Manipulating within-orchard and adjacent habitats to provide better pest control in organic orchards. Some elements for modulating “orchard tree-pest-natural enemy” relationships

The control of pests in organic orchards cannot solely rely on the use of direct control methods. The effect of manipulating the habitat of orchard pests and natural enemies through tree architecture and the increase of plant diversity has been investigated in an experimental organic apple orchard and in a pear orchard, in order to provide information about the potential benefits of these cultural practices. Tree training affected the development of the most detrimental pests of apple trees, and the centrifugal training system globally provided better aphid (Dysaphis plantaginea) and mite (Panonychus ulmi) control than the more classical Solaxe system, whereas codling moth (Cydia pomonella) was favoured compared to Solaxe. The study of an experimental hedgerow designed to optimise protection of the pear orchard allowed us to validate the basic principles of designing plant assemblages to increase plant diversity in the orchard surroundings, namely the introduction of a succession of resources favouring the natural enemies of the key orchard pests, and to avoid detrimental effects (pests or diseases shared with the crops). This experiment and other studies suggest that manipulating the plant diversity adjacent to the orchard has an effect on entomocenosis. However, the potential benefits for the orchard only concern the control of pests that can be tolerated at high infestation rates

Pest management and biodiversity in organic fruit production: the case of apple orchards

Numerous pesticide applications are required for orchard protection, regardless of the guidelines. Organic fruit production (OFP) mainly relies on the use of mineral fungicides and microbiological or naturally-occurring insecticides. The environmental impact of this type of production does not significantly differ from that of conventional production when assessed in terms of synthetic indicators. However, the abundance of earthworms, as well as the abundance and specific richness of arthropod pests and beneficials in the orchards and surrounding hedges, is greater in OFP than in conventional orchards. Generalist predators are usually less affected by OFP compounds than by the chemical pesticides applied in conventional orchards. OFP also benefits avian communities, and above all, insectivorous birds, for which organic orchards offer a suitable habitat similar to that of undisturbed natural areas. In addition to this general trend, discrepancies may be observed in the protection responses of different insect groups. The abundance of hymenopteran parasitoids is the lowest in organic orchards in which outbreaks of phytophagous mites are also recorded in relation to the intensive use of sulphur for scab protection. Biological insecticides often act in ways that are similar to those of chemical ones, and the restricted choice of available compounds is likely to induce resistance selection in insect pests. Although maintaining biodiversity is not a direct result of the implementation of OFP guidelines, it seems to be widely considered as an option by organic growers, both alone and as a complementary tool for pest regulation

A chromosome-level genome assembly of Cydia pomonella provides insights into chemical ecology and insecticide resistance

The codling moth Cydia pomonella, a major invasive pest of pome fruit, has spread around the globe in the last half century. We generated a chromosome-level scaffold assembly including the Z chromosome and a portion of the W chromosome. This assembly reveals the duplication of an olfactory receptor gene (OR3), which we demonstrate enhances the ability of C. pomonella to exploit kairomones and pheromones in locating both host plants and mates. Genome-wide association studies contrasting insecticide-resistant and susceptible strains identify hundreds of single nucleotide polymorphisms (SNPs) potentially associated with insecticide resistance, including three SNPs found in the promoter of CYP6B2. RNAi knockdown of CYP6B2 increases C. pomonella sensitivity to two insecticides, deltamethrin and azinphos methyl. The high-quality genome assembly of C. pomonella informs the genetic basis of its invasiveness, suggesting the codling moth has distinctive capabilities and adaptive potential that may explain its worldwide expansion

Hedgerows and beneficial phytophagous arthropods

Introduction Organic Farming and Integrated Pest Management aim to favour and to rely on natural enemies for pest management. The ability of plant diversity to provide the orchard with natural enemies without any induced damage was studied: (1) in hedgerow lined orchards from different areas in order to assess the effect of hedgerows on the orchard arthropod community and (2) in experimental orchards, in order to test tree assemblages designed for the pear orchard, likely to supply the crop with psyllid (Cacopsylla pyri) antagonists. Materials and methods Arthropods were sampled fortnightly from April to October 1997 in eight (8) commercial pear orchards (Bartlett cultivar) and from main tree species of their lining hedgerows. For each tree species, 30 shoots (1 shoot per tree) were hit (Fauvel et al., 1981) at each sampling date. Three equal areas were delimited within each orchard: one along (one of) the hedgerow, another one in the middle of the orchard (central area) and the last one opposite (due to strong Northern wind, hedgerows are East-West oriented). For each orchard and each sampling date, 30 shoots were hit in each of these 3 areas. Using the same method, arthropods were sampled during 4 years from two experimental pear orchards (Bartlett cultivar) and from each species of the tested mixed hedgerows. All the sampled arthropods have been identified, at least at the family level, allowing to give information about the biology of each arthropod (phytophagous, predatory, parasitic, pollinating, detritiphagous,…). Results and discussion 40 095 arthropods representing 195 taxonomic families were sampled from commercial orchards and associated tree species. Sambucus nigra, Cornus sanguinea, Hedera helix and Coronilla emerus hosted a wide range of beneficial arthropods (generalist predators, parasitic insects) and did not shared major pest with the orchard, unlike Crataegus monogyna (which hosted fireblight), Rubus fructicosus, Populus nigra or Lonicera sp. (which hosted detrimental phytophagous arthropods). Beneficial diversity and numbers were lower for Alnus cordata, Cercis siliquastrum, Cupressus sp., Acer campestre and Robinia pseudacacia. Although they were generally higher in edge areas, orchard arthropod diversity and richness were not significantly different (variance analysis) between inner and edge areas. Pest management is likely to level possible differences within the orchard. The tested assemblages showed to provide psyllid antagonists (Anthocorid bugs, generalist predators) with food and shelter all year long: late flowering and indeciduous leaf species (Arbutus unedo, Hedera helix) offering wintering shelters; early flowering species (Salix capraea, Corylus avellana, Viburnum tinus) offering pollen; species offering alternate preys and/or flowers (Sambucus nigra, Cornus sanguinea, Fraxinus oxyphylla, Corylus avellana). Conclusion This study allowed to provide information about the risk and the benefit of planting different tree species in the agroecosystem. Hedgerow border effect on the orchard arthropods is most probably related to the biology and the ability to move of each arthropod species and needs a specific study; biological and microclimatic effects can therefore cumulate. Further research is needed about the effect of more complex assemblages, including tree species and grass assemblages. Different scale at the landscape level could also be considered. References Fauvel G., Rambier A., Balduque-Martin R., 1981 - La technique du battage pour la surveillance des ravageurs en cultures fruitière et florale. Agronomie, 1(2), 105-113

Evaluation of azinphos-methyl resistance and activity of detoxifying enzymes in codling moth (Lepidoptera : Tortricidae) from central Chile

Fuentes-Contreras, E. Departmento de Producción, Agrícola, Facultad de Ciencias Agrarias, Universidad de Talca, Casilla 747, Talca, Chile.Regular applications of insecticides have been the main management practice against codling moth, Cydia pomonella (L.) (Lepidoptera: Tortricidae) in Chile. Organophosphates are the most widely used insecticides, and azinphos-methyl is an important element in spray programs. In particular, we evaluated diagnostic doses of azinphos-methyl on neonate and postdiapausing larvae from seven apple (Malus spp.) orchards. We also evaluated the activity of detoxifying enzymes, such as glutathione S-transferases (GSTs), cytochrome P450 polysubstrate monooxygenases (PSMOs), and esterases, which are likely to be involved in resistance to insecticides. Such responses were compared with an insecticide-susceptible strain that has been maintained in the laboratory for several years. Neonate larval mortality of field populations to azinphos-methyl was not significantly different from of the susceptible strain. In contrast, postdiapause larval mortality was significantly lower in the six analyzed populations than in the susceptible strain. The C. pomonella populations with reduced postdiapause mortality to azinphos-methyl also showed statistically higher GST activity. Finally, no significant differences were found in total esterase or PSMO activity between C. pomonella populations. Therefore, the observed reduction in postdiapause larval mortality to azinphos-methyl seems to be associated with an increase in GST activity