Plum POSTHARVEST DISORDERS

•Corky Spot •Inking or Skin Burning •Double and Lack of Red Color •Split Pit •Internal Breakdown •Freezing Damage •Ammonium Damage

Plum Corking

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.

OBSERVATIONS

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 (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 nutrientsprays within 15 days of harvest, and following suggested pre-harvest fungicide spray interval guidelineswill reduce inking.

Inking

Effect The Temperature

WATER STRESS

FORCED AIR COOLING

Cold storage injury and chilling

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.

EXCESS NITROGEN

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

SPLIT PIT

INTERNAL BREAKDOWN

Flesh browning

Lack of flavor

Failure to ripen

WHITE FLESH SKIN BURNING DISCOLORATION

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.

Tips to Prevent Skin Burning Disorder

Can we reduce physical damage during harvesting and hauling?

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AMMONIA DAMAGE