Decision making time scales in crop production can vary between minutes and years - four or more orders of magnitude. These time scales can also vary depending on the time of year, crop, location, and for reasons beyond a grower’s control, such as weather or market factors.
The agricultural research and extension model practiced in the United States advocates for “decision support” systems to provide growers and crop consultants with information and guidelines when faced with management choices. These have been embodied in services such as USPest.org, Washington State University’s Decision Aid Systems and AgWeatherNet, and the National Phenology Network. While this is not a criticism, I believe they suffer from a limitation in that they assume a Platonic ideal where the decision maker has the luxury of focusing on a single variable of interest, such as:
- When do I irrigate?
- Should I be actively scouting for this pest?
The agronomy or horticultural manager still needs to put all the pieces together to make it work. But even the most sophisticated growers and crop consultants can fall behind. There is a mounting technical debt that accrues throughout each growing season. Here, I focus on two areas where this occurs: crop load management and crop protection.
Technical debt in crop load management
Crop load refers to the number of fruit on a plant. If you have too many - or too few - you may face unwelcome consequences. For example, fruit that are too small or too large are less valuable, may take more effort to harvest, and their quality may suffer. The effects of crop load on plant health can also be severe: poorly-managed crop load in one year can cause significant plant stress and under-production in the following year. To address this, growers practice crop load management: active measures to manage the quantity and quality of fruit produced by their trees.
Several levers exist to manage crop load. The first is pruning, which occurs after harvest in the fall and into the following winter. Pruning is an expensive, manual activity requiring physical skill and good judgment. It is also subject to weather-related disruptions. In fact, this occurred in 2022 in the Pacific Northwest, when heavy snowfall and freezing temperatures interrupted pruning activities. Delays start adding to the technical debt ledger: Growers get around to pruning, but at the cost of other important activities, or they get around to pruning, but have to do a suboptimal job.
There are other levers to manage crop load, such as pollination and thinning. Pollination can be actively managed by varying the stocking rates for beehives or planting pollinator habitat near the orchard, but in practice, growers typically follow rule-of-thumb recommendations from the land grant universities, some of which were formulated decades ago. Thinning can also be performed around the bloom period by using air blasting or chemical sprays to remove flowers from trees, thus preventing fruit set. It can also take place during fruit development through chemical means or manual removal. Whatever the case, these interventions are costly and the results can vary widely.
By the time active crop load management is underway, another set of critical crop management activities are also getting started.
Technical debt in crop protection
While crop load is focused on the plants, pests and diseases raise their own set of challenges. Managers of orchard crops typically practice some form of integrated pest management (IPM). Two important parts of an IPM program are modeling and monitoring. Pest and disease risk is intimately tied to local weather conditions and landscape characteristics (elevation, slope, soil type, orchard design/trellising, and crop variety). Modeling uses a measure called degree-day accumulation to predict when harmful organisms like codling moth, apple maggot, molds, and mildews are likely to be a concern to growers. For example, a model developed by USDA researcher Alan Knight shows us that at 925 accumulated degree days in a location, we can expect that 95 percent of codling moth eggs from the overwintering population will have hatched and started eating their way through the orchard. In 2023, this happened in Union Gap, Washington on June 9. The previous year, it occurred the weekend before July 4th - another illustration of the conditions beyond the control of growers.
Growers can use their own weather stations and calculate these values themselves, or they can pull data from public and private sources. Their main use is to inform scouting approaches: where do they need to place monitoring traps? How often should they inspect them? When and where should they place pheromone dispensers in the orchards to disrupt mating behaviors?
Similarly to crop load management, crop protection efforts do not always go according to plan. Perhaps scouts can’t get to an orchard because they are putting out fires somewhere else. Maybe there is some ambiguity about when adult pests are detected in traps and a pesticide application is ineffectual. Or perhaps the traps aren’t catching anything and an orchard suffers damage because the grower didn’t even know there was a problem.
Another complication is the fact that pests and diseases are mobile. This issue has created a renewed interest in areawide approaches to managing pests. In particular, codling moth in organic apple and pear production is a major threat to the industry. Organic growers have fewer tools to control codling moth, due to restrictions on the types of products they can use. Even when a grower employs all the best management practices, if their neighbor falls short, or there’s an unmanaged residential tree nearby, then the pest pressure can result in the worst of possible outcomes. Most of the new apples planted in the western U.S. are expected to be grown for the organic market. This raises the possibility of a state change that could be cataclysmic for the industry, as a breakdown in codling moth control in organic apples could spread to conventional orchards.
So what then?
Resight Laboratories is working to enhance real-time observation networks with a new way to see what’s happening in your orchards, vineyards, and fields. While we are excited about the Resight Scouting System, expect to learn more about our other offerings soon.
To learn more about what we're working on and how it might fit in with your IPM programs, on-farm research, and product trials, please get in touch, and subscribe to our free newsletter to stay up to date.