Biological control of western flower thrips on sweet pepper using the ...

<strong>Biological</strong> <strong>control</strong> <strong>of</strong> <strong>western</strong> <strong>flower</strong> <strong>thrips</strong> on sweet pepper using the
predatory mites Amblyseius cucumeris, Iphiseius degenerans, A. andersoni
and A. swirskii
Yvonne M. van Houten, Mai Linn Østlie, Hans Hoogerbrugge & Karel Bolckmans
Koppert <strong>Biological</strong> Systems, P.O. Box 155, 2650 AD Berkel en Rodenrijs, The Netherlands
Abstract: In the present study Amblyseius cucumeris, Iphiseius degenerans, A. andersoni and A.
swirskii were compared with respect to their performance as biological <strong>control</strong> agent <strong>of</strong> <strong>western</strong> <strong>flower</strong>
<strong>thrips</strong> in sweet pepper. When the predators were released in same rates in separate greenhouses, the
establishment <strong>of</strong> A. swirskii and I. degenerans on sweet pepper plant was better than the establishment <strong>of</strong>
A. cucumeris and A. andersoni. An experiment in small cages showed that when A. cucumeris was
released in numbers <strong>of</strong> 30 times more than A. swirskii the establishment on sweet pepper plants and the
impact on the <strong>thrips</strong> populations were still comparable for both predator populations.
Key words: Amblyseius cucumeris, Iphiseius degenerans, Amblyseius andersoni, Amblyseius swirskii,
Frankliniella occidentalis, sweet pepper
Introduction
The predatory mites Amblyseius cucumeris (Oudemans) is successfully used for <strong>thrips</strong> <strong>control</strong> in
Dutch sweet pepper greenhouses, but in Southern Europe it appears not very effective. This
might be caused by the high temperatures in combination with low humidity conditions.
Therefore we are looking for <strong>control</strong> agents that originate from southern regions and are more
adapted to its climatic conditions. I. degenerans Berlese might be a good candidate, but this
predator is difficult to rear in large quantities. Amblyseius swirskii (Athias-Henriot), collected in
Israel, and A. andersoni (Chant), widespread in North and Southern Europe are potential
candidates. Both A. swirskii (Messelink & Steenpaal, 2003) and A. andersoni (personal
observations) are predators <strong>of</strong> <strong>thrips</strong>. In this study the performance <strong>of</strong> A. swirskii and A.
andersoni are compared with A. cucumeris and I. degenerans as biological <strong>control</strong> agents <strong>of</strong>
<strong>thrips</strong> in sweet pepper.
Material and methods
Amblyseius cucumeris compared with A. swirskii, I. degenerans and A. andersoni
The first experiment was carried out in 23 small greenhouses <strong>of</strong> 100 m 2 , each greenhouse having
1 row <strong>of</strong> 13 sweet pepper plants. When the plants had started to <strong>flower</strong> the <strong>thrips</strong> and predatory
mites were released in the numbers as shown in table 1. The trial was done in the summer period.
The maximum day temperature was between 28-30°C with peaks up to 40°C. To monitor <strong>thrips</strong>
and predator populations, samples <strong>of</strong> 30 leaves and 10 <strong>flower</strong>s were taken every week.

Amblyseius cucumeris compared with A. swirskii in cages
The second experiment was done in 4 cages (3x1x2 m) in an experimental greenhouse. 5
<strong>flower</strong>ing sweet pepper plants <strong>of</strong> 60 cm height were placed in each cage. All cages were treated
different (see table 2). To monitor <strong>thrips</strong> and predator populations, 5 leaves and 1 <strong>flower</strong> per plant
(25 leaves and 5 <strong>flower</strong>s per cage) were monitored every week from day 13 onwards.
Table 1: The release rates <strong>of</strong> predatory mites and <strong>thrips</strong> in 23 different greenhouses
Predatory mite
species
A. swirskii
A. andersoni
A. cucumeris
A. cucumeris
I. degenerans
Control
Release rate <strong>of</strong>
predatory mites per plant
in wk 24
30 females
30 females
30 females
1 sachet,Tripex-plus
30 females
-
Release rate <strong>of</strong> F. occidentalis per plant
in wk 23, 24, 25 and 26 per cage
(4 x) 2 females
,,
,,
,,
,,
,,
Table 2: The release rates <strong>of</strong> predatory mites and <strong>thrips</strong> in 4 different cages.
cage: predatory mite
species
cage 1: A. swirskii
cage 2: A. cucumeris
cage 3: A. cucumeris
cage 4: <strong>control</strong>
Results and discussion
Release rate <strong>of</strong> predatory mites per cage
(number/ leaf)
150 adults (1/leaf) on day 6
150 adults (1/ leaf) on day 6
3x 1500 adults (3x10/leaf) day 6, 13, 20
-
Number <strong>of</strong>
replicates
4
4
3
4
4
4
Release rate <strong>of</strong> F. occidentalis in
per cage
(3 x) 10 females (day 0, 7, 14)
,,
,,
,,
Amblyseius cucumeris compared with A. swirskii, I. degenerans and A. andersoni
Iphiseius degenerans and A. swirskii were more successful in establishment than A. cucumeris
and A. andersoni (figure 2). Iphiseius degenerans performed best: the predator population
increased rapidly and reached higher densities, particularly in the <strong>flower</strong>s but also on the leaves,
than A. swirskii.
The <strong>thrips</strong> population in the <strong>flower</strong>s at the last counting is presented in figure 3. Amblyseius
swirskii was most succesfull in <strong>thrips</strong> <strong>control</strong>, followed by A. cucumeris released in sachet, I.
degenerans, A, andersoni and A. cucumeris, in descending order.
Amblyseius cucumeris compared with A. swirskii in cages
The cage experiment showed that even when A. swirskii was released in a 30 times lower dosage
than A. cucumeris, the establishment <strong>of</strong> A. swirskii was better (figure 1). The impact <strong>of</strong> both
predators on the <strong>thrips</strong> population at these release rates was comparable. Based on these results,
A. swirskii can be regarded as a promising candidate for <strong>thrips</strong> <strong>control</strong> in sweet pepper.
Nomikou (2003) showed that A. swirskii is also a good predator <strong>of</strong> the whitefly Bemisia tabaci
(Gennadius). Moreover, Hoogerbrugge et al., (2005) demonstrated a successful <strong>control</strong> <strong>of</strong> B.
tabaci on sweet pepper under Southern European climatic conditions. Thus A. swirskii may be a

new solution for biological <strong>control</strong> <strong>of</strong> both pests in sweet pepper in Northern and Southern
Europe. A mass rearing technique for A. swirskii has already been developed.
Average number per leaf
# F. occidentalis larvae per leaf
# F. occidentalis per <strong>flower</strong>
7
6
5
4
3
2
1
A. cucumeris (1N)
A. cucumeris (3x10N)
A. swirskii (1N)
Untreated
Predatory mite population
0
15 16 17 18 19 20 21 22
7
6
5
4
3
2
1
A. cucumeris (1N)
A. cucumeris (3x10N)
A. swirskii (1N)
Untreated
Week number
Frankliniella occidentalis
larvae on the leaves
0
15 16 17 18 19 20 21 22
16
14
12
10
8
6
4
2
A. cucumeris (1N)
A. cucumeris (3x10N)
A. swirskii (1N)
Untreated
Week number
Frankliniella occidentalis
(mobile stages) in the <strong>flower</strong>s
0
15 16 17 18 19 20 21 22
Week number
Figure 1. Population fluctuations <strong>of</strong> Frankliniella occidentalis
and the phytoseiid mites, Amblyseius cucumeris and A. swirskii,
on leaves and <strong>flower</strong>s <strong>of</strong> sweet pepper plants in 4 cages.

References
# induviduals per leaf
9
8
7
6
5
4
3
2
1
0
A. andersoni
A. swirskii
I. degenerans
A. cucumeris
A.cuc. sachet
Control
Predatory mite population on the leaves
25 26 27 28 29 30
Week number
Figure 2. Population fluctuations <strong>of</strong> 4 predatory mite species on
leaves <strong>of</strong> sweet pepper plants in 23 greenhouses.
individuals per <strong>flower</strong>
25
20
15
10
5
0
Population <strong>thrips</strong> and predatory mites in the <strong>flower</strong>s in wk 30
<strong>thrips</strong> adult
<strong>thrips</strong> larvae
predatory mite
A.c. A.c. sachet A.a. I.d. A.s. Control
Treatment
Figure 3. Mean numbers <strong>of</strong> F. occidentalis and 5 predatory mite
species in <strong>flower</strong>s <strong>of</strong> sweet pepper plants in 23 greenhouses. Ac.
= A. cucumeris, Aa. = A. andersoni, Id. = I. degenerans, As. = A.
swirskii and Ac. sachet = a slow release sachet with A. cucumeris.
Hoogerbrugge, H., J. Calvo, Y.M. van Houten, J. E. Belda & K. Bolckmans. 2004 <strong>Biological</strong>
<strong>control</strong> <strong>of</strong> the tobacco whitefly Bemisia tabaci with the predatory mite Amblyseius swirskii in
sweet pepper crops. In this proceedings
Messelink, G. & Steenpaal, S. 2003: Nieuwe ro<strong>of</strong>mijten tegen trips in komkommer. Groenten &
Fruit 43: 34-35.
Nomikou, M., A. Janssen, R. Schraag & M.W. Sabelis. 2003: Phytoseiid predators as potential
biological <strong>control</strong> agents for Bemisia tabaci.