62A28. Infected stalks may break at a node (Figure 5). Physoderma Brown Spot and Node Breakage . Most seed products have adequate tolerance to PBS. Hybrids vary in their susceptibility to the disease and severe outbreaks of Physoderma have been associated with stalk rot and breakage. Infection at lower stalk nodes causes stalks to become weakened and subject to snapping.Extremely wet weather appears to be a causal factor of Physoderma stalk rot and breakage. SYMPTOMS. Sporangia are abundant at the outer edges of the nodes and to some degree within rotted pith tissues (Figure 6). 111-113 Day Maturity. Stalk nodes where the breakage occurs are black and rotted around the outer edge or rind area (Figure 4). The fungus survives in crop residue and may be more common in continuous corn and conservation tillage systems. This has been confirmed as Physoderma maydis.

Physoderma stalk rot (Physoderma maydis) stalk breakage at lower node (Sept. 2014, Iowa). Infected nodes become weakened over time and snap easily when pushed. Physoderma brown spot and stalk rot of corn caused by Physoderma maydis in Iowa. Microscopic examination of the symptomatic tissue reveals thousands of light brown sporangia (Figure 4 and 5). Physoderma Brown Spot and Node Breakage Small yellow spots appear first at the base of the leaf and over time turn brown in color. Spots in the mid-rib of the leaf become reddish to brown in color and combine to form irregular blotches (Figure 5). SYMPTOMS. Spores produced by the Physoderma brown spot fungus can also infect the stalk rind, usually around nodes, and can make them brittle and prone to breakage. When temperatures are warm (75-85°F) and sporangia are saturated in water for at least 72 hours, they germinate and release copious amounts of motile zoospores. Physoderma Node Breakage = N/A. … Spots in the mid-rib of the leaf become reddish to Page 1 of 2 Figure 3. Responds to high management; Position for early harvest; Very good root rating and good stalks; Well suited for irrigated acres ; Complete Product Details. Figure 1. First symptoms noticed are plants that break at the first or second node (Figure 1). There are few published reports of PSR and associated stalk breakage caused by this pathogen. Disease Cycle and Symptoms of Physoderma Brown Spot Figure 1. Stalk nodes where the breakage occurs are black and rotted (Figure 4). Note that the pith of the stalks are white and free of symptoms (Figure 5), unlike other stalk rot diseases. Small yellow spots appear first at the base of the leaf and over time turn brown in color. 3, right). Physoderma significantly weakens rind strength at the node allowing the plant to be exposed to great risk if a wind event were to occur. This weakens the nodes causing them to become brittle and snap when pushed (Figure 4). Physoderma brown spot lesions. Symptoms. Alright welcome from the field this week My name is Nick Benson here in Northeast Iowa Today, I'm over by Arlington, Iowa today. The nodes at which breakage occurs are black (Figure 2) and some stalk rot of the pith may be present (Figure 3). PLANT HEALTH PROGRESS Vol. Generally, losses are related to lodging. Physoderma stalk breakage generally occurs at the first or second stalk nodes. Figure 2. Physoderma is a fungal pathogen that favors abundant rainfall, temperatures between 73° F to 90° F, and overwinters in and on corn residue. Crop rotation and tillage reduce survival of inoculum. Crop rotation and tillage may reduce available physoderma inoculum in the soil. This weakens the nodes causing them to become brittle and snap when pushed (Figure 4). Physoderma brown spot (Physoderma maydis) does not cause a true stalk rot, fungal spores accumulate and infect at nodes. Physoderma Node Breakage RATINGS :1 = POOR 9 = EXCELLENT R = RECOMMENDED HR = HIGHLY RECOMMENDED NR = NOT RECOMMENDED 12 3456789. P. maydis produces resting spores called sporangia, which allow the pathogen to persist in soils for up to 7 years in the absence of corn. Stalk Breakage / Rot Caused by Physoderma. 2, 2015 Page 92 Management of diseases caused by P. maydis are complicated since it is difficult to … CHAMPION SEED . Microscopic examination of the symptomatic tissue reveals thousands of light brown sporangia (Figure 4 and 5). • Physoderma may be more common in continuous corn and conservation tillage systems. 61P24. Physoderma brown spot (Physoderma maydis) does not cause a true stalk rot, fungal spores accumulate and infect at nodes. The nodes are easily snapped when the plant is pushed, giving the impression that hybrids simply have a greensnap issue. Before opening a bag of seed, be sure to read, understand and accept the stewardship requirements, including applicable refuge requirements for insect resistance management, for the biotechnology traits expressed in the seed as set forth in the technology agreement that you sign. Often infected plants grow well without any noticeable impact on ear or kernel size. Physoderma node rot symptoms are recognized as snapping of the corn stalk at one of the lower nodes (usually 6th, 7th or 8th) during the mid-reproductive stages (R3-R5). Figure 2. Physoderma stalk breakage. Abundant rainfall in corn fields and temperatures ranging between 73 to 90 °F are favorable for PBS. Currently products are being evaluated for reactions to the stalk breakage symptoms. As infection progresses, spots can often be found occurring in bands across the leaf. Infection at lower stalk nodes causes stalks to become weakened and subject to snapping at those nodes. Orange sporangia of P. maydis may be easily rubbed off the rotted node or leaf sheath attached to the rotted node. •Research is underway to better understand the best way to manage the stalk rot phase. Infection at lower stalk nodes causes stalks to become weakened and subject to snapping.Extremely wet weather appears to be a causal factor of Physoderma stalk rot and breakage. Stewart’s wilt on a corn leaf. Left: PBS leaf lesions appearing in a broad band. As infection progresses, spots can often be found occurring in bands across the leaf. This disease has been increasing in prevalence across Iowa over the past decade. Spots in the mid-rib of the leaf become reddish to brown in color and combine to form irregular blotches.