Blight remains one of the most destructive and rapidly spreading crop diseases, and potato farmers in Kenya are currently facing a surge in infections across major growing counties. What starts as a few brown or black spots on leaves or stems can quickly escalate into a full-blown infestation, causing severe yield loss, poor-quality produce, and significant financial setbacks. With the disease already spotted in most potato-growing areas, it is critical that farmers act swiftly and decisively to protect their crops.

Blight, caused primarily by the organism Phytophthora infestans, thrives in moist and warm conditions. It spreads through air, water, contaminated tools, and infected plant debris. Typical symptoms include yellowing leaves, brown or black lesions, soft rot on tubers, and in severe cases, sudden plant collapse. A field can go from healthy to heavily infested in just a few days if no action is taken.

Timely intervention is the most effective weapon against blight. Early management prevents disease spread, stopping the infection before it reaches healthy parts of the field or nearby farms. This is crucial not only for individual farmers but for the protection of entire farming communities. Moreover, early action helps maintain crop yield and quality, as healthy leaves are vital for photosynthesis and tuber development. Damaged foliage directly affects growth, resulting in smaller and fewer tubers.

Another benefit of early management is cost-efficiency. Preventive fungicide applications or early-stage treatments are more affordable and effective than trying to contain a full outbreak. Waiting until blight has taken hold often leads to more frequent spraying with stronger, and more expensive chemicals, raising input costs significantly. Additionally, correct timing helps reduce the risk of fungicide resistance, ensuring that disease-control products remain effective in the long term.

On the other hand, delayed management of blight carries serious consequences. Once the disease becomes widespread, it is nearly impossible to reverse the damage. A significant portion of the crop or the entire harvest can be lost. Produce affected by blight also tends to be of lower quality, leading to rejections at market or by processors, thereby reducing farmer profits. Emergency use of curative fungicides is not only expensive but often yields limited success, consuming more labor and time with diminishing returns. Furthermore, untreated blight becomes a risk to neighboring farms, allowing spores to spread across the region, affecting more livelihoods.

To help farmers manage the ongoing threat of blight, here are key actions to implement immediately:

• Scout your fields regularly: Inspect crops at least twice a week for early signs of blight, particularly during warm, wet periods.

• Use certified seed: This minimizes the risk of introducing blight through infected planting materials.
• Practice crop rotation: Avoid growing potatoes in the same field season after season to reduce disease buildup in the soil.
• Apply preventive fungicides: Don’t wait for symptoms—follow the recommended spray schedules provided by your agricultural extension officer.
• Destroy infected plant material: Promptly remove and burn or bury infected plants to stop the disease from spreading further.

Fields at KALRO Marindas provide a strong visual contrast between infested and well-managed plots. While one section has suffered heavy blight damage, others remain clean and productive thanks to proactive management and regular monitoring.

In conclusion, the message to farmers is clear: Act early, act consistently. Waiting for blight to show its full impact could mean losing your harvest altogether. By staying alert, following good agronomic practices, and applying fungicides preventively, farmers can protect their crops and ensure healthy, market-ready yields. Be proactive, not reactive—because when it comes to blight, timing is everything.