Gordon Johnson, Extension Vegetable & Fruit Specialist; email@example.com
The 2023 strawberry season is still going strong, and we have had a good season due largely to the cool, dry weather. As we look to later June, with annual strawberry production on plastic mulch, many growers may consider carrying the beds over for a second year’s harvest. These are some guidelines for renovation of plasticulture strawberries:
1) Evaluate disease pressure. If the planting had significant anthracnose, botrytis crown rot, phytophthora, or identified viruses do not carry over the planting. In future variety selection, if carry over is desired, choose varieties with high disease resistance, particularly to anthracnose. For example, Sweet Charlie and Flavorfest have anthracnose resistance and can be carried over whereas Chandler does not and should not be carried over. Camino Real is intermediate in anthracnose susceptibility and may be carried over if anthracnose was well controlled.
2) Evaluate plastic mulch and drip lines. Do not carry over beds with deteriorated mulch or plugged drip systems.
3) If relatively disease free, mow the tops with a rotary mower (in smaller plantings this can be done with a line trimmer or with hand clippers). You want to leave some leaves. Do not damage the crown.
4) After mowing, remove any runners that are left by hand. Make any plastic mulch repairs and drip system repairs as necessary. Treat and flush drip lines as necessary.
5) Remove all dead plant material around the crowns. This can be done by hand or with a leaf blower. A fungicide treatment at this time might be warranted.
6) Evaluate crown thickness (number of crown plants). If over 4, crowns must be thinned out. This can be done by breaking off part of the crown by hand or by using an asparagus knife to cut away part of the crown. Leave a minimum of 2-3 crown plants.
7) Apply additional herbicides to row middles using a shielded sprayer to control weeds during the summer months. Hand weed holes during the summer if weeds emerge.
8) Maintain plant health by controlling diseases, insects, and mites throughout the summer months and irrigate regularly. A small amount of nitrogen fertilizer (20 lbs. N per acre) can be applied at this time if needed to maintain plant health. Take leaf tissue samples to evaluate plant nutritional status.
9) In late August or early September, apply 60-60-60 (N, P2O5, K2O) through the drip system.
10) Replant any holes with missing plants by the middle of September.
Research has shown that with proper renovation and care, second year yields will be higher than the first year, but berry size will be smaller.
Renovating Day Neutral Plantings
Fall planted day neutral (repeat blooming) varieties such as Albion, Seascape, or San Andreas will often stop blooming in the heat of the summer. To extend bloom period, manage irrigation so plants have enough water (do not drop lower than 60 % of field capacity) in the hot period and apply 5-7 lbs. of nitrogen per acre every week and add other nutrients as indicated by tissue testing. Remove any runners that form. If crowns are crowded, thin as described above.
If production has ceased in day neutral fields (flowering often stops in mid-July), then renovate as described above but fertilize to stimulate new growth in early August to fruit again in the fall.
Carry over production of day neutral varieties to the next spring can be problematic because of the susceptibility of most varieties, such as ‘Albion’, to anthracnose. The variety ‘Sweet Ann’ may have more anthracnose resistance than other day neutral varieties.
Anthracnose is a major limiting factor in carry over of plasticulture strawberries.