wheat exceeded 92% at 10 mg chlorantraniliprole kg(-1) grain. Offspring emergence was reduced, but 100% progeny suppression was not achieved. For S. oryzae adults, after 7 days of exposure, mortality was generally low at dose rates of ≤1 mg chlorantraniliprole kg(-1) grain. After 14 days of exposure, 100% mortality was noted in whole rice. For T. confusum adults, after 7 days of exposure, mortality was low. After 14 days of exposure, mortality increased proportionately for all commodities. Most progeny production was noted in oats. For T. confusum larvae, after 7 days of exposure, mortality was generally higher in comparison with adults. After 14 days of exposure, mortality in maize was high. Generally, the two formulations performed alike for all the insects tested. Based on the results of the present work, chlorantraniliprole is effective against major stored-product insect species. However, efficacy depends upon the type of commodity, the dose rate and the exposure interval.

Residual activity of methoprene and novaluron as surface treatments to manage the flour beetles, Tribolium castaneum and Tribolium confusum.

The juvenile hormone analog methoprene, and the chitin synthesis inhibitor novaluron, were evaluated by exposing late-stage larvae of Tribolium castaneum (Herbst) or Tribolium confusum (Jacqueline DuVal) (Coleoptera: Tenebrionidae) to it. The larvae were exposed to it in food material, on concrete, on plywood, and on floor tile. Larvae of T. castaneum were more susceptible than T. confusum larvae to both methoprene and novaluron on all surfaces. A further evaluation was done by exposing adult T. confusum to methoprene and novaluron through food placed on concrete treated with methoprene and novaluron, and then assessing resulting progeny production. The emergence of adults with normal morphology was reduced for both chemicals, with more malformed adults appearing in the methoprene treatment, and fewer adults of any form emerging in the novaluron treatment. The results show direct exposures to larvae, or determining progeny production from exposed adults, are valid methods for assessing the susceptibility of flour beetles to insecticides.

Effect of allylisothiocyanate on Sitophilus oryzae, Tribolium confusum and Plodia interpunctella: Toxicity and effect on insect mitochondria

Allylisothiocyanate is a volatile chemical used for insect fumigation. Because its mode of action is not fully understood, the insecticidal efficacy of AITC was investigated using dry and wet-table applications on the major stored-product insects Sitophilus oryzae (L.), Plodia interpunctella (Hübner), and Tribolium confusum Jacquelin Du Val. The LC 50 values 72 h after fumigation with AITC against S. oryzae adults, P. interpunctella larvae, T. confusum adults and T. confusum larvae were 2.0, 2.2, 3.7, and 4.7 μl L −1 air, respectively. The complete mortality (100%) of all four insect pests was recorded after a 72-h exposure to AITC fumes at an atmospheric concentration of 11.5 μl L −1 air, with results similar to those found with insects exposed to a recommended 5 mg L −1 dose of phosphine. No differences were detected between the effects of AITC and PH 3 on the morphology of mitochondria taken from the midgut and integument epithelial cells of treated T. confusum 3rd instar larvae. Rarefaction and vacuolization of the mitochondrial matrix were evident. The quantity of cristae and density of the electron matrix were also reduced. AITC has potential as a biodegradable and safe insect fumigant. The mitochondria alteration confirms the insecticidal effect of AITC, which may act on the respiratory system.

Residual efficacy of synergized pyrethrin + methoprene aerosol against larvae of Tribolium castaneum and Tribolium confusum (Coleoptera: Tenebrionidae)

Wheat flour and different packaging surfaces (cardboard, flour bag, muslin bag, paper bag, pallet wrap, plastic overwrap, polyethylene) were exposed to aerosol formulations of either 1% active ingredient (AI) pyrethrin (synergized with piperonyl butoxide)+ 33.6% (AI) methoprene or 3% (AI) pyrethrin + 33.6% AI methoprene. The mixture was formulated as specified on the insecticide labels to give a 100 to 1 ratio of active ingredient pyrethrin to methoprene. Residual bioassays were conducted every two weeks for 16 weeks post-exposure to the aerosol by placing four-week-old larvae of the red flour beetle, Tribolium castaneum (Herbst), or the confused flour beetle, Tribolium confusum (Jacqueline duVal), on treated flour or a treated packaging surface with untreated flour added. T. castaneum was clearly the more susceptible of the two species. Less than 2% of T. castaneum larvae exposed to aerosol-treated flour or packaging surfaces emerged as normal adults, regardless of the pyrethrin concentration. Most of the T. castaneum larvae on treated flour did not advance to the pupal stage because they were either developmentally arrested or died as larvae. They were able to develop further on the treated packaging surfaces, but still could not emerge as adults. T. confusum larvae exposed to aerosol-treated flour or packaging surfaces were able to develop to the pupal or adult stage. Emergence of normal-appearing adults from T. confusum larvae exposed on the packaging surfaces treated with 1% pyrethrin + methoprene gradually increased (range of 29.7 ± 2.9 to 49.0 ± 6.7%, depending on the surface), whereas adult emergence of larvae exposed to treated flour peaked at 10 weeks post-exposure. However, when T. confusum was exposed to 3% pyrethrin + methoprene treated flour or packaging surfaces, adult emergence was reduced. Overall there were few significant differences attributable to the individual packaging surfaces.

New Larvicidal Acetogenin from the Red Alga Laurencia papillosa

AbstractA new C15 acetogenin, cyclic enyne (12E)‐cis‐maneonene‐E (1) and (12Z)‐trans‐maneonene‐B (2), together with different secondary metabolites including sesquiterpenoid 2,10‐dibromo‐3‐chloro‐α‐chamigrene (3) and fatty acid aldehydes (4–8) were isolated from the petroleum ether extract of a red alga, identified as Laurencia papillosa, collected from the Saudi Red Sea coast. The L. papillosa crude extract and its active ingredient acetogenin (1) have been evaluated for the ability to control two main economically important pests, the confused flour beetle larvae Tribolium confusum and Culex pipiens mosquito larvae. Compound 1 showed high potential as a natural insecticide against these two pests. In the case of T. confusum larvae, the LD50 values were 0.21 and 0.16% after 6 and 12 days of treatment with crude extract and acetogenin, respectively. On the other hand, the resulting LC50 values of mosquito larvae bioassay were 30.7, 36.9, and 41.8 ppm after 24 h treatment against 2nd, 3rd, and 4th larval instars, respectively. Also, an increase of the insecticidal effects against mosquito larvae was recorded after extending treatment time to 48 h.

Penetration ability of Holepyris sylvanidis into the feeding substrate of its host Tribolium confusum

The bethylid wasp Holepyris sylvanidis (Brethes, 1913) is an antagonist of the confused flour beetle Tribolium confusum Jacquelin du Val 1868, a severe pest in the food processing industry and in grain products, primarily in flour mills and bakeries. Females of the larval ectoparasitoid H. sylvanidis have to detect hosts that feed in different depths inside stored products like flour or grist. This study addresses the questions (1) whether successful host finding by H. sylvanidis is dependent on the location of Tribolium larvae in the substrate and (2) whether the type of substrate affects host finding. In laboratory experiments, T. confusum larvae in a Petri dish accessible to the wasps were placed 1, 2, 4 or 8 cm deep in either fine or coarse ground wholemeal grist of wheat (main particle size: < 0.2 mm or 1.4 – 3 mm) in fifteen replicates per substrate and depth. Parasitoids were released onto the surface of the substrate. Tribolium confusum larvae were not able to leave the Petri dish, however they could be pulled outside into the grist by H. sylvanidis . Within the behavioural sequence of parasitisation, pulling away of host larvae is the typical behaviour preceding oviposition. In order to determine host finding success by the parasitoid, the number of missing host larvae was assessed 2 wks after release of the wasps. In fine grist larvae were attacked down to 4 cm depth; however, larvae placed deeper (8 cm) were not found anymore. In contrast, host larvae in coarse grist were still detected at 8 cm depth. The results suggest that host finding by H. sylvanidis is hindered by decrease in particle size of the substrate. Nevertheless, H. sylvanidis may be considered a promising candidate for biological control of T. confusum larvae feeding in coarse grist and in thin layers of fine grist. Keywords : Holepyris sylvanidis, Tribolium confusum , Biological control, Penetration ability, Host finding

Investigation of the semiochemicals of confused flour beetle Tribolium confusum Jaquelin du Val and grain weevil Sitophilus granarius (L.) in stored wheat grain and flour

This investigation sets out to identify specific volatile compounds from both flour infested with the confused flour beetle, Tribolium confusum and wheat grain infested with the grain weevil, Sitophilus granarius. These volatiles could help to aid the early detection of infestation by these pests. Volatiles by the infestation of these insect pests were entrained and analysed using Solid-Phase Micro-Extraction (SPME) coupled with gas chromatography-mass spectrometry (GCMS). Several volatile compounds were identified specific to T. confusum and S. granarius , including the known semiochemicals of T. confusum. The T. confusum larvae specifically emitted the volatiles 1-octen-3-one, benzeneacetaldehyde and decanal, whilst the adults specifically emitted the volatiles 2-methyl and 2- ethyl-1,3-benzenediols, the known semiochemicals 1-pentadecene, 2-methyl and 2-ethyl-1,4- benzoquinones and a series of yet to be fully identified unsaturated hydrocarbons. Both T. confusum adults and larvae emitted 2-methylbutanal and 2-butanone. Furthermore, four volatiles were identified unique to flour infested by T. confusum , 3-penten-2-one, 3-octanone, 2-octenal and 2-butyl-1-octanol. The S. granarius adults specifically emitted the volatiles 2-methylpropanoic acid and 3-methylbutanoic acid, whilst infested wheat grain produced the following volatile organic compounds, 2-methylfuran, 2- ethylfuran, 2-methyl-1-butanol, 2-ethyl-2-pentenal and 2,5-dimethylpyrazine. We believe these specific volatiles may act as semiochemicals for these insects and could aid in semiochemical monitoring for the early detection of infestation by these insects. Keywords : Tribolium confusum, Sitophilus granarius , GC-MS, SPME, Semiochemicals.

Mortality of Four Stored Product Pests in Stored Wheat When Exposed to Doses of Three Entomopathogenic Nematodes

The insecticidal effect of Heterorhabditis bacteriophora Poinar (Nematoda: Heterorhabditidae), Steinernema carpocapsae (Weiser) (Nematoda: Steinernematidae), and Steinernema feltiae (Filipjev) (Nematoda: Steinernematidae) against Mediterranean flour moth, Ephestia kuehniella (Zeller) (Lepidoptera: Pyralidae) (larvae), lesser grain borer, Rhyzopertha dominica (F.) (Coleoptera: Bostrychidae) (adults), rice weevil, Sitophilus oryzae (L.) (Coleoptera: Curculionidae) (adults), and confused flour beetle, Tribolium confusum Jacquelin du Val (Coleoptera: Tenebrionidae) (adults and larvae) was examined under laboratory conditions in wheat, Triticum aestivum L. The nematodes were applied at the following doses: 0 (control), 100, 500, 1,000, 1,500, 5,000, 10,000, and 20,000 infective juveniles (IJs) per ml, corresponding to 10, 50, 100, 150, 500, 1,000, and 2,000 IJs per insect, and their infectivity was tested at 20 and 30 degrees C after 4 and 8 d of exposure. For E. kuehniella larvae wheat treatments with S. feltiae provided mortality that ranged from 36.7 to 78.3% whereas no mortality was noted in the treatment with S. carpocapsae at 100 IJs per ml at 20 or at 30 degrees C. Also, at 20 degrees C, in wheat treated with H. bacteriophora at 100 IJs per ml, very few larvae were dead. For R. dominica adults, at 20 degrees C, the mortality of adults in wheat treated with S. feltiae and S. carpocapsae did not exceed 23.3 and 41.7%, respectively, at 20,000 IJs per ml, with no significant differences among doses. In the case of S. oryzae adults, the mortality was very low at all doses, and temperatures and did not exceed 9%. Mortality of T. confusum adults did not exceed 17% regardless of the entomopathogenic nematode species tested. In contrast, mortality of T. confusum larvae was notably higher and exceeded 56% in wheat treated with 10,000 or 20,000 IJs per ml of S. feltiae at 20 degrees C. Unlike S. feltiae and S. carpocapsae, the application of H. bacteriophora resulted in lower mortality levels. Generally, the increase of temperature reduced the mortality levels of the T. confusum larvae. In most cases, the efficacy level of the tested entomopathogenic nematode species increased with the dose and decreased with the increase of temperature.

Effectiveness of spinosad combined with diatomaceous earth against different European strains of Tribolium confusum du Val (Coleoptera: Tenebrionidae): Influence of commodity and temperature

Laboratory bioassays were carried out to assess the effects of combining spinosad at 0.01, 0.1 and 0.5 ppm, with the diatomaceous earth (DE) formulation SilicoSec at rates of 150, 300 and 600 ppm, against larvae and adults of three different populations of Tribolium confusum du Val (Coleoptera: Tenebrionidae), originating from different European countries (Greece, Portugal and Denmark). Tests were conducted on wheat and maize at 25 and 30 °C. Survival of T. confusum larvae was assessed after 7 d exposure and survival of adults was assessed after 7 d and 14 d of exposure. At each dose of spinosad, survival of T. confusum individuals decreased as the rate of DE increased. As temperature increased, the efficacy of spinosad and Silicosec applied either alone or in combination also increased. The efficacy of spinosad alone was slightly higher on maize than wheat, while the reverse was noted for all the tested combinations of spinosad with DE as well as in the case of the application of DE alone. The strain from Portugal was always the least susceptible of the three tested. Our study indicates that it is possible to combine low doses of DE (<600 ppm) with spinosad (<1 ppm) to control adults and larvae of T. confusum, especially at temperatures >25 °C.

Effect of Paecilomyces fumosoroseus (Wise) Brown and Smith (Ascomycota: Hypocreales) alone or in combination with diatomaceous earth against Tribolium confusum Jacquelin du Val (Coleoptera: Tenebrionidae) and Ephestia kuehniella Zeller (Lepidoptera: Pyralidae)

Abstract The insecticidal effect of the entomopathogenic fungus Paecilomyces fumosoroseus (Wise) Brown and Smith (Ascomycota: Hypocreales) was evaluated against adults and larvae of the confused flour beetle, Tribolium confusum Jacquelin du Val (Coleoptera: Tenebrionidae) and larvae of the Mediterranean flour moth, Ephestia kuehniella Zeller (Lepidoptera: Pyralidae). The fungus was added in stored wheat at two dose rates, 200 and 400 ppm, at two temperature levels, 20 and 25 °C alone or in combination with the diatomaceous earth formulation SilicoSec ® . Mortality of the exposed individuals was measured after 7, 14 and 21 d of exposure. For both T. confusum adults and larvae, mortality was higher at 20 than at 25 °C. In the case of T. confusum larvae, after 14 d of exposure, mortality on wheat treated with the highest dose of P. fumosoroseus with SilicoSec ® was significantly higher than that of SilicoSec ® or P. fumosoroseus alone. At 20 °C larval mortality was 100% after 21 d of exposure in both fungal doses with SilicoSec ® . In contrast, mortality of T. confusum adults was low and did not exceed 34% in any of the treatments tested. Finally, mortality of E. kuehniella larvae did not exceed 56%, while SilicoSec ® alone caused higher mortality in comparison with the other treatments.

Effectiveness of Metarhizium anisopliae (Metschinkoff) Sorokin applied alone or in combination with diatomaceous earth against Tribolium confusum Du Val larvae: Influence of temperature, relative humidity and type of commodity

Laboratory experiments were carried out in order to assess the insecticidal effect of Metarhizium anisopliae (Metschinkoff) Sorokin (Deuteromycotina: Hyphomycetes) formulations against larvae of Tribolium confusum Du Val (Coleoptera: Tenebrionidae) on flour and wheat. M. anisopliae was applied at three dose rates, of 8×10 6, 8×10 8 and 8×10 10 conidia/kg to either wheat or flour, respectively. Also the wheat/flour was treated with the diatomaceous earth (DE) formulation SilicoSec (Biofa, Germany), at two dose rates, 0.2 and 0.5 g/kg of wheat or flour either alone or in combination with M. anisopliae with each fungal rate. Mortality of T. confusum larvae was assessed 7 days after exposure to the treated substrate. The bioassays were conducted at three temperatures, 20, 25 and 30 °C, and two relative humidity (r.h.) levels, 55% and 75%. Larval mortality was notably varied among treatments, as well among temperature and humidity levels. For both fungus and DE, the increase of temperature increased their effectiveness. On the other hand, the increase of r.h. significantly reduced larval mortality for both M. anisopliae and SilicoSec. Both substances, either alone or in combination, were more effective on wheat than on flour. Also, the addition of 0.5 g of SilicoSec in the fungal preparation, especially at the highest dose rate, increased larval mortality, in comparison with the fungus alone or in combination with 0.2 g of SilicoSec. The results of the present work suggest that, under certain circumstances, the effectiveness of M. anisopliae against T. confusum larvae can be benefitted by the presence of DE.

Initial and delayed mortality of late-instar larvae, pupae, and adults of Tribolium castaneum and Tribolium confusum (Coleoptera: Tenebrionidae) exposed at variable temperatures and time intervals

Late-instar larvae, pupae, and adults of Tribolium castaneum (Herbst), the red flour beetle, or Tribolium confusum (DuVal), the confused flour beetle, were exposed for variable durations at 36–54 °C. Beetles were placed in laboratory ovens set at a baseline of 27 °C, the temperature was increased by 0.1 °C per minute until the target temperature was achieved, and beetles were then held for specified exposure durations. There was no mortality after initial exposure or after a 1-week holding period of any life stage of T. castaneum or T. confusum exposed for 32 h to 36, 39, or 42 °C. At 45 °C, there was no initial mortality of either species exposed for different time intervals except for those exposed for 28 h. However, there was a significant increase in mortality after the 1-week holding period of those beetles exposed initially for at least 16 h to 45 °C. There was a sharp increase in mortality after the initial exposures of 4 h at 48 °C; mortality of T. confusum larvae was 90.0±5.7% but was only 10.0±10.0% for larvae of T. castaneum, and no pupae of either species were dead. All life stages of both species were killed after the initial exposure of 12 h, and 1-week mortality of beetles exposed for 4 and 8 h was generally greater than initial mortality. At 51 and 54 °C, 2- and 1-h exposures, respectively, killed all life stages of each species. Mortality in conditions of gradual temperature increase was less than previous studies with sudden temperature increases.

Feeding stimulants eliciting the probing behavior for Peregrinator blannulipes Montrouzier et Signore (Hemiptera: Ruduviidae) from Tribolium confusum (Jacquelin du Val).

Four fatty acid methyl esters identified in the solvent extract of Tribolium confusum (Jacquelin du Val) larvae as kairomones were individually and collectively tested for probing behavior of Peregrinator biannulipes Montrouzier et Signoret. All identified fatty acid methyl eaters, methyl palmitate, methyl linolate, methyl oleate and methyl stearate, exhibited characterisitic kairomonal probing behavior of P. biannulipe toward the lure. These fatty acid methyl ester were active at 0.2 microg/lure but a synergistic effect was not observed among them. Commercially available C8-C14 even-numbered fatty acid methyl esters that were not detected in the extract of T. confusum larvae also elicited a probing behavior but their activities were weaker than those of four fatty acid methyl ester (C16:0, C18:0, C18:1 and C18:2) identified in the extract. On the other hand, C17 and C19 odd-numbered fatty acid methyl esters did not show any activity at all.

The effect of wheat α‐amylase inhibitors incorporated into wheat‐based artificial diets on development of Sitophilus granarius L., Tribolium confusum Duv., and Ephestia kuehniella Zell

Artificial grain kernels made from ground wheat grain, commercial wheat starch and wheat proteinaceous α‐amylase inhibitors were used as diets for adults of the granary weevil (Sitophilus granarius L). For the confused flour beetle (Tribolium confusum Duv.) and the Mediterranean flour moth (Ephesitia kuehniella Zell.), a friable mixture of the diets was used. The results of feeding trials showed that the survival of S. granarius adults was not correlated with the soluble proteins extracted from wheat and amylolytic activity located in this protein fraction. On the other hand, the weight of dust (the index of feeding intensity) produced during feeding depended on the presence of α‐amylase and trypsin inhibitors in wheat‐based diets. Ephesitia kuehniella larvae did not develop at all on a diet consisting of 50% wheat starch and 50% crude α‐amylase inhibitors from wheat. The same diet lengthened the development time of T. confusum larvae by 15.1 days. These results attest to the existence of a specific native enzymatic apparatus in the alimentary canals of these three grain pests. However, the highly active insect α‐amylase inhibitors appear to have a limited influence on the developmental parameters studied although some reduction of insects populations might be expected.

Initial and Residual Activity of Cidial (Phenthoate) Compared with that of Malathion and Lindane on Insects Affecting Stored Products1

The initial activity of Cidial (phenthoate) (ethyl mercaptophenylacetate O, O -dimethyl phosphorodithioate) was compared with that of lindane and malathion on the following insects affecting stored products: Mediterranean flour moth, Anagasta huehniella (Zeller), larvae; khapra beetle, Trogoderma granarium Everts, larvae; lesser grain borer, Rhyzopertha dominica (F.), adults; saw-toothed grain beetle OryzaePhilus surinamensis (L.), adults; canfused flour beetle, Tribolium confusum Jacqueline duVal, larvae and adults; yellow mealworm, Tenebrio molitor L., larvae and adults; granary weevil, Sitophilus granaries (L.), adults; rice weevil, Sitophilus oriya (L.), adults. Cidial proved to be more effective than the other 2 products. Further tests were conducted to compare the residual activity of the 3 compounds. Cidial sprayed at 8 and 4 ppm on wheat gave almost complete control for at least I year of all species except T. granarium and A. kuehniella (poor control obtained after a few months). When applied at 2 ppm by spraying and at 4 ppm by dusting, this product provided almost complete control of T. confusum larvae and S. oryzae adults for I year and of some of the other species for a few months. Larvac;, used as a dust at 2 and 4 ppm, was fully effective for I year against R. dominica, S. granarius ., and S. oryzae and for a few months against T. confusum larvae; its toxicity to all the other species was limited from the outset. Malathion sprayed at 8 ppm gave almost complete kill of T. confusum larvae and S. oryzae adults for 3 months and of S. granaries for 2 months. None of the insecticides affected the germination of the seeds to any extent for I year after treatment.

Studies of Behavior of the Tribolium Flour Beetles. II. Distributions in Depth of T. Castaneum and T. Confusum in Fractionable Shell Vials

Flour beetle distributions, in depth, were studied with plastic replicas of the shell vials employed in the Chicago Tribolium competition model (10—mm rings of Plexiglas tubing, held together with mending tape). No differences were found between distributions of male and female T. castaneum, both of which were found distributed roughly uniformly throughout fresh flour after 10 hr. Less than 2% of T. castaneum imagoes were found on the surface at that time. In contrast, 88% of male T. confusum, and 33% of females, were still on the surface after 10 hr. Mixed populations became stratified during this same period, with the more slowly entering T. confusum imagoes evidently forcing T. castaneum into the lower halves of the vials. In these mixtures, male T. confusum entered four more rapidly than in the controls, evidently in response to its more rapid conditioning with T. castaneum present. The average depth of T. castaneum imagoes was well below that of T. confusum during the first 4 days, but these population centers crossed each other on day 5. Thereafter T. confusum, shown in part 1 to prefer conditioned flour, predominated below the surface, and T. castaneum, shown in part 1 to prefer fresh four, predominated on the surface. After 26 days at 29°C, 70% relative humidity, T. castaneum had produced three times as many larvae as T. confusum, these being also from two to four times larger than the T. confusum larvae, depending on the flour level examined. The numbers of T. castaneum larvae reaching the prepupal and pupal stages also greatly exceeded those of T. confusum. More T. confusum eggs were found, however, and for both species the egg distributions appeared negatively correlated with the larval distributions. This suggests the importance of egg cannibalism by larvae. The roles that imago and larval behavior may play in determining the outcome of competition, and the relevance of the notion of ecological similarity to the Chicago competition model and to evolutionary theory, are discussed.

Establishment of Tribolium confusum populations after stress by parasitism with Hymenolepis microstoma

The hypothesis that parasitism of Tribolium confusum by the cysticercoids of Hymenolepis microstoma reduces the reproduction potential of T. confusum was tested. Before this measurement (an equilibrium experiment) could be made, it was necessary to estimate the level of infestation of T. confusum (an infestation experiment). Mixed size, large and small T. confusumlarvae were used for this purpose. Each sample consisted of 30 larvae. Three replicates were used. The “small larvae” investigation from this infestation experiment was run concurrently with the next (equilibrium) experiment. The equilibrium experiment, for which the “small larvae” group provided an estimate of level of infestation, used a randomized complete block design. There were three groups, each with an original sample size of 30, and three replicates. This design allowed measurement of the numbers of adults at a given time (when the non-parasitized group was in equilibrium). From the analysis of this measurement, the hypothesis could be accepted or rejected. Four things were done to carry out this experimental design. First, pure stock cultures of T. confusum and H. microstoma were obtained. Second, sexing of T. confusum larvae was made unnecessary by using a large enough sample size to insure that a normal distribution of sexes would result. Third, infestation was accomplished by removing gravid proglottids from adult worms, macerating them on moist filter paper, and then leaving the beetle larvae on the filter paper for 48 hours with no other source of food. Finally, the numbers of larvae, pupae and adults in each of the 24 groups were counted twice weekly for 97 days. The infestation experiments compared large larvae with small larvae and larvae of mixed sizes as to degree and uniformity of infestation. While there were no significant differences between different sizes of larvae in either respect, the small larvae were most uniformly infested and were used concurrently and subsequently in the equilibrium experiments. When the numbers of adults that survived the process of infestation were analyzed, no significant difference was found between parasitized and non-parasitized groups. Any later differences in adult number could not be due to differences in initial numbers of adults, for there were none. When the numbers of adult beetles in each group at the time when the non-parasitized groups were in equilibrium were analyzed, the non-parasitized and parasitized groups were significantly different.