Feeding Deterrent Effects Research Articles

Will chemical defenses become more effective against specialist herbivores under elevated CO2?

Elevated atmospheric CO2 is known to affect plant-insect herbivore interactions. Elevated CO2 causes leaf nitrogen to decrease, the ostensible cause of herbivore compensatory feeding. CO2 may also affect herbivore consumption by altering chemical defenses via changes in plant hormones. We considered the effects of elevated CO2, in conjunction with soil fertility and damage (simulated herbivory), on glucosinolate concentrations of mustard (Brassica nigra) and collard (B. oleracea var. acephala) and the effects of leaf nitrogen and glucosinolate groups on specialist Pieris rapae consumption. Elevated CO2 affected B. oleracea but not B. nigra glucosinolates; responses to soil fertility and damage were also species-specific. Soil fertility and damage also affected B. oleracea glucosinolates differently under elevated CO2. Glucosinolates did not affect P. rapae consumption at either CO2 concentration in B. nigra, but had CO2-specific effects on consumption in B. oleracea. At ambient CO2, leaf nitrogen had strong effects on glucosinolate concentrations and P. rapae consumption but only gluconasturtiin was a feeding stimulant. At elevated CO2, direct effects of leaf nitrogen were weaker, but glucosinolates had stronger effects on consumption. Gluconasturtiin and aliphatic glucosinolates were feeding stimulants and indole glucosinolates were feeding deterrents. These results do not support the compensatory feeding hypothesis as the sole driver of changes in P. rapae consumption under elevated CO2. Support for hormone-mediated CO2 response (HMCR) was mixed; it explained few treatment effects on constitutive or induced glucosinolates, but did explain patterns in SEMs. Further, the novel feeding deterrent effect of indole glucosinolates under elevated CO2 in B. oleracae underscores the importance of defensive chemistry in CO2 response. We speculate that P. rapae indole glucosinolate detoxification mechanisms may have been overwhelmed under elevated CO2 forcing slowed consumption. Specialists may have to contend with hosts with poorer nutritional quality and more effective chemical defenses under elevated CO2.

Feeding Deterrence, Acute Toxicity and Sublethal Growth Effects of Kojic Acid Isolated from Aspergillus funiculosus

Aspergillus funiculosus NCIM 1029 has been reported for the production of kojic acid exhibiting antibacterial, antifungal and larvicidal activity against 3rd instar larvae of Aedes aegypti. Aim of the Study: To check the antifeedant, acute toxicity and sublethal growth effects of fungal metabolite, kojic acid against the agriculture pest, Spodoptera litura. Materials and Methods: Kojic acid was checked for feeding deterrence activity against 4th instar larvae of S. litura in comparison to insect antifeedant, azadirachtin. Reduction in the weight and length of the larvae was evaluated after three days of exposure to kojic acid (400μg/ml). The effect of kojic acid on pupation and adult emergence was also studied. Results: On determination of feeding deterrence, the DC50 value for kojic acid was found to be 180.645 ± 6.35μg/ml on comparison to azadirachtin (DC50 = 41.372 ± 2.21). The LD50 & LD90 values of kojic acid were found to be 693.52± 51.31 and 1889.13 ± 279.03μg/ml, respectively. The reduction in larval weight and length were 83.24 and 87.50%, respectively. The percentage pupation and adult emergence were reduced by 69% and 64% for the exposed larvae. Conclusions: Kojic acid showed moderate feeding deterrence, acute toxicity and sublethal growth effects against S. litura. Keywords: Aspergillus funiculosus, kojic acid, Spodoptera litura, acute toxicity, antifeedant.

Feeding deterrent and growth inhibitory activities of PONNEEM, a newly developed phytopesticidal formulation against Helicoverpa armigera (Hubner)

To assess the feeding deterrent, growth inhibitory and egg hatchability effects of PONNEEM on Helicoverpa armigera (H. armigera). Five oil formulations were prepared at different ratios to assess the feeding deterrent, growth inhibitory and egg hatchability effects on H. armigera. Invariably all the newly formulated phytopesticidal oil formulations showed the feeding deterrent and growth inhibitory activities against H. armigera. The maximum feeding deterrent activity of 88.44% was observed at 15 µL/L concentration of PONNEEM followed by formulation A (74.54%). PONNEEM was found to be effective in growth inhibitory activities and egg hatchability at 10 µL/L concentration. It exhibited statistically significant feeding deterrent activity and growth inhibitory activity compared with all the other treatments. PONNEEM was found to be effective phytopesticidal formulation to control the larval stage of H. armigera. This is the first report for the feeding deterrent activity of PONNEEM against H. armigera. This newly formulated phytopesticide was patented in India.

Variation in the number of capitate glandular trichomes in wild and cultivated sunflower germplasm and its potential for use in host plant resistance

The capitate glandular trichomes of wild sunflowers (Helianthus spp.) are considered to be effective defence components that act against some herbivorous insects, but cultivated sunflowers are reportedly deficient in glandular trichomes. To investigate whether glandular trichomes have a role in the protection of cultivated sunflowers against insects, in the present study, Helianthus annuus L. accessions were grown to quantify glandular trichome density in wild and cultivated germplasm types and assess potential anti-insect effects of terpenoids in the glandular trichomes of cultivated sunflowers. Evaluation revealed that capitate glandular trichomes are often abundant in cultivated sunflowers; relative to wild H. annuus, inbred maintainer (HA) lines have similar numbers of glandular trichomes per floret, while commercial hybrids have only ≈ 20% fewer trichomes when compared with wild sunflowers. In the laboratory assay, it was found that glandular trichome extracts increased the mortality rates of sunflower moth, Homoeosoma electellum (Hulst), larvae exposed from the neonatal stage to 9 d. In the surviving larvae, the extracts significantly reduced larval mass and head capsule width. Though there are limitations to the value of glandular trichomes for host plant resistance, the feeding deterrent or toxic effects of sesquiterpene lactones and diterpenes in sunflower glandular trichomes are not limited to sunflower moth larvae, suggesting a potential for resistance to other sunflower insect pests. Additional research is required to understand the inheritance and value of glandular trichomes in commercial sunflower germplasm and how the composition of terpenoids in the glandular trichomes of wild H. annuus may differ from that in cultivated material.

Habituation in Frankliniella occidentalis to deterrent plant compounds and their blends.

Feeding and oviposition deterrence of three secondary plant compounds and their 1:1 blends to adult female Frankliniella occidentalis Pergande (Thysanoptera: Thripidae) and the potential for habituation of the thrips to the pure compounds and the 1:1 blends at various concentrations were investigated. In choice assays, we tested dose-dependent feeding and oviposition deterrence of the two fatty acid derivatives methyl jasmonate and cis-jasmone, the phenylpropanoid allylanisole, and their blends when directly applied to bean leaf discs. The concentration required to reduce the feeding damage by 50% relative to the control treatment (FDC50) was lowest for cis-jasmone and highest for allylanisole. The feeding deterrent effect of both jasmonates was increased when blended with allylanisole. Feeding deterrence and oviposition deterrence were strongly correlated. In no-choice assays conducted over four consecutive days, we discovered that dilutions at low concentrations (FDC15) applied to bean leaves resulted in habituation to the deterrents, whereas no habituation occurred at higher concentrations (FDC50). We observed a tendency that the 1:1 blends reduce the probability that thrips habituate to the deterrent compounds. Our results may be useful in the development of integrated crop protection strategies with the implementation of allelochemicals as pest behaviour-modifying agents.

Semisynthesis and Antifeedant Activity of New Derivatives of a Dihydro-β-Agarofuran from Parnassia wightiana

Five new derivatives (2–6) were semi-synthesized using compound 1, a dihydro-β-agarofuran sesquiterpene with C-2 ketone obtained from Parnassia wightiana, as the starting material by acylation, oxidation, reduction, esterification, and amination, respectively. Structures of 2–6 were confirmed by 1D- and 2D-NMR and HR-ESI-MS spectra. In addition, antifeedant activities of these compounds (1–6) were tested against the 3rd-instar larvae of Mythimna separata. Antifeedant effects of compounds 2 and 4 were greater than the parent compound 1 whereas other compounds exhibited low to no feeding deterrent effects against third instar M. separata larvae in lab bioassays. Therefore, our results suggest that acylated and reduced derivatives at C-8 and C-2, respectively, of 1 may improve the antifeeding effect. This preliminary information will be useful in designing new insect control agents against M. separata and other important pests.

Bioactivities of caffeic acid methyl ester (methyl-(E)-3-(3,4-dihydroxyphenyl)prop-2-enoate): a hydroxycinnamic acid derivative from Solanum melongena L. fruits

Feeding deterrent and growth inhibitory effects of caffeic acid methyl ester (CME) isolated from the fruit extract of eggplant, Solanum melongena L. along with two known phenolic acids, caffeic acid (CA) and chlorogenic acid (CG) and azadirachtin (taken as active control), were evaluated against Spodoptera litura Fab. and Achaea janata L. (Lep., Noctuidae). The structure of CME was determined on the basis of extensive spectroscopic (UV, FTIR, 1H, and 13C NMR) data analysis. CME has exhibited strong feeding deterrent activity against S. litura and A. janata larvae with ED50 values of 52.02 and 41.02 μg/cm2 leaf area, respectively. CA and CG were relatively less effective compounds when compared with CME. The results also revealed that the isolated compound CME caused marked larval growth inhibition in S. litura and A. janata larvae after 7 days of feeding on a treated diet. The effect on growth of larvae was concomitant with the reduced feeding and digestibility of ingested food. So the activities of digestive proteases within the midgut of larvae were examined using specific substrates to understand the digestive physiology in the larval guts. The bulk of the activity was associated with serine proteases comprising trypsin-, chymotrypsin-, and elastase-like enzymes, which decreased in diets containing CME, whereas, interestingly increased with CG. From the results, we conclude that CME isolated from S. melongena fruit extract shows feeding deterrent and larval development inhibitory activities that may prove useful in the management of S. litura and A. janata larvae.

Sublethal Effects of Spinosad (Tracer®) on the Cotton Leafworm (Lepidoptera: Noctuidae)

Abstract The effects of sublethal concentrations of spinosad (Tracer®) on development, fecundity, and food utilization, in the cotton leafworm, Spodoptera littoralis (Boisd.) were investigated. The fourth-instar larvae were fed on castor bean leaves treated with LC25 (13.9 ppm) or LC50 (57.8 ppm) of spinosad. Pupation and pupal weight were significantly reduced in both LC25 and LC50 treatments, compared with those of the controls. The fecundity rates of females in either LC25 or LC50 treatment were also reduced, compared with the controls. The residual activity of spinosad, applied on cotton at labeled field- and subfield-rates (200 and 70 g active substance (a.s.)/ 200 l water, respectively), was examined against the fifth-instar larvae of S. littoralis. Feeding deterrent effects were significantly demonstrated in larvae that fed on leaves collected from field plots with residual deposits of spinosad at 3 and 7 days old after application (DAA). The residual activity of spinosad on feeding and other metabolic parameters was decreased after 21 DAA indicating that the chemical started to degrade under field conditions. A histological study on midgut from larvae that previously fed on leaves treated with a concentration corresponding to the labeled-field rate of spinosad showed some alterations occurred after 48 and 96 h of treatment, compared to the normal midgut from the controls. The histological alterations included degeneration in the epithelial lining of the midgut and in the peritrophic matrix. Such histopathological effects are presumed to be responsible for the reduction in growth and food utilization caused by spinosad. It is, therefore, concluded that spinosad has sublethal effects on S. littoralis that may affect population dynamics in the field via reductions in survival and reproduction

Insecticidal and Feeding Deterrent Effects of Fraxinellone from Dictamnus dasycarpus against Four Major Pests

Fraxinellone, a well-known and significant naturally occurring compound isolated from Meliaceae and Rutaceae spp. has been widely used as a drug for the treatment of tumors. On the other hand, fraxinellone exhibited a variety of insecticidal activities including feeding-deterrent activity, inhibition of growth, and larvicidal activity. The present study focused on the antifeedant and larvicidal activities of fraxinellone against the larvae of Lepidoptera, including Mythimna separata, Agrotis ypsilon, Plutella xylostella, and one kind of sanitary pest, Culux pipiens pallens. Meanwhile, the ovicidal activities and the effects of fraxinellone on the larval development of M. separata were also observed. The LC50 values of fraxinellone against 3rd instar larvae of M. separata, 2nd instar larvae of P. xylostella and 4th instar larvae of C. pipiens pallens were 15.95/6.43/3.60 × 10−2 mg mL−1, and its AFC50 values against 5th instar larvae of M. separata, 2nd instar larvae of P. xylostella and 2nd instar larvae of A. ypsilon were 10.73/7.93/12.58 mg mL−1, respectively. Compared with the control group, fraxinellone obviously inhibited the pupation rate and the growth of M. separata. Once M. separata was treated with fraxinellone at concentrations of 5.0, 10.0, and 20.0 mg mL−1, respectively, the stages from the larvae to adulthood and the egg hatching duration were prolonged to 1/2/3, and 4/3/4 days, respectively. Additionally, fraxinellone strongly inhibited the development rate and the egg hatch proportion of M. separata.

The repellency of lemongrass oil against stable flies, tested using video tracking.

Lemongrass oil (Cymbopogon citratus) is an effective repellent against mosquitoes (Diptera: Culicidae) and house flies (Diptera: Muscidae). In this study, its effectiveness was assessed on stable flies (Diptera: Muscidae) in laboratory conditions. First, we demonstrated that lemongrass oil is an active substance for antennal olfactory receptor cells of Stomoxys calcitrans as indicated by a significant increase in the electroantennogram responses to increasing doses of lemongrass oil. Feeding-choice tests in a flight cage with stable flies having access to two blood-soaked sanitary pads, one of which was treated with lemongrass oil, showed that stable flies (n = 24) spent significantly more time in the untreated zone (median value = 218.4 s) than in the treated zone (median value = 63.7 s). No stable flies fed on the treated pad, whereas nine fed on the untreated pad. These results suggest that lemongrass oil could be used as an effective repellent against stable flies. Additional studies to confirm its spatial repellent and feeding deterrent effects are warranted.

Bioactivity of Selected Eco-Friendly Pesticides AgainstCylas formicarius(Coleoptera: Brentidae)

Seven low risk pesticides including 1.2% azadirachtin (Azadirachta indica), extracts from Morinda citrifolia, petroleum oil 97%, Beauveria bassiana strain GHA, mixed essential oils (rosemary oil: 0.25%, peppermint oil: 0.25%, thyme oil: 0.25%, clove oil: 0.25% and other ingredients: 99.00%), spinosad and malathion, were evaluated against adults of the sweetpotato weevil, Cylas formicarius (Fabricius) (Coleoptera: Brentidae) to determine potential insecticidal, repellent and feeding deterrence effects. Among the pesticides tested, A. indica and spinosad showed high insecticidal, repellent and feeding deterrence activity against C. formicarius. Spinosad, A. indica and malathion showed significantly higher insecticidal activity against C. formicarius. Similarly, these pesticides showed high repellency activity against adults, particularly 3–4 h after the treatment. The lowest food consumption was observed with the A. indica (0.8 g/adult/192 h), and the highest (9.9 g/adult/192 h) was with the petroleum oil spray. The other tested pesticides showed comparable activities. The chemicals we tested—particularly neem and spinosad—are therefore promising candidates as ecofriendly chemicals that could potentially replace broad-spectrum synthetic neurotoxins for control of C. formicarius.

Effect of chemical complexity of essential oils on feeding deterrence in larvae of the cabbage looper

The relationship between chemical composition and feeding deterrent activity of seven essential oils is explored, including those from Syzygium aromaticum (L.) Merr. & Perry (Myrtaceae), Cinnamomum zeylanicum Blume (Lauraceae), Lavendula latifolia (L.) Medicus, Lavendula angustifolia L., Mentha crispa L., Mentha arvensis L. and Mentha piperita L. (Lamiaceae) against an important agricultural pest, the cabbage looper (Trichoplusia ni Hübner, Noctuidae), using a leaf‐disc choice bioassay. Comparison of the deterrent activity of ‘full mixtures' with respective artificial blends missing individual constituents demonstrates that, for most oils, minor constituents in a mixture can be as important as major constituents with respect to the overall feeding deterrent effect. There is a lack of correlation between the feeding deterrent effect of an individual constituent of an essential oil and its contribution to the overall activity of the ‘full mixture’ in some cases. The effect of removing an individual constituent from the mixture of an essential oil depends on the unique properties of the mixture, which in turn may reflect the interaction of its constituents. Understanding the role and contribution of each constituent to the overall activity of the oil can facilitate the creation of artificial blends that optimize their efficacy against different pests.

ENTOMOTOXIC PROPERTIES OF PLANT EXTRACTS OF Azadirachta indica, Piper auritum and Petiveria alliacea FOR THE CONTROL OF Spodoptera exigua Hübner

The purpose of this study was to evaluate the antifeedant effect and toxicity of Azadirachta indica, Piper auritum and Petiveria alliacea ex-tracts on Spodoptera exigua larvae under laboratory conditions and in an open-field crop of organically-grown grape tomatoes var. Santa.The work was carried out with hexane and methanol extracts of A. indica seeds and P. auritum and P. alliacea leaves applied in different concentrations against 4th-stage S. exigua larvae. The variables evaluated were feeding deterrence index (FDI), feeding suppression in-dex (FSI), mortality rate and LC50. The strongest feeding deterrent effect was found in the methanol extract of Azadirachta indica, followed in descending order by that of P. auritum and P. alliacea. The mortality rates for A. indica, P. auritum and P. alliacea were 38.88, 28.8 and 21.22 %, respectively, under laboratory conditions; the same trend was found in the field. The LC50 showed that the methanol extract of A. indica was the most potent (4.03 ppm), followed in effectiveness by that of P. auritum (42.08 ppm). In the field, the LC50 of the methanol extracts of A. indica, P. auritum and P. alliaceae were 9.61, 21.21 and 104.1 ppm, respectively.

Antifeedant and toxic effects of naturally occurring and synthetic quinones to the cabbage looper, Trichoplusia ni

We investigated the feeding deterrent effects and toxicity of naturally occurring and synthetic quinones to the cabbage looper, Trichoplusia ni. Feeding deterrent effects were determined via a leaf disc choice bioassay. Based on DC 50 values, 1,4-naphthoquinone was the most active antifeedant ( DC 50 = 1.8 μg/cm 2) followed by juglone ( DC 50 = 2.1 μg/cm 2), 2-methoxy-1,4-naphthoquinone ( DC 50 = 2.6 μg/cm 2), plumbagin ( DC 50 = 3.3 μg/cm 2), and 2,3-dimethoxy-5-mehtyl-1,4-benzoquinone ( DC 50 = 4.2 μg/cm 2) in third instar cabbage looper larvae. 2-Bromo-1,4-naphthoquinone, 2-chloro-3-morpholino-1,4-naphthoquinone, 1,8-dihydroxy-anthraquinone, 2-methyl-1,4-naphthoquinone and naphthazarin had DC 50 values ranging from 8.4 to 10.1 μg/cm 2. Juglone and plumbagin were able to provide protection to intact cabbage plants in a greenhouse experiment. Cabbage looper larvae consumed less leaf area and weighed less on cabbage plants treated with either of these naturally occurring quinones. Most of the quinones demonstrated levels of antifeedant activity greater than neem, a positive control, in laboratory bioassays. The level of activity for juglone was comparable to neem in the greenhouse experiment. There was also a reduction in the number of larvae on treated plants compared with the negative control. Structure-activity relationships suggest that the antifeedant effects of the tested quinones depend on the number and position of hydroxyl and methoxyl substituents of quinones. Most of the quinones were of medium-low toxicity to third instar cabbage looper larvae via topical administration. Some of these quinones could have potential for development as commercial insect control agents targeting the feeding behavior of insects with minimal toxicity, provided that their impacts on non-target organisms and environment are minimal.

Artemisia annua extracts, artemisinin and 1,8-cineole, prevent fruit infestation by a major, cosmopolitan pest of apples

Context: Extracts of Artemisia annua (L.) (Asteraceae) and artemisinins are used for treatment of malaria, parasitic infections and have potent anticancer properties in cell lines. Eucalyptus oil and 1,8-cineole have antimicrobial, immune-stimulatory, anti-inflammatory, antioxidant, analgesic, and spasmolytic effects. Codling moth, Cydia pomonella, (L.) (Tortricidae), is a major cosmopolitan pest of the apple, potentially causing damage translating to 40 billion US dollars per year, globally. Currently used control measures are either hazardous to agricultural workers and harmful to environment, or ineffective. The potential of plant-derived semiochemicals for codling moth control is heavily understudied.Objective: This study evaluated the potential of A. annua extracts, and two chemicals that this plant contains, artemisinin and 1,8-cineole, for preventing apple feeding and infestation by neonate Cydia pomonella larvae.Methods: We studied effects of A. annua extracts, artemisinin and 1,8-cineole on apple infestation by neonate codling moth larvae using fruit choice assay in laboratory experiments. Preference of fruit treated with test solutions versus fruit treated with solvent was recorded and analyzed.Results: Crude A. annua extracts prevented fruit feeding at 1, 3, and 10 mg/ml. Artemisinin had feeding deterrent effects at 10 and 30 mg/ml, and 1,8-cineole at 100 and 300 mg/ml.Discussion and Conclusions: A. annua contains chemicals that prevent apple infestation by codling moth neonates. Artemisinin and 1,8-cineole are among them, but there are other, polar constituents of A. annua, which have similar effects. There is a potential of using our findings in codling moth control and production of codling moth-resistant apples.

Insecticidal and feeding deterrent activities of essential oils in the cabbage looper, Trichoplusia ni (Lepidoptera: Noctuidae)

AbstractTen essential oils were tested against the cabbage looper, Trichoplusia ni larvae for contact, residual and fumigant toxicities and feeding deterrent effects. Against third instar T. ni, Syzygium aromaticum (LD50 = 47.8 μg/larva), Thymus vulgaris (LD50 = 52.0 μg/larva) (the two positive controls) and Cinnamomum glanduliferum (LD50 = 76.0 μg/larva) were the most toxic via topical application. Litsea pungens (LD50 = 87.1 μg/larva), Ilex purpurea (LD50 = 94.0 μg/larva), Cinnamomum cassia (LD50 = 101.5 μg/larva) and Litsea cubeba (LD50 = 112.4 μg/larva) oils were equitoxic. Thymus vulgaris (LC50 = 4.8 mg/ml) and S. aromaticum (LC50 = 6.0 mg/ml) oils were the most toxic in residual bioassays. Cymbopogon citratus (LC50 = 7.7 mg/ml) and C. cassia (LC50 = 8.5 mg/ml) oils were equitoxic followed by Cymbopogon nardus (LC50 = 10.1 mg/ml) in this bioassay. The remaining five oils showed little or no residual effects. In a fumigation bioassay, L. cubeba (LC50 = 16.5 μl/l) and I. purpurea (LC50 = 22.2 μl/l) oils were the most toxic. Cinnamomum glanduliferum (LC50 = 29.7 μl/l) and Sabina vulgaris (LC50 = 31.2 μl/l) oils were equitoxic. Interestingly, S. aromaticum did not exhibit any fumigant toxicity. Cymbopogon citratus, C. nardus and C. cassia strongly deterred feeding by third instar T. ni (DC50s = 26.9, 33.8 and 39.6 μg/cm2, respectively) in a leaf disc choice bioassay. The different responses of T. ni larvae to the oils in different bioassays suggest that these essential oils exhibit different modes of action. Based on their comparable efficacy with essential oils already used as active ingredients in many commercial insecticides (i.e. clove oil and thyme oil), some of these essential oils may have potential as botanical insecticides against T. ni.

Field efficacy of pyrethroid treated plastic sheeting (durable lining) in combination with long lasting insecticidal nets against malaria vectors

BackgroundInsecticide treated plastic sheeting (ITPS), sometimes known as durable lining, has potential as a long-lasting insecticidal surface for malaria vector control when used as lining for interior walls and ceilings inside the home. Against a backdrop of increasing long lasting net (LN) coverage, we examined the effect of combining permethrin-treated plastic sheeting (ITPS) with LNs in Burkina Faso.MethodsA verandah trap experimental hut trial of ITPS with or without Olyset LN was conducted in the Vallée du Kou near Bobo-Dioulasso, where the two molecular forms of Anopheles gambiae s.s., S (frequency 65%) and M (frequency 35%), occur. The S form is mostly pyrethroid resistant (Fkdr = 92%) owing to the kdr mechanism, and the M form is mostly kdr susceptible (Fkdr = 7%). The treatment arms included ITPS, Olyset, ITPS plus Olyset, ITPS plus untreated net (with or without holes), and untreated control.ResultsITPS was significantly inferior to Olyset LN in terms of mortality (37% vs 63%), blood feeding inhibition (20% vs 81%) and deterrence (0 vs 42%) effects, and hence altogether inferior as a means of personal protection (16% vs 89%). The addition of ITPS to Olyset did not improve mortality (62%), blood feeding inhibition (75%), deterrence (50%) or personal protection (88%) over that of Olyset used alone. Use of untreated nets - both holed and intact - with ITPS provided greater protection from blood-feeding. The intact net/ITPS combination killed more mosquitoes than ITPS on its own.ConclusionsAlthough ITPS has a potential role for community control of malaria, at low coverage it is unlikely to be as good as Olyset LNs for household protection. The combination of pyrethroid IRS and pyrethroid LN - as practiced in some countries - is unlikely to be additive except, perhaps, at high levels of IRS coverage. A combination of LN and ITPS treated with an alternative insecticide is likely to be more effective, particularly in areas of pyrethroid resistance.

Antifeedant, larvicidal and pupicidal activities of Atalantia monophylla (L) Correa against Helicoverpa armigera Hubner (Lepidoptera: Noctuidae)

Antifeedant, larvicidal and pupicidal activities of hexane, chloroform and ethyl acetate extracts of Atlantia monophylla leaf were studied against third instar larvae of Helicoverpa armigera. All the extracts showed feeding deterrent, larvicidal and pupicidal effects in a dose dependent manner. Significant antifeedant, larvicidal and pupicidal activities were observed only in hexane extract. The hexane extract was subjected to fractionation using silica gel column chromatography. Twelve fractions were obtained. Ninth fraction showed good antifeedant, larvicidal, pupicidal activities and disrupted adult emergence. LC 50 value was at 384.57 ppm for larval mortality. The active fraction at 1000 ppm concentration had 100% pupal mortality.

Heart of glass: spicule armament and physical defense in temperate reef sponges

Siliceous inclusions play an important role in deterring terrestrial herbivores, but their role in marine systems remains controversial. Sponges are ubiquitous members of marine benthic communities and represent a potentially valuable food source for many predatory species, yet they have few natural predators. An in situ method was used to assess the deterrent effects of siliceous spicules or whole sponge skeleton, which were hypothesised to act as a physical defense in temper- ate reef sponges. Natural concentrations of spicules from 5 species of sponge and the spongin skele- ton from a sixth species were incorporated into artificial diets, which were similar in nutritional qual- ity to the sponge tissues. These were offered to the sea urchin Centrostephanus rodgersii in feeding choice experiments including control discs containing no spicules or spongin skeleton. Spicules from 4 species, Tedania anhelans, Clathria pyramida, Chondrilla australiensis and Chondrilla sp., deterred feeding by C. rodgersii. Spicules from a fifth species, Callyspongia sp., and intact skeleton isolated from Cacospongia sp., failed to deter C. rodgersii. This is the first demonstration of antifeedant activ- ity associated with skeletal elements against sea urchins. Importantly, unlike previous work in the tropics, very small spicules (microscleres) measuring <100 µm were effective feeding deterrents.

Leaves of Citrus aurantifolia exhibit a different sensibility to solar UV-B radiation according to development stage in relation to photosynthetic pigments and UV-B absorbing compounds production

Plants of Citrus aurantifolia grown in a greenhouse without solar UV radiation (UVR) were transferred outdoors to evaluate the effect of solar UV-B radiation (UVBR, 280–315 nm) in prior-developed leaves, constituted by apical bud and those fully expanded before being taken outdoors, and post-developed leaves, formed by those expanded outdoors. Results demonstrated that over a 40 d outdoor period leaf chlorophyll content and distribution pattern were different with and without solar UVBR. Chlorophyll a, chlorophyll b and total chlorophyll contents in both treatments were higher in prior-developed leaves than in post-developed ones. However, highest values were observed in prior-developed leaves under solar UVBR, whereas in post-developed leaves an opposite trend was observed. Carotenoids content in prior-developed leaves was higher with solar UVBR, whereas in post-developed leaves there were no significant differences in both with and without solar UVBR. In addition, prior-developed leaves under solar UVBR accumulated flavonoids, but not anthocyanins. Growth parameters (e.g. DW, DW/FW ratio, LMA, plant height, length and width of foliar lamina) did not show significant differences between plants grown with and without solar UVBR. Thus, our results demonstrated that C. aurantifolia leaves exhibited a different sensibility to solar UVBR according to development stage in relation to photosynthetic pigments and UV-B absorbing compounds production. In addition, the solar UVBR was not necessary as inductor of photosynthetic protection mechanisms in a short-time growth period. On the other hand, our results also demonstrated that solar UVBR acted as an effective feeding deterrent against citrus leafminer.