Early Drop of Nuts in Response to Insect Infestation

Premature drop of insect-infested fruits of pignut hickory, Carya glabra (Mill.) Sweet, was found in an oak-hickory forest in southeastern Michigan. Infested fruits and to a lesser extent aborted fruits fell mostly during the summer, while viable fruits fell mostly during the autumn. Weights of fallen nuts indicate that (1) infested ones show little or no growth after early August; (2) aborted ones increase in weight until late August; and (3) viable ones also reach full weight in late August but weigh significantly more than the other two categories. This response reduces the tree's wastage of energy on nuts which are unable to germinate.