Efficacy of new-generation acaricides in controlling mites in apple ...

348 Alicja Maciesiak and Ryszard W. Olszak
MATERIAL AND METHODS
The experiments were conducted in 2001–2004 in several commercial orchards
in some regions of Poland. The effectiveness of the new acaricides Envidor 240 SC
(spirodiclofen) and Milbeknock EC (mibemectin) was compared with the standard
preparations Mitac 200 EC (amitraz), Omite 30 WP (propargite), Ortus 05 SC (fenpyroximate).
The experiments, conducted in 4 replicates, were set up in a block design
with plots of 0.1–0.3 ha each as a combination. Treatments were performed with a
tractor sprayer using 600–750 l of spraying liquid per ha. Mobile forms of spider
mites were counted on leaves sampled from the external part of the crown of trees
growing in the middle part of the plot. Population density was evaluated with HEN-
DERSON & MCBURNIE’s (1943) method on 50 leaves for each replicate and date. A
n=
k−1
t n
cumulative index of infestation (CII = ∑ ( ⋅(
x ))
= 1
n + x
n
n+
1 mite unit days where k
2
is the number of occasions on which the mites were counted; n , n+
1 are consecutive
indices; is the time, in days, between the consecutive indices )
(WRATTEN et al. 1979) was calculated for each test. The results were subjected to an
analysis of variance. Duncan’s t test was employed to evaluate the significance of
differences at P=0.05.
x x
t n
n , n+
1 x x
2
Table 1. Effectiveness of Envidor 240 SC and Milbeknock EC in controlling mites on apple trees (2001–
2002)
Treatment
Rate/ha
Mean no. of mites per leaf
Weeks after treatment
3–4 5–6 7–8 11–12
Location A – Grzymkowice, near Grójec, spraying date 17 May 2001
Envidor 240 SC - 0.4 l 0.0 a* 0.0 a 0.0 a 0.1 a 0.5 a
Milbeknock EC - 1.0 l 0.0 a 0.0 a 0.1 a 0.0 a 1.7 ab
Omite 30 WP - 2.25 kg 0.3 b 0.02 a 0.05 a 0.5 a 5.1 b
Control 1.9 c 4.7 b 3.1 b 3.3 b 100.0 c
Location B – Wilcze Piêtki, near Grójec, spraying date 25 May 2001
Envidor 240 SC - 0.4 l 0.0 a 0.0 a 0.0 a 0.1 a 0.6 a
Milbeknock EC - 1.0 l 0.01 a 0.0 a 0.0 a 0.1 a 1.0 a
Omite 30 WP - 2.25 kg 0.5 b 0.0 a 0.8 ab 1.3 b 26.6 b
Control 0.4 b 1.1 b 3.0 c 3.6 c 100.0 c
Location C – Muchnice, near Kutno, spraying date 10 May 2002
Milbeknock EC - 0.75 l 0.6 b 0.4 b 0.3 a – 4.5 a
Milbeknock EC - 1.0 l 0.1 a 0.02 a 0.1 a – 1.2 a
Ortus 05 SC - 1.5 0.1 a 0.7 b 2.4 b – 8.6 a
Control 18.8 c 10.8 c 12.1 c – 100.0 b
Location D – Nowa Wieœ, near Grójec, spraying date 9 May 2002
Milbeknock EC - 0.75 l 0.03 a 0.0 a 0.02 a – 0.8 a
Milbeknock EC - 1.0 l 0.05 a 0.0 a 0.0 a – 0.5 a
Ortus 05 SC - 1.5 l 0.0 a 0.0 a 0.0 a – 0.0 a
Control 8.7 b 1.7 b 3.8 b – 100.0 b
CII – cumulative index of infestation (control = 100%)
* Means followed by the same letter within columns do not differ significantly at P=0.05
CII
(%)