Time to renovate strawberries

Developing a strong stand early with fertilization and irrigation while managing weeds and insects insures a strong start on next year’s strawberry crop.

Strawberry beds to be carried over for another harvest season need to be renovated. Deciding whether to renovate or remove a bed differs with every grower’s circumstances, such as market demand, land availability and production costs. As strawberry fields age, yields and berry size decline while weeds and diseases problems increase. Growers with high market demand, but limited available acreage, will retain beds longer. The decision requires knowledge of your production costs and net returns over the preceding seasons. If you decide to renovate, start after harvest as soon as possible. The earlier runner-plants develop, the higher they yield the following year, so delaying renovation will reduce yields next year. Keep in mind that renovated beds need abundant water in July and August to ensure good growth this year and good returns next year.

Strawberry field
Effective strawberry renovation ensures a healthy productive field in the fall.

In renovating matted-row strawberries, the fields are mowed and the rows narrowed. Fertilizers and herbicides are applied and the fields are irrigated to develop a strong stand for next year’s crop.

Mow off the leaves just above crown height if the plants are healthy. Mowing may not be desired if the plants are stressed by drought or root diseases because weak plants have difficulty developing new leaves. Also, do not mow the leaves if renovation is delayed for more than a few weeks after the end of harvest.

Renovation and mowing
Mowing is often the initial step in renovation.

Narrow the rows to 8 to 10 inches by cultivating with a rototiller or disk. Rototillers with tines removed above the row work very well because they toss some soil on top of remaining plants, encouraging additional rooting. More than an inch of soil may smother the plants.
Some growers have success narrowing rows by treating the row middles with directed or shielded sprays of Gramoxone (paraquat). Gramoxone is a contact weed killer that is not mobile in plants, so it only kills treated tissues. This effectively narrows the plant row and does not expose new weed seeds by disturbing the soil. One problem with this approach is that it does not provide a loosely tilled soil for the rooting of runner plants. It also does not throw soil back over crowns.

Herbicides. Renovation is also a useful time to treat broadleaf weeds with amine forms of 2,4-D, such as Amine or Formula 40. Strawberry plants tolerate 2,4-D after harvest because they are not actively growing. If broadleaf weeds are a serious problem, apply 2,4-D a few days before mowing. This herbicide must be absorbed by the weed leaves to be effective, so don’t mow off the weed leaves before applying 2,4-D.

Sinbar can also be applied at renovation for preemergent weed control. Apply 3-6 oz. of Sinbar 80W per acre, using the lowest rates on sandy ground or weaker plant stands. Mow plants and narrow the rows first, so the Sinbar is applied uniformly to the soil. Irrigate to rinse the herbicide off the plants and into the soil. Michigan has a Section 18 label for the preemergent herbicide Spartan. Spartan is effective on common groundsel, field pansy, mayweed, white campion (white cockle) and pigweeds. Apply 4 to 8 oz. Spartan 4F per acre after plants have been mowed.

Fertilizing. Another step in renovation is to fertilize the planting to encourage new growth and runnering. On heavier loamy soils, apply enough fertilizer to supply 50 lb. N per acre. On sandy soils, apply 30 to 40 lb. N at renovation and again in early August.

Irrigating. Do not neglect watering the field at renovation and during the remainder of the summer. Plants need water to grow and all your other efforts are wasted if the renovated plants do not get off to an early strong start. Runner-plants that develop during July and August need adequate moisture to root and maintain a healthy leaf canopy to store food reserves for next year’s crop. The amount of water available to strawberries is the product of the water holding capacity and the rooting depth, usually considered 8 to 12 inches (Table 1). Irrigate when about half of the available water has been used. During hot weather, this means strawberries may need irrigation every two to three days (sandy soils) to every four to five days (heavier soils).

Table 1. Available water in a strawberry root zone as affected by soil texture.


Soil texture

Available water In root zone (inches)

Per inch of depth

 (8-12 inch depth)

Loamy sand

0.07

0.6 – 0.8

Sandy loam

0.13

1.0 – 1.6

Loam

0.17

1.4 – 2.0

Silt and clay loams

0.18

1.5 – 2.2


 



















Pest control.
Normal care should be taken to protect the new growth from leaf diseases. Renovation also allows the treatment of some root diseases such as red stele. Growers should be prepared to control potato leafhoppers. This insect causes hopper burn on the leaves and stunts strawberry growth.

Potato leafhoppers burn
Potato leafhoppers burn on strawberry leaves. Healthy leaf on the left and affected leaf in
the center. Note the yellowing at the margin of the leaf and the yellow streaks spreading
out to the leaf edge marking the sites of feeding where the insect injected a toxin into the
plant.

Dr. Hanson’s work is funded in part by MSU’s AgBioResearch.