1. Preliminary study of Forficula sp
Preliminary study of Forficula sp. (Dermaptera: Forficulidae) as predator of Cacopsylla pyri, (Homoptera: Psyllidae), under field conditions in Lleida (Spain).   Jauset, A. M., Artigues, M., Avilla J., Sarasúa, M. J. Universitat de Lleida. Centre UdL-IRTA de R+D de Lleida. Àrea de Protecció de Conreus. Rovira Roure, 191, Lleida, Spain.
INTRODUCTION AND OBJECTIVE
Pear psylla (Cacopsylla pyri (L.)), is one of the most damaging pest of pear trees in the area of Lleida. Earwigs (Dermaptera: Forficulidae) are present in pear orchards of the area of Lleida. Some authors have reported that earwigs, are predators of several orchard pest species, including pear psyllids. This study aims to determine the predatory capacity of Forficula sp. on C. pyri populations in field conditions.
MATERIAL AND METHODS
Pear orchard (0.5 ha), Blanquilla (4 rows; 78 trees/row) and Conference (5 rows; 90 trees/row) cv., trees were 10 years old, never had received any insecticide nor acaricide treatment.
Trees were randomly assigned to one of the three treatments applied according to the earwigs population manipulation done:
Treatment 1: Control; no manipulation of the earwigs population.
Treatment 2: Earwig populations were decrease; corrugated cardboard shelter traps, placed in the trunk near the base of pear trees, were used to capture the earwigs ( Fig. 1). Shelter traps were recorded weekly from March to October in 2002 and from March to December in 2003.
Treatment 3: Earwig populations were increased by releasing the earwigs caught in Treatment 2 onto the ground of the five central trees. A total number of 8,920 and 3,147 earwigs were caught and transferred from plots of the treatment 2 in 2002 and 2003 respectively. Corrugated cardboards were wrapped around the base of the tree trunks to provide artificial refuges to the earwig populations (Fig. 2).
The number of immature stages of C. pyri were monitored on the five apical leaves of three young shoots per tree and the number of adults with beating trays (Fig. 3).
Four replicates per treatment and cultivar were used (13-15 trees / replicate).
Results were analysed using a split-plot model (Year and Cultivar main plots, and Treatment the subplot ).
Figure 2. Refuges in treatment 3
Figure 1. Shelter traps in treatment 2
Figure 3. Beating tray
RESULTS AND DISCUSSION
There were significant differences between Treatments (independently of year and cultivar) in the number of C. pyri eggs (Table 1).
Psylla stadia
Year 1,9
Cultivar 1,9
Treatment
Eggs
F=77.02
(P<0.001)
F=10.24
(P=0.08)
F= ,18
(P=0.01)
Nymphs
F=94.52
F=15.58
F=0.20 2,18
(P=0.82)
Adults
F=91.20
F=9.13
F=1.99 2,23
(P=0.16)
Figure 4. Total number of C pyri eggs and nymphs per shoot in each treatment. (Treatment 1= undisturbed control; Treatment 2=earwigs partially removed; Treatment 3= earwigs enhanced). Means with the same letter are not significantly different at P > 0.05 (LSD)
Table 1. Values of F (probabilities) of the factors Year, Cultivar and Treatment in ANOVA of C. pyri eggs and nymphs. Double interactions were not significant. Super indexes show the degrees of freedom
The number of psylla eggs, were higher in pear trees where the earwigs population was decreased (Fig. 4). The results show that Forficula sp. is, a least partially, responsible of C. pyri eggs reduction.
The number of psylla nymphs (Fig. 4) and adults (Fig. 5) was lower in plots where earwigs were increased, but differences were not significantly different (Table 1).
CONCLUSIONS
The predatory effect of earwigs was manifested in both pear cultivars and led to a significant decrease in the number of C. pyri eggs.
The role of earwigs as predators of C. pyri should be considered when IPM pear orchards are proposed.
Figure 5. Total number of C pyri adults in each Treatment (1=control; 2=less earwigs; 3=more earwigs). Means were not significantly different (LSD)