Anthony Roth, Agronomy Research Center Greenhouse Manager
Growing a crop involves many challenges, including weather, equipment, labor, seed, fertilizer, insects, and diseases. Diseases can be caused by organisms such as bacteria, viruses, and fungi. However, disease-causing species account for a small percentage of the total population, with most being harmless or even beneficial to crops. Fungicides specifically target fungi and their spores, which are similar to plant seeds. Fungicides can be divided into different groups based on how they work on or within the plant and how they control fungi.
Contact Vs Systemic
Contact Fungicides: Contact fungicides work as a protectant, similar to a glove on a hand. They create a barrier on the leaf surface that helps prevent fungi from entering the plant through openings such as wounds, stomata, and tiny gaps between cell walls. During periods of ample to excessive moisture, these openings are more susceptible to fungal invasion. The ability to stick and keep foliar applications hydrated on the leaf enhances the success of the application.
Systemic Fungicides: Systemic fungicides are absorbed by the plant and then translocated to other parts. The movement can vary greatly depending on the product:
- Locally Systemic: Has very limited movement from the contact area.
- Translaminar Systemic: Moves from one side of the leaf to the other.
- Xylem-Mobile Systemic: Moves through the plant’s xylem tissue, responsible for most of the water movement in a plant, and moves only upward. Good coverage, especially for the lower leaves, is important for upward movement.
- True Systemic (Amphimobile): Moves through both the xylem and the phloem, which transports sugars and metabolites, allowing movement throughout the plant. Very few fungicides are true systemic.
The ability to stick and keep foliar applications hydrated on the leaf can only help to increase the success of the application. Notice the two droplets in Figure 1. The droplet on the right has Liquid-Carbon Based Fertilizer (L-CBF) added to the spray mix, resulting in less surface tension (flat bubble) and more contact with the leaf. This increased contact helps with better coverage and infiltration into the leaf for improved results.
Figure 1It’s important to note that multiple factors are needed for a disease to become a problem: a susceptible host, favorable conditions for the disease (which are often stressful for the host), the presence of the pathogen, and timing. The health of the plant is often overlooked, and there isn’t a definitive indicator to determine a plant’s health. However, over the years, QLF and its customers have observed that healthier organisms, whether cattle or crops, are better at handling the challenges that arise every year and every day.