Grape pests

Asked August 25, 2017, 4:33 PM EDT

In late fall, I bury four non-bearing canes in heavy mulch and raise them to my trellis in the spring. This year they were loaded with tiny grapes and then disaster struck and they all disappeared. I saw no insects or mold on the clusters. Any idea what happened? The only grapes I got were on the oldest plant and then only a few at the bottom. The other plants are progeny. These Manistees have become my favorite for juice.

Hal Kantrud

Jamestown



Stutsman County North Dakota

5 Responses

Hal,

Do you know the cultivar name of your grape or do you think it's a native wild grape? If it's a native wild grape, I think I have an answer to your question. The native grape is Vitis riparia and this grape is dioecious, which means it has male and female plants. The flower looks very similar on these plants from a distance but if you were to look at the flowers very closely you would see that the male flowers have undeveloped stigmas and styles and erect filaments (signifying functional pollen), while the female flowers have well developed stigmas and styles and recurved filaments (signifying nonfunctional pollen). So similar to apples that require cross pollination, female wild grapes require pollen from a male wild grape for pollination to occur. If this doesn't happen, the tiny green fruit that initially form will drop, just like the apple that wasn't cross pollinated. If your grape is a released cultivar, the same thing could occur only if you have St. Pepin as this is a female grape cultivar. Besides St. Pepin, all other grape cultivars that I am aware of have complete flowers (well developed male and female organs in the same flower) and just need a little wind or insect for pollination. If you want to discuss this, please contact me at 701-799-7063.

As I said, my grape is a Manistee. I think the 'mother' plant is about 6 years old and my four other plants were propagated from her. I had very good luck with the technique of burying four non-bearing canes and covering with heavy mulch to overwinter. Sort of strange that the only plant to have grapes this year is the mother.


Hal

Hal,

It is possible that birds or animals may have harvested your fruit for you. Birds are the typical culprit and may pick the vines clean very quickly. Another potential suspect are raccoons. They are very opportunistic and like the berries as the sugar content goes up.

To protect against these thieves, you may want to invest in netting for next year.

I cannot say why the fruit disappeared from the vines that are the progeny and not the mother plant.

For more information on various animal, bird, and insect pests, please see our publication:

https://www.ag.ndsu.edu/publications/landing-pages/gardens-lawns-trees/growing-grapes-h-1761

Thanks Eshter,

Now that you mention it, I did see what I thought might have been a meadow jumping mouse near my vines last fall. Too pale to be a vole, but darker than a deer mouse. It was living under my mulch

I will try and put a metal barrier around one of my vines next spring to see what happens.

Some pics of my garden attached. You can see my grapes in background on last one.

Hal


Hal,

Protecting against rodents is a good idea. Beautiful photos of your garden. May you have a bountiful harvest this fall!