Spelling suggestions: "subject:"diamondback both"" "subject:"diamondback moth""
1 |
Studies on parasitoids of the diamondback moth, Plutella xylostella (L.) (Lepidoptera:Plutellidae), in South AfricaNofemela, Sicelo Robert. January 2004 (has links)
Thesis (M.S.)--Rhodes University, 2004. / Title from PDF t.p. (viewed on Apr. 30, 2006). Includes bibliographical references (p. 81-92).
|
2 |
Seasonal occurrence and abundance of diamondback moth, Plutella xylostella (L.), and its major parasitoids on brassicaceous plants in South Australia /Hatami, Bijan. January 1996 (has links) (PDF)
Thesis (Ph. D.)--University of Adelaide, Dept. of Crop Protection, 1996. / Includes bibliographical references (leaves 121-151).
|
3 |
Effect of TRANSPARENT TESTA GLABRA1 on trichome development, growth, and insect resistance in a Brassica napus AtGLABRA3+ background2012 December 1900 (has links)
Glabrous Brassica napus cv Westar and very hairy AtGL3+ B. napus were transformed using Agrobacterium tumefaciens and either a full length trichome regulatory gene BnTTG1 (isoform 1 coding region called O-TTG1) or an RNAi cassette with 260 bp of a conserved region between isoform I and II (called K-TTG1), each driven by the CaMV 35S promoter. Agronomic and trichome phenotypes were observed in the resulting lines. Transformed lines developed in the glabrous Westar background showed no changes in growth or trichome density and transformation efficiency was similar to that of an empty vector control construct. Over-expression of BnTTG1 in the AtGL3+ B. napus background resulted in low transformant survival and poor seed viability, with the only surviving line O-3-7 being taller than non-transformed lines and with a completely glabrous phenotype. The two knock-down lines with the lowest BnTTG1 expression showed a dramatic increase in trichome density, with longer trichomes and expanded trichome density (up to the 12th leaf in the K-5-8 line) compared to the AtGL3+ hairy background line, which showed increased trichome density only on the first three leaves. Moreover, K-5-8 plants were healthy, with both vegetative and reproductive growth similar to that of Westar non-transgenic control plants under both greenhouse and field conditions. The relative expression of five B. napus primary trichome regulatory genes and AtGL3 was measured in three different tissues of B. napus Westar, and the AtGL3+, K-5-8 and O-3-7 transgenic lines. Over-expression of AtGL3 resulted in changes in the expression of BnGL3, BnGL2 and BnTRY. Manipulation of BnTTG1 levels also resulted in changes in expression of these three genes in addition to AtGL3. AtGL3+ plants and O-3-7 also showed increased red pigment accumulation in several above ground vegetative tissues including cotyledons, hypocotyl and leaves, whereas the K-5-8 line (knock down of TTG1) had less anthocyanin in the same tissues. The level of anthocyanin accumulation corresponded to the relative expression of the three primary anthocyanin regulatory genes BnDFR, BnANS and BnGST. In a laboratory bioassay, diamondback moth (DBM) adults (Plutella xylostella) laid more eggs on hairy leaves of K-5-8 than glabrous Westar. However, more feeding damage from young DBM larvae was observed on Westar leaves than K-5-8 in both choice and no-choice feeding assays. In a field test comparing Phyllotreta flea beetle feeding, the hairy K-5-8 leaves showed between a 30-50% reduction in feeding over four ratings on 14 to 28 day old seedlings. Curiously, the glabrous cotyledons of the two hairy lines (AtGL3+ and K-5-8) proved to be more resistant than wild type B. napus Westar cotyledons from Helix XTra® insecticide-treated or non-treated seed. These data support the introduction of AtGL3 and the knockdown of BnTTG1 to induce a dense trichome phenotype, into otherwise glabrous B. napus, resulting in an increased host plant resistance to crucifer insects, without agronomic penalties.
|
4 |
The effect of a cabbage-carrot intercropping system on the incidence of cabbage pests / W.J. WeeksWeeks, William James January 2007 (has links)
Thesis (M. Environmental Science))--North-West University, Potchefstroom Campus, 2007.
|
5 |
The effect of a cabbage-carrot intercropping system on the incidence of cabbage pests / William James WeeksWeeks, William James January 2007 (has links)
Cruciferous crops comprise one of the major crop divisions and contribute
significantly to global crop production. Insect pests associated with cruciferous crops
have the potential to destroy harvests. The diamondback moth, Plutella xylostella
(L.) (Lepidoptera: Plutellidae) and cabbage aphids, Brevicoryne brassicae (L.) and
Lipaphis erysimi (Kaltenbach) (Homoptera: Aphididae) are considered the most
important cabbage pests in South Africa. Pest control in cabbage is still heavily
reliant on use of insecticides even though insecticide application usually result in
increased pest status of P. xylostella. Use of integrated pest management (IPM)
strategies may yet prove invaluable as a means of suppressing the more serious
cabbage pests. Global interest in cultural control strategies, that includes
intercropping of unrelated crop plants, has been rekindled because of problems
experienced with pesticide use. A study that involved the planting of two field trials
with cabbage and carrot plants in different ratios, as a substitutive intercropping
system, was undertaken during the 2002/03 and 2003/04 planting seasons. Field
trials had five treatments viz. control (cabbage monoculture sprayed with
mercaptothion), cabbage monoculture (without chemical application), 1:1
intercropping (cabbage:carrots), 1:3 intercropping and 1:5 intercropping, replicated
six times in a randomized block design. Insects were sampled weekly by removing
the third-youngest open leaf, from one plant per plot (six plants per treatment).
Feeding damage to cabbage leaves was assessed visually by rating 14 plants per plot
according to a numeric scale based on damage severity. P. xylostella and aphid
parasitism levels were determined. Prominence values were calculated for P.
xylostella larvae and aphids for each treatment per sampling date. P. xylostella
infestations and parasitism levels were significantly (P ≤ 0.05) lower in control
treatments. Intercropping ratio did not have a significant impact on pest infestations.
P. xylostella infestations and parasitism on intercropping treatments did not differ
significantly (P > 0.05) from that on monoculture plots (except for 1:5 intercropping
during the 2003/04 season). Cotesia plutellae (Hymenoptera: Braconidae) was the
dominant parasitoid and parasitism levels were significantly correlated with P.
xylostella infestation levels. Prominence values showed a decline in P. xylostella
infestations on intercropping treatments towards the last sampling date during both
seasons. Feeding damage severity was lowest on the control treatment but similar for
other treatments for both seasons. Aphid infestations were significantly (P ≤ 0.05)
lower on the control treatment, but did not differ significantly between intercropping
treatments. Aphid prominence values indicated possible suppression of infestations at
low population levels during the early part of the season. Aphid parasitism was low
during both seasons. It seems more likely that the reduction in insect infestation
levels reported from the literature are related more to spatial arrangement of plants
than cropping ratios. The observed suppression of aphid infestation levels on
intercropped plots early in the season may be valuable in reducing the need for early
chemical applications. The limiting of early insecticide application against aphids
may result in a reduced pest status of P. xylostella, due to the conservation of C.
plutellae populations. / Thesis (M. Environmental Science))--North-West University, Potchefstroom Campus, 2007.
|
6 |
The effect of a cabbage-carrot intercropping system on the incidence of cabbage pests / William James WeeksWeeks, William James January 2007 (has links)
Cruciferous crops comprise one of the major crop divisions and contribute
significantly to global crop production. Insect pests associated with cruciferous crops
have the potential to destroy harvests. The diamondback moth, Plutella xylostella
(L.) (Lepidoptera: Plutellidae) and cabbage aphids, Brevicoryne brassicae (L.) and
Lipaphis erysimi (Kaltenbach) (Homoptera: Aphididae) are considered the most
important cabbage pests in South Africa. Pest control in cabbage is still heavily
reliant on use of insecticides even though insecticide application usually result in
increased pest status of P. xylostella. Use of integrated pest management (IPM)
strategies may yet prove invaluable as a means of suppressing the more serious
cabbage pests. Global interest in cultural control strategies, that includes
intercropping of unrelated crop plants, has been rekindled because of problems
experienced with pesticide use. A study that involved the planting of two field trials
with cabbage and carrot plants in different ratios, as a substitutive intercropping
system, was undertaken during the 2002/03 and 2003/04 planting seasons. Field
trials had five treatments viz. control (cabbage monoculture sprayed with
mercaptothion), cabbage monoculture (without chemical application), 1:1
intercropping (cabbage:carrots), 1:3 intercropping and 1:5 intercropping, replicated
six times in a randomized block design. Insects were sampled weekly by removing
the third-youngest open leaf, from one plant per plot (six plants per treatment).
Feeding damage to cabbage leaves was assessed visually by rating 14 plants per plot
according to a numeric scale based on damage severity. P. xylostella and aphid
parasitism levels were determined. Prominence values were calculated for P.
xylostella larvae and aphids for each treatment per sampling date. P. xylostella
infestations and parasitism levels were significantly (P ≤ 0.05) lower in control
treatments. Intercropping ratio did not have a significant impact on pest infestations.
P. xylostella infestations and parasitism on intercropping treatments did not differ
significantly (P > 0.05) from that on monoculture plots (except for 1:5 intercropping
during the 2003/04 season). Cotesia plutellae (Hymenoptera: Braconidae) was the
dominant parasitoid and parasitism levels were significantly correlated with P.
xylostella infestation levels. Prominence values showed a decline in P. xylostella
infestations on intercropping treatments towards the last sampling date during both
seasons. Feeding damage severity was lowest on the control treatment but similar for
other treatments for both seasons. Aphid infestations were significantly (P ≤ 0.05)
lower on the control treatment, but did not differ significantly between intercropping
treatments. Aphid prominence values indicated possible suppression of infestations at
low population levels during the early part of the season. Aphid parasitism was low
during both seasons. It seems more likely that the reduction in insect infestation
levels reported from the literature are related more to spatial arrangement of plants
than cropping ratios. The observed suppression of aphid infestation levels on
intercropped plots early in the season may be valuable in reducing the need for early
chemical applications. The limiting of early insecticide application against aphids
may result in a reduced pest status of P. xylostella, due to the conservation of C.
plutellae populations. / Thesis (M. Environmental Science))--North-West University, Potchefstroom Campus, 2007.
|
7 |
The management of diamondback moth, Plutella xylostella (Linnaeus) (Lepidoptera: Plutellidae), population density on cabbage using chemical and biological control methodsBopape, Malesela Jonas 04 July 2014 (has links)
The diamondback moth, Plutella xylostella (Linnaeus) (Lepidoptera: Plutellidae), is a
cosmopolitan insect pest of Brassica crops. In South Africa, there are no action thresholds
for its chemical control which makes it difficult for growers to make informed decisions on
when to apply insecticides and how frequently to apply them in order to achieve optimal
crop yield. To contribute towards optimum application of insecticides against P. xylostella,
this study compared the impact of weekly and bi-weekly applications of a selective
insecticide Dipel® (Bacillus thuringiensis Berliner var. kurstaki) applied at 250 g/ha, and a
broad-spectrum insecticide Dichlorvos (an organophosphate) applied at 1 ml/L against
biological control (Control) on the pest population density on cabbage during October–
December 2011 and March–May 2012. The use of both selective and broad-spectrum
insecticides for experiments enables us to understand if efforts to optimise cabbage yield
depend mainly on effective suppression of P. xylostella densities. Furthermore,
investigations were carried out to determine the impact of these chemicals on parasitism
rates of P. xylostella and species richness of its primary parasitoids.
During the October–December 2011 growing season, the lowest infestation of P. xylostella
occurred on cabbage plots that received weekly application of Dipel and the highest on
untreated control plots. Cabbage weights were negatively related to infestation levels,
implying that weekly application of Dipel yielded bigger cabbage heads. During March–
May 2012, P. xylostella infestations were again higher on the control followed by weekly
and bi-weekly treatments of Dichlorvos, then weekly and bi-weekly applications of Dipel.
Despite the significant differences observed, infestation levels were much lower (< 1 P.
xylostella per plant on average) in all treatments during this season. Consequently no
significant differences in cabbage weights were observed among the treatments. The lower
infestation levels were attributed to higher parasitism levels (≥50 %), especially during the
early stages of crop development.
A total of four parasitic Hymenoptera species were recorded from P. xylostella larvae and
pupae during October–December 2011, while three species were recorded during March–
May 2012. However, Cotesia vestalis (Haliday) (Braconidae) accounted for >80 % of total parasitism levels in all treatments. Parasitism levels were not significantly different among
the treatments in both seasons. Parasitoid species richness was highest on the control.
Although two parasitoid species were recorded in all Dipel and Dichlorvos treatments
during October–December 2011, only one parasitoid species was recorded in the Dipel
treatments during March–May 2012 compared to two species in Dichlorvos treatments.
Although weekly applications of Dipel ensured good yield and crop quality during
October–December, weekly applications of the chemical did not lead to better quality crop
during March–May crop growing season. Thus, it is not necessary to apply insecticides
during periods in which natural mortality of P. xylostella is high due to parasitoids. Since
P. xylostella abundance was a determining factor of crop quality, these results imply that
insect pest management should focus mainly on suppressing its numbers. Furthermore,
there was no evidence that application of either insecticide type had a negative impact on
parasitism rates of P. xylostella. The lower parasitoid species richness on Dipel treated
plots was the consequence of its higher efficiency in suppressing the pest population which
substantially reduced availability of potential hosts for parasitoids, hence only the efficient
C. vestalis was recorded at low host densities / Agriculture and Animal Health / M.Sc. (Agriculture)
|
8 |
Diamondback moth (Plutella xylostella L.) ; toxicological database, resistance monitoring techniques, and intraplant distributionFongsmut, Anuthep 19 July 1991 (has links)
The diamondback moth (Plutella xylostella L.) is a major
pest of crucifer crops worldwide. It is a particularly
important problem in Southeast Asia where climatic
conditions favor a short generation time and rapid
proliferation. In countries such as Thailand, the
diamondback moth has apparently become resistant to all
classes of insecticides, even the newest ones.
The first part of this thesis is the development of a
computer database of all the available information on
diamondback moth toxicology. About 1,550 records were
extracted from more than 235 published or unpublished
documents. These records include information on the
geographical location of experiments, the insecticide
evaluated, the testing method and the results observed.
Most records in the database are from the last decade, and
are predominantly from Taiwan, Thailand, the USA and
Japan. Trends in the use of various classes of insecticides
can easily be followed. Thirty three records have been
found of insecticide resistance of more than a thousandfold.
An the known mechanisms of resistance are found,
and the diamondback moth has become resistant to all the
classes of insecticides, including Bacillus thuringiensis but
excluding abamectin. Case studies made possible by the
use of the database showed a rapid succession in the use
of 29 insecticides in the last 26 years in a single country
(Thailand). Although this rapid succession is usually
ascribed to the development of resistance, a case study on
the regional differences in resistance to five insecticides
showed marked variations in the level of resistance over
distances of 20 miles or more. The possibility of managing
insecticide resistance at the local level, already suggested
by studies in Hawaii, is thus supported by this analysis.
In the second part of this thesis, the toxicity of Bacillus
thuringiensis var. aizawai and of the bacterial toxin
abamectin was tested by two bioassay techniques on
populations of the diamondback moth from two Chinese
kale fields at locations in Thailand at which the highest
levels of resistance to most insecticides have been
reported. The leaf-dip bioassay was found to be superior to
a residue-vial assay or to the FAO-recommended assay.
More than 70-fold resistance to Bacillus thuringiensis var.
aizawai was observed in the populations of DBM collected
from these two fields, suporting the theory that resistance
resulted in the control failures reported by growers.
Resistance did not explain control failures with abamectin
as no resistance to this compound could be detected.
The third part of this thesis analyzes the intraplant
distribution of the diamondback moth larvae in an effort to
explain the control failures with abamectin on Chinese kale.
Extensive sampling of the various larval instars of the
diamondback moth revealed that a majority of second instar
larvae were sheltered on the young folded leaves of
Chinese kale. The majority of fourth instar larvae and
pupae were found on mature (lower) leaves. Inefficient
spraying practices observed in the field with high volume,
low pressure hydraulic pump sprayers may allow the young
larvae to escape pesticide exposure possibly explaining
control failures in the absence of physiological resistance.
This study shows that resistance in the diamondback
moth is a worldwide problem of major proportions. The
rapid development of resistance to Bacillus thuringiensis in
the field is of practical concern. Resistance management
programs in developing countries should include
mechanisms to optimize insecticide delivery to the
protected habitats of diamondback moth on Chinese kale. / Graduation date: 1992
|
9 |
The management of diamondback moth, Plutella xylostella (Linnaeus) (Lepidoptera: Plutellidae), population density on cabbage using chemical and biological control methodsBopape, Malesela Jonas 04 July 2014 (has links)
The diamondback moth, Plutella xylostella (Linnaeus) (Lepidoptera: Plutellidae), is a
cosmopolitan insect pest of Brassica crops. In South Africa, there are no action thresholds
for its chemical control which makes it difficult for growers to make informed decisions on
when to apply insecticides and how frequently to apply them in order to achieve optimal
crop yield. To contribute towards optimum application of insecticides against P. xylostella,
this study compared the impact of weekly and bi-weekly applications of a selective
insecticide Dipel® (Bacillus thuringiensis Berliner var. kurstaki) applied at 250 g/ha, and a
broad-spectrum insecticide Dichlorvos (an organophosphate) applied at 1 ml/L against
biological control (Control) on the pest population density on cabbage during October–
December 2011 and March–May 2012. The use of both selective and broad-spectrum
insecticides for experiments enables us to understand if efforts to optimise cabbage yield
depend mainly on effective suppression of P. xylostella densities. Furthermore,
investigations were carried out to determine the impact of these chemicals on parasitism
rates of P. xylostella and species richness of its primary parasitoids.
During the October–December 2011 growing season, the lowest infestation of P. xylostella
occurred on cabbage plots that received weekly application of Dipel and the highest on
untreated control plots. Cabbage weights were negatively related to infestation levels,
implying that weekly application of Dipel yielded bigger cabbage heads. During March–
May 2012, P. xylostella infestations were again higher on the control followed by weekly
and bi-weekly treatments of Dichlorvos, then weekly and bi-weekly applications of Dipel.
Despite the significant differences observed, infestation levels were much lower (< 1 P.
xylostella per plant on average) in all treatments during this season. Consequently no
significant differences in cabbage weights were observed among the treatments. The lower
infestation levels were attributed to higher parasitism levels (≥50 %), especially during the
early stages of crop development.
A total of four parasitic Hymenoptera species were recorded from P. xylostella larvae and
pupae during October–December 2011, while three species were recorded during March–
May 2012. However, Cotesia vestalis (Haliday) (Braconidae) accounted for >80 % of total parasitism levels in all treatments. Parasitism levels were not significantly different among
the treatments in both seasons. Parasitoid species richness was highest on the control.
Although two parasitoid species were recorded in all Dipel and Dichlorvos treatments
during October–December 2011, only one parasitoid species was recorded in the Dipel
treatments during March–May 2012 compared to two species in Dichlorvos treatments.
Although weekly applications of Dipel ensured good yield and crop quality during
October–December, weekly applications of the chemical did not lead to better quality crop
during March–May crop growing season. Thus, it is not necessary to apply insecticides
during periods in which natural mortality of P. xylostella is high due to parasitoids. Since
P. xylostella abundance was a determining factor of crop quality, these results imply that
insect pest management should focus mainly on suppressing its numbers. Furthermore,
there was no evidence that application of either insecticide type had a negative impact on
parasitism rates of P. xylostella. The lower parasitoid species richness on Dipel treated
plots was the consequence of its higher efficiency in suppressing the pest population which
substantially reduced availability of potential hosts for parasitoids, hence only the efficient
C. vestalis was recorded at low host densities / Agriculture and Animal Health / M.Sc. (Agriculture)
|
10 |
Patch exploitation by the parasitoids of Plutella xylostella (L.): from individual behaviour to population dynamics /Wang, Xin-geng. January 2001 (has links) (PDF)
Thesis (Ph.D.)--University of Adelaide, Dept. of Applied and Molecular Ecology, 2001. / Includes bibliographical references (leaves 204-230).
|
Page generated in 0.0575 seconds