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NC Strawberry Plasticulture - September 17, 2001 (4:45
pm) In this issue: --Misting schedule and adjustments (we're on DAY 12) General comments on weather and plug propagation - The weather outlook is for warmer temperatures this week after sunny days and cool nights this past weekend. Today, we are expecting a high of 79 at Clayton, and a low of 59 F tonight. Solar radiation will be higher today and Tuesday, and we are expecting partly sunny conditions each day from Wed - Sunday. Temperatures should be in the mid-upper 80's in the day, and high 50's, and low 60's at night. For growers raising strawberry plugs we advise careful monitoring of greenhouses on warm sunny days. Most all growers have started their plugs at this date. At Clayton, we are on DAY 11, and rooting has been excellent this year so far. I think the sunny weather and relatively cool nights have been just ideal. We have been making some changes along the way, and I wish to share several of the adjustments in this advisory. First, we started slightly differently this year, and went to misting every 7 ½ minutes for DAYS 1-5 (instead of 5 minutes). On DAYS 1-3 we misted from 8:30 am - 6:30 pm, and for DAYS 4 and 5 we reduced an hour of misting at both ends of the day (9:30 am - 5:30 pm). Last week, on Day 5 we were somewhat overcast and we "stretched our minutes" for misting to a cycle of every 15 minutes. Then, it became sunny again, and on DAY 6, we returned to the 7 ½ minute cycle (mist burst lasts about 7-10 seconds). But, we also reduced the total numbers of misting hours to 10 am - 5 pm (1 less hour). On DAY 7 we went to a 15 minute cycle - even though if was full sun, the plants were able to handle the 15 minute cycle quite nicely. Then on DAY 8 (Friday Sept. 14) we took 2 hours out of the middle of the day, and misted from 10-12, and 2-5pm. Again, using the every 15 minute cycle. Today, it was sunny most of the day for DAY 11, and we have been going with a cycle of every 30 minutes for 1 ½ minutes, 10-12 and 2-5 pm. We have excellent rooting at this point, and anticipate cutting the misting to only 5 minutes in the morning, and possibly the same number of minutes in the afternoon if it is hot on DAY 12 (tomorrow). Normally on DAYS 11-13, we mist for 10 seconds every 60 minutes from 9am until about 3 pm to encourage rooting and weaning plants on. On DAYS 14-28 we do 5 min of watering at 1 pm each day outside and more frequent if hot (minimal leaching of nutrient is achieved with this program). Some of the plugs look are well enough rooted in 11 days at Clayton this year that we could almost consider transplanting these later in the week! We would not do this, of course. But, we are about 3-4 days ahead of the propagation schedule last year. Our plugs do not require any fungicide for botrytis, but we are seeing some evidence of powdery mildew, and will apply a treatment of NOVA when we move plugs outside next Monday (DAY 18) onto the gravel pad (Nova is applied at 5 oz/acre - we will treat with approximately 1 tsp/3gallon Solo sprayer. In addition, we will possibly treat with Agri-mek if mites are identified - this application will be made before going to the field (much cheaper to apply Agri-mek on gravel pad than in the field). The Nova can be mixed with captan. Botrytis in strawberry plug houses: We had a close call in another state last week where a cold front passed through and kept conditions overcast for several days, and botrytis suddenly appeared and began to spread so rapidly that we thought we were possibly dealing with another disease. An application of Elevate was made this past Friday (Sept 14), and I gather in speaking to the grower this afternoon that the plants are making an excellent recovery. The recommendation for this product is 1 ½ lb, or 24 oz Elevate WDG/acre. Since this particular grower uses a 3 gallon Solo backpack sprayer to treat 50,000 plugs in a 3000 sq ft area, the calculation was as follows: 1) determine portion of an acre covered (3000/43540 = 0.0688); 2) the amount of product per acre is 24 oz x 0.0688 = 1.65 ounces/3 gallon backpak spray. As I said, the plants are recovering (the pictures below show how they looked on Friday). One point to keep in mind about this botrytis outbreak was the influence of having stuck tips from a box where the tips looked very poor and may have suffered injury in transit. Such tips must be discarded right at the outset. As an added sanitation step, my research technician has a practice of clipping off any suspicious looking leaves before sticking in the tray. Good sanitation and not over watering on overcast/cool conditions can do a lot to keep you out of a problem of this kind! Question: What if my plugs are recovering from a botrytis infection fairly well now after treatment with Elevate, and new leaves are emerging…don't I need to delay my overall transplant date? Reply: I would go through the house and determine if there is still a good quantity of tips that can be set on the original planned date. I think a delay of a week or 10 days is going to be costly in overall yields. So, I would let the plugs that were hurt by botrytis recover, and set those somewhat later. However, plugs that were unaffected need to go out as scheduled.
Ridomil use: If a field has had a previous history of P. cactorum , crown rot, then it is recommended that metalaxyl (Ridomil Gold) EC be injected through the drip system just BEFORE transplanting at one pint per treated acre (for drip application to strawberry plasticulture beds covering 50% of an acre this would amount to 1/2 pint per acre). A second fall season injection of Ridomil Gold may be needed about two weeks later. From our summer meeting in Goldsboro, Dr. Louws discussed a strategy for fresh dug plants - it would be well treat the nursery plants with Ridomil to get it systemic into the plant before shipping - perhaps the week prior. Have a good week! Barclay Poling p.s. This week I'll be up in the Western part of the state for
meetings and industry tour with the Grape Research and Extension workers
from the Southern Region - email will not be working most of the time.
Mobile: 919.418.9687 |
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