Harrell’s products allow greenhouse managers to begin propagation with confidence and keep a clean, stress-free growing environment from seedling to adult.
What Comes First Matters Most
One of the most important stages in greenhouse production is propagation. Whether starting from high-quality and healthy plugs (seedlings) or rooted liners (vegetative cuttings), young plants are vulnerable to attack by pests and pathogens. Poor conditions in propagation can lead to persistent issues for both propagators and growers further along in production.
Starting with healthy plant material and maintaining a clean growing environment is not easy for any commercial greenhouse operation; however, it is the best way to protect your plants from day one.
Here are some pointers that should help set the foundation for a successful crop:
Start Clean. Stay Clean.
A clean environment is the best environment. Starting out with issues can lead to major crop losses. Investing the time, money and effort it takes to start out with new or properly sanitized trays, clean benches and clean floors with no sign of dirt (soil that is out of place), algae or weeds will pay off by minimizing pest and disease pressure throughout the growing season.
Seedborne, or seed-transmitted diseases, severely stressed or damaged cuttings, and pest-infested propagation material are just a few examples that can lead to a disastrous season. Do not cut corners in propagation, and there should be zero tolerance for pests and disease.
Eliminating Plant Stress
Just like people, when plants are under stress, they become more susceptible to becoming sick. Many greenhouse operations import propagative plant material, and often shipments don’t arrive in the best quality. Plant stress from shipping and handling is mostly unavoidable, but to minimize stress, growers may consider using biostimulants and soil amendments that promote stress tolerance, encourage faster growth, and enhance root development in propagation.
Adding Harrell’s EarthMAX® Organic to your soil can help aid greenhouse plants micronutrient uptake and increasing water retention.
Products such as Harrell’s EarthMAX® Organic are available as a liquid and granular formulation, so they can easily be soil incorporated or applied as a foliar spray. Harrell’s entire Bio-MAX® product line offers a balanced approach to help alleviate plant stress by promoting stronger and healthier plants.
Pests and Pathogens
Some plant pathogens, including fungi, bacteria and viruses, are seedborne. This means that the source plants (parents) were infected, and it will spread to the offspring. This type of pathogen transmission most often leads to a very high incidence of disease. These types of plant pathogens can also be seed transmitted, meaning the spores of fungi (cells of bacteria or nucleic acid of virus present on or inside the seed) can attack during germination. The same applies to cuttings taken from diseased stock plants. It’s very important to monitor propagation areas closely for any signs or symptoms associated with plant pests and pathogens.
Soil-borne Pathogens
Germinating seeds and newly emerging roots and hypocotyls are often under attack by soil-borne plant pathogens. These pathogens can cause major losses due to post and pre-emergence damping off or low-quality plants with poor performance. Fusarium spp., Pythium spp. and Rhizoctonia solani are the primary culprits, but any pathogens present in the growing medium (i.e., Phytophthora, Botrytis and Thielaviopsis) can attack young plants. Pre-emergence damping off occurs below the soil where the pathogen attacks the emerging root or hypocotyl before full emergence and results in poor stands. Post-emergence damping off results in rotten discolored stems at or near the soil line and root decay. Affected seedlings often appear shriveled brown, collapsed or stunted.
Recognize the Pests and Pathogens That Are Most Harmful
Botrytis is among the most common plant pathogens in greenhouse production, and it thrives in the conditions provided during propagation. The fungus loves moisture and causes leaf spotting on foliage and stem blighting on cuttings and young plants during propagation.
Another common issue is the presence of fungus gnats, which are especially bad in the larval stages when they feed on roots and the lower stem tissue of young plants. The presence of fungus gnats and Botrytis presents a serious quality issue, as it should be unacceptable to ship fungus gnats and diseased plants to the consumer. Therefore, it is vital to screen for them in every shipment.
Bacterial Diseases
Though fungi cause more plant diseases, bacterial diseases can be some of the most difficult to manage. Bacteria are single-celled organisms that can be seen only with a powerful light microscope. Though some bacteria do produce spores, those that cause plant diseases do not. Bacterial diseases in propagation include leaf spots and blights, soft rots, vascular wilts, crown gall and cankers. Bacteria cannot penetrate the cuticle of plants, so must enter the plant through a wound or natural opening.
Some plants have small natural openings along the leaf margin called hydathodes, which function in the transpiration process of the plant, but when open, they serve as a point of entry for bacteria to enter the plant and subsequently cause disease. Bacteria are dependent on outside agents for dispersal. Splashing water is the chief means by which bacteria are disseminated, with the other top reason being through human contact. Simply touching an infected plant and then touching a healthy plant can spread many bacterial pathogens.
Prevention + Management = Success
Success in plant propagation comes down to prevention and management. Once disease has started in propagation, the spread may be reduced by providing drier conditions in the production area, which is the best way to keep fungus gnats and plant diseases in check. This can be done by:
- Increasing greenhouse temperature
- Increasing air circulation and ventilation
- Reducing the frequency of watering
- Providing better water drainage by ditching inside and outside the plant bed structure or greenhouse
- And by increasing the amount of light by removing dirty covers, overhanging branches, shading materials, etc.
Pest monitoring, exclusion, stress mediation, sanitation and good cultural practices all play an important role, but pesticides are essential for effective management. Closely monitoring crops and scouting for pests and diseases allows for early detection and timely and targeted pesticide applications. Pesticides are most cost-effective when used preventatively to eliminate problems before they occur. Don’t forget to choose products and time pesticide applications that provide long-lasting protection during transportation or while sitting on shelves at retail stores.
Reach Out to Your Harrell’s Rep
Be sure to visit www.harrells.com to learn more about solutions for plant health and protection, and reach out to your local Harrell’s representative for product recommendations, disease diagnosis or to help you treat any stubborn diseases/pests. We’re here to help!