Pratiques actuelles et marges de manœuvre agronomiques pour réduire l’utilisation de pesticides sur les cultures pérennes

National audienc

Analyse comparee des populations de Lepidopteres en vergers de Pomacees par piegeage avec des pheromones sexuelles de synthese

Deux essais de piégeage par des attractifs sexuels de synthèse, portant sur 18 espèces de lépidoptères, ont été conduits en 1979 et 1980 dans 2 localités de la région d’Avignon en vergers de poiriers et pommiers. L’ordre d’apparition des adultes varie peu dans les 4 situations, ce qui devrait favoriser la détermination des dates d’intervention contre des ravageurs localement dangereux. L’évolution des captures au cours de la saison est influencée par la plante-hôte pommier ou poirier. Les peuplements, comparables dans ces 2 types de vergers, diffèrent par contre suivant le mode de conduite phytosanitaire des exploitations. Une lutte chimique intensive entraîne une forte prédominance d’un nombre réduit d’espèces.In 1979-1980, 2 trappings with synthetic sex attractants, concerning 18 species of Lepidoptera, were performed in apple and pear orchards around Avignon. The adults of these species always appeared in the same order. This should allow a more accurate determination of treatment dates against locally dangerous pests. The seasonal change in captures varied with the host plant (apple or pear). The populations in the 2 types of orchards showed good similarity, but differed according to the pressure of chemical treatment. An increase in pesticide treatments disturbed the balance of species, favoring some of them

Report on the life history traits of the generalist predator Forficula auricularia (Dermaptera: Forficulidae) in organic apple orchards in southeastern France

The aim of this paper is to provide detailed data on the reproduction of the European earwig Forficula auricularia Linnaeus (Dermaptera: Forficulidae) under natural conditions. We also describe its spring field population structure and dynamics in organic apple orchards in southeastern France using artificial and natural shelters. Two nymph cohorts could be distinguished in a laboratory reproduction study. The first brood, following the first egg-laying event in late November, had significantly higher pre-imaginal survival (1.74-fold) than the second brood in early April. The egg phase was the most vulnerable with a higher mortality rate in the first brood than the second. Independent of brood number, nymphal survival increased from second nymphal instars (N2) onwards with values higher than 96%. In orchards, N3 were generally observed in natural and artificial shelters from the end of April to mid-June. N4 was the most abundant life stage sampled and the only stage present at the majority of sampling dates, especially from early May onwards. Beginning in June, the abundance of new adults of a given year gradually increased especially in the artificial shelters. This descriptive study can now be used to develop phenological models aimed at limiting earwig mortality due to horticultural management practices and increasing their predation level in conservative or augmentative approaches

Effect of codling moth management on orchard arthropods

The effect of codling moth Cydia pomonella management on the arthropod community and on the natural enemies of pests was analysed from 2001 to 2003 in both the tree canopy and the grass cover of three experimental apple orchards under different management strategies: supervised control of codling moth based on chemical protection (C); mating disruption against codling moth, including additional pesticides when needed (MD); and microbiological control with granulosis virus in an organic orchard (O). The three management systems differed in terms of biomass and functional organisation of arthropods. Number of individuals tended to be higher in the O orchard, and the complex of beneficial arthropods of this orchard was based on polyphagous predatory arthropods (including earwigs) in both studied habitats. Conversely, parasitoid Hymenoptera constituted the prevailing group in the arboreal habitat of both the C and MD orchards. The highest diversity and evenness indices were unexpectedly measured in the C orchard. The richness of arthropods was the highest in the grass cover of the O orchard. The opposite was found in the tree canopy, the lowest values being measured in the arboreal habitat of this orchard. Depending on the year, the sampling period and the vegetation strata (apple tree canopy or grass cover), diversity and evenness indices measured in the MD orchard were either closer to the O orchard or to the C orchard

Effect of management strategies on arthropod communities in the colonies of rosy apple aphid, Dysaphis plantaginea Passerini (Hemiptera: Aphididae) in south-eastern France

Apple orchardists are encouraged to adopt pest control strategies with less pesticide use and thus less harmful environmental impacts. In this study, we compared the possible effects of organic, integrated pest management (IPM), and conventional protection strategies on the rosy apple aphid-ant-natural enemy communities in 12 apple orchards in south-eastern France in 2008 and 2009. The organic orchards had the smallest aphid populations and the most diverse and abundant natural enemy populations compared with the other orchards. More diverse and abundant natural enemy populations were observed in IPM compared with conventional orchards. In 2009, the aphid abundance in IPM orchards was, however, significantly higher than in conventional orchards. No significant differences in ant densities were observed among protection strategies in 2008, but in 2009, these densities were significantly higher in conventional compared with organic orchards. Three predator groups were the most common: Coccinellidae, Forficulidae, and Syrphidae. These were significantly more abundant in organic orchards than in the other orchards, except in 2008 when there was no significant difference in syrphid and earwig abundance between organic and IPM orchards. Parasitoids were significantly more abundant in organic orchards in 2009 but not in 2008. The smaller number of aphids in organic orchards appears to results from the absence of toxic insecticides and thus to increased natural enemies compared with other orchards. Our findings emphasize the importance of no or less intensive synthetic pesticide usage for the conservation of natural enemies biodiversity and biological control of rosy apple aphid in apple orchards

Control of fruit tree pests through manipulation of tree architecture

International audienceAlthough chemical aspects of plant-insect relationships are largely studied, the effect of within-plant structure on insects is seldom investigated, especially in perennial crops. In fruit production, the manipulation of tree architecture is generally considered to be involved in pest development through considerations of "tree vigour" or branching density. However, both physiological and physical aspects of tree architecture (i.e., canopy height, width and shape, fruiting and vegetative shoot distribution, branching, connectivity, growth rhythmicity) affect the distribution and abundance of both phytophagous arthropods and natural enemies. Tree architecture can affect arthropod pest by modifying: (a) the attractiveness of the host-plant; (b) the within-plant life conditions including microclimate, availability and accessibility of resources and reproduction sites, and enemy-free spaces; (c) the efficiency of chemical or alternative pest control methods (including the use of pheromones). Despite seasonal effects and variability in species biology, modelling and experimental approaches have shown that a more complex architecture favours phytophagous insects and is detrimental to the foraging of most natural enemies. Orchards are permanent habitats, in which the manipulation of tree architecture is potentially a powerful tool for pest regulation, through the implementation of innovating training systems

Farmer's protection strategies in peach orchards : aphid communities in S-E France as a case study

National audienc

The role of natural enemies on the population dynamics of the rosy apple aphid, Dysaphis plantaginea Passerini (Hemiptera: Aphididae) in organic apple orchards in south-eastern France

Efficient pest control using conservation strategies requires sound knowledge of the dynamics of the pest and its natural enemies (NE). But the role of natural regulation under natural conditions is not easy to prove. The rosy apple aphid (RAA) Dysaphis plantaginea is the most detrimental aphid in organic apple orchards. Our aim was to determine whether and to which point the abundance and composition of arthropod communities associated with aphid colonies affects RAA population dynamics. The present study, based on weekly observations of marked and infested apple shoots was carried out from April to June in 2008 and 2009 in one experimental insecticide-free apple orchard and four organic commercial orchards located in south-eastern France. NE populations were the most diverse (7.3 taxonomic groups for 50 shoots) and abundant (1.44 individuals per shoot) in the experimental orchard compared to organic orchards (3.8 groups for 50 shoots and 0.7 individuals per shoot). The large RAA populations per shoot (more by 1.7-fold) observed in two of the five orchards were presumably related to a lower number of NE (less by 1.9-fold) and a high abundance of ants (more by 6.2-fold). Among the main NE groups, syrphids arrived first, followed by coccinellids and earwigs. Parasitism rates, mainly due to Ephedrus sp. (Braconidae), were between 0.66% and 6.93%. Based on their precocity and abundance, syrphids appeared to be the most efficient group of NE under the study conditions. By surveying the same shoots weekly we could demonstrate that RAA population dynamics were strongly affected by the presence of NE. This predatory effect was however not sufficient to prevent damage to the apple trees. New management practices aimed at favoring natural regulation, especially augmentative approaches, need to be developed

Peach orchard management strategies: aphid communities as a case study

National audienceBecause of the various negative side effects of intensive chemical pest control practices, there is a shift in horticulture towards the adoption of alternative approaches for crop protection. In order to characterise and evaluate management strategies being used, we carried out comprehensive interviews to obtain details of the peach orchard protection schedules of 20 organic and conventional fruit farms in south-eastern France. It appeared that besides the regular use of direct control, farmers also used cultural and/or alternative methods and indicators to optimize their orchard management. Combining the latter methods with IOBC’s technical guidelines for plant protection, four strategies have been identified. Their efficacy on aphid communities was then evaluated through visual monitoring of aphids and of beneficial populations at plot level. Brachycaudus persicae and Myzus varians were the most frequent species. The two most efficient strategies were dominated by chemical treatments, whereas the two others, less detrimental to aphid antagonists, were predominantly used by organic farmers and in agreement with IOBC’s guidelines. Variations in aphid communities could be explained by: (i) the use of efficient and therefore toxic products, correlated with low infestations and low abundance and diversity of antagonists; (ii) the link between pre-blooming treatments, cultural and alternative methods (as weed strips management and manual pruning of infested branches) and high populations of aphid communities. Against all expectations, such communities were neither related with kaolin applications, nor with management of vigour and nearby environment. According to the literature, the strategies identified can be interpreted as steps towards a redesign of orchards’ protection