STRAWBERRY RENOVATION

Editors Note: Many new members have joined WBGA since this article was printed in 1997. It is a wonderful reminder and review for "old time growers" and much needed information for new growers. Thus the decision to reprint this excellent synopsis of renovation duties.

Strawberry renovation is probably one of the most complex cultural practices in commercial production. Many factors will enter into the decision to renovate. The only reason to renovate in the first place is that it is considered a less expensive operation than preparing a field and setting out new plants. Yield will almost always be lower in a renovated field than on a first- year bearing field and pests will also be a greater problem. If a large amount of perennial weeds are present or disease and insect control have been difficult, the planting should not be retained for another fruiting year. A field should also have at least 70% stand to justify renovation. A careful analysis of the costs and benefits therefore should be undertaken.

Once the decision has been made to renovate, the process should begin immediately after harvest. This reason becomes clear if we remember the guidelines for establishment year strawberry plantings. New plants are set as early as possible because the earlier a new runner roots, the heavier the yields will be the following spring. A daughter plant then, optimally should have at least 8 weeks for growth between "pegging down" and flower bud initiation which begins in early September.

Returning to our renovation discussion, this means that if renovation occurs around July 10-15, it is inherently too late to obtain optimum yields on new runner plants the next year. Obviously then, every day becomes critical in determining yield for next spring. The best practice is to renovate each field after harvest is complete. Early, mid-season and late cultivars; with the late cultivars being at the most disadvantaged for producing a heavy crop the next year. This scenario of at least 3 different renovation periods may be impractical due to the large amount of labor required just for the picking season, but it will give you the best yields!

Even though renovation is later than optimum for yields, there is a reduction of inoculum levels for disease and lower numbers of insects to contend with. On one-year and older plantings, the renovation procedure should also theoretically reduce winter injury and invigorate plants as compared to non-renovated plantings. As strawberry plants continue to grow, new roots are initiated from successively higher levels from the base of the crown as older lower roots die so, essentially every year, the crown grows progressively higher above soil level. During renovation, about 1" of soil is thrown over the crown - which reduces winter exposure and encourages desirable new root development on the old crowns.

The general steps in renovation are as follows:

1. Apply 2,4D (Formula 4D at 1-1.5 lb. active ingredient/acre) for broadleaf weed control problems such as dandelions. You must wait 5-7 days for this herbicide to be absorbed before proceeding to the next step.

2. If diseases are a problem, mow the leaves off as close to the ground as possible without causing crown damage. If renovation cannot be done immediately after harvest, leaves should not be mowed off. Row narrowing in later steps will incorporate most of the infected leaves. In the case of severe disease infestations and bacterial infections such as angular leafspot, attempt to remove as much of the residue after/during mowing as possible. If angular leafspot is a problem, it may be beneficial to apply a copper spray after renovation.

Growers in northern Wisconsin may opt not to mow, especially if they feel there is insufficient time for re-growth. In this case, the rows are just narrowed. Sinbar should theoretically not be applied in this case due to increased chances of injury - which only leaves Devinol. Some growers may try to apply herbicides like Sinbar if they can irrigate it off the leaves immediately after application. I do not endorse this procedure since I have no data or experience whether it works reliably to reduce injury. You can try it at your own risk. I only report the possibility, as it does make sense in some circumstances.

3. If your berries are growing in heavy clay soil, compacted areas should be broken up with sub-soiler shanks in between rows running parallel to the sows and set 14"-18" deep.

4. There are many options available for narrowing row width. Note that with most strawberry cultivars, the most production is from row widths of 12-15". Rows of this width should be narrowed by tilling to 8".

An 18" wide row may be rototilled on one side to 12" leaving the outer edge of the untilled side to grow over and fill in with new runner plants. Or, it can be treated according to the following discussion on traditional matted rows. If we assume a traditional 2-foot wide matted row, there are two possibilities.

a. Generally one should till out the oldest most crowded plants located in the middle 1-foot of the row leaving two 6" bands of younger plants on the outside edges to fill in towards the middle. Unfortunately, this method will require control of any new runners that tend to grow outwards from the outside edges. An additional mulch may help suppress this, but it is probably too costly. Continued tilling the rest of the summer is not really an option either. So, option "b" could be considered.

b. Narrow the wide matted row to 1', tilling both outside edges, leaving the older plants in the middle to fill out with runner plants to the original 2' width by the end of summer. This method is not as desirable from an optimum yield viewpoint, but is more practical. The older crowns left in this renovation option should definitely have at least 1" of soil thrown on top of them.

After narrowing the rows in most renovation procedures, the remaining plants should be thinned to about 6" apart. This can be accomplished by dragging a spike-tooth harrow or similar implement once or twice across rows and once down the row.

5. Fertilizers should be applied as needed. Generally, nitrogen will be the most important nutrient needed at this time and should be applied at 40 lbs. actual N/acre on heavier soils. Very sandy plantings may benefit from a split application, 20 lbs. each, 2-3 weeks apart.

6. Pre-emergent herbicide should be applied next. Sinbar is generally recommended since Devrinol tends to inhibit runner plant rooting. If spring applications of Sinbar were made, reduce the rate of Sinbar at renovation. Rates on sandy soils range between 2.0 and 6 oz. Sinbar/acre and on loam or clay, 6 oz/acre.

7. Irrigation is the last major step in the renovation procedure. Strawberries should receive at least 1.25" equivalent of rainfall per week to initiate vigorous growth and runnering.