Pistachio Fruit Physiological Disorders

A Lecture To ToT trainees ( FFS)

By Mr. Allah Dad Khan

Provincial Coordinator IPM KPK

MINFAL Pakistan

Physiological Disorders of Stonefruit

Symptoms Physiological disorders are problems that are not caused by

insects or diseases, but rather by the climate (temperature, rain, humidity) and by management practices that change the micro-climate endured by the plant. Among these practices would be training and pruning, irrigation, fertilization and harvest procedures. In addition to these factors, in many cases, certain varieties are more predisposed to a specific disorder than others. The most common physiological disorders seen on stone fruit in Texas are split and shattered pits, double fruit and cleft sutures, fruit buttons, blind wood and delayed foliation. This article will describe these disorders, explain their causes if known and suggest the possible management strategies to minimize them.

Split and Shattered Pits:

Symptoms When one thinks about split and shattered pits, it is the early ripening

peach varieties such as 'June Gold' and 'Springold' that come to mind. The reason early ripening cultivars are more susceptible to this disorder is that the pit hardening and final swell phases of fruit development occur relatively close together in time. Pit hardening begins about 40 days after full bloom. During this phase, the pit gradually loses flexibility and becomes very rigid while the flesh of the fruit is still tightly adhering to the pit. On early ripening varieties, final swell occurs before the adherence between the pit and the flesh has weakened. Consequently, the expansion of the fruit flesh creates internal forces pulling out on the pit. If great enough, this force will cause the pit to break in the weakest spot which is along the suture. In later ripening cultivars, these two events (pit hardening and final swell) are further apart which allows a weakening of the adherence between the pit and the surrounding flesh cells

Double Fruit/Cleft Sutures:

Symptoms

Double or twin fruit is frequently seen in Texas orchards. In many cases, the extent of the problem is minor and these fruit can be easily eliminated during hand thinning. But in some orchards and on some cultivars, the problem can be of major importance. Whether a fruit will be double or not is determined the summer previous to fruiting when the flower buds are going through their initial development

Buttons:

Buttons are fruit that, although they initially set, do not develop into full-sized fruit. These fruit generally have poorly developed or dead embryos as a result of incomplete fertilization. This can be due to insufficient chilling received, a frost during bloom, or wet, cool weather during bloom. These fruit are hard to identify at thinning time and may cause a grower to thin too heavily. Also, they provide a place for pests and diseases to survive and overwinter in a low fruit year.

Blind Wood:

Symptoms

Blind wood is characterized by no vegetative or flower bud development in the nodes of the plant (blind nodes). Blind nodes become obvious the following year when the one-year old shoots fail to develop leaves or fruit. Trees with blind wood are difficult to train and prune, and have lower yields. A recent study of this problem in the low and medium chill regions of Texas indicated with the development of blind nodes is related to the temperatures during summer months, especially when the high temperatures are consistently in the 85-90° F range or higher

Delayed Foliation:

Symptoms Since 1985, There have been three low-chill years in the

medium-chill region of Texas. One of the most noticeable effects is the delayed foliation of fruit trees in the spring. Normally, trees develop new growth uniformly throughout the canopy soon aster the terminal buds break. Trees with delayed foliation develop a tuft of leaves at the terminal tips but the other vegetative buds break sporadically, if at all, over a prolonged period. Often vigorous sprouts emerge from the base of crotches and the trunk. Delayed foliation results in a tree with poor leaf cover and reduced fruit set. Management of the tree is complicated by excessive water sprouts and root sprouts resulting from the poor leaf cover. The only way to minimize delayed foliation is to carefully select varieties well adapted to your area.

Fruit freezing injury

Symptoms

Freezing injury will appear as glassy, "water soaked" or translucent areas in the flesh. With time these injured areas will dry leaving open "gas pockets" in the flesh. The freeze injured tissue of most fruits will begin to brown as a result of enzymatic oxidation of phenols released by the injured tissue.  When freezing occurs at the fruit surface, the glossy or browning symptoms may be visible without cutting.

Internal browning, chilling injury, dry fruit, mealiness, woolliness

Symptoms

Flesh browning, flesh mealiness, black pit cavity, flesh translucency, red pigment accumulation (bleeding), and low flavor