Portable acoustic device for detection of coconut palms infested by Rynchophorus ferrugineus (Coleoptera: Curculionidae)

Acoustic methods have been developed and used to detect insects in concealed habitats. The larvae of red palm weevil, Rynchophorus ferrugineus (Olivier), a serious pest of the coconut palm, Cocos nucifera L. feed on the soft tissues inside the stem and bud region. Detection of infested coconut palms in the early stages by the conventional method of checking for external symptoms is time consuming, labour intensive and costly. This paper describes the development of a portable and efficient acoustic device and its potential in detection of infested palms in the field. The device comprises a sensor to mount on the palm and to acquire the sounds of red palm weevil larvae, an electronic unit that processes the acquired sounds and a set of headphones to receive the output sound by the listener. It is light weight, user-friendly and powered by batteries. The highest accuracy of identifying infested palms was obtained when the palm was checked at four positions; either side of palm base and bases of the two lowermost leaves. The infested palms were detected with over 97% accuracy, while the probability of not detecting uninfested palms was over 92%. A second check increased the rate of accuracy. Many difficulties encountered with conventional methods could be overcome by the use of this device.     

Assessing the impact of areawide pheromone trapping,pesticide applications,and eradication of infested date palms for Rhynchophorus ferrugineus (Coleoptera: Curculionidae) management in Al Ghowaybah,Saudi Arabia

The red palm weevil, Rhynchophorus ferrugineus (Olivier) (Coleoptera: Curculionidae) is a highly destructive pest of date palms, Phoenix dactylifera L. (Arecales: Arecaceae), in Saudi Arabia. Data spanning a six year period (2007–2012) from Al Ghowaybah, a 1104 ha date producing region in the Al Ahsaa Directorate in Saudi Arabia, were analyzed to assess the impact enhanced management efforts that commenced in Oct. 2009 had against this pest. Within six months of initiating the areawide management program significant reductions in the mean monthly number of weevils trapped and percentage traps with R. ferrugineus were detected. Mean monthly trap captures of R. ferrugineus and the percentage of traps capturing weevils declined significantly from 2009 to 2012 by an average of 65% and 90%, respectively, indicating that trapping and dispersal pressure was significantly reduced. By 2011, average monthly trap captures and percentage of traps with R. ferrugineus were significantly lower than all pre-management capture data and this was maintained through 2012 when data collection ceased. Additionally, over the period 2010–2012, insecticide application and palm eradication rates dropped by 91% and 89%, respectively. The total number of R. ferrugineus captured in 2012 declined by 86% when compared to total captures for 2010. At the end of 2012, the estimated infestation rate of date palms in Al Ghowaybah was 0.36%, which was below the economic threshold of a 1% infestation rate set by the Directorate of Agriculture supervising the program. It is concluded that the mandatory areawide management program that commenced in Oct. 2009 against R. ferrugineus in Al Ghowaybah had a significant and rapid impact against this pest.     

Sublethal effects of spinosad and emamectin benzoate on larval development and reproductive activities of the cabbage moth,Mamestra brassicae L. (Lepidoptera: Noctuidae)

Lepidopteran insect pest management has relied heavily on synthetic chemical pesticides, but their efficiency is declining as a result of emerging insecticide resistance. Recently biopesticides have become the most promising products employed in pest management strategies. We investigated the sublethal effects of two bioinsecticides, spinosad and emamectin benzoate, on larval and pupal development, and reproductive activity including calling behaviour, pheromone production, fecundity and fertility of the cabbage moth, Mamestra brassicae. To assess sublethal effects, second instar larvae were fed with 0.005, 0.05, or 0.5 μg a.i. spinosad/g diet or 0.00005, 0.0005, or 0.005 μg a.i. emamectin benzoate/g diet. Both bioinsecticides significantly increased larval and pupal development time and negatively affected reproductive activity of M. brassicae. The calling activity of females decreased very significantly in the highest sublethal concentration of spinosad and in all treatments by emamectin benzoate. The results suggest that, both spinosad and emamectin benzoate are promising alternatives to conventional insecticides for the control of M. brassicae if successfully introduced into Integrated Pest Management (IPM) programs.     

OBSERVATIONS ON DAMAGE TO GRASSLAND IN EAST YORKSHIRE BY LARVAE OF THE COMMON LEAF WEEVIL, PHYLLOBIUSPYRIL. AND NOTES ON ITS BIOLOGY

An account is given of the damage caused by the larvae of the Common Leaf Weevil, Phyllobius pyri L. to grassland on sandy soils in E. Yorkshire. This insect is probably an insidious pest of grassland causing deterioration of some swards, but occasionally large infestations occur causing severe damage. These investigations suggest that the severity of the damage is related to the degree of larval infestation, the age and the composition of the sward.
Work on the biology of the pest indicates that eggs are likely to be laid from the second week of April up to the fourth week of May. Larvae begin feeding on the grass roots in May and continue until about mid-September, when they start migrating into the 3- to 6-in. level in the soil prior to pupation. When environmental conditions are favourable, all larvae are in the pupal stage by late November and adult beetles emerge from the soil during the second week of April. These beetles feed on the grass for a short period before migrating to their woody hosts, whitethorn, hazel, oak and fruit trees.     

The use of Erianthus arundinaceus as a trap crop for the stem borer Chilo sacchariphagus reduces yield losses in sugarcane: Preliminary results

The oviposition preference of Chilo sacchariphagus (Bojer) (Lepidoptera, Crambidae) to Erianthus arundinaceus (Retz.) Jeswiet (Poaceae) was tested against sugarcane (Saccharum spp. hybrids) to assess whether effective control of the pest can be achieved in the field by using perimeter trap cropping with this plant species. Results from large cage and greenhouse experiments showed that E. arundinaceus clone 28NG7 acted as a dead-end trap plant, attracting oviposition by C. sacchariphagus females and hosting young larvae in terminal green leaves, but reducing by 4.8- to 7.5-fold the survival rate of larvae in stalk. Two field trials demonstrated the efficiency of trap cropping with E. arundinaceus, with a 2 to 9-fold reduction in number of bored internodes per stalk and a 22% mean increase in cane yield. In a third field trial, reduction of injury was observed up to 40 m from the E. arundinaceus border. We conclude that trap cropping with E. arundinaceus may reduce C. sacchariphagus damage in sugarcane crop. Further trials are needed to confirm these results in commercial fields.     

Sitona lineatus (Coleoptera: Curculionidae) Larval Feeding on Pisum sativum L. Affects Soil and Plant Nitrogen

Adults of Sitona lineatus (pea leaf weevil, PLW) feed on foliage of several Fabaceae species but larvae prefer to feed on nodules of Pisum sativum L. and Vicia faba L. Indirectly, through their feeding on rhizobia, weevils can reduce soil and plant available nitrogen (N). However, initial soil N can reduce nodulation and damage by the weevil and reduce control requirements. Understanding these interactions is necessary to make integrated pest management recommendations for PLW. We conducted a greenhouse study to quantify nodulation, soil and plant N content, and nodule damage by weevil larvae in relation to soil N amendment with urea, thiamethoxam insecticide seed coating and crop stage. PLWs reduced the number of older tumescent (multilobed) nodules and thiamethoxam addition increased them regardless of other factors. Nitrogen amendment significantly increased soil available N (>99% nitrate) as expected and PLW presence was associated with significantly lower levels of soil N. PLW decreased plant N content at early flower and thiamethoxam increased it, particularly at late flower. The study illustrated the complexity of interactions that determine insect herbivory effects on plant and soil nutrition for invertebrates that feed on N-fixing root nodules. We conclude that effects of PLW on nodulation and subsequent effects on plant nitrogen are more pronounced during the early growth stages of the plant. This suggests the importance of timing of PLW infestation and may explain the lack of yield depression in relation to this pest observed in many field studies. Also, pea crops in soils with high levels of soil N are unlikely to be affected by this herbivore and should not require insecticide inputs.     

Validation of a microwave radar system for the monitoring of locomotor activity in mice

Background  

The general or spontaneous motor activity of animals is a useful parameter in chronobiology. Modified motion detectors can be used to monitor locomotor activity rhythms. We modified a commercial microwave-based detection device and validated the device by recording circadian and ultradian rhythms.     

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.     

The first report on the winter breeding life history of Epuraea domina (Coleoptera: Nitidulidae) in a citrus grove in Jeju,Korea

Epuraea domina Reitter (Coleoptera: Nitidulidae) is a flower-visiting insect and a pest that causes corky scar on citrus fruit. This study was conducted to investigate the life cycle of E. domina in a citrus grove. E. domina showed the characteristics of cold breeders as they complete key life history events of oviposition and immature development during the winter. E. domina adults spent the summer in uncultivated habits started to lay eggs in soil near fallen citrus fruit in orchards during late autumn. Oviposition activity continued throughout the winter with a large decrease in activity when the minimum air temperature was <0 °C. Hatched larvae fed on decaying citrus and pupated in soil in the spring. The pupae emerged as new adults in mid-May to feed on the pollen and nectar of citrus flowers, probably followed by their migration to uncultivated habitats in the summer.     

Efficacy of endophytic and applied Metarhizium anisopliae (Metch.) Sorokin (Ascomycota: Hypocreales) against larvae of Plutella xylostella L. (Yponomeutidae: Lepidoptera) infesting Brassica napus plants

The internal colonization of Brassica napus plants by Metarhizium anisopliae was demonstrated and the endophytic and direct effects of the fungus against Plutella xylostella larvae were assessed. Internal colonization of the plant by the fungus was shown by re-isolating the fungus from leaves, petioles and stems of the plant that were not the initial site of inoculation. Results indicated that significant differences (at P = 0.05) were obtained in mean % successful re-isolation of the fungus from leaves, petioles and stems at 2, 3 and 4 weeks after inoculation. To assess the endophytic effect of the fungus, larvae of P. xylostella were introduced onto plant leaves distant from the initial site of inoculation with the fungus (one leaf per plant). Results indicated that significant differences (at P = 0.05) were obtained in mean % mortality of larvae that were introduced at 2, 3 and 4 weeks after inoculation compared to the non-inoculated control. Similar significant results were obtained when the direct effect of the fungus against the larvae was assessed. In conclusion, this research provides evidence for the first time of the endophytic action of M. anisopliae against P. xylostella larvae and the ability of the fungus to colonize the internal tissues of B. napus plants.     

Field evaluation of Lymantria obfuscata multiple nucleopolyhedrovirus for the management of Indian gypsy moth in Jammu & Kashmir,India

The Indian gypsy moth (Lymantria obfuscata) is a pest of national significance, which attacks a wide range of forest and fruit crops in India. The outbreaks of this pest over the past few years spurred interest towards sustainable biointensive approaches for quality fruit production of apple and walnut for agricultural export in Jammu & Kashmir (J & K). The exploratory survey's were conducted for the isolation of native strains of L. obfuscata multiple nucleopolyhedrovirus (LyobMNPV) and field evaluation was conducted to determine the most promising strain as a potential biological control agent of this pest. The virus was recovered from different locations of J&K with its natural incidence varying from 0.77 to 7.43 percent. This is the first report from the Indian sub-continent and worldwide of the occurrence of NPVs in natural larval populations of L. obfuscata. The in vivo mass production was optimised by inoculating per os late 3rd instar L. obfuscata larvae with an inoculum dose of 1.44 × 10⁵ OBs/larva and followed by a 10 day incubation period. To prevent the disintegration of larval cuticle and microbial contamination, moribund larvae were harvested with an average yield of 1.42 × 10⁸ OBs/larva. The field application of LyobMNPV against the host populations on apple and willow with the pre-standardised dosage of 2.5 × 10¹² OBs/ha reduced the larval population density by 25–63%. In the year following application, the larval population density in the treated blocks was 19–28% lower as compared to controls on both apple and willow. This suggests that the virus has considerable potential as a biocontrol agent and the timely application with LyobMNPV on non-fruit trees such as willow which are the preferred hosts for egg laying may help to initiate viral epizootics to keep population outbreaks under check.     

Season-long expression of Cry1Ac and Cry2Ab proteins in Bollgard II cotton in Australia

Bollgard II cotton has been grown commercially in Australia since 2003 for control of the primary target species Helicoverpa armigera (Hübner) and Helicoverpa punctigera (Wallengren) Larvae of both species have been reported to survive at low frequencies on Bollgard II with larvae >8 mm recorded in between 7 and 18% of the area planted to Bollgard II cotton between 2005/06 and 2007/08. F₁ and F₂ tests have shown that this is not due to the presence of resistance genes in the surviving larvae. To understand if fluctuations in the expression of the Cry proteins in Bollgard II allow some larvae to survive, plant tissue samples were taken from five Bollgard II cultivars throughout the growing season within fields and from different farms within a production region between 2007 and 2010. The data indicate that the expression of both Cry proteins is similar to the known resistance-monitoring diagnostic concentrations and relatively uniform between fields within a farm and between farms within a region, with less than one-third of the tests at this level of variation being significant. However, there were intra-seasonal changes in expression of both Cry proteins and differences in expression between plant structures and between cultivars for both Cry proteins. Further work is needed to establish if this variation in Cry protein content in Bollgard II cotton affects the control of Helicoverpa spp. in the field or whether plant-physiological and pest-behavioural factors underlie the occasional occurrence of Helicoverpa larval survival on Bollgard II cotton.     

Evidence of genetic transmission of antibiosis and antixenosis resistance of sorghum to the spotted stemborer, Chilo partellus (Lepidoptera: Pyralidae)

Spotted stemborer, Chilo partellus (Swinhoe) (Lepidoptera: Pyralidae), is the most important pest of sorghum in Asia and south and eastern Africa. Host plant resistance is an important control tactic for controlling this pest. Two breeding lines 27B × PB 15881-3 and 463B × PB 15881-3 with their parents, resistant and susceptible genotypes were evaluated in the field, glasshouse and laboratory for different resistance parameters. Breeding lines and genotypes varied significantly in foliar damage ratings, percentage of stem length tunneled, percentage of plants with deadhearts, larval survival, larval and pupal weights, larval and pupal duration, and percentage pupation and adult emergence in diets amended with leaf powder of different sorghum genotypes. The breeding lines 27B × PB 15881-3 and 463B × PB 15881-3 showed antixenosis and antibiosis to C. partellus in terms of reduced eggs per plant, larval survival and development. The levels of antixenosis and antibiosis of both breeding lines were similar to their resistant parents. Results indicate that transmission of characteristics responsible for resistance to the progeny from the resistant parent occurred.     

Sublethal effect of avermectin and acetamiprid on the mortality of different life stages of Brontispa longissima (Gestro) (Coleoptera: Hispidae) and its larvae parasitoid Asecodes hispinarum Bouček (Hymenoptera: Eulophidae)

The beneficial parasitoid Asecodes hispinarum Bouček plays an important role in integrated pest management (IPM) of the coconut leaf beetle, Brontispa longissima (Gestro), in China. A. hispinarum females parasitize 3rd to 4th instars B. longissima larvae. Hatched parasitoid larvae develop within the host, and parasitoid adults emerge through holes that they chew through the cuticle of the host. Although chemicals serve as the main short term control agents, the compatibility of biological and chemical control has never been investigated for this system. This study examined the responses of immature and adult B. longissima and its larval parasitoid A. hispinarum to avermectin and acetamiprid. Avermectin caused complete mortality of 2nd to 4th instar larvae, and of adults of B. longissima at 10, 15 and 2 d after treatment, respectively. However, 26.7% of the 2nd instar larvae, 55.3% of the 4th instar larvae, and 74%, of adult B. longissima were still alive 40 d after acetamiprid application. Following avermectin exposure, 17.5%, 9.2% and 23% of mummified B. longissima larvae contained viable adult parasitoids for the parasitoid egg, larva and pupa treatments, respectively, and the numbers of dead parasitoids per mummy were 3.3, 7.2 and 13.3 for the egg, larva and adult treatments, respectively. However, for acetamiprid treatment, 70–75.9% of mummified B. longissima larvae contained viable adult parasitoids in all three stage treatments, and the number of dead parasitoids per mummy was 2.8, 2 and 3.4 in egg, larva and adult treatments, respectively. This study showed that a sublethal dose of avermectin is more toxic than acetamiprid to B. longissima and A. hispinarum. Therefore, direct contact of the parasitoid with avermectin should be avoided when this insecticide is used to control B. longissima.     

Effects of nitrogen fertilization on insect pests,their parasitoids,plant diseases and volatile organic compounds in Brassica napus

Nitrogen (N) availability is a key factor influencing the yield of Brassica napus L. Thus, mineral fertilization is widely used to improve the quality and quantity of seeds. In this study, we conducted field experiments to determine the impact of nitrogen fertilization on B. napus pests, their parasitoids and plant diseases. The results showed that N treatment had an impact on the abundance of pollen beetles (Meligethes aeneus Fab.) and cabbage seed weevils (Ceutorhynchus obstrictus Marsh.) as well as dark spot disease (Alternaria brassicae (Berk.) Sacc.). Since pest abundance was not correlated with the flower and silique numbers, the feeding and oviposition sites, plant smell bouquets were analysed to determine potentially attractive or repellent volatile organic compounds. We detected 19 different compounds among which acetic acid and several lipoxygenase pathway products were emitted at higher levels from N-treated plants. Emission of a few other terpenoid compounds was correlated with the pest abundance in field conditions. Abundance of parasitoids of both pests was related to the host availability rather than to the fertilization treatment. Therefore, we suggest that plant chemical cues play a minor role in localization of hosts in close proximity to parasitoid. Dark spot disease levels decreased with increasing N availability, possibly reflecting enhanced emissions of acetic acid, a known antifungal volatile. This study demonstrates the effects of N fertilization on bud and flower volatile bouquets, which might play a role in B. napus insect pest host selection and in resistance to fungal plant diseases. Further studies are necessary to investigate the behavioural responses of insects to the changed volatile bouquets.     

Temporal and spatial distribution of an invasive thrips species Scirtothrips dorsalis (Thysanoptera: Thripidae)

Dispersion of a new invasive thrips species in the United States, chilli thrips Scirtothrips dorsalis Hood, was studied on three plant hosts, i.e., cotton (Gossypium hirsutum L.), peanut (Arachis hypogeal L.) and pepper (Capsicum annum L.) in the greenhouse and under field conditions in Homestead, Florida. In the vertical distribution study, a strong negative relationship was observed between thrips density and height, with the significantly highest mean number of larvae and adults reported on host plants placed at the lowest height (45.7 cm) above ground. The study of horizontal distribution showed that S. dorsalis has weak dispersal potential and aggregates in open areas. During the entire six week study period, thrips were found to move a maximum of 12 m from their reservoir population. During two years (2009–2010 and 2010–2011) of study, a high abundance of thrips population was observed during May–October with the highest mean count during July and August in both years. Flight activity of adults was highest between 10:00and16:00 EST, during peak solar radiation (∼337–653 w/m²). Results from these studies will help growers and extension personnel predict farm-scale distribution of S. dorsalis and efficiently monitor the pest for management before they become a serious problem for the vegetable and ornamental industry in the United States.     

Efficacy of entomopathogenic nematodes (Nemata: Rhabditida) to control Brazilian apple leafroller Bonagota salubricola (Meyrick, 1937) (Lepidoptera: Tortricidae)

The Brazilian apple leafroller, Bonagota salubricola (Meyrick, 1937) (Bonagota cranaodes) (Lepidoptera: Tortricidae), is one of the main pest problems in apple orchards is Brazil. The purpose of this work was to evaluate B. salubricola larval and pupal susceptibility to different species of entomopathogenic nematodes, isolated in Rio Grande do Sul state in Brazil, under laboratory and field (apple orchard) conditions. Bioassays for isolates selection and determination of lethal concentration were performed in tubes of 1.5 ml (eppendorf), each containing one B. salubricola third instar larvae and filter paper. Field experiments were performed in commercial orchard, with application of 100 infecting juveniles (IJs)/cm² for each apple plant previously infected with five B. salubricola larvae covered with plastic trays containing thin cloth. Nematodes H. bacteriophora RS107 and H. bacteriophora RS57 had LC₅₀ of 13 and 4.5 IJs/larvae (4.3 and 1.5 IJs/cm²), respectively. In the field, H. bacteriophora RS107 and H. bacteriophora RS57, applied with sorbitol as an adjuvant, reached 70.2 and 61.1% larval mortality, respectively. The results showed that both isolates had biological activity against B. salubricola under laboratory and field conditions.     

The effect of ridge planting and earliness of durum wheat varieties on sunn pest (Eurygaster spp.) damage and grain yield

Sunn pests (Eurygaster spp.) are among the most important insect pests of wheat (Triticum sativum L.) and barley (Hordeum vulgare L.). Cultural practices can prevent or minimize common sunn pest (Eurygaster integriceps Puton) population densities and crop damage. A three-year field experiment (Jun 05 to Aug 07) was conducted in Diyarbakır in the southeast Antolia region of Turkey, to evaluate the effects of planting method (no-till ridge planting and conventional planting) and earliness of durum wheat (Triticum durum L.) varieties (early, mid-season and late varieties) on E. integriceps density, grain damage and overall grain yield. The effect of the planting method on the sunn pest density and percent of grains damaged by sunn pest was not significant; however, there was a significant difference among the different varieties used in this study. While Çeşit-1252 (late wheat variety) had the highest nymph density (11.2 nymphs m⁻²) and percent of sunn pest damaged grains (2.8%), Sarıçanak-98 (early wheat variety) had the lowest nymph density (4.3 nymphs m⁻²) and percent of sunn pest damaged grains (0.8%). Grain yield was the highest (5.99 t ha⁻¹) for Sarıçanak-98 while there was no significant difference between Aydın-93 (5.06 t ha⁻¹) and Çeşit-1252 (4.99 t ha⁻¹). In conclusion, this study suggests that planting methods may not have a significant effect on sunn pest density, percent of sunn pest damaged grains or grain yield; however, the use of early durum wheat varieties, such asSarıçanak-98, may reduce sunn pest population densities, percent of damaged grains, allowing increases in grain yield in southeast Anatolia region, Turkey.     

Azadirachtin avoidance by larvae and adult females of the tomato leafminer Tuta absoluta

The tomato leafminer Tuta absoluta is a serious worldwide threat to tomato production and its control in open-field tomato has relied heavily on synthetic insecticides, which however are not allowed in organic tomato cultivation. Furthermore, insecticide resistance to synthetic insecticides is already a major concern in populations of the tomato leafminer. Azadirachtin is one of the main biorational pesticides in use today, particularly in organic farming, and has potential as an alternative to conventional insecticides for such use. However, the effects of neem-based products of high azadirachtin content on the tomato leafminer have been little studied and very little is known of their sublethal behavioral effects on this pest species. Here we assessed the insecticidal effect of a commercial neem-based formulation (as a source of azadirachtin) against two populations of the tomato leafminer and its behavioral effects on egg-laying preferences, walking by larvae and leaf-mining. Azadirachtin caused heavy mortality in insect larvae allowing only 2.5–3.5% survival at the Brazilian recommended field-concentration (i.e., 27 mg a.i./L) with negligible difference between the populations tested. Azadirachtin also caused egg-laying avoidance (under free-choice conditions, but not in no-choice conditions) and affected walking by larvae, but not leaf-mining. These results indicate the potential of azadirachtin not only as an insecticide potentially important for organic farming, but also as an egg-laying deterrent minimizing T. absoluta infestation although it may also favor escape by larvae to exposure since it sparks behavioral avoidance.     

Acute toxicity and sublethal effects of methoxyfenozide and thiodicarb on survival,development and reproduction of Helicoverpa armigera (Lepidoptera: Noctuidae)

The cotton bollworm Helicoverpa armigera (Hubner) is one of the most destructive pest insects in Iran and many other countries. In this study, lethal and sublethal effects of methoxyfenozide, and thiodicarb were evaluated against H. armigera larvae that fed on insecticide-treated artificial diet. The effects of methoxyfenozide and thiodicarb were assessed in 3rd instars. Methoxyfenozide and thiodicarb showed LC₅₀ values of 4 and 639 mg a.i./ml, respectively, in H. armigera larvae. Sublethal effects on development, adult longevity, and reproduction were observed in H. armigera larvae that survived exposure to an LC₃₀ of the insecticides. Larvae that were exposed to an LC₃₀ concentration of methoxyfenozide exhibited lower pupal weight and increased larval and pupal developmental times compared with thiodicarb treated larvae or control larvae. Adults that were exposed as larvae to an LC₃₀ concentration of methoxyfenozide or thiodicarb showed reduced fecundity (35% and 30%, respectively) compared to control adults. The tested insecticides significantly reduced adult longevity. The longevity of adult females that as larvae were treated with an LC₃₀ concentration of methoxyfenozide or thiodicarb was reduced by 28% and 23%, respectively, in comparison to control females. We predict that the combination of lethal and sublethal effects of the insecticides, especially methoxyfenozide, will induce significant effects on field population dynamics of H. armigera.