A COMPARISON OF THREE METHODS OF EXAMINING THE DENSITY OF LARVAE OF THE BERTHA ARMYWORM, MAMESTRA CONFIGURATA, IN FIELDS OF CANOLA (BRASSICA SPP.)

1985 ◽  
Vol 117 (8) ◽  
pp. 1065-1066 ◽  
Author(s):  
W.J. Turnock ◽  
R.J. Bilodeau
Keyword(s):  
Brassica Napus ◽  
Sampling Methods ◽  
Larval Density ◽  
Ground Surface ◽  
Soil Surface ◽  
Plant Debris ◽  
Brassica Spp ◽  
Metal Frame ◽  
Lepidoptera Noctuidae ◽  
Bertha Armyworm

The bertha armyworm, Mamestra conjigurata Wlk., is a polyphagous climbing cutworm (Lepidoptera: Noctuidae) that attacks canola (Brassica napus L. and B. campestris L.) in the prairie provinces of Canada. Following the outbreaks of 1971–1974 (Turnock and Philip 1977), sampling methods to determine larval density in the field were developed by researchers in Manitoba, Saskatchewan, and Alberta. The methods were basically similar, using a 3-sided metal frame to outline each 0.5-m2 sample unit, with the long side of the frame (1 m) parallel to the rows of the crop. The differences were in the way in which the plants and soil surface were searched for larvae. In Manitoba, the plants within each sampling unit were shaken by hand, then the soil surface was examined for larvae and earthen lumps and plant debris were moved to expose hidden larvae. In Saskatchewan, the plants were shaken, then cut near the base and discarded before the ground surface and debris were searched. In Alberta, the plants were cut near the base, then shaken over a sheet, and the sheet and ground surface were examined for larvae.

EFFECTS OF THE STAGE OF DEVELOPMENT OF CANOLA (BRASSICA NAPUS) ON THE CAPTURE OF MOTHS IN SEX ATTRACTANT TRAPS AND ON LARVAL DENSITY OF MAMESTRA CONFIGURATA (LEPIDOPTERA: NOCTUIDAE)

1984 ◽  
Vol 116 (4) ◽  
pp. 579-590 ◽  
Author(s):  
W. J. Turnock
Keyword(s):  
Brassica Napus ◽  
Sex Attractant ◽  
Larval Density ◽  
Egg Laying ◽  
Mamestra Configurata ◽  
Male Moth ◽  
Stage Of Development ◽  
Crop Development ◽  
Valid Index ◽  
Lepidoptera Noctuidae

AbstractThe number of moths captured during short intervals in traps containing a sex attractant for males of the bertha armyworm, Mamestra configurata Wlk., is related to the stage of plant development in the fields of canola (oilseed rape, Brassica napus L.) in which the traps are placed. More moths were captured in fields with plants in the early bloom stage than in those with plants in earlier (leaf, bud) or later (late bloom, pod) stages of development. The effect of this relationship on the total number of moths captured in any field during the entire period of moth flight depended in part on the synchronization of crop development with moth flight. Neither the total number of moths captured per field nor larval density were significantly related to crop development because of high inter-field variability among groups of fields with similar patterns of crop development. Early-maturing fields contained older larvae than later-maturing fields so they should be sampled first to determine larval density and the need for insecticidal application. The estimated patterns of egg-laying were similar to those for male moth capture in early-, mid-, and late-flowering fields. Therefore, male moth captures in sex attractant traps provide a valid index to the abundance of female moths and their egg-laying activities.

PREDICTING LARVAL ABUNDANCE OF THE BERTHA ARMYWORM, MAMESTRA CONFIGURATA WLK., IN MANITOBA FROM CATCHES OF MALE MOTHS IN SEX ATTRACTANT TRAPS

1987 ◽  
Vol 119 (2) ◽  
pp. 167-178 ◽  
Author(s):  
W.J. Turnock
Keyword(s):  
Sex Attractant ◽  
Larval Density ◽  
Larval Abundance ◽  
Target Species ◽  
Economic Threshold ◽  
Mamestra Configurata ◽  
Trap Field ◽  
Late Instar ◽  
Lepidoptera Noctuidae ◽  
Bertha Armyworm

AbstractTwo cone-orifice-type traps baited with (Z)-11-hexadecen-1-ol acetate (1.0 mg) and (Z)-9-tetradecen-1-ol acetate (0.05 mg) were placed in each of 5–13 canola (Brassica spp.) fields per year for 7 years at locations distributed throughout the area in Manitoba subject to outbreaks of the bertha armyworm, Mamestra configurata Wlk. (Lepidoptera: Noctuidae). The number of male moths per trap varied from 0 to 821 in the 90 fields trapped. Larval density, in the trap fields and in 185 nearby canola fields, varied from 0 to 105 per square metre. There was a direct relationship between the number of moths per trap and the density of late-instar larvae (L4–L6) for the trap fields and for nearby (within 5 km) fields but variability was loo high to allow accurate prediction of larval densities for individual fields. However, the number of moths per trap could be used to predict the proportion of fields in the vicinity of the trap field that would have larval densities above the economic threshold. No fields with above-threshold larval densities occurred with captures of <20 moths per trap. The proportion of fields with larval densities above the economic threshold increased from 0.10 with 20–30 moths per trap, lo 0.19 with 30–60 moths per trap, 0.64 with 70–100 moths per trap, and 0.91 with over 100 moths per trap. Contamination of catches by non-target species of noctuid moths had insignificant effects on the accuracy of these predictions because even if they were misidentified as M. configurata the number of moths per trap changed only marginally. Populations of M. configurara were higher and local outbreaks occurred more frequently in canola-growing areas adjacent to morainic hills along the Manitoba Escarpment, whereas populations were low in areas of the Manitoba Lowlands and of the Western Uplands. A proposed monitoring system for M. configurata in Manitoba is described.

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
Keyword(s):  
Brassica Napus ◽  
Economic Impact ◽  
Laboratory Tests ◽  
Dry Weight ◽  
Feeding Preference ◽  
Field Sampling ◽  
Mamestra Configurata ◽  
Plant Parts ◽  
Lepidoptera Noctuidae ◽  
Bertha Armyworm

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.

SUSCEPTIBILITY OF THE BERTHA ARMYWORM, MAMESTRA CONFIGURATA (LEPIDOPTERA: NOCTUIDAE), TO COMMERCIAL FORMULATIONS OF BACILLUS THURMGIENSIS VAR. KURSTAKI

1986 ◽  
Vol 118 (5) ◽  
pp. 473-478 ◽  
Author(s):  
O.N. Morris
Keyword(s):  
Weight Gain ◽  
Brassica Napus ◽  
Bacillus Thuringiensis ◽  
Choristoneura Fumiferana ◽  
Feeding Activity ◽  
Adult Emergence ◽  
Mamestra Configurata ◽  
Lethal Time ◽  
Lepidoptera Noctuidae ◽  
Bertha Armyworm

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%.

Centrifuge study of seismic response of soil-nailed walls supporting a footing on the ground surface

Géotechnique ◽  
2021 ◽  
pp. 1-41
Author(s):  
Mohammad Hassan Baziar ◽  
Alireza Ghadamgahi ◽  
Andrew John Brennan
Keyword(s):  
Ground Surface ◽  
Soil Surface ◽  
Seismic Stability ◽  
Soil Nails ◽  
Model Soil ◽  
Centrifuge Tests ◽  
Axial Tensile ◽  
Tensile Forces ◽  
Surcharge Load ◽  
Seismic Loadings

Seismic design of soil-nailed walls requires demonstrations of tolerable ranges of wall movements, especially when a surcharge load exists near the wall. In this study, the effect of surcharge location on seismically induced wall movements was investigated using four centrifuge tests. The axial tensile forces, developed along the soil nails during the seismic loadings, were also measured during the tests. At 50g centrifugal acceleration, model tests represented a 12-m-high prototype wall reinforced with five rows of soil nails. To apply a surcharge stress of 30 kPa at the specified location relative to the wall for each model test, a rigid footing was placed on the soil surface. The model soil-nailed walls were subjected to three successive earthquake motions. Surprisingly, it was found that the model wall with the footing located behind the soil-nailed region experienced the largest seismic movements, even more than when the footing was directly behind the wall. Further, the tests showed that the lower soil nails played a key role in the wall stability during earthquake shaking, acting as a pivot for the pre-collapse cases tested, whereas the upper soil nails needed to be sufficiently extended to properly contribute to the seismic stability of the wall.

DENSITY, PARASITISM, AND DISEASE INCIDENCE OF LARVAE OF THE BERTHA ARMYWORM, MAMESTRA CONFIGURATA WALKER (LEPIDOPTERA: NOCTUIDAE), IN MANITOBA, 1973–1986’

1988 ◽  
Vol 120 (5) ◽  
pp. 401-413 ◽  
Author(s):  
W. J. Turnock
Keyword(s):  
Disease Incidence ◽  
Population Declines ◽  
Mamestra Configurata ◽  
Trends Over Time ◽  
Nuclear Polyhedrosis ◽  
Physiographic Regions ◽  
River Plain ◽  
Swan River ◽  
Lepidoptera Noctuidae ◽  
Bertha Armyworm

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.

scholarly journals EFFECT OF THE LARVAL DENSITY OF Chrysodeixis includens (LEPIDOPTERA, NOCTUIDAE) ON COTTON YIELD

Nativa ◽  
2019 ◽  
Vol 7 (5) ◽  
pp. 490
Author(s):  
Sandra Maria Morais Rodrigues ◽  
Rafael Major Pitta ◽  
Nubia Carmo Santos
Keyword(s):  
Larval Density ◽  
Cotton Yield ◽  
Lepidoptera Noctuidae ◽  
Chrysodeixis Includens

EFFECT OF LATITUDE ON THE CRITICAL PHOTOPERIOD FOR DIAPAUSE INDUCTION IN THE BERTHA ARMYWORM, MAMESTRA CONFIGURATA (LEPIDOPTERA: NOCTUIDAE)

1983 ◽  
Vol 115 (8) ◽  
pp. 1039-1042 ◽  
Author(s):  
B. M. Hegdekar
Keyword(s):  
Temperature Regime ◽  
Diapause Induction ◽  
The Other ◽  
Fluctuating Temperature ◽  
Mamestra Configurata ◽  
Ambient Temperatures ◽  
Critical Photoperiod ◽  
Lepidoptera Noctuidae ◽  
H 20 ◽  
Bertha Armyworm

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.

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