Mid-March Update (Noon, Tue, 3/15/16)
Dear Agents, Agronomists and Growers,
I had an opportunity to visit a strawberry patch near Raleigh yesterday, and just wanted to share a few comments in this advisory about that visit, as well as quickly mention how this warmer weather impacting this crop’s ripening schedule.
Yesterday, I saw Camarosa plugs with over one dozen open blooms on a farm near Wilson (Fig. 1).
Fig. 1. The growing degree day unit accumulation from Jan. 1st to March 14th (base 50 F) at a weather station near this farm is now approaching 200 hours! Hard to believe, but back on 3/7 (a week ago) it was only 75 GDDs. That’s right we picked up 125 GDD units in one week. On some Camarosa plants I counted 14 open blossoms yesterday! Most growers think about seeing berries in about 30 days from the open bloom stage! Potentially, these open blooms could be berries ready to pick by mid-April. We are hopeful to have a full crop this season, even after Camarosa plants sent out so many blossoms in late Dec and early Jan. One concern I have with the plants I saw yesterday was the concentration of so many buds that have recently emerged from the crowns.
1. Nitrogen – Strawberry plants need a substantial and steady supply of N during the growing season. Start weekly applications of N as soon as spring growth begins, often around March 1 (or around 45 days from the first planned harvest). This date may be earlier in the southern and eastern parts of North Carolina and later in the western parts. Apply 5.25 lb N/acre/week the first time you inject (0.75 lb N/day), and for the remainder of the season, the weekly N application should depend on tissue testing results.
2. Tissue testing – Plant tissue samples for strawberries consist of (1) the most recently mature trifoliate leaf (MRML) and (2) the associated detached petiole. MRMLs are fully expanded and consist of one petiole (leaf stalk) with three leaflets. They are usually located three to five leaves back from the growing point.
Fig. 4. The web address: www.ncagr.gov/agonomi, and here is the whole chapter on Fertility Mgt: SP_Chapt8 Fertility Management
3. From your tissue sample test, you will be advised about N feeding schedule to follow, as well as other nutrients that may be in “short supply.” This first report is essential to getting a handler on micronutrients like boron. Here is some useful information about boron sources and how much to inject. For example, just 1/2 lb Solubor (20.5%) supplies 1/8th lb (0.125 lb boron)/acre. NEVER exceed 1/8th lb boron!
1 lb borax (11% B) will provide 0.125 lb B/A.
0.5 lb Solubor (20.5% B) will provide 0.125 lb B/A
4. You can still do “field sanitation” – even at this late stage!
The main problem with waiting until new leaf growth has begun for doing field sanitation, or clean-up, is that you lost the best opportunity to do this operation when the plants are still dormant, and different kinds of “brushing” techniques can be used during the late weeks of dormancy without harming the plants. Now, the plants are very succulent, and any new leaves that are “brushed” will be injured. You can still so some beneficial cleaning up now, but it will require hand removal of dead flowers and the older winter leaves. I would still recommend doing this to minimize Botrytis pressure, especially if you are getting back Profile reports (from Clemson) reporting widespread resistance issues, and you are being limited to just a few products, like captan and thiram. It is important to follow your report’s recommendations on chemical spray options! If you are limited in chemical controls, the suggestion of doing some last minute clean-up could really pay-off in a wet season with heavy gray mold pressure during bloom and harvest.
Fig. 5. Dead flower parts on Camarosa. Some Camarosa plants sent out as many as 20-30 blooms before New Year in response to over 150 GGD units that occurred on this same farm from Dec 16-Dec 31, 2015. This is an unprecedented situation where we got more than enough GGD units (base 50) in the 2nd half of December. Normally, we accumulate fewer than 10 GDD units in this period.
Fig. 6. The dead leaves and winter-killed flowers from Dec/early Jan are providing all kinds of botrytis inoculum to infect newly opened blossoms. In the last 2 days in Raleigh area, we have had near ideal conditions for botrytis infection.
When it comes to the pollination process, the worst thing you can do is leave a row cover ON during bloom – the covers interfere with wind movement.
Early season Chandler blooms are generally not the best in structure, and stamens (male part) are frequently recessed, or even missing on some flowers. Further, the stigmas (tips of the female flower part) are receptive before the anthers on the same flower, thus there can be real benefit from cross pollination by honey-bees.
Two active honey-bee hives per acre can really help with fruit shape and berry size.
6. Frost risk in coming week?
Right now, those of you getting SkyBit can see that on both Sunday and Monday mornings next week we could be seeing some frost problems, and the crop will likely be in very heavy bloom at that time in many areas of the state of NC.
NC Min Temp Maps for Sunday and Monday:
Check your city/town for FROST risk over next 10 days, and take appropriate measures to frost protect, if needed.