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NC Strawberry Plasticulture Advisory
Number
135
Area of Study
Agriculture
ID Vol. 1 No. 29
Publication Type
Technical
Category
Production
Contact Person
Barclay Poling
Position
Small Fruit Specialist
Author
E. Barclay Poling
email
email
Org Name
NCSU
Org URL
Organization Web Site
Phone Number
919.515.1195
Date of Publication
October 04, 2000
Article, Abstract, Press Release, etc.
(Best Viewed with 600 x 800 computer screen resolution.)
NC Strawberry Plasticulture Advisory October 4, 2000 Vol. 1 No. 29 ?Getting Ready to Plant? 1. General: Weather patterns have been excellent for transplanting this week in the lower piedmont/upper coastal plain areas of the state. Sunny days and relatively mild to slightly warm temperatures are just what the doctor ordered! In newly planted fields I have visited late last week (Sept. 27) and early this week, I am seeing some very healthy looking plugs, and most growers are taking full advantage of this weather to punch planting holes and plant! Understandably, there isn't much time for reading advisories! However, we are getting a lot of questions related to transplanting and related concerns with fall disease management. So, Frank Louws, Extension Plant Pathology, and I have developed this 10 point ? Getting Ready to Plant? advisory that includes many timely suggestions. 2. Fumigant waiting periods: Be mindful of the post- fumigation ?waiting periods? for safe planting: both Vapam and Telone have a manufacturer recommended 21 day waiting period before transplanting. You can do a dissipation test before planting (e.g. tomato transplants can be set in random areas across the fumigated plasticulture beds starting 14-21 days post treatment). With MITC gas from Vapam, for example, transplants will wilt and turn black within 48 hours if this gas is still present. As stated in the last advisory (Vol. 1 No. 28) the waiting period for MB:C 67:33 is 14 days (not 21). I have not heard of any MB:C 98:2 being available this year. This would be the ideal fumigant solution for anyone who has waited until this point in time to decide to go ahead with "planting some strawberries on plastic". At this late stage, a grower who has not fumigated needs to omit fumigation and go ahead with planting. Delaying the planting of Chandler beyond the recommended window for your region can lead to significant yield reductions. In Smithfield, NC, for example, I might chance planting Chandler as late as the third week of October, and then hope for a mild fall. Just further up the road in Clayton (where we'll be planting tomorrow - Oct 5), it is crucial for us to plant by no later than October 8 - 10 (but, we prefer the first week of October). 3. Scheduling by varieties, spacing and plant types: Growers are setting their Sweet Charlie and Camarosa first, followed by Chandler. I have noted a general trend for growers to go with a greater in-row spacing of 13, 14, or 15 inches in double rows on 5 ft center. Also, fresh dugs should always be set ahead of the plugs (for growers using both). As a final comment regarding plant quality, it appears to several of us that one of the main determinants influencing overall plant yield potential is the actual size, or diameter of the crown itself. A plug plant or fresh dug that has a "stocky" crown of 1/4 inch - 1/2 inch in diameter is going to perform considerably better than a more fragile looking, thin diameter fresh dug plant or plug. In Holland, large plug plants called "tray plants" will have crown diameters of as much as 1" in diameter! If you receive unusually small plugs this year, I would advise against the greater in-row spacings and go with the traditional 12- inch, or maybe even 11-inch spacing, if the plugs appear to be particularly small in crown size. 4. Punching holes for transplanting: I don?t recommend punching holes any further in advance than 2 days - the soil in the planting holes can easily dry out in warm weather like we're having today (upper 80's)! Ideally, you would cut planting holes the day you transplant. A good tool for setting fresh dugs was pioneered by a grower in Smithfield a few years back. The tool is made by bending a piece of 2 inch wide steel at a 90 degree angle such that there is a 4 inch handle and an 8 inch shaft. The base of the shaft is cut to aid in punching. Wrap the handle with cloth or duct tape. This tool is ideal for setting fresh dugs because it simply makes a slit through the black plastic. The idea is to keep as much of the black plastic intact as possible. Large holes will lead to weed competition soon after planting. 5. Inspect your plants upon arrival & fall season disease/mite concerns: This is common sense, but every year I am amazed to learn how often growers have simply unloaded their plant order without really inspecting the contents of any of the boxes (for fresh dugs) or trays (for plugs). On one farm visited late last week, I noted that a new planting of fresh dug Chandlers had a fair amount of leaf disease (mainly leaf scorch) and many of the petioles were broken. If all of the leaf petioles are damaged, the plant will fail. In speaking with Dr. Louws today, it does NOT appear to be such a big issue if plants come in with some leaf scorch. Apparently, there is no research information that shows a benefit from applying fungicides to plants with leaf scorch - they seem to grow out of this disorder. With some plug trays I have noticed evidence of powdery mildew (PM) on the foliage. Nova has recently been registered and will offer good powdery mildew control in fields where there is a real concern. However, in North Carolina, powdery mildew on the plants in the fall has not consistently translated into powdery mildew problems in the spring. Since PM in the fall is usually insufficient to cause yield concerns, Dr. Louws would recommend it is best to observe spring growth for PM and initiate Nova applications in the spring based on a scouting program. Likewise, he has advised that most growers will not need to include Ridomil Gold EC applications in the fall for Phytophthora crown rot control. Growers with a history of the problem or growers who suspect problems with their plants can add Ridomil Gold at 1/2 pint per acre soon after transplanting, subsequent applications can be made based on field observations and weather patterns. We occasionally do find spider mites on plugs in the early fall. These mites can be present on the plug material coming in from the nursery - inspect the undersides of the foliage with a magnifying glass or 10x hand lens. If you don't own one of these lens, get one! In warmer dry falls and early winters, strawberry spider mite can become a real problem in new fields. 6. Fall disease management program (by disease): Dr. Louws wishes to convey that there is normally "no need for any fungicide applications at this time of year right on through mid-November." Here are the exceptions: (a) powdery mildew pressure is high - consider an application of Nova fungicide. (b) crown rot (Phytophthora cactorum) - if a field has had a previous history of crown rot, then it is recommended that metalaxyl (Ridomil Gold) EC be injected through the drip system just after 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). Plugs have been found to be carriers of this pathogen (P. cactorum), and the problem traces back to a water supply that is contaminated. A second fall season injection of Ridomil Gold may be needed (about two weeks later). A final drip injection can be made in late winter (timed with new root development). (c) botrytis - in mid-November, and again in early December, applications of captan with Topsin-M, or captan with Benlate can be made (timed with new leaf emergence). Only the two sprays are recommended (two weeks apart). It is possible to substitute Nova for Topsin-M or Benlate, in the captan tank mix. At this stage in the fall, no control for botrytis is needed (or recommended). (d) botrytis crown rot - in a situation two years ago we experienced heavy plant growth in a warm fall growing season and then had heavy rains in January. In such cases, it can be valuable to consider an application of Rovral in just this situation (it cannot be applied in the bloom period). As Dr. Louws indicated in an advisory last Feb. 23, 2000: ?It is now illegal to use Rovral after first fruiting flower...and, it can only be used for one application per season (for a mid-winter spray where botrytis crown rot may be a problem)." 8. What do I do with my plugs after they arrive? (a) Inspect (as stated in No. 5): Carefully examine your plugs for any sign of obvious problems (especially mites and powdery mildew). (b) Holding recommendations: You can safely hold plugs in the trays for a week or more if necessary. Keep them watered once a day at this time of year while still in the trays. And, be sure to keep them in the open sun for best acclimation for field transplanting. I had a call from Kentucky where the grower was unsure about the importance of having good exposure to the sun to help plugs acclimate for field transplanting (he was holding them in a shaded area!!). Do not refrigerate plugs!! Again, schedule planting of your fresh dugs before the plugs. It is fine to fertilize the plug trays before setting in the field. I like to drench the trays with 1 lb 20-20-20 per 100 gallons each week (in weeks 3 and 4) before transplanting (this supplies roughly 240 ppm N). (c) Rootball condition: While the plugs are still in the tray, you need to carefully inspect their root development. Last evening at Clayton (10/3) I noticed that our rootballs were not as full as I would like especially in the upper 1/3rd of the plug rootball (and, these were rooted 9/7/00!). I think that we have experienced poorer rooting this year because of a lot of rain and overcast weather during September AND because we are following a standard schedule of misting that is actually keeping the rooting media ? too wet? for overcast periods (this reduces rooting). So, if the rootball is still somewhat crumbly (not fully occupied by roots), then you have a decision to make. You can still plant the plugs, but EXTRA care is needed to handle these more fragile plants in field transplanting operations this week. A water wheel planter can make a real mess of setting plugs that are not fully rooted. With the excellent weather we?re having I would still go ahead and ?get them out? and plant them in the field, but use extra care in handling and setting them! These more fragile kinds of plugs need EXTRA careful watering this week and next. These kinds of plugs are candidates for very slow development in the field this fall if they are not carefully watered. Other quality factors I look at in plugs (we've already mentioned the fullness of the rootball, crown diameter, freedom from diseases and mites) are: ** Number of intact leaves - 2 trifoliate leaves are needed. The leaves should not be trimmed, or cut off. ** The petioles must not be injured. Height of oldest trifoliate (nutrition, watering and cultural practices) should be tailored to produce a plug that does not have the older trifoliate extending more than 8 inch height from the base of the small crown (I would strongly prefer 5-6 inches). (d) Calculating the number of good plug plants before transplanting: Often, it is not a bad idea to do a little trouble-shooting a day or two before you transplant plugs and you should try to estimate the number of "good" plugs you will have from each tray. At one time, when the plug propagation industry was in its infancy, we had losses of as much as 10-20% of the plugs in a 50 cell tray (5-10 plants). Today, plug propagators are hitting nearly 100% in terms of usability of each plug in the tray. You can tell what kind of situation you are going to be in at planting time by simply pulling plugs out of the tray, especially toward the middle area. All of the soil media should come out with the plug plant - if the rootball is poorly developed, the plantlet will separate from the media - this is not suitable for transplanting. You need to locate replacement plants if you are finding that even 5% of the plugs appear to be unusable this for planting this week, or next. Also, when you are going through your plugs, be sure to pull out and discard any plants that appear to be infected with botrytis or are showing unusual symptoms. It is a good idea to not brush your hand over the entire tray in evaluating the health and quality of plug trays (do it visually as much as possible). It is my understanding that fresh dug plants are still available (for Chandler mainly), so if you are going to fall short on plug numbers, be sure to consider the potential of setting some fresh dugs to fill out your fumigated plastic beds. (e) One day before transplanting - reduce/eliminate tray watering: The plug media should be allowed to dry sufficiently for field transplanting. If plugs are too moist, transplanting operations will be more difficult. 9. What do I do with my "fresh dugs? after they arrive? (a) Inspect (as stated in No. 5): Carefully examine your fresh dugs for any sign of obvious problems (especially mites, leaf diseases and excess temperature problems). Plants in a nursery box or crate are packed tightly enough to make them prone to what is called a ?heat?. You will ?smell them? instantly if they have gone through such a heat in transit to your farm. These plants are unfit for field transplanting and must be rejected. (b) Holding recommendations: freshly dug plants may be stored in a cold room at 40 F for one to two days before setting. Storing them for a longer period can make them more difficult to establish. (c) In hot weather: it may be necessary to run water through the crates to keep the plants cool. (d) Root trimming: some root pruning may be necessary to shorten roots to 5 to 6 inches before transplanting. This is frequently done as the plants are pulled in bundles of 25 from the box or crate. We? ve used grape type pruners to do this as well as a hatchet and block - be careful! 10. Transplanting equipment, labor and irrigation: Plugs - fewer workers are needed for transplanting plugs and crew of only 5 workers can mechanically transplant about one acre per day (17,400 plugs) utilizing a two-row plug-transplanting device called a water wheel. A well-engineered waterwheel-planting device can consistently plant each plug so that the midpoint of the crown is level with the soil surface. Recommended ?Best Practice Program? for watering-in with overhead irrigation (1/10th inch/hr):Plugs: 5 hrs first day, 3 hrs second, 2 hrs third day. Fresh dugs - we generally try to have on hand at least 10-12 workers for transplanting one acre of freshly dug strawberries (it works out to about 40 hours of actual labor per acre). The idea is to plant about ¼ to 1/3 rd of an acre and then get the overhead running on that section. Warm and windy days (possibly like today) make it desirable to start within 30 - 45 minutes of setting plants in each ¼ to 1/3 acre section. Once you start running water, keep pumping until sundown the first day. Normally growers are advised to turn on each morning at the same time (usually 9 am), but you can observe the plants for the first sign of moderate wilting and turn on then. We have conservatively recommended: 9am-5 pm for 7 to 12 days. This is really a recommendation based on a very hot, dry Florida type weather pattern. Instead, use your judgment! Typically, it is important to plan on at least 5 days of overhead watering. Start the irrigation each morning when the plants show the first signs of wilting and continue to irrigate (1/10th inch per hour) until the hot part of the day has passed. After several days, irrigation can be initiated later in the morning and can be discontinued earlier in the afternoon. The purpose of this type of irrigation is to prevent foliage loss until the root system can get established again. With fresh-dug plants, inexperienced planting crews will frequently fail to set the plants at the correct depth. Set the plants so that the midpoint of the crown is level with the soil surface. If planted too shallow, the root system is exposed (visually). If set too deep, the crown ? growing point? is covered and the plants may rot. The roots must not be ?j-rooted? when set in the hole. Nearly 100% of the plug transplants will survive transplanting. But, with fresh-dugs it is necessary to replace a significant number of weak or dead plants that do not survive the transplanting process keep some plants in the cooler for replanting. An even better idea is to have some extra plugs on hand for re- planting. Try to replant as soon as possible. Have a good planting week! E. Barclay Poling, Small Fruit Specialist Campus Box 7609 Kilgore Hall - Office 252 NC State University Raleigh, North Carolina 27695-7609 919.515.1195 919.515.2505 (fax) barclay_poling@ncsu.edu
