Mold in walnuts

Growing walnuts is a rewarding venture for farmers, but it is also a challenge. One of the most serious problems facing walnut growers is the emergence of mold, which can significantly affect the quality and yield of the crop. In this article, we will review the causes of mold on walnuts, contributing factors, effective management strategies and prevention of this problem based on recent research.

Research has shown that several fungi responsible for walnut blight have been identified. The main causal agents are Fusarium, Alternaria, Botryosphaeriosis and Fomopsis. These fungi can enter the walnut through various vulnerabilities, such as sunburn, insect damage and natural openings in the stem of certain walnut varieties. In addition, certain environmental and management factors can also exacerbate the problem. 

• excessive sun exposure weakens the nut's protective outer layers, making it more vulnerable to fungal infections
• pests create entry points for fungal spores to penetrate
• the fungi often attack during or immediately after cracking of the husk, when the nut's protective barriers are compromised.

To effectively control walnut blight, researchers and growers recommend a combination of proactive management practices and targeted treatments.

                     ·       Fungicide aplication

Pre-shelling and early-shelling applications have been shown to reduce the incidence of mildew.

Fungicides such as Merivon and Rhyme, applied three weeks before cracking of the green fruit, are particularly effective against moulds such as Fusarium and Alternaria.However, late fungicide applications are less effective, highlighting the importance of timing.

·       Timely harvesting

Harvesting walnuts quickly and harvesting them promptly after the husk has cracked are essential to minimize the time walnuts are exposed to potential infection.

·       Integrated pest management

Controlling insect populations reduces the risk of physical damage to walnuts, thereby limiting entry points for fungi.

·       protection from the sun

Measures to protect walnuts from excessive sun exposure, such as using protective covers, can help reduce vulnerability associated with scald.

Walnut blight is a multifaceted problem that requires a proactive and informed approach. By understanding the causes and contributing factors, and implementing effective management practices, growers can mitigate the impact of mildew on the crop. A combination of timely fungicide application, pest control and proper crop management offers robust protection against this persistent problem. With the right strategies, it is possible to ensure the quality and profitability of walnut plantings against the threat of mildew.