Antifeedant Index Research Articles

Effect of the extracts of the spiderflower, Cleome arabica, on feeding and survival of larvae of the cotton leafworm, Spodoptera littoralis.

Aqueous and organic (hexane, chloroform, and methanol) extracts of siliquae, stems and leaves, and seeds of Cleome arabica L. (Brassicales: Capparidaceae) were evaluated in the laboratory for their antifeeding and insecticidal effect on larvae of the cotton leafworm, Spodoptera littoralis (Boisduval) (Lepidoptera, Noctuidae), using a leaf dipping bioassay with castor bean, Ricinus communis L. (Malpighiales: Euphorbiaceae), leaf discs. The polar extracts caused significant mortality. At the highest dose, C. arabica extracts exhibited significant antifeeding and phagostimulating activities against S. littoralis larvae. Under no-choice conditions, the methanol extract of siliquae was the most active, and the antifeedant index calculated over 24 hr for 3rd instar larvae varied significantly from 16 to 37%. Using nutritional indices, it was established that there was a significant decrease in growth rate concomitant with a reduction in consumption. These results suggest the presence of anti-feeding and/or toxic substances in the extracts that may be useful in developing bio-insecticides based on C. arabica extracts for use in integrated pest management of leafworm and other agricultural pests.

Antifeedant, insect growth regulatory and insecticidal effects of Calceolaria talcana (Calceolariaceae) on Drosophila melanogaster and Spodoptera frugiperda

Extracts from Calceolaria talcana exhibited strong bioinsecticidal effects against Drosophila melanogaster and Spodoptera frugiperda. The most active extract was ethyl acetate and its majority compound verbascoside. The highest lethal concentration to the larvae of S. frugiperda and D. melanogaster was 20.0μg/ml of the ethyl acetate extract with 95.8% and 67.0% of mortality, respectively. Against D. melanogaster the ethyl acetate extract showed the highest activity with 75.05% of antifeedant index at 25μg/ml, methanol extract instead showed 100% to 100μg/ml. At very low concentrations ethyl acetate and methanol extracts induce antifeedant and insect growth regulatory activity showing selective effects as deterrent and on the sclerotization showing a pre-emergence effect on S. frugiperda. The results from these extracts were better than showed by methanol extracts from Cedrela salvadorensis, Myrtillocactus geometrizans and Yucca periculosa samples used as positive controls.

Biological activity of essential oils of Athamanta haynaldii and Myristica fragrans to gypsy moth larvae

Ethanol solutions of essential oils obtained from Athmanta haynaldii and Myristica fragrans were tested for their toxicity and antifeedant activity against the second instar gypsy moth larvae in the laboratory bioassay. Both isolated oils were subjected to gas chromatography analysis in order to determine their chemical constitutions. Tested oils showed low to moderate larvicidal effect in both residual toxicity test and in chronic larval mortality bioassay. However, antifeedant index achieved by application of tested solutions in feeding choice assay was significantly higher in comparison to control, and almost same as one provided with botanical standard. Low toxic and high antifeedant properties (AF index 85–90%) make these essential oils suitable for integrated pest management programs. Special attention should be paid to further investigation of endemic and rare A. haynalidii in the terms its cultivation and usage of its unique set of biologically active compounds.

Metabolites from Aspergillus fumigatus, an Endophytic Fungus Associated with Melia azedarach, and Their Antifungal, Antifeedant, and Toxic Activities

Thirty-nine fungal metabolites 1-39, including two new alkaloids, 12β-hydroxy-13α-methoxyverruculogen TR-2 (6) and 3-hydroxyfumiquinazoline A (16), were isolated from the fermentation broth of Aspergillus fumigatus LN-4, an endophytic fungus isolated from the stem bark of Melia azedarach. Their structures were elucidated on the basis of detailed spectroscopic analysis (mass spectrometry and one- and two-dimensional NMR experiments) and by comparison of their NMR data with those reported in the literature. These isolated compounds were evaluated for in vitro antifungal activities against some phytopathogenic fungi, toxicity against brine shrimps, and antifeedant activities against armyworm larvae (Mythimna separata Walker). Among them, sixteen compounds showed potent antifungal activities against phytopathogenic fungi (Botrytis cinerea, Alternaria solani, Alternaria alternata, Colletotrichum gloeosporioides, Fusarium solani, Fusarium oxysporum f. sp. niveum, Fusarium oxysporum f. sp. vasinfectum, and Gibberella saubinettii), and four of them, 12β-hydroxy-13α-methoxyverruculogen TR-2 (6), fumitremorgin B (7), verruculogen (8), and helvolic acid (39), exhibited antifungal activities with MIC values of 6.25-50 μg/mL, which were comparable to the two positive controls carbendazim and hymexazol. In addition, of eighteen that exerted moderate lethality toward brine shrimps, compounds 7 and 8 both showed significant toxicities with median lethal concentration (LC(50)) values of 13.6 and 15.8 μg/mL, respectively. Furthermore, among nine metabolites that were found to possess antifeedant activity against armyworm larvae, compounds 7 and 8 gave the best activity with antifeedant indexes (AFI) of 50.0% and 55.0%, respectively. Structure-activity relationships of the metabolites were also discussed.

Dose–response relationships for the antifeedant effects of Humulus lupulus extracts against larvae and adults of the Colorado potato beetle

Dose-response relationships for antifeedant effects of H. lupulus extracts against larvae and adults of the Colorado potato beetle (CPB) were determined in laboratory conditions. The larval and adult beetles were fed on potato leaflets treated with H. lupulus extract ranging from 0.4 to 40 mg mL(-1) in a no-choice situation. Their feeding behavior was recorded, and larval growth and antifeedant indexes were calculated. H. lupulus treatments significantly affected larval growth rate, and at higher concentrations the larval weights were significantly reduced over the course of the assay. Adults of CPB were more sensitive to the extracts than the larvae, and, even at lower doses, adult beetles were arrested for longer periods than larvae. These results indicate that H. lupulus extracts may have potential for control of CPB, particularly in organic farms where conventional insecticides are not available.

Antifeedant Activity of Citrus Waste Wax and Its Fractions Against the Dry Wood Termite,Cryptotermesbrevis

The wood protective action of citrus wax, a waste from the citrus industry that is a mixture of citrus fruit epicuticular waxes and essential oils, was evaluated against the termite Cryptotermes brevis Walker (Isoptera: Kalotermitidae). The antifeedant index (AI) of the total wax and fractions was calculated. The total citrus wax exhibited an AI50 value of 24.69 mg/cm3, the wax after hydrodistillation showed the strongest antifeedant property (AI50 11.68 mg/cm3). Fractionation of the wax and gas chromatography—mass spectrometric analysis allowed the identification of coumarins and furancoumarins as the active compounds. These results suggest the potential use of these industrial residues as a natural approach to termite control.

Feeding perturbation and toxic activity of five Chrysanthemum species crude extracts against Spodoptera littoralis (Boisduval) (Lepidoptera; Noctuidae)

The effect of the whole methanol extracts of five Chrysanthemum species on feeding and performance of Spodoptera littoralis (Boisduval) larvae has been investigated in vitro. The extracts exhibited an anti-feeding and phagostimulating activities against cotton leafworm larvae when applied either on leaf discs or incorporated into an artificial diet. Under chosen conditions, the antifeedant index calculated over 24 h for sixth instar larvae significantly varied from 78.55 for Chrysanthemum segetum L. to −44.18 for Chrysanthemum fuscatum Desf. at the dose of 1000 ppm. Toxicity of the extracts was manifested by a high mortality, reduced growth rates, and low weight gain by larvae fed on diets containing 1000–10,000 ppm of the extract. Anyone of the larvae treated with C hrysanthemum macrotum (D.R.) Ball. leaves crude extract survived to pupation at the two higher concentrations. The time to pupation increased for Chrysanthemum grandiflorum flowers crude extract from 11.40 ± 0.93 to 28.93 ± 10.92 days as the extract concentration in the diet increased from 0 to 10,000 ppm. The ingestion of crude extract by the third instar larvae reduced significantly the consumption, growth and utilisation of the ingested and digested food, and reduced digestibility. The crude extract of the leaves of C. macrotum, dissolved in acetone and topically applied on sixth instar larvae, showed a quite high mortality (95%). These results suggest the presence in the extracts of anti-feeding and/or toxic substances, active by consumption and topical application. The identification of these compounds and their action mode will be object of further studies.

A new benzil derivative from Derris scandens: Structure-insecticidal activity study

Bioactivity-directed investigation of root extract of Derris scandens has led to the isolation and characterization of a new benzil derivative ( 11), along with ten known compounds ( 1– 10). Their structures were determined on the basis of extensive spectroscopic (IR, MS, 1D and 2D NMR) data analysis and by comparison with the literature data. The insect antifeedant activity and growth inhibitory studies of these compounds were investigated against castor semilooper pest, Achaea janata using a no-choice laboratory bioassay . Several of the isolates displayed potent feeding deterrence and were also toxic or caused developmental abnormalities following topical administration. The new compound, derrisdione A was moderately active with an antifeedant index of 58.6 ± 1.7% at 10 μg/cm 3 against A. janata.

Antifeedant activity of ethanolic extract from Flourensia oolepis and isolation of pinocembrin as its active principle compound

The ethanolic extract from Flourensia oolepis aerial parts showed strong antifeedant activity against the pest larvae, Epilachna paenulata, with an antifeedant index (AI%) of 99.1% at 100 μg/cm 2. Based on chromatographic fractionation of the extract, guided by bioassays on E. paenulata, the flavanone pinocembrin ( 1) was isolated as the most active principle. In a choice assay, compound 1 showed strong antifeedant activity against E. paenulata, Xanthogaleruca luteola and Spodoptera frugiperda with an AI% of 90, 94 and 91% ( p < 0.01) respectively, at 50 μg/cm 2. The dosages necessary for 50% feeding inhibition of the insects (ED 50) were 7.98, 6.13 and 8.86 μg/cm 2, respectively. The feeding inhibitory activity of 1 against E. paenulata was compared with the activity of other structurally related flavonoids like naringenin, which was inactive up to 100 μg/cm 2, catechin which was nearly 6 times less active than 1, and quercetin which was equally active as 1. The effect of these on the feeding behavior of E. paenulata was also studied.

Antifeedant Activty Of Different Organic Solvent Crude Extracts Of &lt;i&gt;Euphorbia hirta&lt;/i&gt; Latex On The Edible Tropical Land Snail (&lt;i&gt;Limicolaria aurora&lt;/i&gt;)

The antifeedant activity of different organic solvents (acetone, carbon tetrachloride, chloroform, diethyl ether and ethyl alcohol) crude extracts of latex of Euphorbia hirta (family Euphobiaceae) against Limicolaria aurora was investigated, and compared with a control, using pawpaw, (Carica papaya) as bait, at a concentration of 200&#956g/g. Results showed no mortalities. E. hirta extracts depressed diet consumption when compared to control with lower antifeedant index range from 12 to 43% after a 96 hr exposure in plastic snaileries under controlled laboratory conditions. Carbon tetrachloride recorded the highest antifeedant index of 43.24% and the lowest consumption of 3.57 ±2.97g. Keywords : Edible tropical land snails, antifeedant, plant extract, Euphorbia hirta Journal of Agriculture, Forestry and the Social Sciences Vol. 4 (2) 2006: pp. 149-155

Antifeedant activities of secondary metabolites from Ajuga nipponensis against adult of striped flea beetles, Phyllotreta striolata

Antifeedant activities of the isolated chemical compounds from Ajuga nipponensis, were studied against adult of striped leaf beetles. The methanol, petroleum ether, ethyl acetate and n-butanol extracts at 1.0 mg/ml, were used in this study. All four extracts exhibited more than 65 antifeedant index at 24 h and ethyl acetate extract showed significant activity against striped leaf beetles with 83.12 antifeedant index. Six compounds and one fraction were isolated by chromatography and their structures were identified by NMR, MS and FTIR spectra. At 2.0 mg/ml for 24 h the three compounds 20-hydroxyecdysone, acacetin and apigenin showed considerable activities with antifeedant indexes 59.29, 51.22 and 61.55, respectively. In contrast to this the antifeedant indexes of acacetin and apigenin, were sharply reduced as the time extended and that of 20-hydroxyecdysone remained unchanged. In addition, the synergistic effects of two mixtures of secondary metabolites, were studied and no sharp difference was observed.

Larvicidal and antifeedant activity of some plant-derived compounds to Lymantria dispar L. (Lepidoptera: Limantriidae)

Ethanol solutions of essential oil of Ocimum basilicum and its main component, linalool (both isomer forms), all in three concentrations, as well as botanical standard Bioneem (0.5%), were tested for their toxicity and antifeedant activity against the second instar gypsy moth larvae in the laboratory bioassay. The essential oil of O. basilicum was subjected to gas chromatography analysis, and totally 37 compounds were detected, of which linalool was predominantly present.All tested solutions showed low to moderate larvicidal effect in both residual toxicity test and in chronic larval mortality bioassay. Chronic mortality tests showed that obtained mortality was a consequence of starving rather than ingestion of treated leaves. However, antifeedant index achieved by application of tested solutions in feeding choice assay was remarkable. Foliar application of all tested compounds deterred feeding by L2 in the same percent as Bioneem. Antifeedant index was relatively high at all tested treatments (85–94%); moreover, the larval desensitization to repelling volatiles has not occurred after five days of observation. Low toxic and high antifeedant properties make these plant-derived compounds suitable for incorporation in integrated pest management programs, especially in urban environments.

Insecticidal activity influence of destruxins on the pathogenicity of Paecilomyces javanicus against Spodoptera litura

Abstract: The bioactivities of destruxins (dtx), depsipeptides isolated from Metarhizium anisopliae, against Spodoptera litura were tested in laboratory. For contacting toxicities, dtx‐E was more effective than dtx‐A and dtx‐B. The LC50s values of dtx‐A, B and E were 197.98, 292.00 and 113.99 mg/l at 48 h after treatment, while the LT50s were 42.65, 59.45 and 23.68 h at 300 mg/l. In the experiment of antifeedant activity, dtx‐A, dtx‐B and dtx‐E at five concentrations (200, 100, 50, 25 and 12.5 mg/l) were bioassayed. Destruxins in a dose‐dependent manner gave an apparent antifeedant activity. Generally, dtx‐A, over dtx‐B and dtx‐E had the significant (P &lt; 0.05) larger choice and no‐choice antifeedant indexes (CAIs and NCAIs). At the concentration of 200 mg/l, the CAIs or NCAIs of dtx‐A, dtx‐B and dtx‐E were 96.78, 84.93 and 85.90 or 89.75, 62.42 and 72.28 respectively. Furthermore, the synergistic activity of crude destruxin (CD) for pathogenicity of Paecilomyces javanicus strain Pj01 was detected. The LC50s values of single Pj01 and the mixtures of Pj01 plus CD at 100 or 200 mg/l (Pj01‐CD100 or Pj01‐CD200) were respectively 474.63 × 105, and 197.45 × 105 or 113.11 × 105 spores/ml at the fifth day after treated. Meanwhile, Pj01, Pj01‐CD100 and Pj01‐CD200 gave the LT50s values of 6.99 day, 5.49 day and 4.21 day at 100 × 105 spores/ml. Clearly, dtx decreased the values of LC50 and LT50 of the strain Pj01.

Toxicity and feeding deterrence of crude toxin extracts of Lecanicillium (Verticillium) lecanii (Hyphomycetes) against sweet potato whitefly, Bemisia tabaci (Homoptera: Aleyrodidae)

Crude toxins [toxin(V3450) and toxin(Vp28,) extracted from Lecanicillium (Verticillium) lecanii (Zimmermann) Gams & Zare strain V3450 and Vp28 respectively] were tested for contact toxicity, feeding deterrence and repellent activity against the sweet potato whitefly, Bemisia tabaci (Gennadius) (Homoptera: Aleyrodidae). Both toxins showed ovicidal activity to eggs, with LC(50) values of 447 and 629 mg L(-1) respectively. Nymphs of B. tabaci were the most susceptible stages (LC(50) values were calculated at 111 mg L(-1) for toxin(V3450) and 216 mg L(-1) for toxin(Vp28)), and adults were the second most susceptible stages (48 h LC(50) values were calculated at 178 mg L(-1) for toxin(V3450) and 438 mg L(-1) for toxin(Vp28)). Applied to seedlings at a concentration of 400 mg L(-1), the toxins significantly (P < 0.001) reduced the hatching of whitefly eggs and the subsequent survival rate of the nymphs, and the emergence and fecundity of the progeny adults. Both toxins exhibited repellent activity at low concentration (100 mg L(-1)), with repellency index (RI) values of 0.645 for toxin(V3450) and 0.642 for toxin(Vp28), and antifeedant activity at high concentration (1000 mg L(-1)) to adults, with antifeedant index (AFI) values of 0.713 for toxin(V3450) and 0.749 for toxin(Vp28). The results of the present study demonstrate the toxicity, repellence and antifeedant properties of the fungi metabolite toxins on B. tabaci, which might develop as environmentally friendly plant protectant(s).

Antifeedant effects of several plant extracts on Colorado potato beetle larvae

The antifeedant activities of methanolic extracts made from seven plant species (Abutilon theophrasti Medic., Ajuga chamaepitys (L.) Schreb., Amorpha fruticosa L., Matricaria chamomilla L., Matricaria inodora L., Tanacetum vulgare L. and Tilia cordata Mill.) were assessed in the laboratory at 0.5% and 5% dosages against Colorado potato beetle (Leptinotarsa decemlineata Say) larvae. Three h and 24 h dual-choice and 3 h no-choice feeding bioassays were carried out with potato (Solanum tuberosum L.) leaf discs. Furthermore, during the no-choice test direct observations on larval behaviour were performed to help to distinguish the mode of action which underlies inhibition of feeding. At a dosage of 0.5% no plant extract deterred feeding of larvae. At 5% Matricaria inodora (and our standard Ajuga chamaepitys with well-known antifeedant properties) was the most potent antifeedant of the seven extracts tested. Antifeedant indexes and results of the behavioural observations suggest that M. inodora acts as a sensory mediated feeding deterrent, rather than as a toxin.

Feeding Response to Host and Nonhost Compounds by Males and Females of the Spruce Bark Beetle Ips typographus in a Tunneling Microassay

Research on host selection by bark and wood boring insects has concentrated on flight orientation behavior. Less is known of the factors that govern the steps successive to host landing. Here, we discuss chemical factors involved in host acceptance by bark beetles and a new microassay. Adult males and females of Ips typographus were offered an artificial diet treated with various concentrations of different plant-derived compounds (host terpenes and nonhost compounds) in a no-choice mode. Beetles were tested individually in a glass tube for 4 hr, and the length of feeding was measured and compared to a control (diet with only solvent). The first effect was diet rejection, especially when nonhost compounds were tested at high concentrations. Most compounds reduced feeding, in proportion to concentration. Females fed more readily than males after addition of both host and nonhost compounds. Diet removal was significantly affected by all the tested factors (sex, compound, dose) as well as by their interactions. With increased concentrations, males were more responsive than females to antifeedants, as all compounds (except juglone) showed clear sex differences of diet consumption. 3-Octanol, 1-hexanol, and a Green Leaf Volatile (GLV)-blend (three C6 alcohols) showed the strongest antifeedant effects, which started at a low dose (0.1%) and had a low Effective Dose 50 (ED50, 0.3-1%). In contrast, host monoterpenes, limonene and alpha-pinene, inhibited feeding at high doses (10-30%) only, with ED50 > 10%. The highest Antifeedant Indexes were shown by verbenone, carvone, and 1-hexanol (AFI = 0.90-1.00). Both host and nonhost compounds inhibited feeding at some concentration. No significant stimulation of feeding by any host compound at concentrations reported in the literature as optimal were found, with the possible exception of alpha-pinene at low concentrations in females.

Antifeedant and toxic activity of Adhatoda vasica leaf extract against Spodoptera littoralis (Lep., Noctuidae)

Abstract: The effect of crude methanolic extracts of Adhatoda vasica leaves on the feeding and performance of Spodoptera littoralis larvae was investigated in the laboratory. Feeding on fresh leaves resulted in 100% mortality of larvae after 26 days of unsubstantial growth. The extract exhibited strong antifeedant and toxic activity against the larvae when applied either on leaf discs or incorporated into artificial diet. Under choice conditions the antifeedant index calculated over 72 h for neonate larvae increased significantly (from 71.5 ± 3.2 to 92.1 ± 4.2) as the concentration of extract in the treated diet increased from 200 to 1000 ppm. Consumption by the sixth instar larvae of leaf discs dipped in 0.01, 0.1 and 0.2% extract solutions was significantly lower than consumption of control discs in both choice and no‐choice tests. The latter two concentrations deterred feeding by 63.4 and 90.4%, respectively, under choice conditions, while only the 0.2% extract solution deterred feeding by 56.8% in the no‐choice test. Toxicity of the extracts was manifested by a high mortality, reduced growth rates, and low weight gain by larvae fed on diets containing 200–2000 ppm of the extract. No larvae survived to pupation under the latter concentration. The time to pupation increased from 15.8 ± 0.4 to 37.9 ± 4.1 days as the extract concentration in diet increased from 0 to 1000 ppm. When fed to the fifth instar larvae, the crude extract significantly reduced consumption, growth, utilization of ingested and digested food, and approximate digestibility. The consumption‐dependent growth efficiency of animals fed on extract‐free diet was significantly higher than the growth efficiency of animals fed on extract‐containing diets, suggesting both antifeedant and toxic activities of the extract.

Perception de substances antiappétentes par des chenilles de lépidoptères phytophages

Antifeeding agents are mainly organic compounds issued from the metabolic pathways of plants that interrupt food intake by phytophagous insects. These substances can be toxic but generally do not directly kill the insect; it will die by inanition. Antifeeding agents are recognized by taste receptors located on the maxilla and epipharynx. In caterpillars, the two medial and lateral sensilla, the main organs involved in chemoreception, are located on the galea. They are uniporous at their apical extremity and contain four bipolar gustatory neurones, and another one that is a mecanoreceptor. As for olfactory organs, the dendritic parts of these neurones are soaked in a sensory liquor that transports chemical stimuli from outside to the membranous receptors. Antifeeding agents belong to various classes of chemicals and it is not possible to correlate their biological activity with common structural features. Main representatives are terpenoids (drimanes, clerodanes, limonoids, agarofurans) and steroids (phytoecdysteroids). Antifeeding activities can be evaluated by the amount of treated food eaten by a caterpillar in comparison with the reference. Antifeeding agents can be classified by their feeding ratio 50: FR 50 or by their antifeedant index 50: AFI 50. These values must be calculated for each studied species, each one showing different sensitivity for the same compound. Responses of gustatory neurones to a stimulation with an antifeeding agent can be recorded at the extracellular level by electrophysiological techniques, derived from the pioneer work of Hodgson. When stimulated, these neurones respond by characteristic spikes that depend of the recognition capacity of the neurone, and many hypotheses have been formulated to explain the modalities of this recognition. The most commonly accepted is that antifeeding agents selectively stimulate a special gustatory cell: the deterrent cell. Activation of this cell is often associated with simultaneous inhibition of other gustatory cells involved in perception of phagostimulants like sugars and free aminoacids. The occurrence of the deterrent cell has been demonstrated for many phytophagous caterpillars and can explain repellence for the non-host plants. Phytoecdysteroids are secondary metabolites widely spread in the plant kingdom and it has been hypothesized that they act as defensive substances against herbivorous. Two categories of caterpillars in relation to their sensitivity to the substance have been proposed: the tolerant ones that accept relatively large amounts of phytoecdysteroids in their diet, and the sensitive ones that reject diet with even low amounts. According to this classification, polyphagous species must be tolerant, and at the opposite monophagous species sensitive (diet breadth hypothesis). To verify this hypothesis, the antifeeding activity of three phytoecdysteroids (ecdysone: E, 20-hydroxyecdysone: 20E, and ponasterone: A ponA) has been evaluated on four caterpillars species, one monophagous Bombyx mori, one oligophagous Mamestra brassicae, and two polyphagous Spodoptera littoralis and Ostrinia nubilalis. Using feeding tests, it has been found that the two last instar larvae of B. mori and M. brassicae avoid diet containing 20E or ponA with a respective threshold of 200 and 500 ppm but are both insensitive to E even at higher concentrations. S. littoralis larvae (L4) are tolerant to the three phytoecdysteroids, but surprisingly O. nubilalis larvae (L5), a polyphagous species, is very sensitive, even at very low concentration (25 ppm). Electrophysiological recordings are consistent with the occurrence of the deterrent cell located in the medial sensilla of B. mori and the lateral one of M. brassicae that answers to 20E and ponA but not to E, revealing the importance of the 20-hydroxyl group on the lateral chain of the steroid nucleus. This deterrent cell is also present in both sensilla of O. nubilalis and responds to the three phytoecdysteroids at very low thresholds. Responses of S. littoralis are not different to the standard (KCl or fructose). The diet breadth hypothesis is verified for B. mori, M. brassicae and S. littoralis. It is not true for O. nubilalis, a polyphagous species, which must be tolerant to phytoecdysteroids acordingly to the hypothesis. The question is to know whether O. nubilalis is an exception, or if the diet breadth hypothesis that has been proposed after observations on a few number of species, is applicable on a large scale.

Antifeedant Properties of Destruxins and their Potential Use with the Entomogenous Fungus Metarhizium anisopliae for Improved Control of Crucifer Pests

Destruxins A, B and E, produced by the entomogenous fungus Metarhizium anisopliae, are insecticidal but comparatively low doses have antifeedant properties. Treatment of cabbage leaf discs with destruxins significantly reduced feeding by larvae of Plutella xylostella and Phaedon cochleariae in both choice and no-choice assays. The Antifeedant Index (AI) was dose related and there were significant differences between treated and untreated leaves. The AI and acute toxicity assays suggest that insect death was due to a combination of the starvation and toxicity effects of destruxins. In whole plant experiments, adults and larvae of P. cochleariae were found to be more susceptible to infection by M. anisopliae V245 if it was used in conjunction with a crude destruxin mixture. Destruxins drove larvae off the plant, irrespective of which leaf surface was treated. Adults could be forced to the adaxial or abaxial surface of leaves using the crude destruxin. Mortality was usually more consistent and generally greater if adults were forced to abaxial than adaxial surfaces inoculated with the fungus. High humidity on the abaxial surface favoured conidia germination and infection. Mortality was also greater for adults dusted with the pathogen and forced to the abaxial rather than to the adaxial leaf surface. The increased movement and starvation associated with destruxin treatment may also have stressed the insects making them more susceptible to infection.

The role of DIMBOA on the feeding of Asian corn borer, Ostrinia furnacalis (Guenée) (Lep., Pyralidae)

The role of 2,4‐dihydroxy‐7‐methoxy‐(2H)‐1,4‐benzoxazin‐3(4H)‐one (DIMBOA), on feeding of Asian corn borer (ACB), Ostrinia furnacalis (Guenée), was observed and quantified. DIMBOA had an antifeedant effect on ACB and a mathematical model was built for the correlation between DIMBOA concentration and antifeedant index. DIMBOA increased the time that the larvae required to reach the pupal stage and the larval weights in treatment were significantly less than those in control. The number of entrances of ACB on the plant sites were positively correlative to the DIMBOA concentrations, suggesting that feeding stimulants in the corn plants could probably override the antifeedant effect of DIMBOA