Pyraclostrobin: An Effective Fungicide for Controlling Various Plant Diseases
Pyrachlostrobin is a broad-spectrum contact and systemic fungicide that belongs to the group of strobilurin fungicides. It was first introduced in agriculture in 1997 by BASF and quickly gained popularity among farmers due to its effectiveness in controlling various fungal diseases in many crops. Pyrachlostrobin works by inhibiting mitochondrial respiration in fungal cells and preventing spore germination.
Mechanism of Action
Pyrachlostrobin belongs to the chemical class of Quinone outside Inhibitors (QoI) or strobilurins. These fungicides interfere with respiration in fungal cells by blocking electron transfer at the bc1 complex in the mitochondria. This complex is also known as the Qo site in the cytochrome bc1 enzyme. Pyrachlostrobin binds irreversibly to the Qo site and prevents energy production in fungal cells. Without energy, the fungus is unable to carry out essential metabolic functions or cell division which eventually leads to its death.
Spectrum of Pyraclostrobin
Due to its broad-spectrum activity, pyrachlostrobin is effective against several economically important fungal diseases in crops. Some of the major diseases it controls are:
- Gray leaf spot and northern corn leaf blight in maize: These fungal diseases cause premature defoliation of maize plants thereby reducing photosynthesis and yield. Pyrachlostrobin provide excellent control of both diseases when applied preventively or curatively.
- Powdery mildew in grapes: Powdery mildew is one of the most prevalent diseases of grapes worldwide. If left uncontrolled, it can destroy entire vineyards. Pyrachlostrobin has shown to be highly effective in managing grape powdery mildew.
- Botrytis bunch rot in grapes: Botrytis bunch rot or gray mold is a serious post-harvest disease of table grapes. Pyrachlostrobin applied close to harvest protects grapes from Botrytis infection during storage and shipping.
- Septoria leaf blotch in wheat: Septoria leaf blotch causes leaf spots and blotches on wheat leaves. Under favorable conditions, it can reduce wheat yields significantly. Studies have proven that pyrachlostrobin provides reliable control of septoria leaf blotch.
- Brown spot of rice: Brown spot is considered the most destructive rice disease globally. Application of pyrachlostrobin at early stages of disease development suppresses the brown spot fungus very well.
Mode of Entry and Translocation
Pyrachlostrobin is both contact as well as systemic in nature. When applied as a foliar spray, it is absorbed quickly by plant leaves and penetrates into the inner tissues. Due to its systemic activity, pyrachlostrobin moves upwards and downwards inside the xylem vessels via transpiration stream. This helps it spread to all parts of the plant including new growth. The fungicide provides persistent protective and curative action for 2–4 weeks depending on other factors.
Factors Affecting Performance
Some important factors that influence how effectively pyrachlostrobin controls fungal diseases are:
- Growth stage of crop and timing of application: For best results, pyrachlostrobin should be applied before disease symptoms appear or very early in the infection cycle. Late stage infections may not be curable.
- Disease pressure: Higher disease pressure due to favorable environmental conditions may require additional sprays for adequate control compared to lower pressure situations.
- Formulation: While technical pyrachlostrobin is highly active, performance may vary with different brand formulations available in the market. Water-dispersible granule (WG), suspension concentrate (SC) and emulsifiable concentrate (EC) are common formulations.
- Tank mix partners: Pyrachlostrobin can be mixed with other contact or systemic fungicides from different chemical classes to achieve broader spectrum activity as well as resistance management. Combining with mancozeb, azoxystrobin, difenoconazole works well.
Advantages
Some major advantages offered by pyrachlostrobin as a fungicide include:
- Broad spectrum fungicidal activity against important diseases
- Highly protective as well as curative properties
- Systemic movement within plants for translaminar and upward-downward activity
- Long residual control of 2–4 weeks with one application
- Compatible with many other fungicides for mixing
- Low use rates of 100–500 grams per hectare depending on crop-disease
- Low risk to beneficial organisms and pollinators at labeled doses
- Favorable toxicological profile with no harmful residues in food/feed crops
Resistance Risk and Management
While QoI fungicides like pyrachlostrobin have significantly boosted global agriculture, overreliance on them has also led to development of resistance in some pathogens. Repeated use of pyrachlostrobin alone selects resistant fungal strains which then become dominant. To delay resistance, it is advisable to practice at least two of these strategies:
- Limit use of QoI fungicides to no more than 1/3 of total sprays in a season
- Follow label instructions and tank mix with non-QoI fungicides
- Crops should be rotated and not remain in monoculture
- Cultural practices to improve air circulation and reduce humidity
- Use pyrachlostrobin as a protective treatment and not curative alone
with increasing global food demand and need to maximize sustainable crop production, pyrachlostrobin promises to play an important role as a reliable broad-spectrum fungicide. New formulation technologies and combination products will help expand its reach to more crops and geographies. Continuous resistance monitoring and integrated disease management approach are necessary to sustain the effectiveness of this valuable fungicide.
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