Back to Dr. Bates Home Page

To the Lake Erie Regional Grape Program Home Page

Floret Development Observations, Terry Bates, (from the 6/11/02 Crop Update)
6/10/02

Kevin Powell brought in some flower clusters on Monday that appeared to be having some developmental problems. Other growers have been commenting on ‘black-tipped’ florets. After closer examination under the dissecting scope, there appears to be two different things going on with the calyptra (or cap). The calyptra is made up of greenish petals that are united at the tip. At ‘cap fall’ the petals typically detach at the base and fall off, exposing the pistil and stamen.

The black tips on the florets we observed are probably phomopsis infections to one or more of the petals near the tip of the floret. The infection caused a localized necrosis of the petal tissue and in some cases has caused the infected petal to detach from the other petals, exposing the internal flower parts. Upon further dissection, the surrounding tissue, the neighboring petals, and the internal flower parts, appear to be developing normally.

In the second situation, all of the petals appear underdeveloped at the tip of the floret where the petals attach to each other. The petals look like that are caving in on the rest of the flower and the internal flower parts are exposed. Dr. Martin Goffinet sent me some pictures of clusters he collected in 1996 that show this situation. Under the dissecting scope, there is a degree to this underdevelopment. Some florets are stunted or falling apart and will not set fruit. In other florets, the anthers (where the pollen comes from) and the pistil appear somewhat small or stunted but are otherwise normal and are probably capable of still setting fruit. The cause of this underdevelopment is not known and it has not been associated with years of poor set or fruit set malady.

Bloom is quickly approaching and many of you may be looking at floret development. It is just as important to look at the number of healthy florets as it is to look at the number of unhealthy ones. Under normal fruit set conditions, only about 30% of the florets will set fruit. Therefore, if you see clusters with 100 healthy florets and 10 underdeveloped ones, you should still expect 25 to 30 berries on those clusters under normal fruit set conditions.