Control of cabbage insect pests, Plutella xylostella, Pieris rapae, and Spodoptera litura, using biological control agents and chemical insecticides Q.J. Li1, X.H. Qiu1, R-U. Ehlers2, A.M. Burnell1, D. Sulistyanto4 and R. Han 1 1. Guangdong

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Control of cabbage insect pests,
Plutella xylostella, Pieris rapae, and Spodoptera
litura, using biological control agents and
chemical insecticides Q.J. Li1, X.H. Qiu1, R-U.
Ehlers2, A.M. Burnell1, D. Sulistyanto4 and R.
Han 1 1. Guangdong Entomological Institute,
Guangzhou 510260, China.2. Department of
Biotechnology and Biological Control,
Christian-Albrechts-University Kiel,
Germany.3. Department of Biology, National
University of Ireland Maynooth.4. Plant
Protection Department, The University of Jember,
Indonesia.
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Objective

• To substitute chemical insecticides by
  introducing integrated biological control agents
  (EPN, Bt, and insect viruses)
• To obtain sustainable control of cabbage pests
  during the growth of the cabbages in the field
• To increase yields, cabbage quality and economic
  output.

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Materials and methods

• Test 1
• The tests were conducted from September to
  November in 2003 in Guangzhou.
• Introduced Bt, Bta, Bt/PxGV, Bt/PrGV, SpltMNPV,
  and Steinernema carpocapsae All to control
  Plutella xylostella, Pieris rapae, and Spodoptera
  litura (Table 1).
• Area per treatment was 30 m2.
• Usually the cabbage plants were harvested before
  47 days, depending on the weather conditions.

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Table 1 The time of application, kind and
concentration of biological insecticides used in
test 1
 
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Results

• Test 1
• (For the control of P. xylostella Fig. 1)
• The density of P. xylostella with biological
  insecticides was controlled at a low level (lt0.9
  larvae/plant) and was significantly lower
  compared with the untreated controls after
  treatment (2.13.3 larvae/plant).
• Seven days after the second spray, Bt/PxGV
  produced the best control among biological
  insecticides.

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Fig. 1 Plutella xylostella density after
treatment with several biological
insecticides.Note Bio-insecticides were
applied on day 37 (without SpltMNPV) and day 40
(with SpltMNPV . Arrows indicate date of
spraying.
With SpltMNPV
Without SpltMNPV
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• Results
• Test 1
• (For the control of P. rapae Fig. 2)
• Four days after the first spray, the Bta, Bt,
  Bt/PrGV, Bt/PxGV, and nematodes produced 0, 62.5,
  100, 100, and 30 P. rapae reduction,
  respectively.
• Three days after the second spray, all treatments
  with biological insecticides produced 87.6100
  P. rapae reduction.

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Fig. 2. Pieris rapae density after treatment
with several biological insecticides.Note
Bio-insecticides were applied on day 37 (without
SpltMNPV) and day 40 (with SpltMNPV . Arrows
indicate date of spraying.
Without SpltMNPV
With SpltMNPV
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• Results
• Test 1
• (For the control of S. litura Fig. 3)
• At 4 days after the first application, all
  treatments failed.
• At 3 days after the second application, S. litura
  population density in the treatments with all
  biological insecticides (lt0.2 larvae/plant) was
  significantly lower compared with the untreated
  controls (0.7 larvae/plant).
• In general, treatments with Bta SpltMNPV and
  nematodes SpltMNPV produced the best control
  among treatments.

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Fig. 3. Spodoptera litura density after
treatment with several biological
insecticides.Note Bio-insecticides were
applied on day 37 (without SpltMNPV) and day 40
(with SpltMNPV . Arrows indicate date of spraying.
With SpltMNPV
Without SpltMNPV
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• Materials and methods
• Test 2
• The tests were conducted from October to November
  in 2003 in Guangzhou.
• The efficacy of biological insecticides ( Bt/PxGV
  and Steinernema carpocapsae All) and chemical
  insecticides (chlorpyrifos/cypermethrin and
  avermectin/phoxim ) to control Plutella
  xylostella, Pieris rapae, and Spodoptera litura
  was compared (Table 2).
• Damage levels of cabbage by pests were evaluated
  after the treatment.
• Area per treatment was 150 m2.

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Table 2 The time of application, kind and
concentration of chemical and biological
insecticides used in test 2
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• Results Test 2
• (For the control of P. xylostella Fig. 4)
• At 4 days after the first application, the
  population density of P. xylostella among all
  treatments was not significantly different.
• After the first application, the population
  density of P. xylostella with biological
  insecticide was kept at a low level (lt0.5
  larvae/plant), but the population density of P.
  xylostella with chemical insecticide increased
  significantly (1.4 larvae/plant).
• The population density of P. xylostella with two
  sprays of biological insecticide was controlled
  at a low level (lt0.5 larvae/plant). The
  population density of P. xylostella with three
  sprays of chemical insecticide was controlled at
  a low level (lt0.5 larvae/plant).

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Fig. 4 Plutella xylostella density after
treatment with chemical and bio-insecticides.Not
e Chemical insecticides chlorpyrifos/cypermethri
n (sprayed on day 22), chlorfenapyr (day 34), and
avermectin/phoxim (day 37) Bio-insecticides
Bt/PxGV (sprayed on day 22) and S. carpocapsae
All (on day 34) . Arrows indicate date of spray.
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• Results
• Test 2
• (For the control of P. rapae Fig. 5)
• At 4 days after the first application, both
  treatments of chemical and biological insecticide
  produced 100 P. rapae reduction.
• The population density of P. rapae treated with
  chemical and biological insecticides was always
  controlled at very low level (lt0.04 larvae/plant)
  and was always significantly lower compared with
  the untreated control(0.140.49 larvae/plant).

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Fig. 5 Pieris rapae density after treated with
chemical and bio-insecticides.Note Chemical
insecticides chlorpyrifos/cypermethrin (sprayed
on day 22), chlorfenapyr (day 34), and
avermectin/phoxim (day 37) Bio-insecticides
Bt/PxGV (sprayed on day 22) and S. carpocapsae
All (on day 34) . Arrows indicate date of spray.
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• Results
• Test 2
• (For the control of S. litura Fig. 5)
• Before the second application, there were not
  significant differences among population density
  of S. litura of all treatments.
• At 3 days after the second application, the
  population density of S. litura treated with
  chemical and biological insecticide (lt0.03
  larvae/plant) was significantly lower compared
  with the untreated control (0.17 larvae/plant).

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Fig. 6. Spodoptera litura density after
treatment with chemical and bio-insecticides. Not
e Chemical insecticides chlorpyrifos/cypermethri
n (sprayed on day 22), chlorfenapyr (day 34), and
avermectin/phoxim (day 37) Bio-insecticides
Bt/PxGV (sprayed on day 22) and S. carpocapsae
All (on day 34) . Arrows indicate date of
spraying.
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• Results
• Test 2
• The foliar damage levels of cabbages increased
  with time .
• Both treatments of chemical and bio-insecticides
  significantly reduced plant damage, and
  biological insecticides significantly reduced
  plant damage compared to chemical insecticides.

Table 11. Mean number of feeding hole damage by
insect pests per cabbage plant (n25) recorded
from the treatments with chemical insecticides,
biological insecticides, and an untreated control
(water only)
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• Materials and methods
• Test 3
• The tests were conducted from October to
  November in 2003 in Guangzhou.
• The efficacy of the biological insecticides (Bta
  and Bt/PxGV ) and the chemical insecticides
  (chlorpyrifos/cypermethrin and avermectin/phoxim
  ) to control Plutella xylostella, Pieris rapae,
  and Spodoptera litura was compared (Table 3).
• Damage levels of cabbage by pests were evaluated
  after treatment.
• Area per treatment was 60 m2.

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Table3 The time of application, kind and
concentration of chemical and biological
insecticides used in test 3
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• Results
• Test 3
• (For the control of P. xylostella Fig. 7)
• At 4 days after the first application, the
  population density of P. xylostella among all
  treatments was not significantly different.
• At 11 days after the first application, the
  population density of P. xylostella with chemical
  insecticide (1.2 larvae/plant) increased rapidly
  and was significantly higher compared with the
  untreated control and the biological insecticide
  (lt0.4 larvae/plant).
• After the second application, the population
  density of P. xylostella with chemical and
  biological insecticide was controlled at a low
  level (lt0.6 larvae/plant) and was significantly
  lower than that with the untreated control (1.0
  larvae/plant).

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Fig. 7 Plutella xylostella density after treated
with chemical and bio-insecticides.Note
Chemical insecticides chlorpyrifos/cypermethrin
(sprayed on day 23) and avermectin/phoxim (day
34) Bio-insecticides Bta (sprayed on day 23)
and Bt/PxGV (on day 34) . Arrows indicate date of
spraying.
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• Results
• Test 3
• (For the control of P. rapae Fig. 8)
• At 4 days after the first application, both
  treatments of chemical and biological
  insecticides produced 100 P. rapae reduction.
• After treatment, the population density of P.
  rapae treated with chemical and biological
  insecticides was always controlled at very low
  level (lt0.03 larvae/plant) and was always
  significantly lower compared with the untreated
  control (0.180.5 larvae/plant).

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Fig. 8 Pieris rapae density after treatment with
chemical and bio-insecticides.Note Chemical
insecticides chlorpyrifos/cypermethrin (sprayed
on day 23) and avermectin/phoxim (day 34)
Bio-insecticides Bta (sprayed on day 23) and
Bt/PxGV (on day 34) . Arrows indicate date of
spraying.
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• Results
• Test 3
• (For the control of S. litura Fig. 9)
• At three days after the second application, the
  population density of S. litura with all
  treatments was very low (lt0.08 larvae/plant) and
  was not significantly different among treatments.
• At 7 days after the second application, the
  population density of S. litura treated with
  chemical (0 larvae/plant) and biological
  insecticides (0.12 larvae/plant) was
  significantly lower compared with the untreated
  control(0.22 larvae/plant).

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Fig. 9 Spodoptera litura density after treated
with chemical and bio-insecticides. Note
Chemical insecticides chlorpyrifos/cypermethrin
(sprayed on day 23) and avermectin/phoxim (day
34) Bio-insecticides Bta (sprayed on day 23)
and Bt/PxGV (on day 34) . Arrows indicate date of
spraying.
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• Results
• Test 3
• The foliar damage levels of cabbages increased
  with time (Table 15).
• Both treatments of chemical and biological
  insecticides significantly reduced plant damage,
  but the biological insecticide treatment
  significantly reduced plant damage compared to
  chemical insecticides.

Table 15 Mean number of damage holes by insect
pests per cabbage plant (n10) recorded from the
treatments with chemical insecticides, biological
insecticides, and an untreated control (water
only )
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• Materials and methods
• Test 4
• The tests were conducted from October to December
  in 2003 in Guangzhou.
• The efficacy of the biological insecticides
  (AcMNPV, PXGV, Bta, Steinernema carpocapsae All
  and Bt/PxGV ) and the chemical insecticides
  (avermectin/phoxim and fipronil) to control
  Plutella xylostella, Pieris rapae, and Spodoptera
  litura was compared (Table 4).
• Damage levels of cabbage by pests were evaluated
  after treatment.
• Area per treatment was 60 m2.

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Table 4 The time of application, kind and
concentration of chemical and biological
insecticides used in test 4
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• Results
• Test 4
• (For the control of P. xylostella Fig. 10)
• During the tests, P. rapae and S. litura larvae
  and pupae were not detected.
• From 7 days after the first application until the
  end of the study, the population density of P.
  xylostella with all treatments of chemical and
  biological insecticides (0.180.60 larvae/plant)
  was controlled at a low level and was
  significantly lower compared with the untreated
  control (0.931.98 larvae/plant).

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T1 Avermetin/phoxim (day 19, 26), fipronil (day
33, 46)T2 AcMNPV with 0.03 adjuvant (day 19,
26), Bta (day 33), Bt/PxGV(day 46)T3 PxGV with
0.03 adjuvant (day 19, 26), S.c. All (day 33),
Bt/PxGV (day 46)T4 Bta (day 19, 26), PxGV with
0.03 adjuvant (day 33), Bt/PxGV (day 46) T5
Control (with water)Fig. 10 Plutella xylostella
density after treatment with chemicals and
bio-insecticides. Note Arrows indicate date of
spraying.
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• Results
• Test 4
• There were no differences in the foliar damage
  levels of cabbages with chemical and
  bio-insecticides at any time.
• All treatments of chemical and biological
  insecticide significantly reduced plant damage.

Table 17 Mean number of damage holes by insect
pests per cabbage plant (n5) recorded from the
treatments with chemical insecticides, biological
insecticides, and an untreated control (water
only)
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• Results
• Test 4
• There were no significant differences among mean
  weights of cabbage plants treated with chemical,
  biological insecticides and water only (Table
  18).

Table 18 Mean weight per cabbage plant (n30)
recorded from the treatments with chemical
insecticides, biological insecticides, and an
untreated controls (water only)
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Conclusions

• The results show that the bio-insecticides used
  in these tests can control P. xylostella and P.
  rapae effectively.
• The population densities of P. xylostella and P.
  rapae were kept at low levels (P. xylostella lt 1
  larva or pupa per plant, P. rapae lt 0.1 larva or
  pupa per plant) at least for one week after
  application of the bio-insecticides with proper
  timing.
• Bio-insecticides were equal or superior to
  chemicals for controlling P. xylostella and P.
  rapae.

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AcknowledgmentsWe acknowledge the financial
support of the EU INCO programme
(ICA4-2001-10003).