Spodoptera Exigua Larvae Research Articles

Beet Armyworm Control in Cabbage, 1985

Abstract This experiment was conducted to evaluate three insecticide treatments for controlling beet armyworm larvae. ‘Greenback YR’ variety cabbage was seeded on 24 Sep into single-row beds with 40 inch centers at the Texas Agricultural Research and Extension Center, Weslaco, TX. Soil type was a Willacy fine sandy loam. Plots measured 30 ft by two beds, and were arranged in a randomized complete block design. Plots were inoculated 21 Nov with 48 h old beet armyworm egg masses obtained from a laboratory reared culture. Five plants were selected from the center of each plot and inoculated by attaching three egg masses/plant to a leaf with a paper clip. Five additional plants, located adjacent to the Ave that were inoculated with eggs, were infested with two-week old beet armyworm larvae that had been reared on artificial diet. Each plot received 50 larvae. Treatments were applied on 5 Dec through a C02 powered, ground sprayer at a rate of 5 gal/acre finished formulation. Efficacy was evaluated on 8 and 12 Dec by recording all beet armyworm, cabbage looper, and diamondback moth larvae on the ten plants that had been previously infested with beet armyworm larvae. Since we violated the assumption of normal distribution by infesting only five plants, we utilized the RANKS procedure to weight each plot within a replication according to the number of beet armyworm larvae present.

Control of Lepidopterous Larvae on Cabbage, 1986

Abstract “Greenback” cabbage was direct seeded in single row beds with 40 in center spacing. Plots were 2 rows wide and 20 ft long with one unplanted row between plots. Experimental design was a randomized complete block with 5 replicates. All chemical applications were applied using a tractor mounted sprayer that delivered 12.4 gal/acre at 40 psi and 4 mph. Control plots were not sprayed. Weekly counts were made of all larvae present (cabbage looper, diamondback moth and beet armyworm) on 5 plants per plot. When the mean number of larvae per plant of all species exceeded 0.3 larvae/plant in methomyl treated plots, all plots were sprayed the following day. A total of 6 applications were made between 22 Apr and 27 May. Percent marketable cabbage heads (excluding wrapper leaves) was determined on 2 Jun. Heads were considered marketable if no visible evidence of feeding damage was observed. Beet armyworm egg masses oviposited on wax paper by moths in a laboratory culture were attached to the underside of wrapper leaves on one plant per plot. Egg masses were placed on 9, 28 Apr and 15 May at a rate of approximately 250 eggs/plant per date. Beet armyworm larvae were counted weekly on these plants. Total larval counts were analysed using AOV and Duncan's mean separation test while beet armyworm count analyses were made using a Ranks procedure (SAS Institute, 1984). Marketable head data was analysed using an arcsin transformation of percentage marketable data and reported as % marketable heads.

Margosan-O Contact and Residual Efficacy Against Beet Armyworm Larvae, 1986

Abstract Leaves were placed in 1 oz plastic creamer cups with moist filter paper. Colony reared larvae were placed on the leaves and sprayed with a hand-held mist bottle for contact/residual efficacy resting. For residual efficacy, leaves were sprayed and air-dried before placement in cups with larvae. Mortality assessments were made at 1 and 14 DAT. Each treatment was replicated 4 times with 10 cups/replicate and 1 larva per cup.

Beet Armyworm Control Using Selecron 6EC, 1986

Abstract Selecron 6EC was evaluated in Jun for control of early and late larval instar beet armyworm. For residual efficacy Mountain Peak var. mum leaves were sprayed with hand-held atomizers, allowed to air dry then placed in 1 oz plastic creamer cups with moist filter paper. Individual beet armyworm larvae, reared on artificial diet, were placed in the cups which were covered with plastic snap-on lids. For contact efficacy, larvae were sprayed then placed on clean mum leaves in plastic cups. Each rate test was replicated 4 times with 10 larvae per replicate. Mortality evaluations were made at 1, 2, & 3 DAT.

Control of Second Instar Beet Armyworm Larvae on Chrysanthemum, Summer, California, 1986

Abstract Two rates of Dimilin 25W were evaluated for control of second instar beet armyworm larvae. Ten 4-week-old chrysanthemum plants were used per treatment. Plants were sprayed with a 1 gal B&G hand sprayer at 55 psi until runoff 3 Sep. After the plants were allowed to dry, 5 second instar beet armyworm larvae were placed on each plant. The larvae were confined to the plants using an inverted, ventilated 1 qt plastic container. Mortality was assessed after 48 h and each surviving larva was placed individually in a 1 fl oz plastic cup filled with a sufficient amount of untreated commercial beet armyworm diet. Mortality was assessed at 48 h intervals thereafter until all surviving larvae pupated. In addition, percent mortality at adult emergence was also determined for all treatments. The data were subjected to arcsin square root transformations prior to ANOVA.

Isolation, Identification, and Determination of Virulence of a Nuclear Polyhedrosis Virus from the Beet Armyworm, Spodoptera exigua (Lepidoptera: Noctuidae)

A multinucleocapsid nuclear polyhedrosis virus (MNPV) was isolated during an epizootic in California's Merced County from a single larva of the beet armyworm, Spodoptera exigua (Hubner). Occlusion bodies produced by this virus isolate, designated Se MNPV-608, measured 1.52 ± 0.11 µm ($\bar x$ ± SD) in diameter and most contained virion; with two to four nucleocapsids per envelope. Restriction enzyme profiles of viral DNA indicate that this virus is markedly different from the Autographa californica (Speyer) MNPV ( Ac MNPV) and from Se MNPVs isolated from Egypt and the Netherlands, but is; similar to other previously described Se MNPV isolates from California. Synchronous per o5 bioassays of the virus against neonate beet armyworm larvae demonstrated that Se MNPV 608 was highly virulent, with an ST50 of 57.39 ± 1.59 h ($\bar x$ ± SD), and more virulent for larvae of S. exigua than Ac MNPV (ST50 = 70.06 ± 2.66 h). Additionally, limited host range studies indicated that this isolate is specific for S. exigua no activity was apparent against larvae of the noctuids Heliothis virescens (F.), Trichoplusia ni (Hubner), or Spodoptera frugiperda (J. E. Smith).

Efficacy of Selected Microbial and Related Insecticides Against Fifth Instar Beet Armyworm Larvae, Summer, California, 1985

Abstract The materials were applied to individual 4-wk-old chrysanthemum plants, cv. Hurricane, with a 1-gaI B&G sprayer at 60 psi 15 Aug. Five fifth-stage larvae were immediately placed on each plant and confined with an inverted, ventilated 1 qt plastic container. Mortality was assessed after 48 h and each surviving larva was placed individually on untreated commercial beet armyworm diet. Mortality was assessed every 48 h thereafter until all surviving larvae had pupated. To correct for differences in escaping larvae between treatments, the data were expressed as percent mortality for each replicate. Arcsin square root transformations were performed on the data prior to ANOVA.

Efficacy of Selected Microbial and Related Insecticides Against Second Instar Beet Armyworm Larvae, Pall, California, 1985

Abstract The materials were applied to individual 4-wk-old chrysanthemum plants with a 1-gaI B&G sprayer at 60 psi 11 Oct. five second-stage larvae were immediately confined to each plant for 48 h by an inverted, ventilated 1 qt plastic container. Mortality was assessed after 48 h and each surviving larva was placed individually on untreated commercial beet armyworm diet. Mortality was assessed every 48 thereafter until all surviviing larvae had pupated. The pupae were held for adult emergence. To correct for differences in escaping larvae between treatments, the data were expressed as percent mortality for each replicate. Arcsin square root transformations were performed on the data prior to analysis by ANOVA.

Control of Fifth Instar Beet Armyworm Larvae on Chrysanthemum, Summer, California, 1985

Abstract Materials were applied to individual 4-wk-old chrysanthemum plants, cvs. Hurricane, with a 1-gal B&G sprayer at 60 psi 27 Aug. Five fifth-stage larvae were immediately placed on each plant and confined with an inverted, ventilated 1-qt plastic container. Mortality was assessed after 48 h and each surviving larva was placed individually on untreated commercial beet armyworm diet. Mortality was assessed every 48 h thereafter until all surviving larvae had pupated. To correct for differences in escaping larvae between treatments, the data were expressed as percent mortality for each ceplicate. Arcsin square root transformations were performed on the data prior to ANOVA.

Temperature-dependent Development, Mortality, and Longevity of Microplitis rufiventris (Hymenoptera: Braeonidae), a Parasitoid of the Beet Armyworm (Lepidoptera: Noctuidae)

Development, mortality, and adult longevity of Microplitis rufiventris Kokujev, an imported parasitoid of the beet armyworm (BAW), Spodoptera exigua (Hubner), was studied in relation to constant temperatures in the laboratory. This study provided estimates of both lower (10.3°C) and upper (29.5°C) thresholds for development. M. rufiventris successfully attacked and parasitized second-instar BAW larvae, and regardless of rearing temperature usually emerged from fourth-instar larvae. Immature mortality ranged from 0.0 to 21% between 17.5 and 32°C; at 33.5°C all individuals died before reaching the adult stage. Adult longevity declined as a function of temperature, ranging from ca. 25 days at 17.5°C to 4 days at 32°C. Results of this study indicate that there is sufficient abiotic potential for M. rufiventris establishment in Arizona.

Encapsulation of Steinernematid and Heterorhabditid Nematodes with Calcium Alginate: A New Approach for Insect Control and Other Applications

The entomogenous nematodes Steinernema feltiae Filipjev (= Neoaplectana carpocapsae Weiser) and Heterorhabditis heliothidis (Khan, Brooks & Hirschmann) were encapsulated in calcium alginate and fed to larvae of Spodoptera exigua (Hubner) in petri dishes. While feeding on the capsules, the larvae released the nematodes. When moisture was present, larval mortality was nearly 100%, but little or no mortality occurred when free moisture was not present. S. feltiae in the capsules survived for 8 months with no detectable loss in survivability or infectivity when stored at 4°C. Capsules coated with a lipid membrane were completely desiccated at 50% RH with no nematode survivors, but at 72% RH, 71.2% of the nematodes were alive after 24 h. Potential use of the capsules containing these nematodes for insect control is discussed.

Beet Armyworm Suppression on Celery, 1984

Abstract Celery was transplanted on 4 Aug into 9 inch greenhouse pots. On 24 Aug, when plants were ca. 16 inches in heiglit, 10 third-stage beet armyworm larvae from a laboratory colony were placed on each of 4 plants/application rate, and allowed to acclimate for ca. 1 h. Each plant was then sprayed to runoff using a Devilbiss #16 nozzle. In a second test, the same experimental design was used except that larvae were placed on the plants after the sprays had dried. Laboratory conditions at the time of treatment were 24°C and a photoperiod of LD: 16-8. All plants were placed in ventilated cages to prevent losses due to the migratory behavior of the beet armyworm. Plants were examined for dead or moribund larvae at 2, 8 and 24 and 72 h posttreatment for the contact plus residue test. In the residue only trial, moribund and dead larvae were recorded at 12, 48 and 72 h following treatment. Plants and larvae in the checks were treated with distilled water only.

Influence of Three Soybean Plant Genotypes and Their F1 Intercrosses on the Development of Five Insect Species

A bioassay technique was used to evaluate soybean Glycine max (L.) Merr. plant introduction(s) (PI) 171451, 227687, 229358, F1 plants of their intercrosses, and soybean cv. Davis for relative levels of resistance to velvetbean caterpillar (VBC), Anticarsia gemmatalis Hubner, soybean looper (SBL), Pseudoplusia includens (Walker), corn earworm (CEW), Heliothis zea (Boddie), tobacco budworm (TBW), H. virescens (F.), and beet armyworm (BAW), Spodoptera exigua (Hubner). Larvae of all five insect species reared on leaves from PI 227687 and 229358 were significantly smaller than those reared on leaves from ‘Davis.’ VBC, SBL, and BAW larvae reared on leaves from PI 171451 were not significantly different from those reared on leaves from ‘Davis.’ Differences among larvae reared on leaves from PI 227687 and 229358 for VBC, SBL, and TBW were not significant. CEW and BAW larvae reared on leaves from PI 229358 were significantly larger than those reared on leaves from PI 227687. Although the same trends observed with larval weights were exhibited by pupal weights, plant genotype influenced pupal weights less than larval weights. Days to pupation were increased, although not always significantly, for larvae reared on the resistant genotypes. Mortality tended to be greater for larvae reared on leaves from resistant genotypes. Weights of larvae reared on leaves from the F1 plants of intercrosses between PI tended to be intermediate to those reared on leaves from the parents. However, CEW larvae reared on leaves from the F1 plants of the PI 171451 × PI 229358 cross were smaller than those reared on leaves from either parent. A strong trend for larvae reared on leaves from F1 plants of the crosses to be smaller than the midparent value was apparent. Also, the trend in days to pupation and pupal weights was very similar to the trend in larval weights. Because larval weight for those reared on leaves from F1 plants tended to be similar to those reared on the most resistant parents, a slight dominance effect for resistance is indicated. The response of insects to the crosses indicates that resistance levels can be increased through a program of intercrossing and selecting.

Feeding and Growth of Noctuid Larvae on Foliar Material and Extracts of Guayule Related Species of Parthenium , and F 1 Hybrids

Artifical diets incorporating powdered foliage or foliar extracts of Parthenium tomentosum DC. or P. schottii Greenman inhibited feeding, growth, and dietary use by 3rd-instar larvae of the beet armyworm, Spodoptera exigua Hubner, relative to larvae feeding on diets incorporating foliage or foliar extracts from guayule, P. argentatu Gray, or an F1 hybrid of guayule with P. tomentosum. Amixture of sesquiterpene lactones isolated from P. schottii added to an artifical diet inhibited feeding, but did not deter growth or dietary use by larvae. Foliage or foliar extracts of P. schottii added to diets also significantly inhibited growth and dietary use by 3rd-instar larvae of the bollworm Heliothis zea (Boddie), although there was no reduction in consumption rate. In contrast, powdered inflorescences of P. schottii or extracts thereof, both rich in sesquiterpene lactones, deterred neither feeding nor growth of H. zea when added to artificial diets. Confertin, the principal sesquiterpene lactone of P. schottii foliage and inflorescences, had no effect on feeding or growth of 3rd-instar larvae, even at a concentration which strongly inhibits growth of neonate H. zea larvae. Chemical factors in P. schottii and P. tomentosum foliage appear to inhibit larval growth of both S. exigua and H. zea, although a contribution to that inhibition by sesquiterpene lactones is uncertain.

Beet Armyworm Control on Eggplant in West-Central Florida, 1982

Abstract Transplants were set 16 Sept., 18 in apart on 2.5-ft wide by 8-in high beds of Myakka fine sand covered with black polyethylene mulch, plots consisted of 10 staked plants and were replicated four times in a randomized complete block design. Treatments were applied 1, 6, 11, 18, and 25 Oct., 1, 8, 16, 22, and 29 Nov., 8, 14, 21, and 28 Dec. 1982, and 6 Jan. 1983 with a 2.5-gal, handheld CO2-powered sprayer which was operated at 40 lb/in2 and delivered 65 to 120 gal/acre (gallonage increased as the plants grew, but averaged 105 gal/acre). On 12 Oct., the foliage of all plants was examined and the number of beet armyworm larvae was recorded. The number and weight of undamaged fruit and the number of fruit damaged by lepidopterous larvae (principally the beet armyworm) were totaled over harvests taken 1, 7, 13, and 27 Dec, and 7, 9, 11, and 24 Jan. Percentage data were transformed arc sine %/100 before analysis, but data are presented in the original scale.

Control of Insects on Tomato in West Florida, Spring, 1982

Abstract Transplants were set Mar 2, 18 inches apart on 2.5-ft-wide by 8 inch-high beds of Myakka fine sand covered with black polyethylene mulch. Plots consisted of 10 staked plants and were replicated 4 times in a randomized complete block design. Treatments were applied Apr 1, 12, 19, 27, May 5, 12, 19, 26, and Jun 3 with a 2.5-gal hand-held CO2 powered sprayer which was operated at 40 psi and delivered 125-200 gal/acre (gallonage increased as the plants grew). On Apr 27 after the foliage dried, 5 fully expanded leaflets were excised from each plot which had been sprayed with water (check), Lannate or Sok (Bacillusthuringiensisvar kurstakiBerliner) and placed on water-moistened filter paper on the bottoms of 2 inch diameter plastic cups. Mve first instar beet armyworm larvae were placed in each cup and the cups were sealed. The cups and larvae were placed in a room at ca 80°F and 14-h photoperiod for 3 days at which time the numbers of apparently healthy, dead and moribund larvae were counted. On May 5, another sample of excised foliage was bioassayed with first instar beet armyworm larvae. On May 12, 14, and 17, excised foliage samples were bioassayed as before using first instar tomato pinworm larvae. Percent mortality (dead plus moribund) was calculated for each post-treatment bioassay and corrected for natural mortality according to Abbott’s formula. Percentage data were transformed arcsine (%)(.01) prior to analysis but data are presented in the original scale. The number of undamaged fruit and number of fruit damaged by noctuid larvae (principally the southern armyworm and tomato fruitworm) and those damaged by southern green stink bugs were totaled over harvests taken on May 24, Jun 1, and 8. On Jun 10, 5 plants per plot were cut and shaken and the number of dislodged southern green stink bug nymphs and adults was counted.

Lepidoptera Control in Broccoli, 1980

Abstract ‘De Cicco’ broccoli was seeded at 3 lb/acre on Aug 24 at the University of California South Coast Field Station in Irvine, California. Experimental plots were 20 m long and 3 rows wide, with 0,76 m between rows. Plants were thinned to 0.33-0.38 m spacings on Sept 9-10. Following thinning, the crop was furrow-irrigated weekly. Each treatment was replicated 4 times in a Latin Square design, with replicates separated by 1.5 m and 1 untreated row of plants. Plants were sprayed weekly with Pirimor 50WP for aphid control at 0.25 lb ai/acre and 100 or 120 psi on Sept 19, 26, Oct 3, 10, and 17. Carrier (H2O) increased from 45 to 100 gal/acre as plant height increased. Pydrin and Nudrin were applied at 0.1 and 0.9 lb ai/acre, respectively, on the same dates, with the same amount of carrier. Treatments were evaluated for cabbage looper, imported cabbageworm, beet armyworm, and diamondback moth larvae and pupae from 10 plants from the center row in each replicate on Sept 25, Oct 2, 9, 16 and 23. All mature plants in each replicate were harvested on Oct 27. No precipitation was recorded at the weather facility on the South Coast Field Station during this experiment.

Preliminary notes on the parasites ofSpodoptera Exigua (Huebner) (Lepidoptera: Noctuidae) in Israel

Larvae ofSpodoptera exigua (Huebner) were collected and their parasites were reared out. From larvae collected in alfalfa fields, 14 parasite species were recovered; from those collected in corn fields, 12 species were recovered; eight species were common to both situations.Meteorus unicolor Wesm. was predominant in corn fields andChelonus inanitus (L.) was predominant in alfalfa fields.

Genetic Variation in Predatory and Cannibalistic Tendencies of Heliothis virescens1 Strains

When raised in the laboratory, Heliothis virescens strains differed in their propensity to cannibalize other H. virescens larvae. Propensity to cannibalize was correlated with rate of predation on Spodoptera exigua larvae and ability to compete with aggressive H. zea larvae. Implications of these findings for pest management are discussed.

Comparative Insecticide Induced Mortality of Nabis americoferus1 in Cotton 2

Nabis americoferus Carayon exhibited differential mortality when exposed to dimethoate, toxaphene-naled, and aldicarb in comparison to untreated plots. Dimethoate at 0.56 kg/ha cause significantly greater mortality to damsel bugs over a 7-day period than did a combination of 3.4 kg toxaphene and 2.2 kg naled/ha. The increased mortality caused by the dimethoate was reflected in the greater numbers of the beet armyworm larvae, Spodoptera exigua (Hubner), than in the plots treated with toxaphene-naled. In a 2nd trial, Nabis mortality was recorded after 48- and 72-h exposure to cotton terminals following treatment. An untreated check, a single side-dressing of aldicarb, and 3 dimethoate applications were compared. Three dimethoate applications produced 3 predator mortality peaks. The untreated plots had the least mortality. Aldicarb produced moderate mortality which increased following each of two irrigations. The increase in Nabis mortality from check, to aldicarb, to dimethoate was reflected in proportional increases in late season larval populations of the cabbage looper, Trichoplusia ni (Hubner).