Managing Plant Stresses with Fungicides
By Bryan Olivi
Throughout the growing season, plant stresses are considered either abiotic or biotic. Abiotic stresses are negative impacts on living organisms by non-living organisms. Biotic stresses are negative impacts on living organisms by other living organisms. Abiotic and biotic stresses encountered by crops affect both growth and yield.
Growing Season Foliar Diseases
During the reproductive stages of soybean and corn plant development, each crop faces different types of stress. Stress imposed on plants can be influenced by several factors. Insect damage can cause a wound that allows pathogens to invade the plant; while temperature extremes or inadequate amounts of moisture can also induce stress. Foliar diseases can initiate stress that may decrease pod or grain fill, cause leaf necrosis, as well as reduce plant vigor. Foliar fungicides are an important integrated management tool proven to help mitigate plant stress. Fungicides provide physiological benefits which help plants expend less energy combating stress.
Before determining if an application of a foliar fungicide is needed, it is critical to scout each crop thoroughly. Scouting crops helps determine if a fungicide may be beneficial when environmental stressors are effecting the plant’s health or if fungal pathogens are present. During this time of the season, a rise in humidity and the probability of afternoon storms influence plant pathogens. When weather conditions favor persistent moisture or humidity, southern and common rust symptomology will develop in corn. Southern rust (Puccinia polysora), which is now developing in the Southern and Midwestern US is influenced by high temperatures and humidity.
Southern rust occurs during ear-fill and can drastically impact yield. Applications of Trevo® TRZ fungicide, before favorable conditions for disease development and onset, provide fungicidal efficacy with excellent residual to protect corn plants well into physiological maturity. Also, coupling Trevo® TRZ fungicide with Verifact™ surfactant, will improve the deposition and penetration of the active ingredients into the plant as well as improve wash-off resistance and rain fastness.
Frogeye Leaf Spot
Frogeye leaf spot, caused by the fungus Cercospora sojina, develops in humid conditions where rainfall is prevalent. Disease symptoms typically appear on the leaf, but can also appear on the pod, and stem. Leaf symptoms appear as light-colored, translucent spots that develop into darker spots enclosed by a dark brown margin. Effected leaves will often wilt and necrosis will occur causing leaves to drop.
The fungus can invade the pod walls as well and impact mature seeds during seed development. This disease has been an issue in soybeans commonly in the mid-South, but has also been observed in the mid-west. Yield can be significantly impacted due to disease severity especially on susceptible soybean varieties. Frogeye leaf spot spreads quickly during periods of frequent rain or wind. Applying fungicides during the R3-R5 reproductive stages can be extremely effective in protecting yield. Often, applying fungicides during this time of the year can be tricky. Popup showers as well as periods of heavy downpours can have a significant impact on fungicides applied during this application timing stage. Using a systemic fungicide, like Trevo® TRZ fungicide, provides a broad-spectrum preventative dual mode of action which often performs better than contact fungicides during rainy periods. This is due to its curative and systemic properties which translocate into the leaf tissue and are less susceptible to wash-off by rain.
Fungicides are extremely important and should be considered a part of any grower’s chemical regiment to protect yield. Building a proactive fungicidal approach into your crop’s plan will strengthen the plant's natural defenses, help the plant combat environmental stressors, and protect yield.
Bryan has worked in the agricultural industry for the past 10 years and has published research. Bryan currently works as a Proprietary Product Agronomist for Pinnacle Agriculture. In this role, Bryan conducts research trials of experimental and commercially released products for Innvictis Crop Care and Mission Seed Solutions to evaluate agronomic characteristics and ensure product performance in the field.