By Dr. Thomas T. Yamashita

The majority of people fall into what might be considered the spectrum of “normality” when it comes to the expression of various genetic traits governed by diet and environmental conditions. However, a few individuals are afflicted with genetic setbacks. In this respect, plants are not unlike people.

Almond trees are at times beset with genetic setbacks such as nonproductive syndrome, bitter almond syndrome, or rootstock incompatibility. However, most commercially grown almond trees are geared for production with few definitive genetic setbacks. Rather, as in man, degrees of expression and lack of expression of genetic potential are influenced largely by environmental conditions, soil and water quality and cultural practices.

Like chronic fatigue syndrome in humans, noninfectious bud failure (NIBF)—also known as ‘crazy top’—of almond trees is not a definitive genetic disorder. Rather, both maladies are a symptom of deficiencies in physiological efficiency as related to disruption of constructive energy dynamics. In humans, fatigue is often borne of stress superimposed on poor diet and lack of rest. In almond trees NIBF is borne of minimized carbon and energy harvest from heat waves superimposed on trees with suboptimal irrigation and/or imbalanced nutrition. That is, just as there are no guarantees for man to go without fatigue, so there are no guarantees for almonds to go without NIBF.

Unfortunately, many tend to unfairly shift the entire blame on nurseries when in fact the lion’s share of responsibility belongs to growers and PCAs.

Cause and Origin of NIBF

Certain varieties of almonds such as Carmel, Price, Merced and Jordanolo are more prone to expressing NIBF. Other varieties such as Padre, Butte, Fritz and Mission are less prone to NIBF expression. The main differences between these two groups are differences in physiological efficiency as related to energy-carbon harvest and utilization.

All almond varieties, as are over 98% of all agronomically grown crops, fall into a physiological classification called “Carbon-3” (C-3). Characteristic to C-3 plants is a tendency to reduce or shut down photosynthesis during heat waves or temperature shifts exceeding 12-15 degrees Fahrenheit from one day’s high to the next. This photosynthesis reduction or shutdown in C-3 plants is referred to as ‘photorespiration.’ During photorespiration, while photosynthesis is reduced, energy-carbon utilizing reactions, called ‘respiration’ are accelerated.

Thus, during heat waves, photorespiration creates an energy drain and energy deficit. In many cases this photorespiration physiological shock is so severe that despite cooler weather, tree will continue photorespiration for extended periods. But, in spite of photosynthesis shutdown via photorespiration, the tree continues to exercise its ultimate goals for perpetuation by continuing to size and mature the crop. Thus, what little energy and carbon remains is funneled towards the crop, and additional tissues, including leaf and flower buds, must get leftovers.

With minimal energy and carbon remaining, new buds are formed with lower tissue integrity and are thus hyper-sensitized to the elements. If heat waves continue, these weakly formed buds will be inactivated with relative ease. Weakened buds that get past the summer heat must still contend with winter freezes, which can also easily deactivate the buds. Hot spring or summer weather, coupled with cold, freezing winters are conditions conducive to NIBF expression as well as various other maladies, including bacterial canker. Furthermore, a reason why NIBF shows up in almonds and not peaches has a lot to do with the disproportionate energy-carbon demands of an almond crop (with considerable oil production) versus a crop that is kept reasonably balanced in energy loads via thinning.

Prevention and Management of NIBF

Stress free irrigation and balanced nutrition can increase the tolerance or resistance to photorespiration and thus, NIBF. This is akin to a well-trained Olympic athlete’s increased resilience in physically taxing situations. Tissues of higher density and integrity in plants are more tolerant of heat and/or cold inactivation.

Stronger tissues and membranes are also associated with enzymes with enhanced resilience to heat and/or cold inactivation. That is, when one deals with a heat or cold inactivation phenomenon, this points to denaturation of the enzymes. It is a well-known phenomenon that healthier plants have more perfectly formed, efficient and stable enzymes.

Physiological efficiency and higher tissue integrity distinguish healthy plants from unhealthy plants more prone to NIBF. Many are under the mistaken notion that by virtue of appearance, their trees are healthy. But fine tuning of tree health requires characterization of multiple factors and field-specific programs by a trained professional. There is no magic bullet, and keeping trees from NIBF and recovering trees in NIBF will require work and matriculation. You can’t win the Indy 500 in the first mile.