Laboratory evaluation of diatomaceous earth deposits mined from several locations in central and southeastern Europe as potential protectants against coleopteran grain pests

Diatomaceous earth (DE) deposits from regions of central and southeastern Europe were evaluated for their insecticidal efficacy against Sitophilus oryzae (L.) (Coleoptera: Curculionidae), Rhyzopertha dominica (F.) (Coleoptera: Bostrychidae) and Tribolium confusum Jacquelin du Val (Coleoptera: Tenebrionidae) in comparison with the commercially available DE formulation SilicoSec. The effects of temperature, RH, grain commodity (wheat, barley, maize, rice), application method (spraying vs. dusting) were evaluated. FYROM, a DE from the Former Yugoslavian Republic of Macedonia, was the most effective of the DE deposits for grain treatment, whereas the least effective was from Greece (named Crete). However, for surface treatment, Slovenia was the most effective followed by Elassona 1 and Begora. Increase of temperature increased DE efficacy, while the reverse was noted with the increase of RH. Furthermore, the DEs were more effective in barley or wheat than in maize or rice. Neither the mined DEs nor SilicoSec were able to suppress progeny production of the tested species after previous exposure on the treated commodities. Generally, dust application of DEs was more efficacious than spraying against S. oryzae and T. confusum. However, spraying of wheat significantly reduced the bulk density (test weight) compared to dusting. For surface treatment, after 1 d of exposure, Slovenia was the most effective of the mined DEs followed by Elassona 1 and Begora, whereas after 6 d of exposure the mortality was almost complete (>99%) with all three DEs. More than 6 d of exposure were required for an effective control of T. confusum adults with the remainder of the mined DEs.     

Persistence and efficacy of spinosad on wheat,maize and barley grains against four major stored product pests

The insecticidal and residual effect of spinosad on wheat, maize and barley grain was evaluated in the laboratory against adults of Sitophilus oryzae (F.) (Coleoptera: Curculionidae), Rhyzopertha dominica (F.) (Coleoptera: Bostrychidae), Tribolium confusum (DuVal) (Coleoptera: Tenebrionidae), Cryptolestes ferrugineus (Stephens) (Coleoptera: Laemophloeidae) as well as against larvae of T. confusum. Spinosad was applied as a solution to 2 kg lots of each commodity at three concentrations, 0.1, 0.5 and 1 ppm, and the treated grain quantities were kept at 25 °C and 65% RH. Samples were taken from each concentration-commodity combination at the day of storage and every 30 d for 6 consecutive months (6 bioassays). The test species were exposed for 14 d to the samples and mortality and reproduction were assessed over this exposure interval. With the exception of T. confusum, 1 ppm of spinosad was highly effective against the remainder of the tested species and provided protection for a period of storage at least 4 months. Although in general, spinosad performance was not very much affected by the grain type, efficacy on maize was less stable over the 6-month period of storage and declined sooner compared to the other commodities. Spinosad almost suppressed progeny production of R. dominica during the storage period, but did not suppress progeny of the other species, since progeny were recorded even 30 d post application especially with the lowest of the tested concentrations. The results of this study indicated that spinosad may provide suitable protection for 6 months against S. oryzae or R. dominica, but is not suitable for long-term protection against T. confusum or C. ferrugineus.     

Insecticidal efficacy of phosphine fumigation at low pressure against major stored-product insect species in a commercial dried fig processing facility

We investigated the application of phosphine at low pressure for various exposure durations against major stored-product insects in a commercial dried fig processing facility in Central Greece. Trials were carried out inside a chamber, in which phosphine, in the form of aluminium phosphide pellets, was introduced with the use of a phosphine generator. The generator unit was also equipped with a vacuum pump to achieve low pressure inside the chamber. The chamber was filled with pallets with boxes containing figs. The insects tested were Tribolium confusum (all life stages), Ephestia elutella (eggs and larvae), Sitophilus oryzae (adults), Sitophilus granarius (adults), Rhyzopertha dominica (adults), Oryzaephilus surinamensis (adults) and Prostephanus truncatus (adults). Moreover, wheat grains containing immature stages of S. oryzae were also used. All insect-life stage combinations were exposed to phosphine at low pressure for 18, 48 and 72 h. In most cases, significant differences in mortality of insects treated with phosphine at low pressure compared to the control treatments were recorded. However, complete control (100%) was recorded only in the case of O. surinamensis adults and T. confusum larvae after exposure for 48 and 72 h, respectively. We conclude that the combined application of phosphine and low pressure at short exposure durations (up to 72 h) cannot provide sufficient control at least against the stored-product insect species and life stages tested in the present study.     

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.     

Bioassays with diatomaceous earth formulations: Effect of species co-occurrence,size of vials and application technique

Two series of laboratory bioassays were carried out in order to evaluate the effect of the simultaneous presence of two insect species inside the experimental vials and the effect of different sizes (50, 65, 90, 145 mm in diameter) of experimental vials on the efficacy of diatomaceous earth (DE) formulations as wheat (Triticum durum Desf.) protectants. Three DE formulations were tested; Insecto, SilicoSec and one DE enhanced with pyrethrum, PyriSec. In a third series of bioassays the influence of application technique of DE formulations in wheat and maize (Zea mays L.) on their insecticidal efficacy was also evaluated in the laboratory. Two DE formulations were tested; SilicoSec and Protect-It. The application technique was based on the duration of admixing (0.5 or 3 min) and surface treatment (without admixing) of DE formulations in grain. In all series of bioassays three species were tested; Sitophilus oryzae (L.) (Coleoptera: Curculionidae), Rhyzopertha dominica (F.) (Coleoptera: Bostrychidae) and Tribolium confusum Jacquelin du Val (Coleoptera: Tenebrionidae). Significant differences were noted in mortality levels of the tested species among the three DE formulations and among doses for the simultaneous presence of two insect species in all combinations and the different size of vials. In contrast, no significant differences were found in the mortality levels among the adult densities of any of the insects tested. The progeny production was low for all tested species. The increase of diameter of vials used in the bioassays decreased the mortality of S. oryzae and T. confusum adults significantly whereas no significant differences were noted for R. dominica adults. The increase of dose and exposure interval reduced differences of R. dominica adult mortality in admixture durations in the case of wheat. For S. oryzae, no significant differences in adult mortality in maize were found among admixture durations while significant differences were detected in wheat.     

Insecticidal efficacy of two pirimiphos-methyl formulations for the control of three stored-product beetle species: Effect of commodity

Laboratory bioassays were conducted to evaluate the insecticidal effect of two pirimiphos-methyl formulations, an emulsifiable concentrate (EC) and a capsule suspension (CS) against adults of Sitophilus oryzae, Rhyzopertha dominica and Tribolium confusum in wheat, maize and rice. Pirimiphos-methyl was applied at two dose rates, 2 and 4 ppm, and adult mortality was measured after 2, 7, 14 and 21 days of exposure in the treated commodity. Progeny production was assessed 65 d after the removal of the parental adults. S. oryzae adult survival was significantly higher in rice than in wheat and maize, whereas T. confusum mortality was significantly higher in maize than in the other grains. From the species tested, the most susceptible species was S. oryzae, for which mortality reached 100% after 7 days of exposure in treated wheat and maize, followed by T. confusum and R. dominica. Progeny production was significantly suppressed by pirimiphos-methyl in the case of S. oryzae, but not in the case of R. dominica. In general, only few differences in performance between the EC and the CS formulation were detected. We conclude that the type of grain commodity significantly affects mortality after the application of the two pirimiphos-methyl formulations tested, but this effect is species-dependent.     

Insecticidal and repellent activity of selected essential oils against of the pollen beetle, Meligethes aeneus (Fabricius) adults

The essential oils from 9 aromatic plants were tested on repellency and mortality of Meligethes aeneus adults. All the tested essential oils caused high mortality of M. aeneus adults in the tarsal tests. The lethal doses after 6 h exposure were ranged between 197 and 1508 μg cm⁻². Essential oils obtained from Carum carvi and Thymus vulgaris were most efficient where LD₅₀ was estimated as 197 and 250 μg cm⁻², respectively.Repellency declined in all the essential oils as a function of time. The longest persistence time was determined for essences obtained from C. carvi and T. vulgaris where significantly the highest repellent index of 65.6% and 63.8%, respectively, was determined. Repellent index lower than 15% was determined for the remaining essential oils.     

Comparative susceptibility of Ostrinia furnacalis, Ostrinia nubilalis and Diatraea saccharalis (Lepidoptera: Crambidae) to Bacillus thuringiensis Cry1 toxins

Transgenic corn hybrids that express toxins from Bacillus thuringiensis (Bt) are highly effective against the European corn borer, Ostrinia nubilalis (Hübner), and the closely related Asian corn borer, Ostrinia furnacalis (Guenée). Since the registration of Bt corn hybrids in the U.S. in 1996, there has been a great deal of information generated on O. nubilalis. However, relatively little information exists for O. furnacalis. To help determine whether the information generated for O. nubilalis can be leveraged for decisions regarding the use of transgenic Bt corn against O. furnacalis, experiments were designed to determine whether the pattern of sensitivity to various Bt Cry1 toxins is similar between the two species. Test insects included laboratory-reared O. furnacalis originating from Malaysia, a Bt-susceptible laboratory colony of O. nubilalis maintained at the University of Nebraska-Lincoln (UNL) and an out-group consisting of the sugarcane borer, Diatraea saccharalis (F.), from Louisiana which represents a different genus from the same family. O. furnacalis and O. nubilalis exhibited a similar pattern of susceptibility to all the Cry1 toxins and were highly susceptible to the range of Bt toxins tested including Cry1Aa, Cry1Ab, Cry1Ac and Cry1F. Both of the Ostrinia species were more tolerant to Cry1Ba compared with D. saccharalis, although sensitivity of O. furnacalis was intermediate and did not differ significantly from that of O. nubilalis and D. saccharalis. D. saccharalis was also susceptible to the range of toxins tested but unlike the two Ostrinia species, was more tolerant to Cry1F and more susceptible to Cry1Ba. These results indicate that both of the Ostrinia corn borer species are similar in sensitivity to the Cry1Aa, Cry1Ab, Cry1Ac, Cry1Ba and Cry1F toxins, thus suggesting shared toxin receptors and mechanisms of toxicity for the two species.     

Comparison of spinetoram,imidacloprid, thiamethoxam and chlorantraniliprole against life stages of Tribolium confusum Jacquelin du Val (Coleoptera: Tenebrionidae) on concrete

Spinetoram, imidacloprid, thiamethoxam and chlorantraniliprole are new insecticides with novel mode of actions, low mammalian toxicity and low impact to environment. In the present study, the efficacy of these insecticides was tested against Tribolium confusum Jacquelin du Val on concrete. Among the tested insecticides, spinetoram proved to be more effective, providing complete control of T. confusum adults and young larvae after 14 days of exposure. For the young larvae, thiamethoxam at the highest dose and chlorantraniliprole at both doses were equally effective with spinetoram. On the other hand, none of the tested insecticides were able to control T. confusum pupae. Moreover, none of the insecticides had ovicidal effect, with the exception of chlorantraniliprole in some combinations. From the mobile life stages, the most tolerant life stages were old larvae and the most susceptible young larvae. The presence of food (flour) moderated T. confusum mortality. From the results of the present study, we can conclude that spinetoram, thiamethoxam and chlorantraniliprole showed potential and need be further evaluated for surface treatments in stored product facilities. Our work underlined the need for good cleaning and sanitation procedures in warehouses and food processing facilities.     

Single versus multiple releases of predatory mites combined with spinosad for the management of western flower thrips in strawberry

Western flower thrips, Frankliniella occidentalis (Pergande), is a major pest of strawberry and other horticultural and ornamental crops. Biological control of F. occidentalis with predatory mites is recommended as an additional management strategy to chemical control in glasshouse and protected crops. However, it is not known whether multiple (two or three) species releases of predatory mites are more effective than single species releases. The effect of an application of spinosad followed by mite releases could further increase suppression of F. occidentalis. In a series of trials in the glasshouse, we evaluated three commercially available predatory mite species, Typhlodromips montdorensis (Schicha), Neoseiulus cucumeris (Oudemans) and Hypoaspis miles (Berlese). Strawberry plants were sprayed once with either spinosad at the recommended rate or with water. F. occidentalis adults were released onto plants 24 h after spraying, and mites were released six days later. Spinosad significantly reduced F. occidentalis compared to the control (water). T. montdorensis, N. cucumeris and H. miles significantly reduced F. occidentalis compared to the ‘no mite’ treatment. Spinosad had no effect on T. montdorensis and N. cucumeris, as their numbers did not differ between the spinosad and control treatments; H. miles was not recovered. When mites were released after an application of spinosad, greater suppression of F. occidentalis was achieved than with releases of predatory mites alone. When released as a double species combination, ‘T. montdorensis and H. miles’ was the most effective combination. There was no difference in efficacy between releases of ‘T. montdorensis and H. miles’ or ‘T. montdorensis, N. cucumeris and H. miles’. We conclude that multiple species releases are more effective than single species releases, and that biological control of F. occidentalis with predatory mites can be used together with spinosad.     

Isolation of entomopathogenic Bacillus from a biodynamic olive farm and their pathogenicity to lepidopteran and coleopteran insect pests

The occurrence of Bacillus entomopathogenic bacteria on a Tunisian biodynamic farm was determined by examining 75 samples from olive tree (Olea europaea L.) habitats. A total of 40 Bacillus isolates were characterized according to their phenotypic, physiological and biochemical parameters. Isolates of the species Bacillus subtilis, Bacillus mycoides, Brevibacillus brevis, Paenibacillus polymyxa, Bacillus licheniformis, Bacillus sp. (1), Bacillus sp. (2) and a standard strain Btk HD-1 were used separately in feeding bioassays on fresh artificial diet against larvae of lepidopterans Prays oleae (Bernard) and Palpita unionalis (Hübner) and coleopterans Hylesinus oleiperda (F.) and Phloeotribus scarabaeoides (Bernard), which are olive tree pests. Larvae were successfully reared on an artificial diet with 25 g powdered olive tree leaves. Compared to the control data, only Btk and the isolates of B. licheniformis, P. polymyxa and B. brevis were entomopathogenic. Larval mortality assessed 7 days post-treatment showed high mortality rates with Btk to lepidopteran larvae (86.6% for P. oleae and 80.9% for P. unionalis) and low mortality against coleopteran pests. B. brevis isolates showed high mortality rates against P. oleae (up to 67.9%). B. licheniformis isolates caused up to 59.2% larval mortality for P. oleae and 43.6% for P. unionalis. Highest coleopteran mortality was achieved by P. polymyxa isolates (up to 55%). According to the 16S rDNA results, isolates of each of the three entomopathogenic strains were similar. Proteins in the strain supernatants were toxic to P. oleae larvae with LC50 values of 10.0 (B. brevis), 12.5 (B. licheniformis) and 37.6 μg/ml (P. polymyxa). Also, P. polymyxa showed an LC50 of 12.4 mg/l against P. scarabaeoides. Our results suggest that entomopathogenic Bacillus present locally in the biodynamic farm could be used in biological control programmes of olive tree pests.     

Effects of different brassicaceous host plants on the fitness of Pieris brassicae (L.)

Pieris brassicae (L.) is a destructive cosmopolitan pest of cruciferous crops. It is present wherever its host plants occur and it is considered to be one of the most widely distributed of all the Lepidoptera. We investigated the affect of various host plants on the fitness of P. brassicae to survive, develop and reproduce. We quantified development time, survival and mortality on cabbage (Brassica oleracea capitata), cauliflower (Brassica oleracea botrytis), radish (Raphanus sativus), broccoli (Brassica oleracea italica), and mustard (Brassica campestris) under laboratory conditions. The developmental time from eggs to adult eclosion was the shortest (30.3 days) on cabbage and the longest (38.0 days) on radish. However, adult longevity was significantly (P < 0.001) greatest on cabbage compared with the other host plants tested. Similarly, the developmental rate of P. brassicae was found to be faster on cabbage than other cole crops. Moreover, the lowest immature mortality was evident on cabbage and highest on mustard and radish. Differences in reproductive parameters of the P. brassicae among host plants were analyzed using pseudo-values, which were produced by jackknife re-sampling. The data showed that the higher intrinsic rate of natural increase (0.116 females/female/day) was found on cabbage. Cabbage was recognized as the most suitable host for P. brassicae because of shorter developmental period, higher percentage survival, lower doubling time (6.00), and higher number of adult emergence (29.7%).     

Differential response of pea (Pisum sativum) to Orobanche crenata, Orobanche foetida and Phelipanche aegyptiaca

Several broomrape species including Orobanche crenata, Orobanche foetida and Phelipanche aegyptiaca are reported to infect various grain and forage legumes in the Mediterranean and West Asia. Pea (Pisum sativum) is severely damaged by O. crenata, but there are no reports on O. foetida or P. aegyptiaca infection. We report here that pea can induce high germination of seeds of O. crenata, O. foetida and P. aegyptiaca but only O. crenata success infecting pea roots and developing further. Some differences in levels of infection by O. crenata were observed among pea accessions what can be exploited in pea resistance breeding programmes. On the contrary, all pea accessions studied were highly resistant to infection by both O. foetida and P. aegyptiaca, preventing any tubercle attachment and development. This makes pea a promising candidate as trap crop for O. foetida and P. aegyptiaca seed bank demise in infested soils.     

Management of the root-knot nematode Meloidogyne incognita on tomato with combinations of different biocontrol organisms

The nematicidal effect of Pseudomonas fluorescens, Paecilomyces lilacinus, Pichia guilliermondii and Calothrix parietina singly or in combination was tested against root-knot nematode, Meloidogyne incognita. Treatments with P. fluorescens and P. lilacinus caused mortality of M. incognita as 45% and 30% of juveniles after 48 h of exposures, respectively compared to water control in vitro. Under greenhouse conditions, all treatments reduced the disease severity and enhanced plant growth compared to untreated control. Application of P. fluorescens, P. lilacinus and P. guilliermondii Moh 10 was more effective compared to C. parietina. There was a negative interaction between C. parietina and either P. lilacinus or P. guilliermondii. Fresh and dry weight of shoots and roots of plants were significantly reduced as a result of infection with M. incognita, however application of biocontrol agents singly or in mix recovered this reduction. Moreover, they enhanced the growth parameters compared with the control. Our results proved that application of different biocontrol agents (P. fluorescens, P. lilacinus and P. guilliermondii) not only has a lethal effect on nematode, but also enhances the plant growth, supplying many nutritional elements and induction the systemic resistance in plants. Presence of C. parietina as a soil inhabitant cyanobacterium could antagonize biocontrol agents leading to the reduction of their practical efficiency in soil.     

Efficacy of entomopathogenic nematodes (Nematoda: Rhabditida) and insecticide mixtures to control Spodoptera frugiperda (Smith, 1797) (Lepidoptera: Noctuidae) in corn crops

The main insect pest in Brazilian corn is fall armyworm, Spodoptera frugiperda (Smith, 1797) (Lepidoptera: Noctuidae). Entomopathogenic nematodes (EPNs) can be used to control this pest, and can be applied together with various insecticides. Thus, the objective of this work was to evaluate the efficacy of mixtures of EPNs and insecticides to control S. frugiperda in corn crops. In laboratory bioassays three species of EPNs were tested (Heterorhabditis indica, Steinernema carpocapsae and Steinernema glaseri) together with 18 registered insecticides to control S. frugiperda in corn. Efficacy of association between insecticides and EPNs on S. frugiperda larvae was evaluated against the insect's third instar, 2 and 4 days after applications in laboratory. Experiments in the field were performed in two consecutive years, with located application of H. indica and S. carpocapsae (250 IJs/cm²) mixed with chlorpyrifos (0.3 L/ha) and lufenuron (0.15 L/ha) on the corn husk. In laboratory, after two days exposure the interaction between chlorpyrifos and H. indica was synergistic, while interaction with cypermethrin, spinosad, methoxyfenozide and deltamethrin + triazofos was additive, as was interaction between lufenuron, chlorpyrifos and cypermethrin with S. carpocapsae. In contrast, the interaction between chlorpyrifos (Vexter™ and Lorsban™) and lufenuron with S. glaseri was synergistic. In the field, the best treatment was the mixture of H. indica with lufenuron (0.15 L/ha), with 62.5% and 57.5% larval mortality in the two evaluation years in the field, respectively.     

How many Orius laevigatus are needed for effective western flower thrips, Frankliniella occidentalis, management in sweet pepper?

Frankliniella occidentalis (Pergande) is a primary pest of greenhouse crops worldwide, in organic and integrated pest management control practices, Orius spp. are frequently released for thrips control. However, Orius spp. are relatively expensive to produce. More cost-efficient rearing systems and reduced release rate might reduce the expense. In these trials, we released Orius laevigatus (Fieber) at different rates with or without simultaneous release the predatory mite Amblyseius swirskii Athias-Henriot, another known thrips predator, which is less expensive to rear. There was no significant difference in the number of O. laevigatus recovered in which either 2 or 6 individuals were released per square meter, and there was no difference in thrips control among any of the release strategies using O. laevigatus, suggesting that a reduced release rate can maintain effective thrips control. There was no significant difference in the quality or quantity of the pepper yield between treatments in which either 2 or 6 Orius/m² or Orius plus A. swirskii were released.     

Effects of middle-viscosity chitosan on Ramularia cercosporelloides

The inhibitory properties of middle-viscosity Chitosan on the growth of fungus Ramularia cercosporelloides were studied in vitro. The inhibitory concentration that delayed 50% of the radial growth (IC₅₀) was 3.4 g l⁻¹ for middle-viscosity Chitosans with molecular weights of about 133 and 187 kDa (middle molecular weight) dissolved in lactic and acetic acids, respectively. At 96 h of incubation and under the same growing conditions, inhibitions of 91.79% and 73.13% of the radial growth of the fungus were observed when 3.4 g l⁻¹ of Chitosan was dissolved in 0.05 M acetic and 0.05 M lactic acid, respectively. The biomass production was significantly lower than that observed in the controls at 72 h. Based on these in vitro results; Chitosan could be a good alternative to control the disease caused by R. cercosporelloides on safflower.     

Repellent effects of five monoterpenoid odours against Tribolium castaneum (Herbst) and Rhyzopertha dominica (F.) in Calabar, Nigeria

Secondary plant compounds are recognised as important components of plant defence system against herbivores and pathogens. Five monoterpenoids, (R)-linalool, 1,8-cineole, (S)-2-heptyl acetate, (S)-2-heptanol and citral, which are natural components of the essential oils of Aframomum melegueta (K. Schum) and Zingiber officinale (Roscoe), were tested at the ratios in which they occur naturally for repellent activity against Tribolium castaneum (Herbst.) and Rhyzopertha dominica (F.) in a 4-way olfactometer. The results showed the repellent properties of the compounds as both beetles spent less time in the olfactometer arm containing the test stimuli. (R)-linalool and (S)-2-heptanol were stronger repellent compounds than the others. Linalool showed good repellent activity against T. castaneum (P = 0.001) as the insect spent 1.22 min in the test arm compared to the control arms (2.78 min), and R. dominica (P = 0.001) with 0.89 min in the test arm compared to 2.87 min in the control arms. With (S)-2-heptanol, T. castaneum spent 1.23 min in the test arm compared to 2.83 min in the control arms. R. dominica spent 1.61 min in the test arm and 2.69 min in the control arms. For the number of entries or visits made, while both insects were significantly repelled (P < 0.05) by the linalool-treated arm than the control, only R. dominica was repelled by the (S)-2-heptanol-treated arm (P = 0.038) compared to the control arms. The results indicate that A. melegueta and Z. officinale essential oils and their components could be suitable as safer repellents or fumigants against T. castaneum and R. dominica.     

Compatibility of entomopathogenic nematodes (Nematoda: Rhabditida) with registered insecticides for Spodoptera frugiperda (Smith, 1797) (Lepidoptera: Noctuidae) under laboratory conditions

The fall armyworm, Spodoptera frugiperda (Smith, 1797) (Lepidoptera: Noctuidae) is considered the main key pest of corn crops in Brazil. Entomopathogenic nematodes (EPNs) may be used to control this pest, applied together with other different entomopathogen agents or phytosanity products in the spraying mixture. Thus, the objective of work was to evaluate the compatibility of EPNs with different insecticides used of S. frugiperda control in laboratory conditions. Three species of EPNs (Heterorhabditis indica, Steinernema carpocapsae and Steinernema glaseri) and 18 insecticides registered to control of S. frugiperda in corn crops were tested. Compatibility of the insecticides with EPNs was evaluated by observing mortality and infectivity of infecting juveniles (IJs) 48 h after immersion in solution of the insecticide formulations. Among all insecticides tested, Lorsban™ (chlorpyrifos), Decis™ (deltamethrin), Match™ (lufenuron), Deltaphos™ (deltramethrin + triazophos), Dimilin™ (diflubenzuron), Stallion™ (gamacyhalothrin), Karate Zeon™ (lambdacyhalothrin) Tracer™ (spinosad), Vexter™ (chlorpyrifos), Galgotrin™ (cypermethrin), Certero™ (triflumuron), and Talcord™ (permethrin) were compatible (class 1) with the three nematode species tested under laboratory conditions.     

The effects of nitrogen rate and the ratio of NO3:NH4 on Bemisia tabaci populations in hydroponic tomato crops

Nitrogen fertilization is one of the factors that influences Bemisia tabaci (Gennadius) population density. The aim of this study was to determine the effects of three N application rates (75, 205 and 335 mg/l) and three ratios of NO₃⁻:NH₄⁺ ions (92:8, 75:25 and 55:45) in standard nutrient solution (205 mg/l N) on the population density of B. tabaci. The experiments were conducted on spring-summer hydroponic crops of tomato. The effect of plant stratum on the whitefly population was also determined. The aggregation of B. tabaci adults as well as their oviposition rate was higher at 205 and 335 mg/l N than on plants grown at 75 mg/l N. By the end of the experiment (60 d after infestation), the number of nymphs on plants at 205 mg/l N was higher than on plants at 75 mg/l N. The number of pupae was lowest on plants supplied with 75 mg/l N. An increase in NH₄⁺ percentage in standard nutrient solution (from 25% to 45% of the total N) reduced adult population density and oviposition rate. The density of nymphs and pupae, at 60 d after infestation, was lower on the tomato plants grown at 75:25 and 55:45 NO₃⁻:NH₄⁺ ratios compared to the 92:8 ratio. The 75:25 and 55:45 NO₃⁻:NH₄⁺ ratios resulted in a higher incidence of blossom-end rot of tomato fruit, with a lower incidence of disorder at 75:25 than at the 55:45 ratio. Plant stratum influenced adult whitefly distribution in two years of the study. Middle stratum leaves were more attractive to adults in both years. The results demonstrate the effects of N fertilization (N rate and the ratio of NO₃⁻:NH₄⁺) and plant stratum on B. tabaci population density.