Effects of dietary protein and lupine alkaloids on growth and survivorship ofSpodoptera eridania

Toxic chemicals and nutrients are often positively correlated within and among plants. We studied how such correlations affect the suitability of plants as food for herbivores by assessing the growth and survivorship ofSpodoptera eridania (army worm) on artificial diets containing lupine alkaloids and casein. We found that (1) the effects of casein were determined by other dietary components: increased dietary casein led to increased larval growth only when the diet was also high in wheat germ. (2) Dietary alkaloids were effective at very low concentrations, reducing both growth and survivorship. The alkaloids lupanine and sparteine were not synergistic in their effects, and the interaction between alkaloids and casein was significant only in the low-wheat-germ diets. (3) The effects of casein and alkaloids were generally apparent only in the first instar, and the growth of fifth-instar larvae was unaffected by diet. (4) Using these artificial diet experiments, we can make simple predictions about the food quality of plants grown under various nutrient regimes. These predictions are consistant with recent ideas about optimal plant defenses.     

Influence ofAmaranthus hybridus L. allelochemics on oviposition behavior ofSpodoptera exigua andS. eridania (Lepidoptera: Noctuidae)

Common pigweed,Amaranthus hybridus L., is a favorite host of the beet army worm (BAW),Spodoptera exigua L. Chemicals extracted from homogenized pigweed with distilled water, ethanol, or dichloromethane and sprayed back on pigweed deterred oviposition by the BAW. Similarly, water extracts of frass from conspecific larvae or southern armyworm (SAW) larvae,S. eridania (Cramer), fed pigweed leaves and sprayed back on pigweed plants also deterred BAW oviposition, thus confirming that deterrence was due to plant allelochemics rather than specific compounds associated with the metabolic or excretory products of the larvae. Confirmation of the presence of oviposition-deterring chemicals in pigweed was used to explain a previously observed seasonal displacement of BAW by SAW on pigweed in the field.Mention of a commercial or proprietary product does not constitute an endorsement by the USDA.     

Effect of qualitative and quantitative variation in allelochemicals on a generalist insect: Iridoid glycosides and the southern armyworm

The behavioral and physiological effects of plant allelochemicals have been difficult to demonstrate; it is not often clear whether the compounds are deterrent, toxic, or both. In this study, we compared the qualitative and quantitative effects of several iridoid glycosides on a generalist lepidopteran herbivore,Spodoptera eridania (Noctuidae). Larval growth and survivorship and larval preference or avoidance were measured on artificial diets containing different iridoid glycosides at different concentrations. We also tested the toxicity/deterrence of these compounds. We found that iridoid glycosides retarded larval growth significantly at relatively low concentrations and that they were usually avoided in preference tests. The toxicity/ deterrence test did not always reflect the results of these other tests. The merits of using a variety of methods for determining deterrence and/or toxicity of plant allelochemicals are discussed.     

Behavioral responses ofSpodoptera littoralis males to sex pheromone components and virgin females in wind tunnel

The major component of the sex pheromone of femaleSpodoptera littoralis, (Z,E)-9,11-tetradecadienyl acetate (1), elicited all steps of the male behavioral sequence, i.e., wing fanning and taking flight, oriented upwind flight and arrival to the middle of the tunnel, close approach and contact with the source. The activity was equivalent to that elicited by virgin females. In the range of doses tested, the dosage of1 had no significant effect on the number of source contacts. Male response was significantly affected by light intensity, being optimum at 3 lux. Activity of the minor components (Z)-9-tetradecenyl acetate (2), (E)-11-tetradecenyl acetate (3), tetradecyl acetate (4), (Z)-11-tetradecenyl acetate (5), and (Z,E)-9,12-tetradecadienyl acetate (6) was significantly lower than that of the major component when assayed individually. In multicomponent blends compound4 appeared to strongly decrease the number of males arrested at the source, the effect being particularly important when compound5 was present in the blend. Results of single sensillum experiments confirmed the existence of two main physiologically distinct sensillar types. The most common type of sensilla contained a neuron that responded specifically to compound1. A second type of sensilla, located laterally on the ventral sensory surface, contained two receptor neurons responding to compound6 and to (Z)-9-tetradecenol. Among short sensilla, one hair responded to compound4 and could represent a minor sensillar type. No sensory neuron was found to detect the other minor pheromone compounds2, 3, and5.Dedicated to the memory of the late Prof. Félix Serratosa (1925–1995).     

Identification of sex pheromone components ofSpodoptera sunia Guenée (Lepidoptera: Noctuidae)

Moths belonging to the speciesSpodoptera sunia have been recognized as a new pest of cotton in Central America. By means of electro-physiologic investigations, solid sample injection gas chromatography, and combined gas chromatography-mass spectrometry, (Z)-9-tetradecenyl acetate, (9Z,12E)-9,12-tetradecadienyl acetate, (Z)-9-tetradecen-1-ol, and (Z)-11-hexadecenyl acetate, in a ratio of 10053120, were identified in the pheromone gland of female insects. These substances should serve as a base for the development of a pheromone-monitoring system for this lepidopteran pest.Pheromones, 60. Pheromones 59: Bestmann, HJ., Attygalle, A.B., Brosche, T., Erler, J., Platz, H., Schwarz, J., Vostrowsky, O., Wu Cai-Hong, Kaissling, K.E. and Chen Te-Ming. 1987. Z.Naturforsch. 42c:631–636.     

Roles of amino acids,protein, and fiber in leaf-feeding resistance of corn to the fall armyworm

The free amino acids have been shown by isolational work and choice bioassays to be more important than all other factors evaluated in defining leaf-feeding resistance of corn (Zea mays L.) to fall armyworm (FAW) [(Spodoptera frugiperda J.E. Smith)] larvae. 6-MBOA (6-methoxybenzoxazolinone) and maysin, toxins present in corn, were shown not to be significant factors for leaf-feeding resistance to first-instar FAW larvae because of their low concentrations in the whorl. Amino acid analysis showed that while the ratios of the essential amino acids in susceptible (S) and resistant (R) lines were similar, there were differences in the nonessential amino acids, particularly aspartic acid, which was higher in R lines. Also, the ratio of essential amino acids to nonessential amino acids was important, being too low in expressed whorl leaf juice (obtained from V₈–V₁₀ growth stage plants) to support larval growth, although juice was stimulatory in choice tests. The total protein content of whorls in S lines was about 15% higher than in R lines, but the significance of this difference is uncertain, because nutritional tests showed that larval growth increased with total protein only up to 12% protein. Sugars were only slightly stimulatory. Thus, the amino acids along with higher hemicellulose content of R lines, established by us earlier, appear to explain much of the basis of resistance in corn to larval leaf-feeding of the FAW.     

Insect antifeedant activity of clerodane diterpenoids against larvae ofSpodoptera Littoralis (Boisd.) (Lepidoptera)

Antifeedant activities of nine clerodane diterpenoids, isolated in this laboratory from different species ofAjuga plants, have been studied against larvae of Egyptian cotton leafwormSpodoptera littoralis (Boisd.) (Lepidoptera) by application of the leaf disk method. Evaluation of activity was carried out by calculating, at different time intervals, the feeding ratio (FR) from the relationship between the consumed areas of treated disks (CTD) and control disks (CCD); for comparison purposes a FR₅₀ defined as the FR at a CCD of 50% was established. Some compounds exhibited activity at a 0.01 g/cm² dose (0.3 ppm). Structure-activity relationships are discussed     

Effect of meliaceous seed extracts on growth and survival ofSpodoptera frugiperda (J.E. Smith)

Hexane and ethanol extracts of seeds from 10 plant species (including neem—Azadirachta indica A. Juss.) of the family Meliaceae were incorporated into artificial diet at various doses and fed to fall armyworm [Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae)] larvae in nochoice tests. All produced significant mortality, reduced larval growth rate, increased time to pupation, or all three, at some concentration. The two highest doses of all of the ethanol extracts caused 100% mortality before pupation, but the hexane extracts tended to be less effective.Aglaia cordata Hiern. ethanol extract was as potent as the comparable neem seed extract at virtually all levels, and its hexane extract was active at much lower concentrations than the neem extract was. The sublethal effects (slower growth and increased time to pupation) were usually detectable at lower doses of extract than mortality was.Mention of firm or product names does not imply recommendation or endorsement by USDA over others not mentioned.     

Investigation of oviposition deterrent in larval frass ofSpodoptera littoralis (Boisd.)

Previous experiments demonstrated an oviposition-deterring effect of larval frass in the Egyptian cotton leaf worm,Spodoptera littoralis (Boisd.). In this study, females were shown to perceive the oviposition-deterring substance(s) with their antennae. During dark, airtight, and cold (–10 °C) storage, the deterrent was persistent for at least 395 days. On the other hand, larval frass retained its activity for only two days when applied to cotton leaves. The deterrent activity of frass was independent of larval density. Frass of larvae reared at high densities deterred oviposition as well as frass of larvae feeding separately or in small groups. For significant oviposition deterrence, the minimum amount of frass was in the range of 5–10 mg frass per cotton leaf. An acetone extract of larval frass was highly deterrent, in contrast to extracts prepared with water, ethanol, chloroform, or pentane.     

Effects of cotton leaf surface alkalinity on feeding ofSpodoptera littoralis larvae

The high leaf surface pH in cotton (Gossypium hirsutum) var. Acala SJ2 was bioassayed againstSpodoptera littoralis larvae. Weight gain and leaf consumption of the larvae feeding on leaves devoid of alkalinity, due to daily washing, were recorded. Untreated cotton, with a leaf surface pH of 9.5–10.0 was used as control. The gland exudates contained potassium and magnesium cations, and the gland surface and intergland leaf areas were rich in calcium and phosphorus and low in K or Mg. The role of this plant antibiosis in the insect-host-plant relationship is discussed.Contribution No. 1885-E 1986 series, from the Agricultural Research Organization, The Volcani Center, Bet Dagan, Israel.     

Systemic induction of feeding deterrents in cotton plants by feeding ofSpodoptera SPP. Larvae

Cotton,Gossypium hirsutum L., has been shown to exhibit systemic induced resistance to arthropods under certain conditions. We conducted experiments to determine the effects of previous feeding ofSpodoptera exigua Hübner andSpodoptera littoralis (Boisd.) larvae on feeding behavior, growth, and survival of larvae subsequently feeding on cotton. In one feeding choice test,S. exigua larvae preferred young leaves from undamaged control plants to undamaged young leaves from a previously damaged plant. Feeding deterrence was noticeable after only 6 hr of initial feeding damage by larvae, and there was almost complete deterrence after 30 and 54 hr of continuous feeding. In a second feeding choice test,S. littoralis larvae fed more on mature leaves from undamaged control plants than on undamaged mature leaves from previously damaged plants. In no-choice tests, third instars ofS. littoralis fed undamaged young leaves from damaged plants did not gain weight and died by the seventh day, whereas larvae fed young leaves from undamaged control plants gained weight and pupated within 11 days. Sixth instars ofS. littoralis fed either old damaged leaves, old undamaged leaves, or young undamaged leaves all from previously damaged plants gained weight slowly and took more than 12 days to pupate, whereas larvae fed young leaves from undamaged plants gained weight rapidly and pupated within five days of the beginning of the experiment.     

Mating and oviposition byCotesia (=Apanteles) marginiventris (Hymenoptera: Braconidae) in presence of synthetic pheromone ofSpodoptera frugiperda (Lepidoptera: Noctuidae)

Two blends of fall armyworm,Spodoptera frugiperda (J.E. Smith), pheromonal components were evaluated in the laboratory for possible close-range effects on mating and oviposition byCotesia marginiventris (Cresson). Neither a two- nor a five-component blend had any significant effect on mating or parasitization ofS. frugiperda larvae by this parasitoid. Dosages of 200, 400, and 800 g were tested.     

Biological amplification for increasing electroantennogram discrimination between two female sex pheromones ofSpodoptera littoralis (Lepidoptera: Noctuidae)

MaleSpodoptera littoralis stimulated by a mixture ofS. littoralis female sex pheromone with a positional isomer and by the pheromone alone, gave greatly amplified electroantennograms (EAGs) when the antennae were connected in series. The technique is described and examples are given of its use in screening extracts for EAG activity. Dose-response curves obtained with this technique are presented and discussed. Through biological amplification, EAG discrimination between the pheromones was increased.Contribution from the Agricultural Research Organization, The Volcani Center, Bet Dagan, Israel, No. 238-E, 1980 series.     

Chemical correlates of rhesus monkey food choice: The influence of hydrolyzable tannins

Feeding behavior was quantified of free-ranging adult rhesus monkeys in the Himalayan foothills of northern Pakistan. Twenty-eight food and 63 nonfood plant samples were collected and analyzed for tannins, alkaloids, fiber, lignin, protein, amino acids, total nonstructural carbohydrates, and free glucose. Most major foods of the rhesus were low in tannins and high in nutrients. The rhesus ate mainly parts of herbaceous plants, although woody plants were more abundant, possibly because herbs were lower in condensed tannins than woody plants. Feeding was negatively correlated with the astringency of tannins, ellagitannins, and total phenolics among all samples. Among leaves of both herbs and woody plants, feeding was negatively correlated with measures of hydrolyzable tannins. Total protein, total nonstructural carbohydrates, and water were not related to food choice and may not have been limiting at the site.     

Effect of oviposition deterrents from elderberry on behavioral responses byHeliothis virescens to host-plant volatiles in flight tunnel

In flight-tunnel assays, mated femaleHeliothis virescens (F.) moths responded by positive anemotaxis to volatiles from extracts of two host plants (cotton and tobacco), but they did not fly to an extract from elderberry (Sambucus simpsonii Rehd.), a nonhost that contains an oviposition deterrent forH. virescens. When the elderberry extract was mixed with extract from either cotton or tobacco, the flight response by moths to volatiles emanating from the extract blends was reduced significantly at most doses when compared to the positive response to extracts from either host alone. The number of landings (including brief contacts) and landings that resulted in oviposition on the substrates treated with extract blends also were reduced significantly in most tests.This article reports the results of research only. Mention of a proprietary product does not constitute an endorsement or the recommendation of its use by USDA.     

Consumption and utilization of experimentally altered corn by southern armyworm: Iron,nitrogen, and cyclic hydroxamates

The effects of differential leaf water, leaf nitrogen and cyclic hydroxamate (DIMBOA) concentrations in corn seedlings were analyzed for a polyphagous insect, the southern armyworm (Spodoptera eridania Cram.). Six different combinations of nutrients and allelochemicals [DIMBOA = 2,4-dihydroxy-7-methoxy(2H)-benzoxazin-3(4H)-one] were generated using two corn genotypes (WF9 and CI3IA) and three fertility regimes (complete nutrient, Fe-deficient, and N-deficient solutions) in the University Biotron. Poorest larval growth was observed in the low-nitrogen treatments (1.2% and 1.7% leaf N) and was the result of both low consumption rates and high metabolic costs (low efficiency of conversion of digested food, ECD). Fastest growth rates were observed forthe larvae fed leaves from the high-nitrogen treatments (4.6% and 4.4% leaf N). It is noteworthy that these treatments also contained the highest concentration of cyclic hydroxamates, which are generally believed to be the primary defensive chemicals mediating resistance against the European corn borer,Ostrinia nubilalis (Hubner). If these hydroxamates do have any deleterious or costly effects (perhaps accounting for a large portion of metabolic expenditures), the high digestibility of the leaf tissue and the increased consumption rates more than compensate, resulting in rapid growth (growth rate = consumption rate × approximate digestibility × efficiency of conversion of the digested food). These studies illustrate that variation in key nutrients and allelochemicals within a single plant species (Zea mays L.) may have significantly different effects upon various potential leaf-chewing caterpillars, such as these armyworms versus corn borers (which cannot handle the cyclic hydroxamates, even if provided with young nutritious leaf tissues).     

Flight response ofHeliothis subflexa (Gn.) females (Lepidoptera: Noctuidae) to an attractant from groundcherry,Physalis angulata L.

Mated femaleHeliothis subflexa (Gn.) (HS) moths 1–7 days old responded positively in a Plexiglas flight tunnel to an attractant extracted with methanol from fresh whole-leaf washes of groundcherry,Physalis angulata L. Response to the groundcherry extract, as indicated by plume-tracking (i.e., upwind flight toward the odor source) and contact with the chemical dispenser did not change significantly during the first 5 hr of scotophase. Overall, ca. 50% of the responding moths also landed on the chemical dispenser; ca. 50% of the moths that landed also deposited eggs. There were no significant differences in the behavioral responses of females mating only once and those that had mated two or more times. Virgin females and male moths were significantly less responsive to the groundcherry attractant than mated females. The flight tunnel bioassay described provides an excellent system for evaluating plant allelochemics associated with host-plant selection.This article reports the results of research only. Mention of a proprietary product does not constitute an endorsement or the recommendation for its use by USDA.     

Developmental inhibition ofSpodoptera litura (Fab.) larvae by a novel caffeoylquinic acid from the wild groundnut,Arachis paraguariensis (Chod et Hassl.)

A novel compound, 1-caffeoyl-4-deoxyquinic acid (1-CdQA) has been identified along with 3-caffeoylquinic acid (3-CQA) and 5-caffeoylquinic acid (5-CQA) (syn. chlorogenic acid) in the foliage ofArachis paraguariensis, a wild species of groundnut that is highly resistant to attack by the larvae ofSpodoptera litura. When neonate larvae were fed on diets treated with 3-CQA or 1-CdQA, their development was severely inhibited compared to larvae on untreated diets, and the effects were similar in nature and magnitude to those observed for larvae feeding on diets treated with 5-CQA, rutin, and quercetin. The effects of all the compounds were dose related, and their optimal concentration was approximately 3 mM, which corresponds to the total foliar concentration of both caffeoylquinic acids and quercetin diglycosides inA. paraguariensis. After 24 h, the development of third stadium larvae feeding on diets treated with 5-CQA, rutin and 1-CdQA was promoted compared to larvae on control diets, but after 96 hr larvae feeding on treated diets had gained significantly less weight than those on the control diets. 1-CdQA, 3-CQA, and quercetin dyglycosides (previously identified in the foliage ofA. paraguariensis) are considered to be valuable components in resistance of groundnuts toS. litura and may provide useful genetic markers in future breeding for resistance to this pest.     

Toxicity of linear furanocoumarins toSpodoptera exigua: Evidence for antagonistic interactions

The linear furanocoumarins psoralen, bergapten, and xanthotoxin were tested for toxicity to the beet armywormSpodoptera exigua (Hübner) under short ultraviolet (UVB) radiation. Increased dietary concentrations of each furanocoumarin significantly decreased insect larval weight, extended generation time, and induced higher mortality. Xanthotoxin was the most toxic, followed by psoralen and bergapten. Combining psoralen with bergapten, xanthotoxin, or both resulted in significantly antagonistic effects on insect mortality. The combination of bergapten and xanthotoxin, however, produced additive effects. The implications of these observations forS. exigua resistance in the wild plant accession ofApium prostratum and the enigma the findings represent for plant-insect relationships are discussed.     

Identification of volatile sex pheromone components released by the southern armyworm,Spodoptera eridania (Cramer)

Analysis of sex pheromone gland extracts and volatile pheromone components collected from the calling female southern armyworm,Spodoptera eridania (Cramer), by high-resolution capillary gas chromatography and mass spectroscopy indicated that a number of 14-carbon mono- and diunsaturated acetates and a monounsaturated 16-carbon acetate were produced. Gland extracts also indicated the presence of (Z)-9-tetradecen-1-ol. However, this compound was not found in collections of volatiles. Field trapping studies indicated that the volatile blend composed of (Z)-9-tetradecen-1-ol acetate (60%), (Z)-9-(E)-12-tetradecadien-1-ol acetate (17%), (Z)-9-(Z)-12-tetradecadien-1-ol acetate (15%), (Z)-9-(E)-11-tetradecadien-1-ol acetate (5%), and (Z)-11-hexadecen-1-ol acetate (3 %) was an effective trap bait for males of this species. The addition of (Z)-9-tetradecen-1-ol to the acetate blends tested resulted in the capture of beet armyworm,S. exigua (Hubner), males which provides further evidence that the alcohol is a pheromone component of this species.