“Which Fungicide Do Your Plants Need – Contact or Systemic?”
When it comes to protecting plants from fungal diseases, choosing the right fungicide can make all the difference. But with so many products on the market, terms like contact and systemic fungicides can feel confusing. Let’s simplify these terms for better understanding.
🌱 Contact Fungicides – “The Shield on the Surface”
Contact fungicides act as a raincoat for your plants.
a) They stay on the leaf and stem surface where they were sprayed.
b) When a fungal spore lands on the plant surface, it meets this chemical shield and is stopped before starting infection.
c) These fungicides act quickly, but here’s the catch: if it rains, the shield can wash away. That’s why re-spraying is often needed after heavy rainfall.
🌿 Systemic Fungicides – “The Medicine Inside”
Systemic fungicides are like antibiotics for your plants.
a) Instead of sitting on the surface, they are absorbed by the plant.
b) The chemical travels inside (sometimes throughout the whole plant, sometimes only locally around the sprayed area).
c) This means even new leaves can be protected for some time.
d) They can also cure early stages of infection; something contact fungicides cannot do.
Some chemical formulations exhibit dual mode of action (i.e. both contact & systemic) due to presence of multiple ingredients such as Fantic F, Vincare, Mikal etc.
v Here are some smart tips to use them wisely!
1. Relying on a single product throughout the season is not advisable. Rotating between different fungicides helps to reduce resistance risk and improve effectiveness. The need for rotation often depends on disease pressure, thus, review both the previous week’s and the upcoming week’s disease forecasts on databaum platform for your field, to make an informed decision.
2. Spray at right time. Disease pressure overview also helps in selecting most favorable spray regime for the fields. Often when farmers notice the oil spot predictions, they start switching to systemic fungicides applications for optimal protection of their fields.
3. Regular watch out for the DSS alerts and rainfall predictions[SP1] . Keep a regular check on rain amounts and DSS alerts to maintain proper field protection cover. If it is too much rain, replace the washed-off fungicides. You can set alarms on databaum App for an efficient pro-active approach towards field protection.
How much rain is good to go?? Is my plant still protected after so much rain?? Stop your worries and investigate the rain-fastness as well as rain protection window of your chemical of interest. At databaum, we have enlisted these details for >100 plant protection products, helping you to understand the efficiency of your field sprays in adverse weather conditions.
Ø Rain-fastness
It is defined as the time required after spraying, for a product to become resistant to wash-off by rain. For contact chemicals, it depends on how strongly they stick to the plant surface. However, for systemic chemicals, it is determined by how long they take to penetrate plant tissue before it rains. It is a crucial factor influencing the efficiency of both contact as well as systemic fungicides. The time frame for rain-fastness is often mentioned on the labels of the products and can differ for different chemicals.
Ø Rain-protection
In addition to the time factor, another important parameter is the amount of rain a chemical encounter. For example, 1mm of rain in 1-2h may have different affect than 10-15mm of rain within same time. Therefore, before spraying fungicides it is crucial to know weather conditions in your area. A simple click on databaum app helps you to know the weather pattern in addition to the plant’s protection cover status which helps to plan the optimal spray time. This protection cover status indicates whether the sprayed fungicides are still active on plants to full potential or compromised following a sudden rain-event.
Generally, as a rule of thumb, contact fungicides such as mancozeb, copper, or sulfur remain on the surface and usually need about 24 hours of drying to be considered rain-fast; even light showers of 1–2 mm can remove a significant portion of residue, while heavy rains of 25–50 mm often require re-application. In contrast, systemic fungicides such as triazoles and strobilurins are absorbed into the leaf tissue and usually achieve rain-fastness within 1–12 hours depending on chemistry and formulation; once absorbed, they are much less affected by rainfall and can provide longer-lasting protection inside the plant. Overall, contact sprays need about a day of dry weather, while systemics need only a few hours before rain for reliable plant protection. So next time you’re choosing a fungicide, ask yourself:
Do I need a shield, a medicine, or both?
Reference
1. McLaughlin MS, Roy M, Abbasi PA, Carisse O, Yurgel SN, Ali S. Why Do We Need Alternative Methods for Fungal Disease Management in Plants? Plants (Basel). 2023 Nov 10;12(22):3822. doi: 10.3390/plants12223822. PMID: 38005718; PMCID: PMC10675458.
2. Fungicides properties and weather conditions. Annemiek Schilder, Michigan State University Extension, Department of Plant Pathology - June 15, 2010. (https://www.canr.msu.edu/news/fungicide_properties_and_weather_conditions#:~:text=Since%20systemic%20fungicides%20are%20absorbed,the%20outside%20of%20the%20plant.&text=Also%2C%20fungicides%20and%20formulations%20differ,to%20adhere%20to%20plant%20surfaces)
Disclaimer
The information in this blog post is for educational purposes only and is based on current research and expert opinion. While we strive for accuracy, we make no guarantees regarding the completeness or reliability of the information. Users should consult a qualified agricultural professional before applying any fungicide or implementing crop management practices, as effectiveness may vary based on specific conditions. The authors and publishers accept no liability for any loss or damage resulting from the use of this information. Please ensure compliance with local and/or country laws and regulations regarding fungicides use.
[SP1]Watchout for DSS, and rain amounts in your field