Organic Orchard Management: Pest Management Concerns
Any pest management program needs to be a multi-faceted plan of action. A well balanced “toolbox” for an organic pest management program may include careful cultivar selection, orchard management practices to discourage habitat and conditions for disease, beneficial insects, bat boxes, insect-specific bacteria or viruses, mating disruption, tangle foot, baits, traps, and less toxic organic pesticides. Which tool is employed will depend on the pest and the grower’s threshold for damage.
Vertebrate pests such voles, pocket gophers and other rodents can become a serious problem in orchards during the winter where surrounding hedgerows, brambles, or fields provide an ideal rodent habitat. When snow cover deprives them of other food sources, they tend to gnaw on the lower branches and the crown of trees, which can cause damage or even death. Pocket gophers may feed on tree roots throughout the growing season. In organic orchards, management relies on trapping, protecting trees, and managing the orchard to reduce food and cover for these pests. Keeping vegetation short especially as fall approaches, protecting trees with guards and limiting the use of heavy mulch, in particular black plastic mulch, are integral to reducing rodent populations. Encouraging predators can also help. See Chapter 9 “Rodent Management,” for more details on reducing habitat and excluding rodents from the orchard.
For insect pests, many organic biological and chemical sprays are available for primary fruit pests, but should be used in conjunction with other prevention measures and timed carefully with available models and degree day tracking. Other strategies for controlling insect pests like codling moth in orchards include pheromone disruption, sterile releases, reducing overwintering habitat, crop thinning, kaolin clay sprays and the encouragement of beneficial insects (Richter, et al. 2021). When possible use local resources for determining the best management approaches and timing for controls.
Similarly, managing pathogens should begin with selecting resistant cultivars and using good sanitation practices in the orchard including removing infected branches or trees, mowing leaves and pruned branches, avoiding overhead irrigation and disposing of infected fruit. Additionally dormant sprays using copper or sulfur may be effective against fruit pathogens including fire blight, scab and peach leaf curl (Smith et al. 2019). For very fire blight susceptible varieties, like many cider cultivars, antibiotics, currently not approved for organic certification, may be necessary. Growers should weigh the advantages of organic certification against fire blight management strategies if they choose to grow these cultivars. More information on the performance and fire blight susceptibility of cider cultivars grown in the Intermountain West can be found at https://agresearch.montana.edu/warc/research_current/apples/cider_cultivar_research.html.