Bud failure in almonds: Variability of bud failure in Nonpareil almonds
Noninfectious bud failure (BF) affects certain almond varieties and has become increasingly widespread in recent years.Symptoms are produced by failure of vegetative buds (particularly on middle and terminal portions of shoots) to grow in the spring. This is followed by vigorous wide-angled growth from surviving buds. In some trees, particularly when other symptoms are severe, bands of roughened bark appear on some branches. As this pattern of bud failure develops, BF trees develop wild, disoriented growth patterns and hence the disorder is frequently called “crazytop.”Early work on the BF problem developed the concept of increased BF incidence with successive vegetatively propagated generations. At that time BF was attributed to a ienetic disorder with unstable characteristics. Since then, observations suggest that mvironmental conditions affect the stability m d expression of BF. Vegetative propagations done on the premise that plants propagated from a common parent remain the same, but this premise is not fulfilled in the 3F disorder. In other cases where variations lave occurred after vegetative propagation, the problem has most often been attributable :o environmental influences, virus infections or mutations. However, variability of noninfectious BF cannot, at present, be directly accounted for by any one of these factors. This series of articles adds further information on he nature of BF and discusses selection for reedom from BF within the Nonpareil variety. It documents the impact of environment on BF potential and expression and provides lata on yield reduction due to BF. Finally, it iutlines a system of management decisions or orchardists faced with almond trees afected with BF.