The difference between disease and disorder

Scouting your vegetables in the greenhouse and field will help you identify potential issues early on. In most cases, the earlier you detect an issue, the more effective the management tactics can be. But what are the differences between a disease and a disorder? Among the webinars Michigan State University Extension is offering at the Online Integrated Pest Management (IPM) Academy, the webinar titled “What is wrong with my vegetable plants?” discusses the differences between vegetable diseases and disorders.

Vegetable transplant production will start soon, so it will be best focus on how to pinpoint disorders in the greenhouse. The nutrients plants require are available as soluble salts. Nitrate, ammonium, potassium, calcium, magnesium, chloride and sulfate contribute to the soluble salts in greenhouse growing media. The substrate can be charged with nutrients but sometimes it is not. Guidelines for soluble salt content can be found in the MSU Extension article “Diagnosing plant problems – don’t forget about pH and soluble salt content” and the MSU Extension bulletin E1736, “Greenhouse growth media: Testing and nutrition guidelines.” Electrical conductivity (EC) is a measure of the soluble salts and indicates salt accumulation in the growing media.

On the other hand, the pH of the media influences the availability and uptake of nutrients. Vegetable transplants grown in media with inadequate pH (lower or higher than optimum) can develop nutrient deficiencies or toxicities. Monitor growth media and irrigation water pH frequently. Closely monitor nutrient and soluble salt content weekly, or twice a week if possible, by randomly selecting plug trays throughout the facility. This proactive approach is very important in maintaining your greenhouse fertility plan when needed while preventing nutrient deficiency and toxicity. Consider investing in a portable instrument that allows you to measure pH, EC and meters for nitrate-N and K petiole sap testing and nutrient solutions.

Read the full article from Michigan State University here.