Potential uses of kairomones for behavioral manipulation ofCotesia marginiventris (Cresson)

The effects of kairomone pattern and preconditioning on parasitization rates of fall armyworm larvae,Spodoptera frugiperda (J.E. Smith) byCotesia (=Apanteles)marginiventris (Cresson) were investigated in the laboratory and greenhouse using a hexane extract of frass and actual fall armyworm frass. Parasitization rates increased 55 and 26% in Petri dishes and on corn seedlings, respectively, when the entire experimental area was sprayed with the frass extract. Applying the extract in spots resulted in a 20–30% reduction in parasitization compared to treating the entire area. However, spot application produced significantly better parasitization rates compared to the control treatment. Exposing the parasitoids to actual fall armyworm frass resulted in ca. 50% greater retention in the release area and an increase of ca. 60–75% in the number of parasitoids searching.C. marginiventris parasitized factitious hosts topically treated with an extract of fall armyworm frass.Mention of a commercial or proprietary product does not constitute an endorsement by the USDA.Submitted in partial fulfillment of the requirements for the degree Doctor of Philosophy, Department of Entomology and Nematology, University of Florida, Gainesville     

Role of host-produced stimuli and learning in host selection behavior ofCotesia (=Apanteles) marginiventris (Cresson)

The study was conducted to determine how various factors, including learning, influence the host-selection behavior of the larval parasitoid Cotesia (=Apanteles)marginiventris (Cresson). Frass, silk, and feeding damage fromSpodoptera frugiperda (J.E. Smith) larvae elicited visits and antennal examinations by females of the parasitoid. Learning played a role in the effective response to these stimuli in that previous contact experience with hosts and/or chewed leaves, exuviae, frass, or hemolymph significantly enhanced the response of the parasitoid. Previous contact with host plants alone did not improve the responses. Experienced parasitoids were more active and spent less time at rest than inexperienced parasitoids. Previous experience was also found to be of significant importance in the ability of the parasitoid to discriminate between parasitized and unparasitized host larvae.Hymenoptera: Braconidae.In cooperation with the University of Georgia College of Agriculture Experiment Stations, Coastal Plain Station, Tifton, Georgia 31793-0748.Mention of a proprietary product in this paper does not constitute endorsement of this product by the USDA.Visiting scientist with the Department of Entomology, Coastal Plain Station, Tifton, Georgia, during this study.     

Sources of fall armyworm,Spodoptera frugiperda (Lepidoptera: Noctuidae), kairomones eliciting host-finding behavior inCotesia (=Apanteles) marginivenitris (Hymenoptera: Braconidae)

Bioassay responses inCotesia marginiventris (Cresson) females to materials derived from fall armyworm (FAW) larvae,Spodoptera frugiperda (J. E. Smith), were most intense for frass and somewhat less intense for larval and pupal cutical materials, scales, exuviae, silk, and oral secretion, with FAW larval hemolymph eliciting only a slight response. The highest percentage of ovipositor probing was caused by frass (100%) and moth scales (90%). Various types of corn-leaf damage when assayed alone did not produce responses as intense as when assayed in combination with frass, cuticle material, and oral secretion. Parasitoid response was somewhat better to frass derived from FAW larvae feeding on corn and peanut leaves than from larvae feeding on the foliage of soybeans, Bermuda grass, cowpeas, or laboratory diet. Hexane and chloroform were better than methanol and water for extracting active material from FAW frass, and chloroform was the best of these solvents for extracting corn leaves. Serial dilutions of frass extracts resulted in a reduction in parasitoid response.This paper was submitted in partial fulfillment of the requirements for Doctor of Philosophy, Department of Entomology and Nematology, University of Florida, Gainesville.     

Sex pheromone of fall armyworm,Spodoptera frugiperda (J.E. Smith)

Analyses of extracts of pheromone glands and of volatiles from calling female fall armyworm moths,Spodoptera frugiperda (J.E. Smith), revealed the presence of the following compounds: dodecan-1-ol acetate, (Z)-7-dodecen-1-ol acetate, 11-dodecen-1-ol acetate, (Z)-9-tetradecenal, (Z)-9-tetradecen-1-ol acetate, (Z)-11-hexadecenal, and (Z)-11-hexadecen-1-ol acetate. The volatiles emitted by calling females differed from the gland extract in that the two aldehydes were absent. Field tests were conducted with sticky traps baited with rubber septa formulated to release blends with the same component ratios as those emitted by calling females. These tests demonstrated that both (Z)-7-dodecen-1-ol acetate and (Z)-9-tetradecen-1-ol acetate are required for optimum activity and that this blend is a significantly better lure than either virgin females or 25 mg of (Z)-9-dodecen-1-ol acetate in a polyethylene vial, the previously used standard. Addition of the other three acetates found in the volatiles did not significantly increase the effectiveness of the two-component blend as a bait for Pherocon 1C or International Pheromones moth traps.Mention of a commercial or proprietary product does not constitute an endorsement by the USDA.     

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.     

Biochemical activity of centipedegrass against fall armyworm larvae

Centipedegrass,Eremochloa ophiuroides (Munro) Hack, severely inhibits growth of the fall armyworm larva,Spodoptera frugiperda (J.E. Smith). Fresh centipedegrass extracts and extract fractions were deposited on Celufil, incorporated into meridic-based diets and bioassayed against neonate larvae of the fall armyworm in the laboratory. The methanol extract (F₁) caused the greatest reduction in larval weight. When F₁, was partitioned between méthylene chloride and water, the activity was transferred to the water-soluble fraction (F₅), which, when further fractionated using preparative C-18 reverse-phase chromatography, yielded active F₇ and F₈ fractions. Gas chromatograph-mass spectrometry and high-pressure liquid chromatography (HPLC) showed F₇ to be 95% caffeoylquinic acids with chlorogenic acid as the major constituent. HPLC analysis of F₈ revealed maysin [2-O- -L-rhamnosyl-6-C-(6-deoxy-Xylo-hexos-4-ulosyl)luteolin] and other luteolin derivatives. Chlorogenic acid and other caffeoylquinic acids, maysin, and other luteolin derivatives are the major factors responsible for the antibiotic resistance of centipedegrass to larvae of the fall armyworm.     

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.     

Microsomal oxidation of allelochemicals in generalist (Spodoptera frugiperda) and semispecialist (Anticarsia gemmatalis) insect

Midgut microsomes prepared from larvae of the fall armyworm [Spodoptera frugiperda (J.E Smith)], a generalist insect, and the velvetbean caterpillar (Anticarsia gemmatalis Hubner), a semispecialist, were used to study their oxidative activity toward a variety of allelochemicals. Allelochemicals such as terpenoids, alkaloids, indoles, glucosinolates, flavonoids, coumarins, cardenolides, phenylpropenes, and a ketohydrocarbon were all metabolized by the microsomal cytochrome P-450 monooxygenases in both species. Fall armyworm microsomes oxidized monoterpenes more favorably than other types of terpenes, indicating a preference for these compounds. In all instances, the oxidative metabolism of these allelochemicals can be induced by dietary allelochemicals such as indole 3-carbinol, indole 3-acetonitrile, menthol, flavone, or peppermint oil ranging from 1.3- to 9.5-fold. In the case of certain triterpenes, tetraterpene, alkaloid, coumarin, and cardenolides, metabolic activity can only be observed after induction. The monooxygenase activities toward these allelochemicals were generally higher in the generalist than in the semispecialist. These findings provide strong evidence that microsomal monooxygenases play an important role in the detoxification of plant toxins and hence host-plant selections in herbivorous insects.     

6,10,14-Trimethylpentadecan-2-one: A Bermuda grass phagostimulant to fall armyworm (lepidoptera: Noctuidae)

A phagostimulant, 6,10,14-trimethylpentadecan-1-one (phytone), was isolated and identified from Bermuda grass,Cynodon dactylon (L.). The phagostimulant activity of this isoprenoid ketone was established from bioassays of fall armyworm larvae,Spodoptera frugiperda (J.E. Smith). Larvae displayed increased body mass accumulation as well as preference to diet supplemented with this molecule. Neonate larvae fed diet supplemented with chromatographic isolates of phytone-containing fractions from six Bermuda grass cultivars showed a 10–40% increase in body mass accumulation as compared with controls. This variation in larval body mass accumulation seems attributable to a differential concentration of phytone in the cultivars, which ranged from 0.5 to 43 ppm. Additionally, first-instar larvae responded preferentially to diet pellets topically treated with phytone in concentrations as low as 0.1 ppm.     

Sex pheromone of fall armyworm

Two components of the fall armyworm,Spodoptera frugiperda (J.E. Smith), sex pheromone, (Z)-9-dodecen-1-ol acetate (DDA) and (Z)-9-tetradecen-1-ol (TDA), were tested alone and in combination to determine their effects on male sexual response and inhibition of mating in the laboratory. The threshold response for FAW males was lower for TDA than for DDA, and males responded to TDA over a wider range of dosages. Although TDA is not attractive to FAW males in the field, this compound was highly effective in reducing mating under laboratory conditions.cooperating with the Insect Attractants, Behavior, and Basic Biology Research Laboratory, Gainesville, Florida 32604.     

In vitro metabolism of a linear furanocoumarin (8-methoxypsoralen,xanthotoxin) by mixed-function oxidases of larvae of black swallowtail butterfly and fall armyworm

Studies were made of the comparative in vitro metabolism of [¹⁴C]xanthotoxin and [¹⁴C]aldrin by homogenate preparations of midguts and bodies (carcass minus digestive tract and head) of last-stage larvae of the black swallowtail butterfly (Papilio polyxenes Fabr.) and the fall armyworm [Spodoptera frugiperda (J. E. Smith)]. The two substrates were metabolized by 10,000g supernatant microsomal preparations from both species. Evidence gained through the use of a specific inhibitor and cofactor indicated that mixed-function microsomal oxidases were major factors in the metabolism and that the specific activity of this enzyme system was considerably higher in midgut preparations fromP. polyxenes than in similar preparations fromS. frugiperda. Aldrin was metabolized 3–4 times faster byP. polyxenes, and xanthotoxin 6–6.5 times faster.     

Influence of pheromone trap color and design on capture of male velvetbean caterpillar and fall armyworm moths (Lepidoptera: Noctuidae)

Three pheromone traps were evaluated in paired field trials for effectiveness in capturing wild male velvetbean caterpillar moths (VBC),Anticarsia gemmatalis Hübner, and fall armyworm moths (FAW),Spodoptera frugiperda (J.E. Smith), using a wind-oriented trapping device. The traps were: (1) the standard multicolored bucket trap consisting of a forest green canopy, yellow funnel, white bucket and open (i.e., single wire) pheromone holder; (2) a forest green monocolored bucket trap; and (3) the Multi-Pher-1 trap consisting of a blue-green canopy, white funnel, white bucket, and white, multislotted pheromone holder. The Multi-Pher-1 trap differs primarily from the other two in that its entrance is smaller in diameter and is partially obstructed by the pheromone holder. Significantly fewer VBC and FAW males were captured in pheromone-baited monocolored (forest green) bucket traps than standard multicolored bucket traps. The Multi-Pher-1 trap also caught significantly fewer VBC moths than the standard multicolored bucket trap, but there was no significant difference in numbers of FAW moths caught in the two traps. The results further demonstrate the importance of considering visual cues, in this case color, in the design of pheromone traps for nocturnal insects.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.     

Hemicellulose is an important leaf-feeding resistance factor in corn to the fall armyworm

The fall armyworm,Spodoptera frugiperda (J. E. Smith), (FAW) is a major pest of corn,Zea mays L., in the southeastern United States. The damage to pretassel corn is caused by larvae feeding primarily on immature inner whorls. In this study, resistant lines were found to contain more crude fiber in whorls, mostly hemicellulose and cellulose. While hemicellulose, chiefly an arabinoxylan, was higher in resistant (R) lines than in susceptible (S) lines, the distribution of constituent neutral sugars was very similar in the lines. Both lines also containedp-coumaric and ferulic acids. These phenolic acids are known to occur both in the free state and in the cell wall as complexes bound by ester linkages to the arabinose moiety of the arabinoxylan.¹³C NMR data showed that the intensity of the carbonyl carbon (184 ppm) in resistant hemicellulose was stronger, indicating a greater degree of cross-linking. Thus, resistant hemicellulose is both structurally different from susceptible hemicellulose and present in greater quantities. In two of three laboratory dietary tests, FAW larval weight gains were significantly higher on diets with (S) hemicellulose incorporated at the same level as (R) hemicellulose. Therefore, resistance to the FAW appears to be correlated with both a greater amount and a higher degree of cross-linking of the hemicellulose of (R) lines.Mention of a trademark, proprietary product, or vendor does not constitute a guarantee of warranty of the product by the U.S. Department of Agriculture and does not imply its approval to the exclusion of other products or vendors that may also be suitable.     

How contact foraging experiences affect preferences for host-related odors in the larval parasitoidCotesia marginiventris (Cresson) (Hymenoptera: Braconidae)

Responses of individual females of the parasitoidCotesia marginiventris to the odors of four different complexes of host larvae feeding on leaves were observed in a four-arm olfactometer. The plant-host complexes were composed of fall armyworm (FAW) larvae or cabbage looper (CL) larvae feeding on either corn or cotton seedlings. Prior to testing, each female was given a brief foraging experience on a plant-host complex and was then exposed to the odors of the same complex in the olfactometer. The experienced females responded to familiar odors in a dose-related manner, and these responses were virtually identical to all four complexes. Preferences for the odors of one of two plant-host complexes were tested in dual choice situations. Generally, FAW odors were preferred over CL odors and corn odors over cotton odors. A short foraging experience significantly affected the females' odor preferences in favor of the odors released by the experienced complex. Additional experiments revealed that neither longer bouts of experience nor bouts that included ovipositions resulted in a stronger change in preference. Experience affected preference in combinations where only the host species was varied as well as in combinations where only the plant species was varied. The results, therefore, strongly indicate that both the plants and the hosts somehow are involved in the production and/or release of the semiochemicals that attractC. marginiventris.Mention of a proprietary product does not constitute an endorsement or the recommendation for its use by the USDA.     

Chemical and ultrastructural analysis of corn cuticular lipids and their effect on feeding by fall armyworm larvae

The cuticular lipid composition of lower and upper leaves of five genotypes of field-grown corn,Zea mays L., was determined by combined gas chromatography-mass spectrometry. Surface lipids of the upper leaves had a higher proportion ofn-alkanes (45–52%) than the lower leaves, while the lower leaves had higher percentages of fatty alcohols (12–18%) than the upper leaves. Scanning electron microscopy showed that the upper leaves of two corn genotypes, MpSWCB-4 and Cacahuacintle X's, had a smooth amorphous appearance, while the lower leaves had a dense array of wax crystals.Spodoptera frugiperda (J.E. Smith) larvae weighed more and developed more rapidly when they were reared on diet containing corn foliage from which the cuticular lipids had been removed than when they were fed untreated foliage. However, growth was not inhibited when larvae were fed diet containing the cuticular lipid extracts or individual cuticular lipid components.     

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).     

Orientation behavior and effect of experience and laboratory rearing on responses ofCotesia melanoscela (Ratzeburg) (Hymenoptera: Braconidae) to gypsy moth silk kairomone

Cotesia melanoscela responds the same way to the silk of its host, gypsy moth larvae,Lymantria dispar L., whether or not it has previously been exposed to hosts. Parasites maintained in the laboratory for six or 25 generations also responded similarly, suggesting that orientation behavior is not modified by laboratory rearing. Details of silk-related orientation behavior were analyzed by tracing paths of female parasites when on or off silk-covered substrates. Females made 31 ° average turns every 0.5 cm whether or not they were examining silk. They tended to turn back onto a silked area when encountering a border, and their speed of movement when not examining silk was about three times higher than when examining silk.     

Multispecies trapping ofHelicoverpa (Heliothis) zea,Spodoptera frugiperda,Pseudaletia unipuncta,andAgrotis ipsilon (Lepidoptera: Noctuidae)

Multispecies sex pheromone trapping (trapping of more than one species in the same trap) for the bollworm,Helicoverpa (Heliothis) zea (Boddie); fall armyworm,Spodoptera frugiperda (J.E. Smith); armyworm,Pseudaletia unipuncta (Haworth); and the black cutworm,Agrotis ipsilon (Hufnagel) was evaluated. Baiting of individual traps with all possible combinations of the four species taken two at a time caused a reduction in the catches of at least one of any two species involved when compared to traps baited for only one species. These results demonstrated the species specificity of sex pheromones identified for these species. Although the effects were reduced in some cases, the interaction between species also was observed when adjacent traps were baited with the sex pheromone dispensers of the different species. These results indicate that the spacing between pheromone traps when more than one species are being trapped at the same site affects trap capture and should be evaluated further.This paper reports the results of research only. Mention of a commercial or proprietary product does not constitute an endorsement by the USDA.     

Analysis and field evaluation of volatile blend emitted by calling virgin females of beet armyworm moth,Spodoptera exigua (Hübner)

The volatile blend emitted by calling virgin beet armyworm females was collected and analyzed by capillary gas chromatography and mass spectrometry. Five compounds were detected and identified in this blend: (Z)-9-tetradecenyl acetate, (Z)-9-tetradecen-l-ol, (Z,E)-9,12-tetradecadienyl acetate (Z,Z)-9,12-tetradecadienyl acetate, and (Z)-l 1-hexadecenyl acetate. They were emitted in a ratio of 47.9 4.040.2 6.5 1.7, respectively. This five-component blend and several other blends with one or more components deleted were formulated on rubber septa to release the components in about the same ratios as the females. Field tests of these formulations in bucket traps indicated that a blend of (Z)-9 tetradecen-1-ol, (Z,E)-9,12-tetradecadienyl acetate, and (Z)-l 1-hexadecenyl acetate was most effective for trapping beet armyworm males and that (Z)-9-tetradecenyl acetate actually decreased trap captures. Blends that did not contain both (Z)-9-tetradecen-l-ol and (Z,E)-9,12-tetradecadienyl acetate were ineffective as trap baits.     

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.