Henry N. Pitre

Influence of Roundup Ready Soybean Production Systems and Glyphosate Application on Pest and Beneficial Insects in Narrow-Row Soybean

Roundup Ready® soybeans, Glycine max (L.) Merrill, in narrow-row planting systems were investigated in 1998 in Mississippi to evaluate the effects of the transgenic crop and glyphosate herbicide on pest and beneficial insects. Insects found in sufficient numbers for meaningful analysis included adult bean leaf beetle, Cerotoma trifurcata (Forster); adult three-cornered alfalfa hopper, Spissistilus festinus (Say); adult big-eyed bug, Geocoris punctipes (Say), and; larvae of green cloverworm, Plathypena scabra (F.), and velvetbean caterpillar, Anticarsia gemmatalis (Hubner). Populations of C. trifurcata, S. festinus, P. scabra and A. gemmatalis were not reduced in genetically altered Roundup Ready soybean, or by recommended (by label) or delayed applications of glyphosate. Numbers of G. punctipes also were not reduced in Roundup Ready soybean, but were reduced by recommended applications of glyphosate during weeks three and four following the second recommended herbicide application. Geocoris punctipes dens...

Relationship of Fall Armyworm (Lepidoptera: Noctuidae) from Florida, Honduras, Jamaica, and Mississippi: Susceptibility to Insecticides with Reference to Migration

Fall armyworm (FAW), Spodoptera frugiperda (J. E. Smith), cultures established in 1985 from larvae collected on corn in Florida and Jamaica and on sorghum in Mississippi and Honduras were tested in the laboratory for susceptibility to carbaryl, permethrin, methomyl, chlorpyrifos, and methyl parathion using leaves from sorghum plants sprayed with insecticide in the field. Methomyl and chlorpyrifos were effective (85% mortality) against 3rd instar FAW larvae from Jamaica and Mississippi whereas mortality of similar larval stages from Honduras was 50%. The Florida culture appeared to be about equally tolerant to all the test insecticides. Carbaryl, methyl parathion and permethrin were ineffective against 3rd instar larvae from all test areas. However, preliminary field tests indicated that 1st instar Honduras FAW larvae are susceptible to methyl parathion. Also, materials shown to be ineffective against 3rd instar larvae in the whorl were effective on FAW when applied to the sorghum seed head in a separate study. Susceptibility responses to insecticides indicate that the FAW population from Mississippi was more similar to test populations from Jamaica and Honduras, than to the test population from Florida, suggesting that the FAW source from Florida may not be the source of insects invading Mississippi.

Soyabean looper and cabbage looper (Lepidoptera: Noctuidae) populations in cotton and soyabean cropping systems in Mississippi.

Colonization and abundance of soybean looper, Pseudoplusia includens (Walker), and cabbage looper, Trichoplusia ni (Hubner), adults and larvae were monitored in cotton and soybean cropping systems in the Delta region of Mississippi for three growing seasons (1994–1996). Soybean looper and cabbage looper adults were initially observed in pheromone traps during the last week of May or first week of June, although adults may have been present in the collection area prior to trap establishment. Adult populations of both species remained low until early August, after which moth density increased coincident with the bloom stages of cotton and soybean. Larvae were first collected from the crops when plants were in bloom, with the greatest increase in population density occurring in early to mid-August. Although samples were not taken after mid-August, looper populations generally decline to low levels during September in Mississippi. More soybean looper larvae usually were collected from soybean than in cotton, ...

Soybean Looper (Lepidoptera: Noctuidae) Oviposition on Cotton and Soybean of Different Growth Stages: Influence of Olfactory Stimuli

Abstract Soybean looper, Pseudoplusia includens (Walker), oviposition in cotton, Gossypium hirsutum L., and soybean, Glycine max (L.) Merr., of various stages of plant phenological development was evaluated in field cages in 1994, 1995, and 1996. Overall, females preferred to oviposit on soybean over cotton when both crops were compared in vegetative or prebloom stages, when both crops were blooming, and when soybean was blooming or in early pod stage compared with prebloom cotton. Females preferred to deposit eggs on the lower leaf surface in the upper two-thirds of the plant canopy in cotton and soybean. Oviposition in upper and middle canopy levels varied with plant growth stage. Females tended to lay more eggs in the upper canopy compared with the middle canopy in prebloom cotton and vegetative soybean; more eggs were laid in the middle canopy of blooming cotton and reproductive stages of soybean. Females responded to both cotton and soybean volatiles in an olfactometer. There was no significant difference in response to the two sources of volatiles.

Influence of Transgenic Corn Expressing Insecticidal Protein of Bacillus thuringiensis Berliner on Natural Populations of Corn Earworm (Lepidoptera: Noctuidae) and Southwestern Corn Borer (Lepidoptera: Crambidae)

A 2-yr study was conducted to measure the influence of transgenic corn, Zea mays L., expressing the CrylAb endotoxin of Bacillus thuringiensis (Berliner) (Bt) by means of Event MON810 on natural populations of Helicoverpa zea (Boddie) and Diatraea grandiosella (Dyar). The studies were conducted at Leland and Morgan City, MS, in 1999 and at Morgan City in 2000. Although total numbers of H. zea larvae were not significantly different on transgenic corn hybrids compared with their near-isogenic parent lines, fewer large larvae were found on the transgenic hybrids. Differences in H. zea larval growth were noticeable when larvae fed on Bt corn vs non-Bt corn. The delay in larval growth for insects within a single generation, which could possibly result in asynchronous mating between insecticide resistant and susceptible insects, was observed for larvae feeding on plants expressing the Bt toxin. Diatraea grandiosella caused limited damage to the transgenic corn hybrids compared with their near-isogenic parent l...

FEEDING AND DEVELOPMENT OF NABIS ROSEIPENNIS (HEMIPTERA: NABIDAE) ON HELIOTHIS VIRESCENS (LEPIDOPTERA: NOCTUIDAE) LARVAE

Feeding, development, and duration of life stages of Nabis roseipennis Reuter, on different size (2, 3, 4, or 5 mm) early instar Heliothis virescens (F.) larvae were studied in the laboratory. Thre...

Oviposition Preference of Spodoptera latifascia (Lepidoptera: Noctuidae) for Sorghum, Maize and Non-Crop Vegetation

Oviposition preferences of Spodoptera latifascia (Walker) (Lepidoptera: Noctuidae) for sorghum [Sorghum bicolor (L.) Moench (Poaceae)], maize [Zea mays (L.) (Poaceae)], and various non-crop species were examined in field cage experiments. A higher percentage (pooled means) of the total number of eggs per plant were laid on Amaranthus sp. (probably A. hybridus L. or A. viridis L.) (Amaranthaceae) 24%, maize 32%, and Ixophorus unisetus (Presl.) Schlecht (Poaceae) 26%, than on Ipomoea sp. [(probably I. purpurea (L.) Jacq.] (Convolvulacea) 2%, Melampodium divaricatum (Rich. ex pers.) Dc. (Asteraceae) 6%, Portulaca oleracea L. (Portulacaceae) 7%, and sorghum 3%. Only maize had a significantly higher percentage of the total number of eggs laid per plant than the other plant species in one of two experiments. Plant growth stage (seedling vs. older) did not appear to influence oviposition on any of the plant species tested. Moths exhibited a wide host oviposition range in our cage experiments. In contrast, eggs were collected only from Amaranthus sp., I. unisetus, and maize in the field in southern Honduras, suggesting that S. latifascia oviposition response in nature may be somewhat restricted to certain non-crop species and maize. Our data support results from previous investigations revealing the potential benefits of non-crop host plants in reducing damage by S. latifascia to sorghum and maize in intercropped production fields during the early growing season in southern Honduras.

Influence of Roundup Ready Soybean and Roundup Ultra Herbicide on Geocoris punctipes (Say) (Heteroptera: Lygaeidae) in the Laboratory

Roundup Ready® crops have become the dominant weed control system throughout the United States. Therefore, laboratory studies were conducted to evaluate the effects of Roundup Ready soybean, Glycine max (L.) Merrill, and glyphosate on the fecundity and mortality of Geocoris punctipes (Say). Mortality of third instars and adults (∼30 d old) and fecundity of females exposed to glyphosate by direct spray application or residual on soybean foliage were not affected over a 10-d posttreatment period. Mortality of nymphs and adults exposed to transgenic soybean foliage did not differ from mortality of nymphs and adults exposed to foliage of conventional, glyphosate-susceptible soybean. Exposure of G. punctipes eggs to glyphosate spray had no effect on egg hatch. The knowledge of the minimal effects of Roundup Ready soybeans and glyphosate on predaceous arthropods promotes the use of the Roundup Ready soybean system.

Activity of Rubidium and Cesium in Soybean Looper (Lepidoptera: Noctuidae): Insect Feeding on Cotton and Soybean Measured by Elemental Markers

Abstract Uptake and translocation of the elemental markers rubidium (Rb) and cesium (Cs) within adult soybean looper, Pseudoplusia includens (Walker), were determined using atomic absorption spectrophotometry in the laboratory in various feeding and mating treatments. Neonates were tested to determine marker transfer from male and female adults fed rubidium chloride (RbCl)-treated artificial nectar, cesium chloride (CsCl)-treated artificial nectar, or both. All females contained detectable levels of Rb, Cs, or both, which were obtained either through direct feeding or via spermatophores. Rubidium was present in females at significantly greater levels than Cs. No significant differences in Rb levels were observed between feeding or spermatophore acquisitions. Most neonates had significantly higher levels of Rb than Cs. In a field cage study to evaluate adult feeding and oviposition behavior on blooming cotton and blooming soybean treated with RbCl and CsCl, respectively, more eggs contained Rb than Cs, indicating greater feeding on cotton nectar than soybean nectar, regardless of the host plant upon which eggs were laid. Females laid more eggs on blooming soybean than on blooming cotton. Higher levels of Rb in cotton than Cs in soybean were recorded and may be attributed to initial elemental marker quantities available to the insects. This study provides the support for the generalized observations that soybean looper infestations in soybean can be related to feeding activities by adults in cotton.

Development of Fall Armyworm, Spodoptera Frugiperda, from Honduras and Mississippi on Sorghum or Corn in the Laboratory

Fall armyworm, Spodoptera frugiperda (J. E. Smith), larvae from Choluteca, Honduras and Starkville, Mississippi, U.S.A., were reared on sorghum or corn at 26 or 27@*C and 14 hours of light. Head capsule widths were measured to determine instar change. Larval development time was shorter for insects from Mississippi than insects from Honduras. No difference in development time for larvae in either culture was due to the host plant. The duration of prepupal and pupal stages was not significantly different for any of the treatments. Moths from Mississippi appeared to be more fecund than moths from Honduras, and insects fed corn appeared to be more fecund than those fed sorghum.