Drought may increase stalk lodging in corn
click image to zoom Drought conditions experienced during grain fill often increase the potential for stalk rot and lodging problems in corn. When stalk rot occurs late in the season as it often does, it may have little or no direct effect on yield. However, stalk lodging, which results from stalk rot, can have such an impact on harvest losses that many plant pathologists consider stalk rots to be the most significant yield limiting disease of corn.
For a corn plant to remain healthy and free of stalk rot, the plant must produce enough carbohydrates by photosynthesis to keep root cells and pith cells in the stalk alive and enough to meet demands for grain fill. When corn is subjected to drought stress during grain fill, photosynthetic activity is reduced. As a result, the carbohydrate levels available for the developing ear are insufficient. The corn plant responds to this situation by removing carbohydrates from the leaves, stalk, and roots to the developing ear. While this "cannibalization" process ensures a supply of carbohydrates for the developing ear, the removal of carbohydrates results in premature death of pith cells in the stalk and root tissues, which predisposes plants to root and stalk infection by fungi. As plants near maturity, this removal of nutrients from the stalk to the developing grain results in a rapid deterioration of the lower portion of corn plants in drought stressed fields with lower leaves appearing to be nitrogen stressed, brown, and/or dead.
Other plant stresses which increase the likelihood of stalk rot problems include: loss of leaf tissue due to foliar diseases (such as gray leaf spot or northern corn leaf blight), insects, or hail; injury to the root system by insects or chemicals; high levels of nitrogen in relation to potassium; compacted or saturated soils restricting root growth (recent flooding); and high plant populations.
click image to zoom Most hybrids do not begin to show stalk rot symptoms until shortly before physiological maturity. It is difficult to distinguish between stalk rots caused by different fungi because two or more fungi may be involved. Similarly, certain insects such as European corn borer often act in concert with fungal pathogens to cause stalk rot. Although a number of different fungal pathogens cause stalk rots, the three most important in Ohio are Gibberella, Collectotrichum (anthracnose), and Fusarium. For more information on stalk rot in corn, consult the OSU Plant Pathology web site "Ohio Field Crop Diseases" (http://www.oardc.ohio-state.edu/ohiofieldcropdisease/) for more details and pictures of the disease symptoms associated with these pathogens.
The presence of stalk rots in corn may not always result in stalk lodging, especially if the affected crop is harvested promptly. It’s not uncommon to walk corn fields where nearly every plant is upright yet nearly every plant is also showing stalk rot symptoms. Many hybrids have excellent rind strength, which contributes to plant standability even when the internal plant tissue has rotted or started to rot. However, strong rinds will not prevent lodging if harvest is delayed and the crop is subjected to weathering, e.g. strong winds and heavy rains.
A symptom common to all stalk rots is the deterioration of the inner stalk tissues so that one or more of the inner nodes can easily be compressed when squeezing the stalk between thumb and finger. It is possible by using this "squeeze test" to assess potential lodging if harvesting is not done promptly. The "push" test is another way to predict lodging. Push the stalks at the ear level, 6 to 8 inches from the vertical. If the stalk breaks between the ear and the lowest node, stalk rot is usually present. To minimize losses from stalk lodging, avoid harvest delays. Identify fields which are at greatest risk and harvest these fields first. Fields which experienced drought stress, defoliation due to hail, foliar disease injury, etc. would be prime candidates for early harvest.
- DuPont Crop Protection to sell certain assets to Bayer
- New research study shows the value of neonicotinoids
- Alltech Crop Science acquires South African distributor
- Monsanto invests to transform plant breeding
- Fungicide-resistant soybean diseases spreading
- Most crop futures are starting Thursday on a strong note
- ValueAct buys stake in fertilizer dealer Agrium
- Critics of Dow herbicide sue U.S. EPA over approval
- Six tips to help professionals take leaps of faith
- Nitrogen fertilization rates for corn production
- Landmark Services Co-op, Curry Seeds sign agreement
- No-till may not bring boost in global crop yields
- Los Angeles City Council votes to explore ban on GMO plants
- ASA issues statement on EPA’s neonicotinoid study
- Economist: Taxing P could reduce risk of algal blooms
- Commentary: Government wants farmers to quit farming
- Resistant weeds not controlled by fall residuals
- First responders need to prepare for agroterrorism