Chestnut seed speck disease, also known as chestnut seed kernel dry rot or chestnut black blotch, is a common issue in major chestnut-producing regions of China, such as Hebei and Shandong provinces. Although the nuts appear normal at harvest and during the growing season, they develop small spots during storage and transportation, leading to decay and rot. This makes it a significant concern during the post-harvest handling and sale of chestnuts. **Symptoms:** The kernels show dark gray, black, or dark green lesions that gradually progress to dry rot, creating hollow spaces. These areas are often filled with gray-black fungal hyphae, making the seeds brittle and easy to crush. Infections can lead to bacterial soft rot, producing foul odors. The seed coat may become covered in a black-gray layer of mycelium, with granular structures forming on its surface. When stored, the seed coat can break, exposing the infected tissue and creating a visible "sore." Sometimes, the outer shell appears normal, but the kernel inside is already blackened and decayed. The disease can also affect branches, causing dry rot and further damage. Research has classified the symptoms into three types: 1) **Black spots**: The seed coat looks normal, but the kernel has irregular dark brown to black spots. Internally, there are grayish-white to reddish-black streaks. 2) **Brown spots**: Brown necrotic spots appear on the kernel surface, varying in shade and depth. Cross-sections show white, light brown, or yellowish-brown areas with gray to black streaks. 3) **Rotten type**: The kernel turns brown to black, becoming either soft or dry. During pre-storage, brown spots are more common, while black spots dominate later, accounting for about 90% of infected seeds. Rot symptoms often emerge as an advanced stage of earlier lesions, worsening over time. **Pathogens:** The disease is caused by a complex mix of fungi, including *Plastigomys*, *Phytophthora*, *Fusarium*, *Coccothraax*, and other dark conidia fungi. *Ascomycota* spores, particularly those from grapevine, are the main culprits. The pathogen can develop within diseased branches of the tree, thriving between 20–30°C, with an optimal temperature of 28°C. According to research from Hebei Agricultural University, the primary pathogens include *Bacillus anthracis*, *Alternaria sp.*, *Fusarium solani*, *Fusarium trifoliatum*, *Fusarium moniliforme*, and *Penicillium sp.* *Bacillus anthracis* and *Alternaria alternata* are mainly responsible for black spot symptoms, while *Fusarium* and *P. palustris* cause brown spots. Rotten types usually result from the progression of earlier symptoms. The disease typically begins in the near-mature stage of the chestnut. It becomes more apparent during ripening and harvesting. At room temperature, especially in sand storage and transport, the condition worsens rapidly. Sand storage at around 25°C favors disease development. Below 15°C, the disease progresses slowly, and below 5°C, it stops. Water loss on the seed surface promotes infection, but excessive drying can slow lesion expansion. Healthy, vigorous trees are less affected than older or weaker ones. Chestnut groves with good air circulation and sunlight tend to have fewer cases compared to dense, poorly ventilated areas. Trees with wounds, insect damage, or mechanical injuries are more susceptible. Early harvesting also increases the risk of infection during storage and transport. Chestnuts begin showing symptoms in late August and early September, but the incidence is low, averaging 0.5%. During the collection period, the rate rises to about 3%, which is not yet economically damaging. After harvesting, during sand storage and before sale, the disease rate jumps to an average of 8%. After processing and selection, the number of infected seeds increases again, reaching an average of 10%—the highest point. After this, as temperatures drop, the disease stabilizes. The critical period for disease development is between 15–25 days after harvest, when high temperatures accelerate the spread of the disease. **Prevention and Control:** Controlling chestnut seed speck disease requires reducing the number of handling steps, improving storage and transportation conditions, shortening the time spent at room temperature, and promptly moving the nuts to refrigeration or cold ships. Water management is crucial. Enhancing tree health and resistance is also an essential part of an integrated control strategy. 1. Improve cultivation practices to strengthen tree vigor and boost disease resistance. Prune trees to reduce the number of infected branches.
2. Promptly remove dry rot lesions from trunks and cut off dead branches to reduce the source of infection.
3. During harvesting, minimize mechanical damage to the nuts. Wash the fruits with a 7.5% saline solution, remove floating diseased nuts, and dry the healthy ones before storage. Basic inorganic chemicals, compound, materials Basic Inorganic Chemicals,Ammonia Water Solution,Ammonium Hydroxide Solution,Ammonium Hydroxide Wuxi Yangshan Biochemical Co.,Ltd. , https://www.yangshanchem.com