Physiological disorder of plum Dr. Nihad AL Smairat BY :Walaa AL Zyood
Plum POSTHARVEST DISORDERS •Corky Spot •Inking or Skin Burning •Double and Lack of Red Color •Split Pit •Internal Breakdown •Freezing Damage •Ammonium Damage
OBSERVATIONS Most importantly, in seasons in which March and April temperatures are significantly cooler than normal. Check cultivars and avoid stimulating excessive vigor. Of the options that are commonly available to growers, reduction of nitrogen and summer pruning offers the greatest potential for reducing corking expression in orchards. Trees should be summer pruned sometime in May or early June by significantly reducing the number of total growing points.
Heavy summer pruning ~ 60 days BH reduced corking. right). Summer pruning reduces the competition between growing shoots and developing fruits, allowing resource(s) to be diverted to fruit Detailed view of heavy summer pruning showing removal of many shoot growth points
Inking Inking (black staining) is a cosmetic problem affecting only the skin. This disorder is characterized by black/brown spots or stripes. These symptoms appear generally 24 to 48 h after harvest. Inking occurs as a result of abrasion damage, in combination with heavy metal (iron, copper and aluminum) contamination. This occurs usually during harvesting and hauling operations, although it may occur another steps during postharvest handling. Gentle handling of fruit, short hauling, avoiding foliar nutrient sprays within 15 days of harvest, and following suggested pre-harvest fungicide spray interval guidelines will reduce inking.
EXCESS NITROGEN Excess nitrogen fertilization (3.0%) did not increase fruit yield or improve fruit quality. •Reduce red color formation. •Increase shoots, flowers and fruit brown rot susceptibility. •Increase OFM & PTB damage. •Increase weight loss. •In plum, leaf N levels between 2.8 and 3.0% were sufficient for optimum crop production.
SPLIT PIT • plum with split pit are flattened at end of the fruit. Often symptoms are not seen until the fruit is cut open. The pit is torn apart or split along the dorsal-ventral suture. • •Plum split pit is caused by cultural practices that promote rapid growth such as excessive thinning , temperature changes, or irregular watering during the pit hardening stage. • •Avoid thinning until after pits are mature and hard
INTERNAL BREAKDOWN Flesh browning Lack of flavor Failure to ripen
Tips to Prevent Skin Burning Disorder Based on our current work, it looks like the skin burning disorder is triggered by the combination of physical damage during harvesting-hauling combined with ‘postharvest stresses’. -Reduce physical damage during harvesting-postharvest handling. - Control your pH during washing-brushing. - Use room cooling (R.C.) rather than forced air cooling (F.A.C). - Reduce fruit water losses during harvesting-postharvest handling.