Test Insects Research Articles

FUMIGANT AND CONTACT TOXIC POTENTIAL OF ESSENTIAL OILS FROM PLANT EXTRACTS AGAINST STORED PRODUCT PESTS

ABSTRACT Essential oils isolated from pine (Pinus longifolia L.), Eucalyptus (Eucalyptus obliqua L’Her) and coriander (Coriandrum sativum L.) were screened for contact and fumigant activities against rice weevil, Sitophilus oryzae L. (Coleoptera: Curculionidae), adzuki bean weevil, Callosobruchus chinensis L. (Coleoptera: Bruchidae) and rice moth Corcyra cephalonica (Stainton) (Lepidoptera: Pyralidae) in laboratory assays. Responses varied with test material, insect species, and exposure time. In fumigation assay, coriander and eucalyptus oils at 130µg/cm2 , caused 100% toxicity to all the species within 24 hrs of treatment, whereas pine oil revealed, 90% mortality at same concentration after 72 hrs of treatment. In contact assay, the test oils were effective against adults of S. oryzae, C. chinensis and C. cephalonica producing about 90% toxicity only after 72 hrs of treatment. Against C. chinensis adults, all test materials revealed potent insecticidal activities than other two insects in both fumigation and contact assays even at lower concentrations. These studies showed the strong insecticidal activity of coriander, eucalyptus and pine oils and its potential role as a fumigant for S. oryzae, C. chinensis and C. cephalonica. From this study we conclude that these essential oils have potential for applications in IPM programs for stored-grain pests because of its high volatility and fumigant activity.

Assessment of gamma ray-induced DNA damage in Lasioderma serricorne using the comet assay

We attempted a DNA comet assay under alkaline conditions to verify the irradiation treatment of pests. Lasioderma serricorne (Fabricius) were chosen as test insects and irradiated with gamma rays from a 60Co source at 1 kGy. We conducted the comet assay immediately after irradiation and over time for 7 day. Severe DNA fragmentation in L. serricorne cells was observed just after irradiation and the damage was repaired during the post-irradiation period in a time-dependent manner. The parameters of the comet image analysis were calculated, and the degree of DNA damage and repair were evaluated. Values for the Ratio (a percentage determined by fluorescence in the damaged area to overall luminance, including intact DNA and the damaged area of a comet image) of individual cells showed that no cells in the irradiated group were included in the Ratio<0.1 category, the lowest grade. This finding was observed consistently throughout the 7-day post-irradiation period. We suggest that the Ratio values of individual cells can be used as an index of irradiation history and conclude that the DNA comet assay under alkaline conditions, combined with comet image analysis, can be used to identify irradiation history.

Effect of acclimation on heat-escape temperatures of two aphid species: Implications for estimating behavioral response of insects to climate warming

An aphid usually stays at one feeding site for a long time to achieve its development and reproduction, while high temperatures can make it decide to escape from heat stress. Climate warming increases daily high-temperature both in degree and time. However, it remains unknown whether such heat-escape behavior will be influenced by those daily temperature changes. In this study, a wheat-leaf temperature gradient was created based on field microhabitat temperatures. We defined a parameter, heat-escape temperature (HET) to describe the critical temperature at which an aphid turns back when it walks along the gradient from mild temperature to high temperatures. HET indicates behavioral responses of the aphids to heat stress. Two aphid species, Sitobion avenae and Rhopalosiphum padi, main economic pests in temperate areas were selected as test insects. Detailed studies were conducted on the temperature gradient to reveal effects of acclimation temperature, time, and condition (temperature×time) on HET of both species. Results showed that HET decreased non-linearly (S. avenae: 41.4–38.6°C, R. padi: 41.3–39.4°C), when acclimation temperature increased from 25 to 36°C. For both species, HET declined linearly (S. avenae: 40.1–38.0°C, R. padi: 41.3–38.5°C) as acclimation time increased from 0.5 to 6h at 35°C, whereas HET descended non-linearly with reduction of acclimation time at 10°C. HET for both species acclimated under constantly warm conditions (future daily temperature) were significantly lower than those acclimated under gradually warm conditions (current daily temperature). These results suggest that aphids’ heat-escape behavior is significantly influenced by brief thermal history, implying that aphids make decision to avoid heat stress based on the combination of temperature and exposure time and escape before they were hurt by high temperatures under the conditions of climate warming. Avoiding high temperatures may cost a lot of time and resources of aphids and thus potentially reduced growth, development, and reproduction. Changes in insect behaviors caused by ongoing climate warming and their ecological consequences should be more concerned.

Insecticidal Constructure and Bioactivities of Compounds from Ficus sarmentosa var. henryi

Insecticidal activities of the petroleum ether-, chloroform-, ethyl acetate-, and water-soluble fractions of the methanolic extract of Ficus sarmentosa var. henryi were assayed against Musca domestica adults. The chloroform- and ethyl acetate-soluble fractions were the most active with 92.6 and 88.9% mortalities (24 h after treatment) respectively. Therefore, the two fractions were combined and four compounds, isolated from the fractions by activity-guided fractionation, were elucidated as 7-hydroxycoumarin, apigenin, eriodictyol, and quercetin by spectroscopic method and displayed excellent insecticidal activities against adults of M. domestica and 4th instar larva of Aedes albopictus. Among those, 7-hydroxycoumarin showed the strongest insecticidal activities with lethal concentrations (LC 50) values of 72.13 μg g −1 sugar and 4.87 μg mL −1 (48 h after treatment) against the test insects respectively. The cytoxicities of these compounds on BTI-Tn-5Bl-4 cell were also investigated for the insecticidal mechanism and found that quercetin represented superior inhibitory activity with MTT assay and reactive oxygen species (ROS) against BTI-Tn-5Bl-4 cell, but slightly weaker than that of the positive control (azadirachtin) and significantly greater than the negative control (DMSO only). Meanwhile, eriodictyol demonstrated the strongest effect on the mitochondrial membrane potentials (MMP). In conclusion, based on their comparative toxicities to commercial insecticides and their cytotoxic effects, some of the compounds from the F. sarmentosa have potential as botanical insecticides.

COMBINED EFFECT OF SOME PLANT EXTRACTS UNDER MODIFIED ATMOSPHERE OF CARBON DIOXIDE AGAINST STORED GRAIN INSECTS

Where, tests were conducted inside fiberglass bins during summer time, the temperature of grain was 32 ± 2°C.The plant extracts tested were the acetone and petroleum ether extracts of Poinciana seeds (Delonix regia); Cloves flowering buds (Syzgium aromaticum); Cinnamon (Cinnamonum zeylancicum); Radish seeds (Raphanus sativus); and Mustard seeds (Brassica alba). Test insects were Sitophilus orzae(L); Rhizopertha dominica (F.) and Tribolium Castaneum. The various plant extracts were tested alone at 0.4% and 0.8% (w/w) concentrations and under modified atmosphere (MA) of 20 ± 5% Co2. Results concerning Co-toxicity values resulted from addition of 20 ± 5% Co2 to the acetone and petroleum ether extracts of various plants revealed that the extracts at 0.4% and 0.8% produced additive effects for all tested insect species at all exposure periods. Comparing the toxicity of these materials to the insect species, the rice weevil Sitophilus oryzae (L.) was the most sensitive, followed by the lesser grain borer Rhizopertha dominica (F) and the red flour beetle Tribolium castaneum (Herbst) adults. Meanwhile, treatment of various insect species with the plant extracts under modified atmosphere of Co2 produced obviously higher mortality values than each treatment alone and proved to be effective against the three insect species under study.

Use of teflubenzuron alone and combined with Metarhizium anisopliae and Phenylacetonitrile as control agent against the desert locust, schistocerca gregaria (Forskal) (Orthoptera: acrididae)

The efficacy of the Insect growth regulator (IG R) teflubenzuron (Nomolt 50 ULV) was evaluated against desert locust (DL) nymphs (3rd and 4th instars) during two seasons (2008 and 2009). All experiments were carried out under semi-field conditions, on irrigated plots planted with millet, and large cages (2x2x1m) and bomas (2x6x1m) were erected to enclose the test insects. The IGR was applied by means of a battery driven hand held (Micro ULVA) sprayer either as direct spray on the nymphs or as a simulated barrier treatment. The impact of the IGR on the feeding rate of the nymphs was investigated as well. The IGR was tested at the recommended dose (450ml/ha), and at fractional doses (225, 112.5 and 56.25ml/ha) in combination with Metarhizium anisopliae (Green Muscle®) at 50g/ha and the pheromone Phenyl Aceto Nitrile (PAN) 98% at 10ml/ha. Diesel was used as a dilutant in all formulations. Nomolt 450 m/ha resulted in 100% nymphal mortality in 20 days after treatment. The fractional doses of the IGR combined with the pheromone PAN, proved to be effective in the manipulation of nymphs, 100% mortality was obtained in 21, 20 and 21 days after treatment, in both seasons of the study. The fractional doses of the IGR combined with Metarhizium GM resulted in 100% mortality within 14 days of the treatment. Tests in bomas using barrier treatment in the 1 st season of the study revealed that the recommended dose of Nomolt applied on the nymphs resulted in 72.5, 88.5, 89 and 53% mortality after the 1 st , 6 th , 12 th and 24 th day after treatment respectively. Percentage mortality of 78.5, 68.5, 74 and 61.5 were achieved in the 2 nd season. The Nomolt either alone or in combined with PAN and GM revealed a clear negative impact on the feeding rate of nymphs.

Potential of some volatile oils in protecting packages of irradiated wheat flour against Ephestia kuehniella and Tribolium castaneum

Six essential oils of Citrus reticulate (mandarin peel), Pimpinella anisum (anise), Anethum graveolens (dill), Allium sativum (garlic), Ocimum basilicum (basil) and Zingiber officinale (ginger), were evaluated for fumigant toxicity against Ephestia kuehniella and Tribolium castaneum and for contact toxicity against larvae of both species. The major compounds in these volatile oils were identified using gas chromatography- mass spectrometry. Both O. basilicum and Z. officinale oils gave 100% mortality within 24 h with doses of 32 μl/l air for E. kuehniella adults, and 128 μl/l air for T. castaneum adults. The oil of A. graveolens was the most effective against larvae of both species; treated filter papers giving 100% mortality of T. castaneum and E. kuehniella larvae with exposure periods of 24 h and 96 h, respectively. The persistence of toxicity of the six tested oils varied according to their chemical components with A. graveolens and O. basilicum proving the most persistent, and C. reticulate and P. anisum the least. The possible use of the oils applied as a 30% aqueous solution for protection of wheat flour irradiated with gamma radiation (1.5 KGy) from infestation by the test insect species during a 60-day storage period in damour and gunny plastic pouches was investigated. The effect of these oils on acetylcholinesterase activity also was examined to explore their possible mode of toxic action. Dill oil was the most active against E. kuehniella larvae while ginger oil had the greatest depressive action against T. castaneum larvae.

Optimizing immunomarking systems and development of a new marking system based on wheat.

Immunomarking systems used to track large-scale movement patterns of insects are highly dependent on the efficiency of the enzyme linked imunosorbent assay (ELISA) reaction and logistical factors (e.g. concentration of marker applied, ability of the marker to wet the insect cuticle, and trapping methods). This paper examines ways to increase ELISA efficiency and mediate logistical factors, and provides information on a new immunomarking protein based on wheat gluten. The present studies on improving efficiency of the ELISA reactions showed that specially treated microplate surfaces were needed for soymilk and gluten assays, but not for egg albumin and casein assays. Sample dilution was investigated and was found to improve the signal/noise (S/N) ratio for the albumin and casein assays, but S/N ratios for the gluten and soymilk assays were less sensitive. However, for all assays, marked specimens were still detectable even with dilutions down to 6% of the original sample, which would allow more tests to be run on the same initial sample volume. For the logistical factors, these studies showed that marking of an insect by having it walk across a dried residue could be virtually eliminated for the casein and soymilk assays when the concentration applied was reduced to < 4%, but residues of 0.125% egg that had been aged in the field seven days still marked 37.5% of test insects placed on the residues. Also, the adjuvant Sylgard® 309 used at 80 ppm enhanced wetting of the insect cuticle and had little or no effect on the ELISA reaction, but the wetting agents R-11 and Silwet® L-77 were much more likely to negatively affect ELISA performance. Five different trapping adhesives were also evaluated and found to reduce ELISA efficiency 38–45% for the casein assay and 61–78% for the soymilk assay, while the albumin and gluten assays were unaffected. The information provided in this paper can be used to help correct for inherent differences in marking efficiency of the different proteins by manipulation of sample preparation, adjuvants, and concentrations applied.

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.

Laboratory studies on the competition for insect haemocoel between Beauveria bassiana and Steinernema ichnusae recovered in the same ecological niche

Laboratory assays evaluated the combined action of the entomopathogenic nematode Steinernema ichnusae and the entomopathogenic fungus Beauveria bassiana isolated from the same ecological niche, an oak forest in Sardinia (Italy). Galleria mellonella larvae were used as the test insect with the aim of understanding what happens in host haemocoel during a simultaneous infection with two different entomopathogens. Larval mortality assays were performed using nematodes and fungi both alone and together, at the same and different times, and in different concentrations. No additive or synergistic effects were observed, but there was a clear antagonism and competition for survival space in the haemocoel. Moreover, mutual effects between the symbiotic bacteria of the entomopathogenic nematode Xenorhabdus bovienii and entomopathogenic fungi were investigated. In laboratory experiments, X. bovienii crude extracts were tested for their activity against fungal growth. Compounds produced by B. bassiana were tested for their activity against the growth of bacteria, revealing that X. bovienii and B. bassiana are antagonistic to each other.

Evaluation of resistance in wheat against Rhopalosiphumpadi (L.) (Homoptera:Aphididae) Under laboratory Conditions

AbstractAims and introduction All over the world aphids are pests of economic importance, affecting all varieties of plants like cereal crops, vegetables, ornamental plants and fruits. Aphids damage plants either directly or indirectly. Aphids are one of the major agricultural pests. There are only a few plants that are not susceptible to infestation by this destructive pest. They cause direct damage by sucking the sap of leaves, blocking photosynthesis which results in leaf distortion, gall production, discoloration, stunting, leaf curling, wilting, twisting and premature leaf falls. They are directly involved in transmission of plant viruses and indirectly by depositing honey dew that reduces photosynthetic activity and induces sooty mold production and premature leaf senescence.Methodology Hosts were wheat and maize. There was twenty varieties of National Uniform Wheat Yield Trials (NUWYT) Normal (N) of year 2004-05, and twelve varieties of (NUWYT) Rain Fed (R.F) of year 2004-05 while there were twenty-two varieties of maize of year 2005-06. All these varieties were evaluated against bird cherry oat aphid R. padi L pest. Evaluation for resistance was done by seedling bulk test and by comparing the results of components of resistance like antibiosis, antixenosis and tolerance tests. These experiments were performed under controlled environmental conditions. Experiments were of randomized complete design and replicated. The data obtained was statistically analyzed of variance (ANOVA) and the mean values were compared by Duncan’s new multiple range test (DMRT) at 5 percent level of significance (Steel and Torrie, 1980). Results Among the tested germplasm (one variety and 11 lines of wheat), the V-5 line was found resistant and the NRL-2017 line was found susceptible to Rhopalosiphum padi. The results of the Antixenosis Test indicated that two wheat lines, V-5 and PR-83 were least preferred and three lines viz., NRL-2017, V-00055 and V-00BT004 were highly preferred by the test insect. The results of the Antibiosis Test showed that PR-83 line was least fecund whereas NR-241 and V-00055 lines were highly fecund. The results of the Tolerance Test indicated that four varieties, PR-83, V-5, SN-128 and NR-241 were highly tolerant, while only one line, V-00BT004 was least tolerant. Conclusion To avoid harmful effects of this insect pest, only resistant, least preferred, least fecund and highly tolerant lines must be used in wheat breeding programs.

Evaluation of resistance in wheat against Rhopalosiphumpadi (L.) (Homoptera:Aphididae) Under laboratory Conditions

Aims and introduction All over the world aphids are pests of economic importance, affecting all varieties of plants like cereal crops, vegetables, ornamental plants and fruits. Aphids damage plants either directly or indirectly. Aphids are one of the major agricultural pests. There are only a few plants that are not susceptible to infestation by this destructive pest. They cause direct damage by sucking the sap of leaves, blocking photosynthesis which results in leaf distortion, gall production, discoloration, stunting, leaf curling, wilting, twisting and premature leaf falls. They are directly involved in transmission of plant viruses and indirectly by depositing honey dew that reduces photosynthetic activity and induces sooty mold production and premature leaf senescence.Methodology Hosts were wheat and maize. There was twenty varieties of National Uniform Wheat Yield Trials (NUWYT) Normal (N) of year 2004-05, and twelve varieties of (NUWYT) Rain Fed (R.F) of year 2004-05 while there were twenty-two varieties of maize of year 2005-06. All these varieties were evaluated against bird cherry oat aphid R. padi L pest. Evaluation for resistance was done by seedling bulk test and by comparing the results of components of resistance like antibiosis, antixenosis and tolerance tests. These experiments were performed under controlled environmental conditions. Experiments were of randomized complete design and replicated. The data obtained was statistically analyzed of variance (ANOVA) and the mean values were compared by Duncan’s new multiple range test (DMRT) at 5 percent level of significance (Steel and Torrie, 1980).ResultsAmong the tested germplasm (one variety and 11 lines of wheat), the V-5 line was found resistant and the NRL-2017 line was found susceptible to Rhopalosiphum padi. The results of the Antixenosis Test indicated that two wheat lines, V-5 and PR-83 were least preferred and three lines viz., NRL-2017, V-00055 and V-00BT004 were highly preferred by the test insect. The results of the Antibiosis Test showed that PR-83 line was least fecund whereas NR-241 and V-00055 lines were highly fecund. The results of the Tolerance Test indicated that four varieties, PR-83, V-5, SN-128 and NR-241 were highly tolerant, while only one line, V-00BT004 was least tolerant.ConclusionTo avoid harmful effects of this insect pest, only resistant, least preferred, least fecund and highly tolerant lines must be used in wheat breeding programs.

Chemical composition and the insecticidal activity of certain plants applied as powders and essential oils against two stored-products coleopteran beetles

Powders and essential oils were prepared from the aerial parts of Cinnamomum camphora, Ocimum basilicum, Chenopodium ambrosioides, and seeds of Pimpinella anisum. Their adulticidal activities and effects on the F1 progeny of Trogoderma granarium (Everts) and Tribolium castaneum (Herbst) were evaluated. The chemical composition of the plant oils were identified by gas chromatography (GC) and GC/mass spectrometry (MS). All of the tested botanicals showed insecticidal activities against the test insects in a dose-dependent manner with T. granarium was more susceptible to the tested plant products than T. castaneum. At a concentration of 5 g kg−1, many of the plant powders caused 100% mortality of both insects after 14 days of exposure. The powders of C. camphora, O. basilicum, and C. ambrosioides were effective against T. granarium, while that of C. ambrosioides caused 100% adult mortality of T. castaneum under the same assays conditions. A dose of 1.50 ml cm−2 of the oils of C. camphora and O. basilicum completely controlled T. granarium, while 100% mortality of T. castaneum adults was recorded with P. anisum oil. A significant and/or complete reduction (100% inhibition) of the F1 progeny of both insects was obtained as a result of parental exposure to the tested botanicals, especially at the highest doses applied. Botanicals under investigation showed a considerable grain protecting activity against the tested insect species and could be included in integrated pest management (IPM) strategies.

Generic Insect Repellent Detector from the Fruit Fly Drosophila melanogaster

BackgroundInsect repellents are prophylactic tools against a number of vector-borne diseases. There is growing demand for repellents outperforming DEET in cost and safety, but with the current technologies R&D of a new product takes almost 10 years, with a prohibitive cost of $30 million dollar in part due to the demand for large-scale synthesis of thousands of test compounds of which only 1 may reach the market. R&D could be expedited and cost dramatically reduced with a molecular/physiological target to streamline putative repellents for final efficacy and toxicological tests.MethodologyUsing olfactory-based choice assay we show here that the fruit fly is repelled by not only DEET, but also IR3535 and picaridin thus suggesting they might have “generic repellent detector(s),” which may be of practical applications in new repellent screenings. We performed single unit recordings from all olfactory sensilla in the antennae and maxillary palps. Although the ab3A neuron in the wild type flies responded to picaridin, it was unresponsive to DEET and IR3535. By contrast, a neuron housed in the palp basiconic sensilla pb1 responded to DEET, IR3535, and picaridin, with apparent sensitivity higher than that of the DEET detectors in the mosquitoes Culex quinquefasciatus and Aedes aegypti. DmOr42a was transplanted from pb1 to the “empty neuron” and showed to be sensitive to the three insect repellents.ConclusionsFor the first time we have demonstrated that the fruit fly avoids not only DEET but also IR3535 and picaridin, and identified an olfactory receptor neuron (ORN), which is sensitive to these three major insect repellents. We have also identified the insect repellent-sensitive receptor, DmOr42a. This generic detector fulfils the requirements for a simplified bioassay for early screening of test insect repellents.

Vapor-Phase Toxicity of Derris scandens Benth.-Derived Constituents against Four Stored-Product Pests

The vapor-phase toxicity of Derris scandens Benth.-derived constituents was evaluated against four stored-product pests ( Callosobruchus chinensis L., Sitophilus oryzae L., Rhyzopertha dominica L., and Tribolium castaneum H.) using fumigation bioassays and compared to those of commonly used insecticides. The structures of all constituents of were characterized by spectroscopic analyses [nuclear magnetic resonance (NMR) and mass spectrometry]. The sensitivity of the test insect to compounds varied with exposure time, concentration, and insect species. Over 100% mortality after 24 h was achieved with the compounds osajin (2), scandinone (5), sphaerobioside (8), and genistein (9) against all of the test insects, while laxifolin (3) and lupalbigenin (4) showed 100% mortality after 72 h against T. csataneum and R. dominica . Scandenone (1), scandenin A (6), and scandenin (7) were less effective. Among the insects, C. chinensis , S. oryzae , and R. dominica were more susceptible to the treatments, whereas T. castaneum was less susceptible. The results of fumigation tests indicated that compounds from D. scandens whole plant extract are potential candidates to control stored-product pests.

Effects of diatomaceous earth on the mortality and progeny production of Rhyzopertha dominica (Coleoptera: Bostrychidae

Laboratory experiments were conducted to assess the insecticidal effect of the diatomaceous earth (DE) formulation Insecto ® against adult stage of Rhyzopertha dominica (F.) at two levels of relative humidity i.e. 40 and 55%, and three exposure periods of 7, 14, and 21 days . Test insects were placed in vials containing 40 g of soft winter wheat mixed with 0.25, 0.50, 1.00, 1.50 and 2.00 g kg -1 DE. After respective exposure periods, mortality in all dose rates except 0.25 and 0.50 g kg -1 was found to be significantly different from mortality in control. After each exposure interval, dead and live insects were counted and removed, and then the vial containing wheat was returned to corresponding humidity chamber for 8 weeks until F 1 adults emerged. For F 1 production, applications at all dose rates were significantly different from control group. Mortality regardless of dosage for 7, 14 and 21 days exposure intervals were between 27.67– 33.40 %. Despite the fact that mortality increased with the increasing dose rate, total mortality was not obtained even at the highest rate of DE. F 1 production decreased with the increasing dose rates for both r.h. conditions. Containment of population was achieved at 1.50 g kg -1 of DE for 7 days of exposure period and at 2.00 g kg -1 of DE for 14 and 21 days of exposure periods . For each exposure intervals, F 1 production of R. dominica decreased with the increasing dose rates of DE. Mortality regardless of exposure interval was 59% at 1.50 g kg -1 of DE and 75% at 2.00 g kg -1 of DE.

Laboratory evaluation of grain protectant efficacy of different foliar extracts against maize weevil – Sitophilus zeamais (Motschulsky)

The present study was aimed to evaluate six indigenous plant extracts for their ability to protect maize from infestation by maize weevil Sitophilus zeamais (M). The plant extracts were tested for its toxicity by fumigation and grain surface coating methods. Further, the effects of botanical treatments on F1 progeny, seed emergence and antifungal activities were studied. The results indicated that the extracts of Eicchornia crassipes controlled the test insect in grain surface coating method (100%, P = 0.05). Further, the same plant extract had significantly reduced the development of F1 progeny (97 ± 0.7%). In germination experiments, T + UEx samples showed normal seed germination of maize. However, in T + Ex samples, the seed germination depended on the grain protectant efficacy of the tested botanical extracts. Always higher percantage seed germination was recorded in those treatments where there was less infestation. Extracts of Carica papaya had significantly reduced the incidence of seed-borne fungus Aspergillus flavus (4 ± 2.4%) and did not affect the seed germination when compared to other treatments and untreated control.

A newly devised electric field screen for avoidance and capture of cigarette beetles and vinegar flies

A bifunctional electric field screen was proposed to physically exclude insect pests from warehouses. The screen consists of insulated iron wires (ICW) arranged in parallel and two earthed conductor nets placed on both sides of the ICW. A negative charge (0.1–8.0 kV) was applied to the insulated wires with a voltage generator to polarize an insulator sleeve used to cover the wire, negatively on the outer surface and positively on the inner conductor wire surface of the sleeve. The negative surface charge of the ICW caused an electrostatic induction in the earthed nets and an opposite charge on the net surfaces facing the ICW. An electric field formed in a space between the ICW and the earthed net, and the field strength increased in direct proportion to increasing voltages applied to the ICW. Adults of the test insects (cigarette beetle ( Lasioderma serricorne) and vinegar fly ( Drosophila melanogaster)) reaching the outer surface of the earthed net were deterred from entering the inside of the charged screen, whereas all insects immediately passed through the screen when the ICW was not charged. This avoidance was directly proportional to the increase in the voltage. In addition, the capability of the screen to capture insects that enter inside the screen was proven by introducing insects into the space between the ICW and the earthed net. Strong capture was observed when the ICW was negatively charged with more than 4.1 kV, under which conditions a short-term electric current (peaking at 0.3–0.6 μA, for 3 min) occurred transiently. This electric current was due to the release of electricity from the insects, giving a net overall positive charge to the insects, which therefore were attracted more strongly to the negatively charged ICW. A test using an attractant-set chamber showed that the insects were completely prevented from passing through the charged screen, in contrast to a rapid transfer of all insects when the screen was not charged. Thus, the present results show that the described screen is a promising physical tool for controlling insect pests in warehouses.

Insecticidal Effects of the Insecticide Based on Porous Starch and Cinnamon Oil against &lt;i&gt;Sitophilus zeamais&lt;/i&gt;

We investigated that the bioefficacies of cinnamon oil and insecticide based on the mixture of porous starch and cinnamon oil. They were evaluated for their insecticidal activities and their mortality on adults of Sitophilus zeamais. Fumigant toxicity assayed by hanging in glass jars showed that these chemicals caused significant mortality of the test insect. Cinnamon oil evoked high repellent action and high fumigant toxicity (LD50 = 0.030μL/cm3) against adults of Sitophilus zeamais. The two concentrations of the new insecticide 0.030μL/cm3 (LD50) and 0.040μL/cm3 (the highest) lose their insecticidal activity after a minimum of 144h and 168h, respectively. These results suggest that cinnamon oil starch powder is the most effective insecticide, and could increase its efficacy for use as an alternative to synthetic insecticides.

A novel approach to limit the development of phosphine resistance in Western Australia

Escalating development of resistance to phosphine is of concern to grain storage operators world wide. In Western Australia 85% of grain produced is exported with a guarantee through legislation that it is free of all grain insects. Phosphine plays a vital part in shore-based fumigations to achieve this insectfree status but it is also available for unrestricted use by growers for grain stored on farms. For more than 20 years a campaign has been in place to encourage better use of phosphine. Central to the program is the preservation of phosphine for long-term use by exporters and growers. Over this period weak resistance frequency has increased to the current rate of about 48% averaged across all species. Strong resistance has been confirmed in two strains of Tribolium castaneum . The three key components of the strategy are: 1. Inspection of central and farm storages for grain insects, and testing insects to discover phosphine resistance. 2. Education of grain-storage managers on farms and commercial premises on effective management of grain stocks and correct use of phosphine. 3. Eradication of highly resistant insect colonies found on farms and commercial premises as well as management of strains with elevated levels of tolerance to phosphine. Keywords : Farm silo, Fumigation, Phosphine resistance, Extension, Western Australia.