1. Pest management practices and environment factors affect the natural regulation of the codling moth
Monteiro L.B.1, Dor C.2, Franck P.2, Lavigne C.2, Sauphanor B.2
1 UFPR, Paraná Federal University, DFF/LAMIP, CEP , Curitiba, Brazil
2 INRA, URM 1115 Plants and Cropping Systems in Horticulture (PSH), Agroparc, F Avignon, Cedex 9, France.
Introduction: Codling moth, Cydia pomonella L. is a major pest in apple and pear orchards, damaging a large part of the world production. It has been controlled by synthesis insecticides that select resistant populations in both production systems: organic and conventional. New control techniques have been adopted recently, such as mating disruption, but success is subject to biological and environmental factors. Studies on regulating the codling moth by parasitoids and predators are of economic and ecological interest, and are influenced by the type of production system and the plant species diversity that make up the plant strata and the surrounding hedges. Objective: To assess how the environment and the production system (organic and conventional) affect the parasitism of diapausing larvae and the predation / parasitism of codling moth eggs the low valley of Durance, France.
Material and Methods: Parasitism of diapausing larvae was studied in 79 apple and pear orchards in southeastern France. Bands of geo-referenced corrugated cardboard were placed on tree trunks in August 2006 and 2007 and collected in October. After weighing, the larvae were placed in closed recipients (15x15 cm) and kept under outdoor shelters. The organisms started to emerge in April 2008.
The predation and the parasitism of codling moth eggs were assessed in a sub sample of 13 orchards. Codling moth egg batches obtained from a laboratory rearing were set on 2x1 cm cards containing on average fifteen 12 hour-old eggs. The cards were exposed for three days close to fruits. The number of parasited and predated eggs was assessed seven days after placing in the orchards, in early July and August. The orchards were divided according to production system: organic and conventional. In the conventional system, the orchards that controlled the codling moth exclusively with insecticides were differentiated from those that used mating disruption (integrated).
Results (diapausing larvae): The parasitism of diapausing larvae occurred in 21% and 16.4% of the sampled orchards in 2007 and 2008, respectively. The mean of parasitism in these two years, between the production systems, was 3.7, 2.3 and 0.8%. The percentage of parasitism was significantly higher (P= ) in the biological system than in the conventional one (integrated + conventional) when considering the total number of orchards (Figure 1), while no difference was observed when considering only the orchards hosting parasitoids (Figure 2).
Figure 1. Parasitism (%) of C. pomonella in Figure 2. Parasitism (%) of Cydia
The whole orchard sample pomonella in orchards hosting parasitism.
Figure 3. Cydia pomonella parasitoids Figure 4. Emergence of Cydia
in years and pomonella and its parasitoids, in day degrees.
Ascogaster Pristomerus Perilampus Elodia
Results (eggs): The predation of Cydia pomonella eggs was significantly greater in organic orchards than in conventional orchards (Figure 5). The percentage of cards with predated eggs per orchard (n=30) was 65% in the organic orchards and the mean in the conventional orchards was 45% (Figure 6). Predation in the month of August was significant compared to July.
Figure 5. Predation (%) of Cydia pomonella Figure 6. Predation (%) of
Eggs in 13 orchards. Cydia pomonella egg cards
It was verified that Trichogramma cacoeciae parasited card eggs, but this occurred only in August in a single orchard under conventional system (3.8%)
Figure 6. Codling moth eggs parasited by T. cacoeciae.
Discussion: The presence of parasitoids of several species was detected in the two years of study. The low rate of parasitism indicated that the regulation Cydia pomonella was not strongly under the dependence of these organisms. The highest egg predation occurred in the organic orchards (p<0.0001). However, the percentage of parasitism in the ten orchards where diapausing larvae were parasited were quite similar in the three different production systems.
Furthermore, both predation and parasitism rates were significantly lower in the orchards surrounding by high surfaces of conventional orchards in the 100 m around. This suggests than the insecticide practices in the landscape may also affected the immigration of the natural enemies within the orchard.