Effectiveness of three Bt corn events against feeding damage by the true armyworm (Pseudaletia unipuncta Haworth)

A 3-yr study (2002-2004) was conducted to evaluate the resistance of three Bt corn events to herbivory damage by the armyworm, Pseudaletia unipuncta (Haworth). Resistance was assessed by damage ratings and fresh mass measurements. Greenhouse studies were run in 2002 and 2004, and a field study was conducted in 2003. Hybrids expressing the Cry1A(b) insecticidal protein, Mon810 and Bt176 events, and their near isolines, as well as the TC1507 event, which expresses the Cry1F protein, were evaluated. Bt hybrids suffered less damage in all 3 yr and had higher fresh masses in 2002 and 2003 than the non-transgenic isolines. In 2002 and 2003, hybrids expressing the Cry1A(b) protein were significantly less damaged than the hybrid expressing Cry1F. In both 2002 and 2004, the Mon810 event suffered less damage than the Bt176 event, despite expressing the same Cry1A(b) protein. Bt corn, especially the Mon810 event may be used as an effective method of preventing P. unipuncta herbivory damage in corn. Key words: True armyworm, Pseudaletia unipuncta, Bt corn, Cry1A(b), Cry1F, epistasis

Armyworm, Pseudaletia unipuncta (Haworth) (Insecta: Lepidoptera: Noctuidae)

EENY-394, a 5-page illustrated fact sheet by John L. Capinera, describes this "true armyworm", a light reddish brown nocturnal moth bundant in North America east of the Rocky Mountains, whose larvae are notorious for appearing out of nowhere to inflict a high level of defoliation in grain crops. Includes selected references. Published by the UF Department of Entomology and Nematology, October 2006. EENY-394/IN702: Armyworm, Mythimna unipuncta (Haworth) (Insecta: Lepidoptera: Noctuidae) (ufl.edu)

Differentiation and gene flow among island and mainland populations of the true armyworm, Pseudaletia unipuncta (Haworth) (Lepidoptera: Noctuidae)

The genetic structure of populations of the true armyworm, Pseudaletia unipuncta (Haworth) (Lepidoptera: Noctuidae), in the Azores archipelago was studied using polyacrylamide-gel electrophoresis. Four enzyme systems (aldehyde oxidase, esterase, phosphoglucomutase, and phosphoglucose isomerase) were examined in six populations from islands in the Azores (Santa Maria, São Miguel, Terceira, Pico, Faial, Flores) and compared with those from populations from mainland Portugal and Canada. The North American and European populations are not clearly separated from the Azorean ones. Similarly, studies of different enzyme systems (aldehyde oxidase, esterase, malic enzyme, sorbitol dehydrogenase, manose-6-phosphate isomerase, and phosphoglucomutase) over 2 years (1997 and 1998) at different times of the year (spring, summer, and autumn) and at three different altitudes (0, 250, and 500 m above sea level) on three different islands (Santa Maria, São Miguel, and Faial) uncovered no distinct differences. These results, obtained from classically used loci, suggest that there is still some gene flow between sites or that island populations have not been isolated for sufficient time to have diverged from founder populations.

Impact of True Armyworm (Lepidoptera: Noctuidae) Feeding on Wheat Yields in Arkansas

Wheat leaf consumption by the true armyworm, Pseudaletia unipuncta Haworth, was determined in the laboratory in 1993, 1994, and 1995. Total mean wheat leaf area consumed per larva from eclosion to pupation varied significantly from year to year (77.4–135.4 cm2) with an overall mean leaf area consumed of 103.2 cm2. Wheat field plots were infested with third-instar armyworms and allowed to consume wheat foliage at boot and anthesis stages until preset defoliation levels were met (0, 10, 25, and 50% defoliation in 1993, and 0, 35, 50, 65, and 75% defoliation in 1994, and 0, 35, 50, 65, and 75% defoliation in 1995, and 1996). Overall, no significant differences were seen between treatments in number of heads or mean weight of seeds per head in any year suggesting that at boot and anthesis stages Arkansas wheat can sustain up to 75% defoliation by armyworms with little loss in yield. Even at population levels that resulted in 75% defoliation head cutting was negligible.

Enhanced haemolymph circulation by insect ventral nerve cord: hormonal control byPseudaletia unipunctaallatotropin and serotonin

SUMMARYThe ventral diaphragm (VD) in many insects is a muscular membrane that essentially partitions a perineural sinus from the rest of the abdomen. In the true armyworm moth Pseudaletia unipuncta (Lepidoptera: Noctuidae) we describe how the VD is characterized by a series of aliform muscles inserted into a tissue matrix that is fused to the dorsal surface of the ventral nerve cord (VNC) itself. Because of this arrangement, the abdominal VNC can attain high rates of lateral oscillation, and is capable of directing haemolymph flow. We have previously demonstrated Manduca sexta allatotropin(Manse-AT)-like immunoreactivity throughout the central nervous system (CNS)in P. unipuncta, and that both Manse-AT and serotonin (5-HT) are dose-dependent stimulators of the dorsal vessel. Here we describe both Manse-AT- and 5-HT-like immunoreactivity associated with the VD. Furthermore,both Manse-AT and 5-HT are dose-dependent stimulators of the rates of VNC oscillation, and together are capable of maintaining highly elevated rates of VNC oscillation for extended periods of time. These data indicate that both the dorsal vessel and the VD/VNC are similarly modulated by both Manse-AT and 5-HT, and that VNC oscillations play a more active role in overall haemolymph circulation than previously recognized.