- Author: Steven A. Tjosvold
The previous post described the importance of inspecting incoming plants and keeping a clean nursery to avoid pest introductions. Many important root pathogens and other pathogens, weeds, and insects can be introduced in contaminated soil and growing media, and so the focus of this post will be on ways to prevent introductions from these potential sources.
Soil- inhabiting plant pathogens can be found in growing media and associated root and crop debris. Anything that has contacted the ground, such as equipment, tools, irrigation hoses, and workers' hands and shoes could be contaminated. Pots should not sit directly on the ground. Phytophthora infecting the roots of just one potted plant can produce thousands of propagules that can move in water draining from the pot and infect roots of nearby plants.
Likewise, during a vigorous rain storm, these propagules can be splashed from the contaminated pot or ground onto nearby plants. Benches or similar structures that support plants above the ground can eliminate or minimize this. In greenhouse structures, concrete floors or other impervious surfaces are ideal for walkways between benches. Floor surfaces should be kept clean of plant debris, soil, or growing media. After a crop cycle, benches should be cleaned of plant debris, washed and dried. Drying can kill sensitive plant pathogens.
Benches can be sprayed with diluted chlorine bleach (0.5 % sodium hypochlorite solution) or other suitable disinfectant. Potting media and plant debris will inhibit the activity of most disinfectants.
There are many clever ways to raise pots and containers off the ground.
The bottom of clean shoes can be sanitized with disinfectants such as quaternary ammonium compounds .
Store and handle growing media so it does not come in contact with the ground or water runoff. Cover the media when not in use.
- Author: Steven A. Tjosvold
A pest-free nursery should be the resolve of every grower in the New Year. Start the New Year with a clean nursery and keep pests from being introduced. It is more important than ever now because there is increasing risk that serious invasive pests and diseases can be moved through the nursery trade. Phytophthora ramorum (the cause of Sudden Oak Death) and light brown apple moth (LBAM) are current notable examples that could cause ecological or economic damage and trigger regulatory oversight.
Keeping a nursery clean and preventing introductions of new pests and diseases is often difficult in the complex and fast-paced nursery industry. But here's a short list of things that you could do:
Know the source of propagative material you plant, and insure that the propagator is doing everything possible to provide healthy seed or plants to you. Inspect seed, transplants, or other plants when they are delivered to your nursery or greenhouse. Make sure no diseases or pests are evident. Use your hand lens (See link below).
Pull transplants or other plants out of their containers and look for healthy root tips. Insects such as aphids, thrips or mealybugs hide in young folded leaves or tightly angled stems. There are field test kits to detect Phytophthora and common viruses such as tomato spotted wilt, impatiens necrotic spot and cucumber mosaic. If a pathogen or insect infestation is detected, controlling the problem before you plant in the field is much easier than after the problem is established in the field. “Controlling the problem” sometimes means destroying the plants before they are planted or introduced into a nursery or greenhouse.
Start clean and stay clean in the New Year, and have a Happy New Year!