It's caused by the Pythium fungus and is typically brought on by over-watering your plants. Pythium Root Rot. The Begonia Society also serves as the International Registration Authority for cultivars of Begonia. The pathogen that causes this disease is closely related to Phytophthora species so root rot symptoms are similar. It will also describe how to restart your plant from tubers in the spring, as well as provide additional information about tuberous begonias in general. These spots can enlarge at a rapid rate. This pathogen doesn’t cause branch blight, only root rot and damping off of seedlings. Stem and root rot. A common problem among acetosas is the stem and root rot. The mums, in contrast, had Pythium aphanidermatum and P. myriotylum both of which are summer-season loving Pythiums, favored by 95-104° F and 98-104° F, respectively (but both species can tolerate temperatures below 86 and above 104° F). From your pictures, it appears your begonias have a disease called stem rot. Registration of new cultivars is one of the best ways of documenting cultivated plants with detailed descriptions which facilitate the use of proper cultivar names in the future. Prevention & Treatment: See root rot management information under Phytophthora Stem Blight and Root Rot. In the spring, start begonia plants by placing the … Store tubers in a dry, dark, cool (above freezing) area. This disease typically comes from contaminated soil. The spots appear suddenly during warm to hot humid weather. Leaves in these patches appear water-soaked and dark in the early morning. Put them on screen trays or pack them in dry peat, sawdust, sand or other insulating material. Symptoms include rotting stems above soil level, darkened foliage, and rotting roots. You can prevent this disease by sterilizing your potting soil, pots, and tools. But as stated above, begonias are sensitive to overwatering and are susceptible to root and stem rot caused by Pythium, Phytophthora or Rhizoctonia. This leaves the Begonia vulnerable to sunburns. Once any signs of a begonia disease appear on a plant, the owner should remove the affected begonia and quarantine it from other plants. Begonia Pythium rot. Pythium rot causes the leaves to wilt, whereby they start dropping prematurely. We literally kill them with kindness. Spotted leaves must be carefully removed and burned. Common Problems with Begonia acetosa . Popularly known as pythium rot, it’s caused by a fungal-like organism called Pythium ultimum. We found these agents of Pythium root rot in pots containing either healthy or sickly looking plants. Leaf Spot Diseases July 15,1942 PytMum Disease of Fibrous-rooted Begonia 91 FIGURE 1.—Pythium disease of fibrous-rooted begonia: A, Non-inoculated con- trol; B, symptoms produced on fibrous-rooted begonia plant, variety Fire Sea, by Pythium ultimum after inoculation in the greenhouse. The first symptoms of Pythium Root Rot are normally circular spots, usually between 2-5cm, however, they can reach up to 15 cm. Begonia plants also are susceptible to Armillaria root rot, crown gall, black root rot, root knot nematode, cottony rot and foliar nematode. This article will provide you with all the information you need to know to dig up your tuberous begonias and store their roots over the winter. Pythium rot is the likely culprit if plants wilt and break at the soil line. Pythium rot - Shiny, blackened areas on the stems and petioles of established plants. Any stalk or root left has the potential to rot and spread to the tuber. Once infected, the plant cannot be treated; the only option is to dispose of the plant. Pests/ Insects You will mostly find insects like aphids, thrips or caterpillars on Begonia. It’s a fungal disease that represents Begonia stem and root rot. This disease typically comes from contaminated …