Aspergillus niger is a species of fungus that can infect many types of plants, including fruit and vegetable crops. The fungus is parasitic and can inflict tremendous damage to plants and crops if left unchecked. You can understand the structure and spread of Aspergillus niger by learning about the nature of the fungus and its effects on plants.
Aspergillus niger is a widespread fungus that lives in soil and plant or crop debris. The fungus usually infects dead, dying or injured plant tissues. In crops, Aspergillus niger is seen around the time of harvest, insect infestations or mechanical damage to plants. The fungus enters plants through a wound and infects the vascular tissues, spreading through the shoots. Infections of vines with Aspergillus niger fungi are sometimes called Aspergillus vine canker.
Aspergillus niger is especially prevalent during the warm season, when temperatures are 83 to 93 degrees F. In many parts of the United States, the prime season for Aspergillus niger infections is from late April through July. Unfortunately, the signs of the infection don’t usually emerge until later in the warm season or even the beginning of the cooler season, such as October and November. In crops, Aspergillus niger fungi can continue to grow and wreak destruction long after the harvest.
Aspergillus niger infections have been seen in crop vines and plants, including corn and onions. In crop plants, the fungal infection can continue to ravage the crops after the harvest during the storage of the vegetables or fruits. For decades, Aspergillus niger has affected various crops. For instance, multiple counties in California experienced a severe outbreak of Aspergillus vine canker in the region’s vineyards, says the University of California Cooperative Extension.
You can find Aspergillus niger in infected soil, seeds and plant debris or residues, as well as in the form of airborne spores. You’ll most often see Aspergillus niger infections as a type of black mold growing on a plant. Related fungi like Aspergillus flavus and Aspergillus glaucus usually form a greenish-colored mold. In Californian vineyards, infections emerged as large cankers that extended up to 12 inches long on the grapevine shoots and sometimes girdled the vines. You’ll typically see the signs of the fungal infection near the plant nodes or shoot crotches, or around any wounded areas where the Aspergillus fungus can access the plant sap in order to grow. Infections of harvested crops are often seen as powdery-black spore masses, arranged in streaks or covering the entire crop. In some crops like onions, Aspergillus niger fungi can cause a secondary bacterial infection of soft rot, turning the onion mushy.
You can control Aspergillus niger infections in your plants or crops by avoiding any damage, insect infestations, diseases or other wound-inflicting problems that would allow the fungi access to the plant sap. Planting seeds and bulbs that aren’t infected with Aspergillus and storing these seeds in a cool, dry place can help prevent the fungal infection as well. Also, storing your crops in a low-humidity, cool environment can deter fungal growth. Because Aspergillus niger infections are rare, using fungicides is usually ineffective or unnecessary, says the University of California Cooperative Extension. In the case of the Californian vineyards, growers controlled the fungal infection by selective pruning, specifically cutting back and retraining the infected vines during the following spring.