Annual differences in migration of stem weevils to - IHAR

Annual differences in migration of stem weevils to - IHAR

TOM XXXI
ROŚLINY OLEISTE – OILSEED CROPS
2010
Jiří Havel
OSEVA Research and Development Ltd., Department at Opava, Czech Republik
Annual differences in migration
of stem weevils to rapeseed crop at Opava*
Sezonowe zróżnicowanie nalotu chowaczy łodygowych
na plantacje rzepaku w rejonie Opawy
Key words:
Brassica napus, stem weevils, monitoring of fly, term of treatment
Migration of weevils to rapeseed crop was monitored using yellow traps. Dominant species was
Ceutorhynchus pallidactylus. In 2008 females flied to rapeseed after two weeks of males migration,
low number of imagoes was caught in traps. In 2009 males and females migrated simultaneously,
high number of imagoes was caught in traps. The counts of larvae in untreated stems were
approximately equal at both seasons, whereas counts in yellow traps were substantially differing. The
weevil monitoring using yellow traps in cold and rainy seasons can give biased results.
Słowa kluczowe:
rzepak, chowacze łodygowe, monitorowanie nalotu, termin stosowania preparatów
chemicznych
Nalot chowaczy na plantacje rzepaku był monitorowany przy użyciu żółtych naczyń.
Dominującym szkodnikiem okazał się Ceutorhynchus pallidactylus. W 2008 r. nalot samic chowaczy
był odnotowany dwa tygodnie po nalocie samców, a liczebność odłowionych szkodników była niska.
W 2009 r. samce i samice naleciały równocześnie, a liczebność odłowionych szkodników była
wysoka. Liczba larw w łodygach roślin niechronionych przed szkodnikami była podobna w obu
latach prowadzenia doświadczenia. Natomiast liczba osobników w żółtych naczyniach była
zróżnicowana. Monitorowanie chowaczy przy wykorzystaniu żółtych naczyń w czasie zimnej i deszczowej pogody może okazać się nieprecyzyjne.
Introduction
Two species of weevil Ceutorhynchus napi and Ceutorhynchus pallidactylus
fly to rapeseed crops at the beginning of spring. The rapeseed growers mostly do
not distinguish these species although these species are different in their life cycles
and harmfulness. Ceutorhynchus pallidactylus is less harmful (Volker 2003), but it
does not cause plant deformation and stem growth disorders such as those induced
by Ceutorhynchus napi. Hoffmann and Schmutterer (1999) state that larvae
of Ceutorhynchus pallidactylus are found mainly in bottom half of stem and larvae
*
This work was supported by Czech Ministry of Agriculture, project No. QH81218.
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Jiří Havel
of Ceutorhynchus napi in upper half. C. napi should leave the winter covers
markedly earlier than C. pallidactylus. These authors did not published any
information about differences in male and female migration. The aim of this work
was to determine the actual spectrum of weevils, to monitor the specificity of
weevil migration and differences in migration of males and females and to test the
different timing of insecticide treatment to weevil control.
Material and Methods
The yellow traps were used for the monitoring of weevil migration. The
plastic saucers with 20 cm diameter were painted with bright yellow colour. The
traps containing water with some drops of detergent were placed in test locality, the
number and organization of traps depended on actual situation at the locality and
locality size. 22 traps (five year distance of rapeseed in crop rotation) and 5 traps
(rapeseed after rapeseed, small experimental field) in 2008 and 18 traps in 2009
were used. The minimal distance from the field edge was usually 10–20 m. The
traps were placed to rapeseed crop at spring as soon as possible, first they were laid
at soil surface, later the traps were placed to adjustable holder. The traps in the
course of the study were at the level of plant tops. Numbered traps were used for
monitoring differences in pest attack and for observation of weevil migration
course. The test field was not controlled by insecticides. The traps were every week
twice checked and caught weevils were stored in numbered vials containing some
drops of ethyl acetate for killing. Using binocular magnifier in laboratory species
and sex of weevils were determined. For females the phase of egg development
was stained.
The field trials were based on guidelines of EPPO (www.eppo.org). The fully
randomised blocks with four replications and mid-season blooming and ripening
varieties Exagone, Oponent, Opus were used. Treated plot area was 30 m2. In 2008
the experiment was carried out at two locations: Chvalíkovice and U školky. Two
informative trials were placed at headland, where the high occurrence of weevils
was expected. The aim was to test the influence of different rapeseed distance in
crop rotation (five years and rapeseed after rapeseed), the seed yield of these trials
could not be evaluated. In 2009 the trial was situated in Chvalíkovice. The trials
were treated consecutively by registered dose of insecticides from the group of
synthetic pyrethroids. In 2008 Cyperkil 25 EC 0.1 l/ha, cypermethrin was applied.
In 2009 Vaztak 10 EC 0.15 l/ha, alphacypermethrin was used. Pyrethroids were
used for elimination of residual insecticide influence. Terms of individual
treatments were based on numbers of caught weevils in yellow traps. If the results
from yellow traps were ambiguous, the term of treatment was discussed with
cooperating workplace Agritec Šumperk.
Annual differences in migration of stem weevils ...
325
The treatment was planned in 2008 at the following terms:
before migration — spring treatment at the beginning of suitable conditions
(temperature),
2) at the beginning of female migration to crop, female have unripe eggs,
3) at the beginning of egg laying ( most females have ripe eggs).
In 2009 extension to four treatments was presupposed:
1) before migration — spring treatment at the beginning of suitable conditions
(temperature),
2) at the beginning of male migration,
3) at the beginning of female migration,
4) after migration to rapeseed crops.
In the two years of investigations the effect of Nurelle D (chlorpyrifos +
cypermetrin) was evaluated. Nurelle D was applied at presupposed optimal timing
of first treatment (mostly at rapeseed developmental phase BBCH 53), registered
dose 0.6 l/ha was used. The guideline PP1/219(1) (Ceutorhynchus napi and
Ceutorhynchus pallidactylus on rapeseed) was used for trial evaluation. When the
larvae in stems were sufficiently developed, 20 stems from each replication were
dissected and larvae and exit holes were counted. Collected data were elaborated
using Abbott´s efficacy. ANOVA and subsequent Tukey´s test were used for
analysis of yield at harvested trials.
1)
Results
2008
The winter 2008/09 was temperate and without snow. January and February
were markedly dry. Last decade of February was unusually warm, the day
temperatures extended 10oC. The conditions seemed to be favorable for the
beginning of weevil migration. This temperate period terminated at the beginning
of March. The milder and colder periods alternated in March, warm weather was at
the end of March. The beginning of April was cold and rainy, favorable weather
came at the end of the first April decade.
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Jiří Havel
Table 1
Number of weevils in yellow traps, Opava 2008
Liczba chowaczy w żółtych naczyniach, Opawa 2008 r.
Date
Data
U školky
rapeseed after rapeseed, 5 traps
rzepak po rzepaku, 5 pułapek
C. pallidactylus
C. napi
male
samce
female
samice
other
inne
Chvalíkovice
rapeseed after 5 years, 22 traps
rzepak po 5 latach, 22 pułapki
C. pallidactylus
C. napi
male
samce
1
7
female
samice
other
inne
4.3.08
10.3.08
1
2 nd
14.3.08
17.3.08
1
21.3.08
25.3.08
31.3.08
11
5
1 co
3.4.08
4,2?
3
1 cs
1
1
1 co
7.4.08
11.4.08
14.4.08
2 we 1 ue
5,1?
5 we 1 re
22.4.08
4 sr
2 co
1
1 we
1 co
1?
7 we
25.4.08
1
3 co
2.5.08
1
7 co
20 we
1 sr
221 co
co — Ceutorhynchus obstrictus,
sr — Stenocarus ruficornis
cs — Ceutorhynchus suicatus
nd — not determined — nie określone
we — without eggs — bez jaj
ue — unripe eggs — jaja niedojrzałe
re — ripe eggs — jaja dojrzałe
? — sex not determined credibly — płeć nie określona wiarygodnie
No. of females without remark – egg development was not determined (weevils were too dried)
Liczby samic bez komentarza – rozwój jaj nie został określony (chowacze zasuszone)
The presence of weevils was observed at two locations. At locality Chvalíkovice
the distance between rapeseeds in crop rotation was 5 years. At locality U školky
rapeseed was grown immediately after previous rapeseed (Table 1). During March
the catches of weevils were only individual, small increase was observed at the end
of March. At the beginning of April the migration was not recorded. The second
small increase of migration was recorded at the mid of April, the females with ripe
327
Annual differences in migration of stem weevils ...
eggs were not recorded here. The outstanding migration of Ceutorhynchus obstrictus
was recorded at the end of April. Ceutorhynchus pallidactylus was a dominant
species among stem weevils. Only one individual of C. napi was caught (probably
the species was not identified credibly). Small presence of C. napi was verified
by observations of crops, at whole test locality only two plants having infection
symptoms caused by C. napi were found.
The results of field insecticide trials are displayed in Table 2. Both trials were
situated at headland of field, they are informative only. The number of larvae in
stems shows that the real occurrence of weevils in crops was markedly higher than
the catches in yellow traps from the same fields (Table 1). It was expected that the
plants in trial No. 2 (rapeseed after rapeseed) were mostly infected. The height of
plant in this trial was only half than in trial No 1 and the medulla of stems was
totally destroyed by larvae eating. The incidence of larvae was significantly higher
here.
Table 2
The occurrence of weevil larvae in stems and percentage of infected plants, Opava 2008
Występowanie larw chowaczy w łodygach i procent porażonych roślin, Opawa 2008 r.
Trial
Doświadczenie
Treatment, date of treatment
Zabieg, termin zabiegu
Number of
larvae in 1 stem
Liczba larw
w łodydze
Infected plants
Rośliny porażone
[%]
1
untreated — bez ochrony
3.30 a
95
1
cypermetrin 2008, February 29
2.45 a
85
1
cypermetrin 2008, April 9
0.85 a
45
1
cypermetrin 2008, April 18
1.60 a
70
2
untreated — bez ochrony
6.15 b
100
2
cypermetrin 2008, April 9
0.45 a
35
2
cypermetrin 2008, April 18
2.35 a
85
Trial No. 1 — 5 year distance between rapeseeds 1 — 5-letni okres pomiędzy uprawą rzepaku
Trial No. 2 — rapeseed after rapeseed, small experimental field (about one hectar)
rzepak po rzepaku, małe pole doświadczalne (około 1 hektar)
The first treatment at the earliest term was performed already on 29th
February 2008, while markedly warm weather came at this period. No efficiency of
this treatment was recorded. Second treatment at the beginning of female migration
was carried out on 9th April 2008, this treatment decreased significantly the
number of larvae in stems. At the presupposed beginning of egg laying treatment
was performed on 18th April 2008. The term of this treatment was not verified,
while the females having ripe eggs were not found in yellow traps. The efficiency
of this treatment was decreased, since this treatment was probably too late.
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Jiří Havel
Nurelle D (Table 3) was applied on 9th April 2008. This trial was situated
near the field edge in the middle of 400 m long side of field. The application timing
was optimal, the efficacy of treatment was high and significant. The treatment
increased the seed yield, the difference was not significant. The localization of trial
can markedly influence the results, the counts of larvae in stem at headlands were
twice higher.
Table 3
The occurrence of weevil larvae in stems, percentage of infected plants and seed yield
Występowanie larw chowaczy w łodygach, procent porażonych roślin i plon nasion
Opava 2008
Treatment
Zabieg
Number of larvae in 1 stem
Liczba larw w łodydze
mean
średnio
% of infected plants
% porażonych roślin
Seed yield
Plon nasion
efficacy
skuteczność
[%]
[%]
efficacy
skuteczność
[%]
[t/ha]
[rel. %]
7.5
90.6 b
5.55
107.4 a
80.0
0a
5.17
100.0 a
Nurelle D
0.21
85.8 b
Untreated
Bez ochrony
1.5
0a
2009
March 2009 was very rainy and cold, the conditions for flying of pests were
unfavorable. Markedly warm weather started at the beginning of April. Spring
vegetation period started markedly late at the end of March, warm weather
accelerated the crop development. Flowering of rapeseed started after 20th April,
the extreme drought continued to the mid of May.
The cold weather in March eliminated the flying of weevils. The yellow traps
were placed to rapeseed on 2nd April, earlier the soil surface was too soaked. On
3rd April started warm and dry weather. This sudden change supported markedly
the migration of weevils to rapeseed crop. The top of migration was detected
on 6th April (Table 4). The dominant species was Ceutorhynchus pallidactylus,
C. napi occurred rarely . Twice higher quantity of males was caught, females had
eggs in all stages of development. A slightly increased migration was detected after
10th April, later only individual weevils were caught. The main part of females
caught in last terms was without eggs by this time.
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Annual differences in migration of stem weevils ...
Table 4
Number of weevils in yellow traps, Opava 2009, 18 traps
Liczba chowaczy w żółtych naczyniach, Opawa 2009 r., 18 pułapek
Date
Data
C. pallidactylus
♂
♀we
♀ue
♀ue/re
♀we/ue
♀re
3
52
15
6.04.2009
273
22
29
9.04.2009
7
11
4
14.04.2009
39
16
19
16.04.2009
2
1
20.04.2009
4
4
23.04.2009
5
6
1
C. napi
Other
Inne
♀2
6
1
17
5
11
1
2
9
we — without eggs — bez jaj
ue — unripe eggs — niedojrzałe jaja
re — ripe eggs — dojrzałe jaja
Other species — inne gatunki: Stenocarus ruficornis, Ceutorhynchus suicatus, C. obstrictus, C. picitarsis
and undetermined species — gatunki nieokreślone
The influence of insecticide treatment was tested in two field trials. First trial
was situated at the west side of the field. For treatment Vaztak 10 EC was used
with the aim to eliminate the residual effect. First treatment (2nd April) was
performed as soon as possible after thaw (Table 5). Treatment was carried out in
cold weather, the next day mild weather started and immediately started also the
migration of weevils. These circumstances caused probably the best efficiency of
this treatment. The treatment at the beginning of male migration could not be
realized, since males and females migrated simultaneously. The top of migration
was detected on 6th April, the treatment on 10th April was slightly late and the
efficiency decreased. The effect of treatment after migration was insufficient. Seed
yield highly decreased due to drought, the highest yield was obtained at the first
treatment, the lowest at untreated variant.
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Jiří Havel
Table 5
The occurrence of weevil larvae in stems, percentage of infected plants and seed yield
Występowanie larw chowaczy w łodygach, procent porażonych roślin i plon nasion
Opava 2009
Date of
treatment
Data zabiegu
Number of larvae in 1 stem
Liczba larw w łodydze
mean
średnio
efficacy
skuteczność
[%]
% of infected plants
% porażonych roślin
mean
średnio
Seed yield
Plon nasion
efficacy
skuteczność
[%]
[t/ha]
[rel. %]
2.04.2009
0,20 b
89,6
7,5 b
90,0
1,83 a
126,7
10.04.2009
0,58 a
70,1
45,0 a
40,0
1,76 a
122,2
16.04.2009
1,02 a
46,8
47,5 a
36,7
1,67 a
116,2
Untreated
Bez ochrony
1,92 a
0
75,0 a
0
1,44 a
100,0
The next trial was situated at the north side of the same field, the results are
shown in Table 6. The share of infected plants was similar to a previous trial,
slightly increased number of larvae was counted in stems. The trial was treated on
10th April by Nurelle D (0,6 l/ha, chlorpyrifosethyl + cypermetrin) exhibiting
systematical and residual effect. Number of larvae in stems and share of infected
plants significantly decreased. The distance of this trial to field edge (50 m) was
bigger than in a previous trial (10 m), but the counts of larvae in untreated stems
were higher here. Seed yield increased significantly, this increase could have been
influenced by drought in April and May.
Table 6
The occurrence of weevil larvae in stems, percentage of infected plants and seed yield
Występowanie larw chowaczy w łodygach, procent porażonych roślin i plon nasion
Opava 2009 r.
Treatment
Zabieg
Number of larvae in 1 stem
Liczba larw w łodydze
% of infected plants
% porażonych roślin
Seed yield
Plon nasion
mean
średnio
efficacy
skuteczność
[%]
[%]
efficacy
skuteczność
[%]
[t/ha]
[rel. %]
Nurelle D
0,2 b
96,3
10,0 c
86,6
5,18 a
114,9
Untreated
Bez ochrony
4,8 a
0
71,3 a
0
4,51 g
100
Annual differences in migration of stem weevils ...
331
Discussion and conclussions
It is evident that migration of weevils depends on concrete conditions in
a year and locality. The occurrence of larvae and share of infected stems was
comparable in year 2008 and 2009, the numbers of weevils caught in traps were
markedly different. The small amount of weevils was caught in traps in 2008. The
relatively high number of weevils was caught in traps at the same time at near 100
km distant Šumperk (Seidenglanz et al. 2008). This disproportion is caused
probably by differences in weather conditions. The locality Opava is shadowed by
mountains Jeseníky from west and opened to north-east, this causes local weather
differences at Opava. It is possible that weevils prefer creeping at lower
temperatures and therefore the catches in traps were low. This hypothesis must be
tested again. Seidenglanz et al. (2008) also state that females of C. pallidactylus
migrate to crops two weeks later than males. It was possible to find such tendency
in Opava in 2008, but the results are not significant enough since the number of
caught weevils is too low in this year. This tendency did not appear in 2009
because in this year the males and females migrated simultaneously.
The placement of trial in the field influences markedly the infection density.
Increased intensity of infection is at headlands and edges of the field, this tendency
appeared in 2008 in trials No. 1 and 3. Extremely highly infected was rapeseed
after rapeseed (trial No. 2 in 2008). The weevils migrated more intensively to small
experimental field, because this field was the nearest to their overwintering sites in
neighborhood of previous bigger rapeseed crop. The infection intensity in 2009
was probably influenced by different distance to grassland in loamy field and
brooklet in neighborhood. Trial No 2 was localized substantially nearer to this
grassland than trial No.1.
Miller (1956) described the life cycle of C. pallidactylus. He wrote that equal
quantities of males and females migrate to crop simultaneously. Our results show
larger quantity of males at the beginning of migration. Sekulic and Keresi (2007)
recommend the usage of yellow traps for monitoring of the activity of different
serious rapeseed pests for optimal control of these pests. No information about
reliability of this method is published here. Our findings say that the reliability of
yellow traps is strongly influenced by weather. Marczali et al. (2007) monitored the
incidence of Ceutorhynchus species on rapeseed in Hungary. C. napi occurred in
the trial plot every year but its percentage was far behind the dominant species
(C. pallidactylus); its frequency of occurrence was 7–10%. The occurrence of local
dominance of some species from stem weevil was confirmed.
For both stem weevils the verified damage threshold is not disposable (Volker
2003). Weevils should be controlled if in one yellow trap is caught more than 10
weevils in three days. The results from year 2008 show that these methods may not
give the credible results, when rapeseed is growing after rapeseed, because the real
332
Jiří Havel
occurrence of weevils in crops was markedly higher than the catches in yellow
traps. In 2009 this method gave the correct results for control of weevils.
Based on the results of subsequent treatments the optimal term for insecticide
control is at the beginning of female migration (2008) or at the beginning of main
migration of males and females (2009). This term is in accordance with the
beginning of pollen beetle (Meligethes aeneus) migration, therefore one treatment
can control both pests all at once. For best efficacy it would be necessary to repeat
the treatment by synthetic pyretroids; the use of insecticides having long-term
efficacy is able to protect the crop markedly better. If the difference in male and
female migration of C. pallidactylus will be verified, it will be possible in areas
with dominant occurrence of C pallidactylus to leave the first spring treatment
pointed only towards weevils. Significant increase of yield by insecticide treatment
observed in 2009 could be influenced by drought, such increase was not observed
in previous seasons.
Literature
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Kulturpflanzen. Verlag Eugen Ulmer Stuttgart 1999.
Marczali Z., Nadasy M., Simon F., Keszthelyi S. 2007. Incidence and life cycle of Ceutorhynchus
species on rape. Cereal-Research-Communications, 35 (2): 745-748.
Miller F. Zemědělská entomologie (Agricultural entomology). Praha 1956.
Seidenglanz M., Poslušná J., Havel J., Hrudová E. 2008. Rozdíly v průběhu náletu samců a samic
krytonosce čtyřzubého (Ceutorhynchus pallidactylus) do porostů a účinnost insekticidů
aplikovaných v různých obdobích. Sborník SPZO 25. vyhodnocovací seminář Hluk 20-21.11.
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