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.

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 (CsCI)-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.

Colonization and abundance of soybean looper, Pseudoplusia includens (Walker), and cabbage looper, Trichoplusia ni (Hübner), 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, whereas fewer cabbage looper larvae were collected from soybean than cotton. Cabbage looper larvae were collected in soybean on the same sample date in 1995, but approximately 5 wk after soybean looper larvae in 1996. The occurrence of soybean and cabbage loopers in cotton and soybean agroecosystems in Mississippi appears to be similar to patterns of activity recorded for these insects 20 to 40 years ago in other areas of the southeastern United States.

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