USE OF A “LATE WATER” FLOOD FOR PEST CONTROL IN CRANBERRY PRODUCTION: IMPACT ON PEST POPULATIONS, PLANT GROWTH, AND PRODUCTIVITY

In commercial cranberry (Vaccinium macrocarpon Ait.) production, flooding is used as a cultural practice for harvest and for winter protection. In addition, after the withdrawal of the winter flood, cranberry bogs may be reflooded in the spring, a practice known as holding “late water” (LW). This practice was used by early cranberry growers in Massachusetts to avoid spring frost and to promote keeping quality in the harvested fruit. Recently, LW has been “rediscovered” as a cultural tool with the potential for reducing inputs of chemical pesticides and fertilizers. We have begun to document the effects of LW on pest populations and on cranberry plants to provide growers with a solid basis for deciding whether to use this cultural practice. In 1993, 11 LW bogs were studied and compared to control bogs. All of the bogs showed acceptable levels of insect and disease damage on the fruit at harvest. The average number of pesticide applications for the LW bogs vs. controls was 0.9 vs. 2.6 for insecticides and 1.3 vs. 2.8 for fungicides.