When starting new crops, either from seeds or from cuttings, it’s important to implement an effective, proactive disease control program. Plants in this stage are extremely sensitive, with soft tissue and very little root structure. They’re also typically grown in warm, humid environments which can support disease activity. However, there are various cultural practices that growers can execute to help prevent common diseases from impacting their young, delicate crops.
Clean up. Prevention needs to begin before you even plant a new crop – that is, after moving out the previous crop or at the beginning of the year. Clean and sanitize the area, including raking up any litter that’s accumulated in the growing area, sweeping up spilled soil and disinfecting walls and floors with an oxidizing material.
Review inputs. Next, review your crop inputs, because all of them will impact how the crop performs, as well as which media works best with which crop. New, hardier plant species are continually becoming available, so it’s important to consider your plug and seed source selections. Quality growing media will prevent many problems if it has good porosity and adequate air flow and water flow for a particular plant’s needs. Trays and pots can also impact how water and air flow through the growing media.
Consider water source and quality. Many growers must inject water modifiers like acid at a specific rate because of their water’s alkalinity. Growers who reuse their existing water must ensure their filters are working correctly and that pathogens are removed, oxidized or UV lighted to prevent infecting the new crop.
Check moisture levels and airflow. Monitoring greenhouse air moist add is important, at least in the initial propagation stages, but not so moist that diseases can sporulate easily and infect the crop. Growing on benches can improve airflow around the plant depending on how tightly spaced plants are within the propagation area. Airflow above the plant material will improve with the use of circulation fans and heaters, which also dry latent moisture out of the air and make it more difficult for diseases to sporulate.
Monitor temperature and lighting. Keeping the bottom areas of new crops warm induces rooting, but that warm temperature might also be a sweet spot for diseases to sporulate and infect your crop. That’s why it’s crucial to always monitor greenhouse temperature. Furthermore, because growers typically start new crops in the springtime, plants can become stressed by overcast, rainy and cold weather. Plants may also start to get leggy because they’re not getting enough light. Growers who have the capacity for supplemental lighting past the point where they want to induce top growth over root growth can take that option.
If you suspect you already have a disease problem, it’s a good idea to send a plant sample to a pathology lab at your local university or an independent lab for analysis. Unfortunately, that process takes time – and it’s another reason why it’s best to proactively prevent diseases before they develop. It’s always much easier to protect a crop from a disease than it is to eradicate a disease once it’s taken hold.
If the lab determines that you have a disease problem, Mary Hausbeck, Ph.D., extension specialist at Michigan State University, recommends various product rotations to effectively treat plants with Pythium, Thielaviopsis, Phytophthora or Rhizoctonia, the four most common soil-borne diseases affecting crops in this growth stage. Dr. Hausbeck’s recommendations include various Nufarm fungicides including Phostrol®, 3336® EG/3336® F, Spirato®, Tourney® and Adorn® along with other products in different MOA groups, the basis of any sound resistance management program.