Sanitation When Transitioning High Tunnels

Integrated Pest Management, or IPM, is a strategy for pest management that uses a combination of practices to minimize risks to people and the environment while reducing pest problems.

Figure 1 below, Overview of the IPM Strategy, depicts the IPM process using a pyramid. The IPM process starts at the bottom of the pyramid with sanitation and cultural methods as the first step. The last step, pesticide application, is used only when other practices are ineffective at keeping pests below acceptable levels. Today, Scott DiLoreto, manager of the College of Agricultural Sciences' 50,000 ft2 greenhouse facility, talked with students in our Hydroponics and Aquaponics course and reminded us about the importance of sanitation.

Sanitation practices limit the resources pests need to survive, kill existing pests, and prevent them from spreading. Practices include cleaning equipment, removing infested plants and plant parts, removing crop residues, weeding, avoiding the reuse of potting mix, and disinfecting pruning and cutting tools, as well as pots and flats. When transitioning high tunnels from spring/summer to fall/winter crops or vice versa, sanitizing tunnels before planting next season's new seed or planting stock is a great strategy to avoid the spread and build-up of certain pests.

It can be difficult to find the time to clear and clean out a tunnel entirely before planting the next crop, and having a combination of spring/summer crops with fall/winter crops during the transition is common. However, this sanitation step can significantly aid in pest management later in the growing season, as shown in Figure 2. Crop Production Timeline.

Two situations are presented in the figure. The top arrow, labeled "dirty start", illustrates what can happen when a crop is started without adequate sanitation practices. The bottom arrow, labeled "clean start", illustrates what can happen when a crop is started after sanitation practices have been used. In both situations, crop seeding is conducted simultaneously. For the dirty start, pests are discovered and exceed thresholds much sooner than for the clean start, requiring four pesticide applications before harvest. In this example, when plants are started in a clean, sanitized growing space, only two pesticide applications are required to secure the crop. Good sanitation practices provide growers with a longer pest-free window, reducing the need for pesticides and reducing labor and expenses associated with pesticide application.

How does this apply to transitioning high tunnels? For example, if summer crops are not removed and tunnels are not cleaned out before switching to new crops, pests can use the summer crops as hosts and then easily move to the newly planted crops. We are observing this phenomenon in a high tunnel experiment where we are investigating aphid management. Aphids will move from tomato plants to the next crop of lettuce or other leafy greens. When this happens, aphid outbreaks in lettuce and leafy greens usually occur very early in the crop production timeline. Good sanitation practices when transitioning to high tunnels can go a long way in avoiding this problem.