tipburn

Tipburn is a physiological disorder that affects lettuce and other leafy vegetables, in which tissue at the tips of young leaves becomes necrotic. It is not caused by a pathogen and is most common in intensive greenhouse or hydroponic production where rapid growth or uneven water supply can limit calcium delivery to growing tissues.

Symptoms typically appear as brown, corky necrotic lesions at the tips or along the margins of young leaves, often on inner leaves near the head. Affected areas may expand and cause leaf curl or collapse, reducing marketable quality even when overall plant vigor remains good. Older leaves are usually not affected.

Causes are linked to insufficient calcium reaching rapidly expanding tissues. Calcium movement is tied to water flow in the xylem, so conditions that cause transient water stress or very rapid growth can outpace calcium supply. Contributing factors include irregular irrigation, high transpiration rates from heat or intense light, high plant density, root problems, and nutrient imbalances such as excessive potassium or ammonium, salinity, or suboptimal pH that reduce calcium uptake.

Diagnosis relies on symptom pattern and exclusion of pathogens; tissue calcium analysis can support the diagnosis, but management is typically based on cultural practices rather than lab tests.

Management focuses on ensuring steady calcium delivery to developing tissues. Key practices include: providing uniform, frequent irrigation or nutrient solution supply; maintaining stable pH and electrical conductivity; supplying calcium through fertigation (for example calcium nitrate) and avoiding high ammonium levels; balancing nutrients to favor calcium uptake; reducing growth rate through environmental control when possible; and selecting tolerant cultivars. Foliar calcium sprays may offer limited short-term relief but are not a substitute for adequate root-zone calcium.

Prevention centers on consistent moisture management, balanced nutrition, moderate growth rates, and crop selection to minimize tipburn risk.