Lodging of cereal crops can be a major harvest issue and can cause significant yield loss when it occurs early in the growth of the crop. Huge varietal differences exist in resistance to lodging (visit www.gocrops.ca). Nitrogen rates, use of manure, seeding rates, seeding dates, and disease infections all play a major role in lodging susceptibility.
Plant Growth Regulators (PGRs) can be used to shorten the crop and improve resistance to lodging. PGRs stiffen the stem, and often improve lodging resistance without shortening the plant at all. Typical height differential is 5–7 cm (2–3 in.). Some PGRs have impacts beyond plant height: for example, chlormequat chloride can reduce apical dominance, increase tillering, or allow tiller’s to catch up in development. It also affects stomatal closure; often increasing yield slightly even when lodging is not an issue. However, under severe moisture stress, yields may be reduced for this same reason.
Cereal crops vary greatly in their response to PGRs, and potential concerns for phytotoxicity (crop injury from PGR application). Weather extremes interact with most PGRs, occasionally causing severe injury. When possible, avoid low (<5°C) temperatures, high (>25°C) temperatures, or wide temperature fluctuations (>20°C), the day before, the day of, and the day after application. Typically, winter wheat is far more tolerant than spring cereals, and spring wheat can be the most sensitive. Varietal differences also exist within species. Read and follow label directions carefully when using PGRs.