Effects of Inherited Sterility and Insect Resistant Dent-Corn Silks on Helicoverpa zea (Lepidoptera: Noctuidae) Development

1992 ◽  
Vol 27 (4) ◽  
pp. 413-420 ◽  
Author(s):  
J. E. Carpenter ◽  
B. R. Wiseman

Male and female corn earworm, Helicoverpa zea (Boddie), adults were exposed to a substerilizing dose (10 krads) of gamma radiation after which their progeny were reared on a meridic diet containing selected concentrations of dry silk collected from resistant dent corn genotypes. Significant interactions were observed between the developmental time of progeny from irradiated females and progeny from normal parents and meridic diets with increasing degrees of resistance. A significant interaction also was observed between the mean larval weights of normal and substerile larvae and diets with increasing degrees of resistance. The 9-d weight of normal larvae was significantly higher than the weight of substerile larvae at the lowest degree of resistance, but differences between the weight of normal and substerile larvae at the highest degree of resistance were not significant. Larvae from irradiated male by normal female crosses were equally competitive with normal larvae for all measured parameters. Data from this study suggest that plant resistance and inherited sterility would be compatible control strategies for the management of H. zea populations.

1997 ◽  
Vol 32 (2) ◽  
pp. 148-153 ◽  
Author(s):  
J. J. Hamm ◽  
J. E. Carpenter

Inherited sterility has been proposed as a means of suppressing the populations of the corn earworm, Helicoverpa zea (Boddie), and the fall armyworm, Spodoptera frugiperda (J. E. Smith). If nuclear polyhedrosis viruses could be used to kill larvae, thereby reducing the number of moths in the field populations, fewer moths treated with substerilizing doses of irradiation would need to be released. However, for these two methods to be compatible, the progeny of substerile moths should be no more susceptible to the virus than the progeny of the field populations. The corn earworm nuclear polyhedrosis virus (Elcar™) was bioassayed against corn earworm larvae from untreated moths and larvae from male, female, and male and female moths treated with 100 Gy of irradiation and larvae from male moths treated with 150 Gy of irradiation. The fall armyworm nuclear polyhedrosis virus was bioassayed against fall armyworm larvae from untreated moths and larvae from male moths treated with 100 to 150 Gy of irradiation. There was no significant difference between susceptibility of larvae from untreated moths and larvae from irradiated moths. Thus, the use of nuclear polyhedrosis viruses for control of larvae should be compatible with the release of substerilized moths as part of an integrated pest management approach for area-wide management of the corn earworm and fall armyworm.


1991 ◽  
Vol 26 (3) ◽  
pp. 303-309
Author(s):  
B. R. Wiseman ◽  
D. J. Isenhour ◽  
V. R. Bhagwat

Weight of larvae, developmental time to pupation, weight of pupae, length of stadia, and width of head capsule were determined for larvae of the corn earworm, Helicoverpa zea (Boddie), that were fed on meridic diets with silks of ‘Stowell's Evergreen’, a susceptible genotype, or low, intermediate, and high levels of ‘Zapalote Chico’, a corn, Zea mays L., cultivar with antibiotic resistance. As the level of resistance increased, the weight of larvae at 9 days and weight of pupae significantly decreased, and developmental time to pupation significantly increased. Also, as the concentration of resistant material increased in the diet, stadial length also significantly increased. The intermediate and high levels of resistance also resulted in a significant reduction in the width of the head capsule of larvae. Thus, two new characteristics of resistance in maize silks to the corn earworm were identified: increased stadia and decreased width of head capsule.


1996 ◽  
Vol 31 (3) ◽  
pp. 340-346 ◽  
Author(s):  
Steven R. Sims ◽  
Jay C. Pershing ◽  
Barbara J. Reich

Twelve independently transformed lines of transgenic corn (Zea mays L.) expressing the CryIA(b) insecticidal protein from Bacillus thuringiensis var. kurstaki were field tested to evaluate their resistance to the corn earworm, Helicoverpa zea (Boddie). Silks of the primary (=top) ears of transgenic [CryIA(b) positive] and isoline control plants [no CryIA(b) protein] were artificially infested with first-instar H. zea larvae and the length of ear penetration was measured after 19 d. Eight of the 12 lines had significantly less ear damage than their respective isoline controls; 3 transgenic lines reduced H. zea feeding damage by > 75% and stunted surviving H. zea larvae. Concentration of the CryIA(b) protein (μg/g fresh weight) in silks of the transgenic lines, determined using ELISA, ranged from 0.0 to 1.28 μg/g. Within transgenic lines, there was a weak (P < 0.06) negative relationship between the concentration of CryIA(b) protein in fresh silks and the length of H. zea ear penetration.


1991 ◽  
Vol 26 (4) ◽  
pp. 419-424
Author(s):  
J. R. Chamberlin ◽  
J. N. All

The influence of panicle maturity on oviposition by the corn earworm, Helicoverpa zea (Boddie), and sorghum webworm, Celama sorghiella (Riley), was investigated on grain sorghum in Georgia during 1986 and 1987. Stage of panicle development, density of corn earworm and sorghum webworm, and egg parasitism by Trichogramma spp. were recorded at 2–3 day intervals in three field tests. Sorghum webworm and corn earworm began oviposition as panicles emerged from the boot. Oviposition peaked 4–8 days later, near the time panicles began anthesis, but then declined quite rapidly. Oviposition by sorghum webworm ceased approximately 10–12 days after panicle emergence began. Corn earworm oviposition continued at low levels until sampling was terminated 14 - 17 days after panicles began emgergence. Rainfall appeared to mediate effects of panicle maturity on oviposition. Corresponding peaks in larval density were not observed for corn earworm or sorghum webworm, possibly because of heavy parasitism by Trichogramma spp. A paired comparison procedure was used to determine preference of small, medium, and large corn earworm larvae for panicles of different maturity. Early instars preferred newly flowered panicles and concentrated feeding on pollen filled anthers. Late instars preferred panicles in the soft-hard dough stages, while intermediate instars exhibited no significant preference. These data suggest that corn earworm oviposition is concentrated at anthesis because pollen enhances larval development and survival.


Sign in / Sign up

Export Citation Format

Share Document