PERFORMANCE OF PLUG STRAWBERRY PLANTS ESTABLISHED FROM UNROOTED RUNNERS

Two types of plants are currently used by French strawberry growers, fresh runners and cold-stored plants. French production of certified strawberry plants amounts to 13 x 10⁶ fresh runner plants and 120 x 10⁶ cold-stored plants in 1991.

The planting date of runner plants for spring cropping extends from early August to mid-September. Fresh runners give earlier production and higher fruit quality (larger size and fewer malformed fruits) compared with cold-stored plants. However, yield is lower and plant establishment is more difficult with fresh runners. Earlier planting might be worth considering to improve yield, but available planting stock is often scarce by August.

The planting date of cold-stored plants extends from mid-June in most northern areas to mid-August in the south. Extension of the storage period increases the risks of storage problems and of poor establishment at planting.

While the sanitary quality of French certified plants has been generally acknowledged, it is dependent on a large use of soil disinfectants (mainly methyl bromide). A possible cancellation of methyl bromine may jeopardize the quality of our plants.

Thus, the production of plug plants (Poling and Parker, 1990; Stallen, 1992) should answer the following objectives:

• Plants free from root diseases,
• Easier establishment at planting compared with fresh runners,
• Production higher than fresh runners and, as far as possible, similar to cold-stored plants,
• Plants available earlier (e.g., July),
• Fruit quality similar to that of fresh runner plants.