Plum Pocket: The inedible alien fruit

Submitted Photo

Recently, someone called asking why “my plums are swelled up and empty?” As our conversation continued, I decided I needed to take a look at this alien fruit being described to me. At the homeowner’s yard, I was shocked at the size and color of the fruit on the tree. Some of the plums were the size of pingpong balls, light green in color, soft, and empty. I have never encountered anything like this before.

My research led me to Plum Pocket. Plum Pocket is caused by a fungus called, Taphrina communis. This unusual disease causes unripe plums to be deformed and grow abnormally large within a month or two of blooming.

Not to worry though, most of the dessert plums grown in North Dakota are unlikely to be affected by Plum Pocket. Typically, wild plums and American-type plums are more commonly infected.

Plum Pocket can be identified by small blisters on the developing fruit, which quickly grow and cover the entire fruit. Infected fruit may grow10 times its normal size and have a spongy texture. The fruit becomes light green in color and covered with velvety, gray fungal spores. The fruit eventually will dry out, becoming mummified, brown-black in color, and will have an empty center. Infected fruit usually falls to the ground, but some can remain on the tree over winter. The fungus may also cause leaves of the plum tree to thicken and curl, but is not common.

Plum Pocket does not affect the health of the tree and no management of the disease is necessary. It can be reduced however, by removing infected plums before they are covered with spores. Infected fruit should be disposed of by burying or being placed in the garbage. Do not leave infected fruit under the tree.

If Plum Pocket has destroyed most fruit for several years in a row, fungicide can be applied before bloom time for disease management. Use a fungicide that is a Bordeaux mixture (copper-sulfate), liquid lime sulfur, or Chlorothalonil. If fungicides are to be used, the name of the plant being treated MUST BE LISTED on the label or the product cannot be used. Some products are only registered for use on ornamental Prunus species and are not safe for use on stone fruits that will be eaten. Always read and follow all instructions on the fungicide label. Take care to wait the complete ‘post-harvest interval’ (PHI) stated on the label, as well. The PHI is the number of days you must wait to harvest after applying a fungicide. This time period is necessary as it allows the fungicide residue to break down to a safe level.

CAUTION: Mention of a pesticide or use of a pesticide label is for educational purposes only. Always read and follow the pesticide label directions attached to the pesticide product container you are using. Remember, the label is the law.

You are now probably wondering if plums from an affected tree are safe to eat. Personally, I would not eat or use fruit from a tree that is greatly affected (over 40%) by the disease. If the tree has a just a few fruits affected by Plum Pocket, the unaffected fruit is safe to eat. Use your discretion when choosing to consume fruit found on an affected tree.

Be Safe and Happy Gardening!


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