The past few days of cloudy, wet/rainy weather 10 to 14 days before Romaine and leaf lettuces are ready to harvest means that evapo-transpiration (Et) rates have dropped significantly. These are the exact conditions identified by California researchers that favor localized Calcium deficiencies in the rapidly growing inner leaves of lettuces that lead to lettuce tipburn.
We were too late to recognize these conditions last year but discussed it in detail here after several growers experienced significant losses. Now, however, is the time to act to try to prevent damage or at least avoid losing marketable product. Recommendations include:
- foliar applications of Ca with an air-assisted and/or electrostatic sprayer in order to get the Ca into the inner leaves where it is needed, and
- consider harvesting earlier than planned in order to market small heads with little or no damage rather than risking significant losses by waiting to full maturity.