Seasonal occurrence and abundance of diamondback moth, Plutella xylostella

175 Pages·2016·8.49 MB·English

by  Bijan Hatami

R.to'ott
SEASONAL OCCURRBNCE AND ABUNDANCE OF DIAMONDBACK
MOTH, ?LUTELIA, XYLOSTELLA (L.), AND ITS MAJOR PARASITOIDS ON
BRASSICACEOUS PLANTS IN SOUTH AUSTRALIA
by
BIJAN HATAMI
Thesis submitted for the degree
of
DOCTOR OF PHILOSOPHY
The University of Adelaide
Department of Crop Protection
Faculty of Agricultural and Natural Resources
October 1996
To my late brother
Siavash Hatami
For his spiritual inspiration and support
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TABLE OF CONTENTS
Page
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LIST OF FIGURES
LIST OF TABLES x
xii
SUMMARY
DECLARATION xv
xvi
ACKNOWLEDGMENTS
xviii
LIST OF PUBLICATIONS
ABBREVIATIONS xix
CHAPTER 1 Introduction. 1
CHAPTER 2. Literature review 4
2.1. The pest species Plutella ryIostella (L.) 4
2.2. Parasitoids of diamondback moth. t4
2.3. Measurement of parasitism. 19
2.4. Management of diamondback moth 23
CHAPTER 3. Assessment of parasitism in the diamondback moth,
Plutella xylostella (L.) (Lepidoptera: Plutellidae). 25
3.1. Introduction. 25
3.2. Materials and methods. 26
3.3. Results. 34
3.4. Discussion 46
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CHAPTER 4 Seasonal occulrence of Plutella ryIostella (Lepidoptera:
Plutellidae) and its parasitoids on brassicaceous weeds
in the Adelaide region. 58
4.1. Introduction. 58
4.2. Materials and methods 59
4.3. Results. 62
4.4. Discussion. 67
Adelaide
CHAPTER 5 Adult activity of the diamondback moth in the 73
regron.
5.1. Introduction. 73
5.2. Materials and methods 74
5.3. Results. 77
5.4. Discussion 80
CHAPTER 6. Parasitism by Diadegma semiclausum: effects of
diamondback moth larval instars. 84
6.t. Introduction. 84
6.2. Materials and methods. 85
6.3. Results. 87
6.4. Discussion 88
CHAPTER 7. Parasitism by Diadegma semiclausum: effects of host
plants(cabbage, wild radish, and wild mustard). 93
7.1. Introduction. 93
7.2. Materials and methods. 93
7.3. Results. 95
7.4. Discussion 95
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CHAPTER 8 Oviposition by diamondback moth, Plutella xylostella
(L.)on different host plants 98
8.1. Introduction. 98
8.2. Materials and methods. 100
8.3. Results. 101
8.4. Discussion. 101
CHAPTER 9 Suitability of different host plants for diamondback
r04
moth
9.1. Introduction. 104
9.2. Materials and methods. 105
9.3. Results. 105
9.4. Discussion. 106
CHAPTER 10. Summary and conclusions. 108
APPENDICES 113
I Total numbers of DBM emerged and percent parasitism by Diadegma
semiclausum during a field survey on rapeseed and kale plants at
Lenswood, South Australia. 113
) Total numbers of DBM emerged and percent parasitism by Diadegma
tt4
species during a field survey on kale atLenswood, South Australia.
J Number of DBM and parasitoids based on larvae per quadrats per week
and average percentage parasitism and mortality of DBM larvae at
Lenswood, South Australia. 115
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4 Seasonal trend and percentage parasitism of P. xylostella larval
populations on rapeseed and kale per quadrats per week at Lenswood,
SA, during the first year survey 1993-94. t16
5 Seasonal trend and percentage parasitism of P. rylostella larval
populations on kale per quadrats per week at l-enswood, SA, during the
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second year survey 1994-95.
6 The phenology and general growth stage of more prevalent
brassicaceous weeds in the Adelaide region, South Australia, 1993-95. 118
7 Number of DBM and parasitoids based on larvae per sweeping net per
week and average percentage parasitism and mortality of DBM larvae
in the Adelaide region, South Australia, 1994. 119
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REFERENCES
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LIST OF FIGURES
Page
Figure 2.1. Cabbage moth (Plutella rylostella). Top, the eggs and adult moth
resting on cabbage leaf. Centre, a fourth instar larva on a damaged
cabbage leaf. Bottom, a pupa within the cocoon 6
Figure 2.2. Diadegma semiclausum, an endoparasitoid of larval cabbage
moth. Top, adult. Bottom, cocoon of the parasitoid within the host
cocoon. 18
Figure 3.1.. Location of sampling sites for field surveys of P. xylostella and its
parasitoids in the Adelaide region. 27
Figure 3.2. Age structure of larval P. xylostella from rapeseed and kale at
Lenswood, South Australia 1993-1994. 35
Figure 3.3. Age structure of larval P. xylostella from kale at I-enswood, South
Australia 1994-1995. 36
I'igure 3.4. Larval density, percent parasitism and unexplained mortality of
DBM based on the conventional density sampling method on rapeseed
and kale at lænswood, South Australia 1993-1994; (a) larval density of
DBM; (b) percent parasitism attributed to D. semiclausum of three last
instars (open circles) and 4th instars only (closed circles); (c) percent
parasitism by A. ippeus; and (d) unexplained mortality. 37
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Figure 3.5. Larval density, percent parasitism and unexplained mortality of
DBM based on the conventional density sampling method on kale at
Lenswood, South Australia 1994-1995; (a) larval density of DBM; (b)
percent parasitism attributed to D. semiclausum of three last instars
(open circles) and 4th instars only (closed); (c) percent parasitism
attributed to D. rapi of three last instars (open circles) and 4th instar
only (closed); (d) percent parasitism by A' ippeas; and (e) unexplained
mortality. 38
Figure 3.6. Seasonal change in number of P. xylostella pupating per m2, and
percentage parasitism due to B. phya, and D. collaris at a kale field at
Lenswood in 1993-1994 (a), and 1994-1995 (b) respectively. 42
Figure 3.7. Daily recruitment of pupal DBM and its parasitoids on kale at
Lenswood, South Australia 1994-1995; (a) by Diadegma semiclausum
and (b) D. rapi 45
Figure 3.8. Schematic linkages between DBM and parasitic Diadegmø species
50
Figure 3.9. Percent parasitism of DBM based on the conventional density
sampling and recruitment methods on kale at Lenswood, South Australia
1994-1995. Conventional density estimates were used to calculate
larval parasitism on instars 2, 3, 4 together and instar 4 alone. (a)
percent parasitism by D. semiclausum; (b) percent parasitism by D. rapi;
and (c) DBM larval density calculated by conventional sampling and
recruitment of pupae. Points for recruitment \ryere shifted one day
forward and for instar 4 one day backward to distinguish means and
error bars. Error bars indicate standard error of mean. 51
Figure 3.10. Correlations between percent parasitism of DBM by D.
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semiclausum as estimated by three different methods: conventional
density sampling, recruitment, and 4th instar hosts 53
Figure 3.1L. Correlations between percent parasitism of DBM by D. rapi as
estimated by three different methods: conventional density sampling,
recruitment, and 4th larval instars 54
Figure 4.1. Wild radish stands growing peripheral to and amongst cultivated
cabbage at Virginia, a vegetable production area to the north of
Adelaide, SA. 60
Figure 4.2. Densities of 2nd to 4th instar larval DBM from (a) wild radish at
Lenswood; (b) wild mustard at Turretfield; (c) wild radish and wild
mustard at Virginia, 1993. 63
Figure 4.3. Age structure of P. xylostella (a) on wild mustard at Virginia; (b)
on wild mustard in the northern Adelaide Hills; (c) on wild radish at
Lenswood,
1994. 65
Figure 4.4. Larval densities of P. xylostella and Vo parasitism by D.
semiclausum (a) on wild radish at Lenswood, (b) on wild mustard at
Virginia, and (c) by D. rapi on wild mustard in the northern Adelaide
Hills 1994. 66
Figure 5.1. The rope wick system for maintaining moisture in pots in the field.
76
Figure 5.2. Seasonal distribution of male DBM attracted to sex pheromone
traps at Lenswood, SA. Plotted points show data
Logro(DBM+l)ltraplday) and solid lines are three-point moving
averages. 78
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Figure 5.3. Seasonal distribution of male DBM attracted to sex pheromone
traps at Turretfield, SA. Plotted points show data (Log16(DBM+1)/
traplday) and solid lines are three-point moving averages. 79
Figure 5.4. Seasonal distribution of male DBM attracted to sex pheromone
traps at Flagstaff Hill, SA. Plotted points show data (Logro (DBM+l)/
trap/day) and solid lines are three-point moving averages. 79
Figure 5.5. Number of eggs oviposited by DBM adults on kale sentry plants, at
Lænswood, SA, 1994-95. Vertical bars indicate standard error of means.
The solid line is a three-point moving average. 81
Figure 6.1. Parasitism of 2nd-, 3rd-, and 4th-instars of DBM larvae by D.
semiclausum, with separate instars or mixed instars on cabbage plants.
Error bars are mean + SE. Different letters above columns indicate
statistically significant differences (P<0.05, Tukey HSD) 89
Figure 6.2. Parasitism of lst-, 2nd-, 3rd-, and 4th-instars of DBM larvae by D.
t
semiclausum in caged choice tests. Error bars are mean SE. Different
letters above columns indicate statistically significant differences
(P< 0.05, Student Newman-Keuls Test) 90
Figure 7.1. Parasitism of third instar of DBM larvae by D. semiclausum. The
same letter at the top of each bar indicates no significant difference
(P=0.05, Tukey HSD). 96
Figure 8.1. Ovipositional preferences of DBM on wild radish and wild
mustard with and without the presence of crop plant (rapeseed). Values
are mean + SE. Rs, Rapeseed; 'Wr, Wild radish;Wm, Wild mustard. r02