Chestnut seed speck disease, also known as chestnut kernel dry rot or black blotch, is a common issue in major chestnut-producing regions of China, such as Hebei and Shandong provinces. While the nuts appear normal during harvest and seem healthy, they develop small spots during storage and transportation, leading to decay and rot. This disease significantly affects the quality and marketability of chestnuts during storage and sale. **Symptoms:** The kernels show dark gray, black, or dark green lesions that gradually progress to dry rot, creating hollow spaces. These areas are often covered with gray-black fungal hyphae, making the seeds fragile. In severe cases, bacterial infections may lead to soft rot and foul odors. The seed coat can become cracked, exposing the infected tissue and forming a "sore" appearance. Sometimes, the outer shell looks normal, but the kernel inside has turned black and decayed. The disease can also affect branches, causing them to dry out and rot. Research categorizes the symptoms into three types: 1) Black spots—where the seed coat appears normal, but the kernel has irregular dark brown to black spots, with internal streaks of grayish white to reddish black; 2) Brown spots—characterized by varying shades of brown necrotic spots on the kernel surface, with gray to black lines visible when cut open; and 3) Rotten type—where the kernel becomes soft or dry, turning brown to black. Most pre-storage symptoms are brown spots, while black spots dominate later, together accounting for about 90% of affected grains. Rot symptoms often appear as a progression from earlier lesions. **Pathogens:** The disease is caused by multiple fungi, including *Plastigomys*, *Phytophthora*, *Fusarium*, and *Coccothraea*, among others. *Ascomycota* spores, especially those of *Grapevine* origin, are commonly involved. Studies from Hebei Agricultural University indicate that *Alternaria alternata* and *Bacillus anthracis* are the main pathogens for black-spot symptoms, while *Fusarium* species and *Penicillium palustris* cause brown spots. The rot type typically develops from these earlier symptoms over time. The disease begins during the near-mature stage of chestnuts, with mild symptoms at harvest. As the nuts are stored and transported, especially at room temperature (around 25°C), the condition worsens rapidly. Lower temperatures slow down the spread, while high humidity increases susceptibility. Healthy, vigorous trees are less affected, whereas weak or old trees suffer more. Dense plantings with poor air circulation and damaged trunks or branches are more prone to infection. Early harvesting can also increase the risk of disease during storage. Disease incidence starts low at around 0.5% in late August and early September, rising to about 3% during collection. After harvesting, the rate increases to an average of 8%, and further rises to 10% after processing and selection. The peak occurs within 15–25 days post-harvest, highlighting the importance of quick cooling and refrigeration to prevent losses. **Prevention and Control:** Controlling this disease involves reducing handling, improving storage conditions, and minimizing exposure to warm temperatures. Quick refrigeration after harvest is critical. Additionally, maintaining tree health through proper cultivation and pruning helps reduce disease susceptibility. Other measures include removing infected branches, avoiding mechanical damage during harvest, and using saltwater rinses to detect and remove diseased nuts before storage. Potassium Salt,Potassium Oxalate,Oxalic Acid Anhydrous,Oxalic Acid Monohydrate Wuxi Yangshan Biochemical Co.,Ltd. , https://www.yangshanchem.com