Low Rainfall Increases Chance of NOW Survival
Winter sanitation is critical to reduce overwintering populations of navel orangeworm (NOW) and the potential for damage and aﬂatoxin contamination in next year’s crop. As a baseline, current guidelines are to reduce mummies to an average of two or fewer per tree by Feb. 1, and destroy them by ﬂail mowing by March 15, with a goal of having an average of fewer than four grounded nuts remaining per tree. A model that predicts NOW damage has been developed for the southern regions, and shows the guidelines should be tailored to growing regions, based on the amount of rainfall, which reduces NOW survival. In the drier southern region, the model and ﬁeld experience show the mummy threshold is less than the current standard.