WITHIN PLANT PREFERENCES OF LARVAE OF MAMESTRA CONFIGURATA (LEPIDOPTERA: NOCTUIDAE) FEEDING ON OILSEED RAPE

1984 ◽  
Vol 116 (1) ◽  
pp. 45-49 ◽  
Author(s):  
G. K. Bracken

AbstractThe order of feeding preference on plant parts of rape (Brassica napus L.) by sixth instar (L6) larvae of bertha armyworm, Mamestra configurata Walker, in laboratory tests was leaves, bracts, immature pods, and mature pods. Field sampling showed that upper, immature pods are attacked with greater frequency than lower, more mature pods. In a greenhouse test, a slightly larger proportion of L6 larvae was recorded on inflorescences of rape plants during darkness than during light; the proportion of larvae found on the inflorescences was about 20%. Larvae pupated more quickly, formed heavier pupae, and gained more dry weight when fed exclusively from mid L4 on leaves than when fed mature or immature pods; mortality for larvae fed mature pods was 30% compared with none for larvae fed leaves or immature pods.The finding that pods are neither as preferred nor as adequate a dietary source as leaves is discussed in relation to the phenology of leaf retention of rape on the economic impact of bertha armyworm infestations.

1986 ◽  
Vol 118 (5) ◽  
pp. 473-478 ◽  
Author(s):  
O.N. Morris

AbstractCommercial Bacillus thuringiensis var. kurstaki (B.t.k.) (Dipel 132® and Thuricide 48 LV®) were bioassayed at 20 and 25°C against 3rd- (L3), 4th- (L4), 5th- (L5), and 6th- (L6) instar larvae of the bertha armyworm, Mamestra configurata Walker, on greenhouse-grown canola, Brassica napus L. cv. Westar. The L4 was the most susceptible stage to B.t.k. but it was much less susceptible than the spruce budworm, Choristoneura fumiferana (Clem.), a species against which this bacterium is currently used. The lethal time of B.t.k. to the larvae was inversely related to dosage applied. Younger instars (L3 to L4) were more sensitive to Dipel than older instars (L5 to L6) at 20°C but the reverse was true for Thuricide-treated larvae. All B.t.k. treatments reduced weight gain and frass deposition (by inference feeding activity) compared with untreated controls. The LC50 concentration of B.t.k. for larvae reduced survival to adult emergence by 87–100%.


1988 ◽  
Vol 120 (5) ◽  
pp. 401-413 ◽  
Author(s):  
W. J. Turnock

AbstractPopulations of larvae of the bertha armyworm, Mamestra configurata Wlk., in four physiographic regions of Manitoba showed similar trends over time: a decline from the outbreak of 1971–1972 to very low densities in 1975–1977, an increase to a peak during the years 1979–1981, and a subsequent decline. During the period of peak larval populations, brief (1 or 2 years) outbreaks [at least some fields with > 20 larvae per square metre) occurred at five locations in two regions, the Swan River Plain and the Valley River Plain, but not in the Western Uplands or the Manitoba Lowlands. In the first two regions, larval densities rose rapidly (from < 1.6 to > 13.8/m2) in 1 year. Although the general trend of population density was similar, there were differences in density among and within regions, and in the timing, severity, and duration of peak populations. Two parasitoids (Banchus flavescens Cress., Athrycia cinerea (Coq.)) and two pathogens (a nuclear polyhedrosis virus (NPV) and fungi of the Entomophthorales) occurred regularly in larval populations. Of these, B. flavescens had the highest constancy among collections and may help to keep bertha armyworm populations at low densities. NPV was rarely found among larvae from low-density populations but appeared in all populations that reached outbreak levels. No single biotic agent could be associated with the population declines because of multiple parasitism and the difficulty in partitioning mortality when only a single sample could be taken. The rapid increase of bertha armyworm larvae from very low to outbreak levels in 1 year will prevent predictions of outbreaks from being based on larval densities in the preceding year.


1983 ◽  
Vol 115 (8) ◽  
pp. 1039-1042 ◽  
Author(s):  
B. M. Hegdekar

AbstractThe critical photoperiod for diapause induction in pupae of Mamestra configurata Walker in Manitoba was 16 h 06 min at Glenlea (49°38′ N), 16 h 20 min at Grandview (51°10′ N), and 16 h 42 min at Birch River (52°24′ N). The differences in cirtical photoperiods observed at Glenlea and Grandview were not significant. At least two different photoperiods exist, one in the Glenlea and Grandview areas and the other in the Birch River area. In the laboratory, the critical photoperiod was 13.5 h when larvae were exposed to a daily fluctuating temperature regime of 12 h at 25 °C and 12 h at 10 °C. Longer critical photoperiods found for the field populations may be related to the relatively low ambient temperatures to which the larvae were exposed in field cages.


1986 ◽  
Vol 118 (12) ◽  
pp. 1221-1230 ◽  
Author(s):  
M.A. Howlader ◽  
G.H. Gerber

AbstractThe effects of age, egg development, and mating on calling behavior of the bertha armyworm, Mamestra configurata Walker, were studied at 20°C, 60% RH, and a 16-h L: 8-h D photoperiod. Most virgin females called and copulated for the first time during the second or third scotophase after emergence. The first copulation was 17.0 ± 0.2 h (mean±SE) long and was terminated within 1 h after lights off in the scotophase following the initiation of copulation. The ovaries contained the first chorionated eggs before the beginning of the second scotophase after emergence. The first egg laying occurred during the same scotophase in which the first copulation was terminated, i.e. scotophase three or four. Almost 75% of the eggs were laid by the end of the seventh scotophase after emergence. Mated females resumed calling after a refractory period of about 2 days. Once calling was resumed after copulation, most females laid eggs and called nightly, with egg laying occurring during the first 5–6 h and calling during the last 2–3 h of the scotophase. Mated females called for a shorter period during each scotophase than virgin females of the same age (1–3 h vs. 4–6 h). In virgin females, the diel periodicity of calling was advanced and the length of the daily calling period was increased with age until the seventh scotophase after emergence; thereafter, both remained relatively unchanged.


1972 ◽  
Vol 104 (11) ◽  
pp. 1745-1750 ◽  
Author(s):  
Y. W. Lee ◽  
R. J. Ford ◽  
H. McDonald ◽  
K. S. McKinlay ◽  
L. G. Putnam ◽  
...  

AbstractResidues of methomyl in rape plants and seed were determined after its application for bertha armyworm control. In one experiment application of 3 oz of methomyl per acre left 17 p.p.m. residue on the rape plants immediately after application. This level rapidly declined to 1.5, 1.0, 0.4, and 0.2 p.p.m. 1, 2, 5, and 9 days later, respectively, and no residue was detected (less than 0.02 p.p.m.) in seed harvested 22 days after application of the toxicant. Rape plant samples collected from several farms immediately after the application of 3 to 4 oz of methomyl per acre had 2.5 to 16 p.p.m. residues, indicating inefficient application of the insecticide in some cases. Analysis of rape seed samples collected from 36 farms showed little residue in three samples (0.02 to 0.03 p.p.m.) and none in 33, indicating that the use of methomyl for bertha armyworm control is not likely to contaminate rape seed with undesirable levels of residues.


Author(s):  
P. G. Mason ◽  
W. J. Turnock ◽  
M. A. Erlandson ◽  
U. Kuhlmann ◽  
L. Braun

1985 ◽  
Vol 117 (10) ◽  
pp. 1249-1255 ◽  
Author(s):  
A.P. Arthur ◽  
P.G. Mason

AbstractBanchus flavescens Cresson is the most abundant hymenopterous parasitoid of the bertha armyworm, Mamestra configurata Walker, in western Canada. The females attack 1st, 2nd, and 3rd instars of the host. The speed of parasitoid development is adjusted so that the 2nd instar is completed when the host finishes feeding. Banchus flavescens has an obligate diapause and overwinters as a prepupa within a cocoon in the soil. Notes on life history and descriptions of the egg and 5 larval instars of B. flavescens are given.


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