Heat Affects Early Lima Beans

Gordon Johnson, Extension Vegetable & Fruit Specialist; gcjohn@udel.edu and Emmalea Ernest, Associate Scientist – Vegetable Crops; emmalea@udel.edu

We are seeing heat effects on pod set in lima beans again in 2016. Affected plantings have heavy bud, flower, and pod drop. In some instances a split set is also present because favorable conditions for pod set were interrupted by high temperatures, which are unfavorable for pod set. Pod drop may also be caused by feeding from piercing/sucking insects (i.e. stink bugs) which damage developing seeds. This type of insect feeding can also cause misshapen pods and irregular, dimpled, or misshapen seed. Larger pods, beyond the pin pod stage, are generally not aborted because of heat stress but may be aborted due to drought stress or insect feeding.

Research by Emmalea Ernest has shown that pollen production is reduced under high night temperature conditions in the lima bean varieties that we currently grow. Among the genetically diverse varieties that have been tested, those which produce more pollen under heat stress, produce a higher yield under heat stress. The aim of current lima bean breeding activities at the University of Delaware is to select for greater pollen production, and thereby better yield, under high temperatures.