Sept. 13, 2012

In this advisory

Introduction

A. Questions from growers on plugging (storage of tips, misting, and fertility)

B. Irrigation schedules for plug planting and bare-root plants

C. What is my goal at say 3 weeks after planting?

D. Scouting of plug beds should be very high priority right now – send suspicious plug samples to Plant Disease and Insect Clinic

E. Fungicide usage during plugging is very limited

F. Erosion control with annual ryegrass

G. Final points on when to plant annual ryegrass, and Ridomil Gold application timing

 Introduction – We are enjoying some excellent weather this week across the Mid-South. I spoke to one farmer in Franklin County yesterday morning after he came in from being on the tractor pulling beds (and, also fixing beds that had washed in recent rains), and he simply described the day as “scrumptious.”  It truly did feel like a classic California weather day — dry air, mid-70s, nice breezes.

Cool temperatures this week – temperatures have been so cool this week that I have even noticed a real “slowing down” in the muscadine crop’s ripening rate! Harvesting muscadines from our NCSU research trials is what I do on my days off during the week! And, what a slow down we have seen in the muscadine harvest over the last 2 weeks! One really good thing about the cooler temperatures is how well fields are able to “hold moisture” before pulling beds and fumigating. In most years when it is quite warm/hot in early September, we are actually having to set-up solid set sprinklers to irrigate the field with about 1/2 inch the day prior to bed making to “get the soil right” on our sandy loam soil at Clayton Central Crops (by the way, we will not be fumigating until next Monday, 9/17; thus, it will not be safe for us to transplant until Oct 8 (21 day plant back). This is pretty close to the “edge” as far as planting dates for Chandler at Clayton, and it is frankly about 5 days late for Camarosa and about one week late for Sweet Charlie. It would be better to set Camarosa no later than Oct 3 at this location, and Sweet Charlie should be set at end of September.

Too much rain in August and early Sept. Many strawberry farmers in ENC have been quite frustrated by all the rains in recent weeks, and a newspaper article appeared in one paper last week about this! http://www.wect.com/story/19477519/wet-weather-threatens-strawberry-crops-in-pender

Overall plant quality is excellent! I have been speaking with different plug propagators this week, and I am hearing very good comments about plug plant quality and health. In the bad old days (e.g. 2003), we were already in a full blown industry crisis by this time in September with anthracnose issues. Last year we had some challenges with P. cactorum in early September, but I am not aware of any problem on that front this season. One propagator who does about 2 million plugs told me he had one box of tips (about 1,000) out of 2 million that did not “take off” (he called them blind tips). It would be naive to say that we can ever relax when it comes to plant health issues, but overall I am very pleased and impressed with how well things are shaping up with this year’s crop of plug transplants.

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A. Questions from growers on plugging

Question 1: I am in Eastern NC and I just received my tips today (9/11), and I was wondering how long can I hold the tips? I won’t have any labor to stick tips until this Saturday (9/15).

Answer: My experience with tips that are coming down from PEI or Nova Scotia is that they have a very good shelf life. If you are able to hold them in a cooler at say 35 F, then you should have no problem with holding these tips until this weekend. You can pretty much count on having a good week of excellent shelf-life if the tips are kept cooled and are in plastic liner. Another pointer is to get you labor there early in the morning! Try not to stick tips in the warm part of the day.

Question 2: What is a good misting schedule?

Answer: One large propagator I know simply runs the mist every 3 minutes for 30 seconds for the first 3 days. I know of another propagator who insists on running the mist constantly the first day if it is hot. Below you will find a “recipe” that I have been following for plug misting under NC conditions in late summer for a number of years. I would like to say that if it is quite hot on the first day of rooting (Day 1), I am willing to go with running 20 seconds of mist every 1 1/2 minutes. You have to use your judgment! Your goal is to keep the leaves moist until the tips start to create their own roots. Hot, sunny days will require extra mist, while cooler, cloudy days less mist.

Day 1: 20 seconds every 2 ½ min. from as soon as you start rooting in the early morning, and then keep running the mist until about 6:00 to 6:30 p.m. If temperatures are mild you may find that a 3 minute cycle with 10-15 seconds is adequate the first day

Day 2: plugs should be standing up and turgid in the morning (not flopped over), and if the day is warm, I would continue with the more intensive misting cycle (20 seconds every 2 ½ min) for the 2^nd day, from around 8 a.m. until about 6:00 to 6:30 p.m. (DAY 2 and 3 are ultra critical, and you must have someone be responsible for monitoring the system very closey).

Day 3: if warm/hot, stay with 20 seconds every 2 ½ min from 8 a.m. until 6:00 to 6:30 p.m.

Days 4-5: I tend to be more conservative than some “pluggers” and I am inclined to go with 10-15 seconds every 5 minutes. This may result in too much misting? You do not want to saturate the soil media with water (you will know this if the trays are “heavy” to lift up). The idea is to make sure the leaves always have some droplets of water. Some propagators will go to a 10 seconds every 10 minutes for days 4-5.

Day 6-7: By the the 6th day you should be seeing some new rooting in the plug cell. At this stage you may be able to go with misting from 9 a.m. to 6 p.m. for 10 seconds every 15 minutes. On day 6 the first watering of the day should be long enough to completely wet the soil.

The misting schedule after the first week must really be determined on the basis of how well the plugs are rooting up until this point and weather conditions. In other words, the right misting schedule will vary depending on conditions. Some propagators have found success on days 8-10 by misting from 9 a.m. to around 6 p.m. for 15 seconds every 30 minutes, and then they lengthen the interval each day. The actual misting period may stay at 15 seconds, but on days 11-13, you can consider misting from 10 a.m. to 3 p.m. each hour. By day 14 the plugs should have an excellent root system, and from this point on, the practice is to sprinkle for 5 minutes at 1 p.m., and then again in the late afternoon if temperatures are high.

Question 3. What about fertility of plugs?

Answer 3. There is not very extensive literature on the subject of strawberry plug propagation, and there is definitely very little information on plug fertility (while in plug tray). Though it would be nice to have more “research-based” guidelines on  fertility strategies for strawberry plug plants, the fact remains that a great deal more research is needed! In reference to the fertility information below, I am very indebted to David Dycus, NCDA Regional Agronomist, for the work he has done to gather information on the different approaches that growers are taking to plug fertility. David surveyed several farmers on their plug fertility practices and here is what he learned about one farmer who was spraying his plugs with an 18-18-18 fertilizer:

• The grower mixes 4 lbs of 18-18-18 and 3 lbs. of Epsom salts in 100 gallons of water and sprays on the plants directly. These 100 gallons covers about 4/10^th of an acre. Thus, on an acre basis, the farmer is applying 250 gallons of water. If you use the standard formula for calculating ppm (below), it is apparent that this grower is using about 345 ppm. If the farmer would drop back to 2.25 lbs. this would be around 200 ppm – that is all that is needed for good plant growth
• If you are dissolving fertilizer in a bulk tank or sprayer and then applying directly from that tank the formula you would use is: ppm = % fertilizer x lbs. added to tank x 16 x .75 x 100/gallons of tank or sprayer (for spraying one acre)
• Thus, 18 (%) x 3 (lbs) x 16 x .75 x 100/250 = 345 ppm
• Recommendation:  drop down to 2.25 lbs to reduce this rate to 200 ppm (1.125 lbs = 100 ppm)

Why might it be important for this grower to do is to reduce his fertility down to 200 ppm, or perhaps even lower? Dr. Louws gives us the main clue in his article (that appears in this newsletter):  “Avoid excess fertility and misting. Excess moisture and fertility favor disease.”  In another article that recently appeared in another article on  plug recommendations it was pointed out that:

“Do not fertilize just planted tips. The fertilizer charge in most potting media will be sufficient until the plants are well-rooted. Fertilize for the first time at two weeks after planting using 100 ppm of nitrogen with calcium nitrate as the source, and repeat at weekly intervals. If you are holding the plants for longer than 4-5 weeks (thus creating super plants), switch to 20-20-20 at 100 ppm of nitrogen for later applications.”

Thus, an argument is being made here to go with only 1.125 lb  of the 18-18-18 fertilizer, or about 100 ppm. We do not have any guidelines to provide on fertilizer source at this time, and for many years I have been saying that a greenhouse grade 20-20-20 would be ok to use, but this article from PA is saying that calcium nitrate is a better source in the 3^rd and 4^th week. I have taken the view that it may be better to apply the fertilizer in the morning, than the evening, so that the plugs are not too wet going into the night.

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B. Irrigation schedules for plug planting and bare-root plants?

The best advice is to simply download this document from the SRSFC website and review it on irrigation of plug transplants as well as fresh dug bare-root plants: 

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C. What is my goal at say 3 weeks after planting?

Plants should have three or more fully green leaves remaining at the end of the initial three- to four-week establishment period, regardless of whether they are fresh dugs or plugs. If the “original” leaves on a fresh dug or plug are lost to drought stress, plant establishment will be significantly delayed or “set back” and spring yields will be significantly reduced. The number of leaves and total plant leaf area in the late fall/early winter can be correlated with fruit production the following spring.

Runners that develop in the fall can be removed to prevent competition with branch crown formation and overall growth of the main plant that was transplanted in September/October. Runners that develop in the fall can be removed to prevent competition with crown formation and floral bud development.

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D. Scouting of plug beds – send suspicious plug samples to Plant Disease and Insect Clinic

Large commercial plug propagators in our region routinely scout their plug trays for signs of any problem. In fact the day they receive an order of tips (usually from Canada), they immediately inspect the tips for grade (they need to be in the range of 3-5″ tips), and freedom from disease, insects, and mites. The load is rejected by the propagator if they are not satisfactory. In the course of rooting the tips, it is routine practice to cull out any tips that appear to be infected with botrytis, or showing unusual symptoms. Once the plug trays are set out in the open on the plugging pad, they are routinely inspected by the workers for any unusual symptoms. Plugs showing any unusual symptoms should be submitted to the NCSU Plant Disease and Insect Clinic asap. If you are not experienced in plug propagation it is not uncommon to run into problems with foliar burn on the edges of the leaves due to inadequate misting in the early days of rooting, or perhaps an environmental stress like high winds (especially on the edges of the plug pad). It is always a good idea to “get things checked out” before you go spraying any chemical! Here is the address of the NCSU Plant Disease and Insect Clinic for out-of-state growers:

Plant Disease and Insect Clinic

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E. Fungicide usage during plugging is very limited (this information is adapted from an article that appeared in the August 2012 NCSA strawberry newsletter by Dr. Frank Louws, “Disease Management Considerations for Producing Strawberry Plug Plants.”

“Use of fungicides is can be difficult to sort out. Some production facilities produce plug plants successfully without fungicide applications. Others find fungicide use provides benefits in plant quality. Still others receive recommendations that are not legal or will not be effective against the main diseases of concern. According to the EPA Registration Division, if a label bears general directions for use on a crop without restrictions, such as, “for outdoor use only”, “for field use only”, or “not for use in greenhouses”, the EPA Registration Division would most likely determine that the use of that product in a greenhouse on the specified crop would NOT be consistent with the label. It appears plugs produced outdoors would be exempt. Captan should not be used during the early rooting phase since it inhibits rooting. In our field trials where Captan was drenched (i.e. not sprayed on foliage) over plug trays just prior to field setting, plants remained stunted all year.”

“Limited research is available so these recommendations are based on research results in plug production facilities but appear to be consistent with the label and experience. For fungicide rates, take the per acre rate, add this to 100 gallons and spray for adequate (not over soaking) coverage. Thus, if you need 10 gallons of water to cover the area, use 1/10 the per Acre rate on the label.

Phytophthora/Pythium: Keep Sweet Charlie plugs separate from others. This variety seems to be very susceptible. Growers may consider using a phosphite-based product (e.g. Prophyt, Aliette, Phostrol etc) 2-3 weeks after setting. Complement this with field application of Ridomil Gold in fields with a history of Phytophthora. (see our recommendations). Do not mix copper with Aliette or plant damage may result. ProPhyt is compatible with copper but damage could result if the product is too concentrated in the application volume. For example, the Prophyt label specifies use “2-4 pints/acre”. The ProPhyt concentration should be at or less than 0.5% of the total volume of liquid sprayed (4 pt/100 gal of spray solution). We have done work with Prophyt dips with good success prior to plugging (2 pt/100 gal rate). However, this can present high risk for spreading bacterial leaf spot (Xanthomonas). Therefore it is better to add this product as a foliar spray after setting and within 7 days. Ridomil Gold and related generic products are not registered for use as a dip nor for producing transplants. Ridomil Gold/generic use may cause plant stunting if too concentrated.

Botrytis: We highly recommend against the use of Switch or Elevate in the plug facility. This would encourage the selection of fungicide resistant Botrytis populations resulting in poor gray mold control in the spring. If you decide you must apply these products they should not be used more than once each e.g. Week 2 = Switch; week 3 = CaptEvate; week 4 = Captan.

Anthracnose: USE certified plants or plants from a reputable source. The Captan sprays for botrytis will suppress anthracnose. Outdoor plugs appear to get less disease than greenhouse plugs. Quadris, Cabrio and Pristine labels state “Do not use for disease control in food crops grown in greenhouses” or “Not for greenhouse or transplant production”. If used on transplants, resistance may develop rapidly and then the strawberry industry will have a serious problem. If hot spots develop, cull these spots and surrounding trays. If the disease is widespread, seek an alternative source of plants. Initiate spring fungicide programs in problem fields (these have worked very well). Make sure plants are sent to a diagnostic clinic for a positive diagnosis.

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F. Annual ryegrass – I just received this comment from Powell Smith, Clemson, late yesterday about the use of annual ryegrass for erosion control in strawberry bed middles. I sent him a note earlier in the day about a meeting I attended this summer where a few growers were indicating problems with not being able to kill back resistant annual regress in late winter. Here is what Powell has to say:

“We have looked at one ‘resistance’ instance that I did not think it was resistance. Wayne Mitchem, Weed Specialist, agreed; it was actually improper application technique. If the grower does not let the ryegrass seed out, he can’t be selecting for resistant populations. Most growers wait too long to apply, do not use the graminicides properly (leave out the crop oil, etc, use too low of a rate, don’t reapply), and other management failures. Unless a weed scientist tells me that the grass is resistant, I would lean toward poor application practices rather than chemical failure. Ryegrass or some cover in the middle is essential to avoid erosion. It also improves the quality of the crop.”

J. Powell Smith, PhD, Extension Associate – Small Fruits and Vegetables
Lexington, SC  29072
Off:  803-359-8515, FAX:  803-359-4245, Mob:  803-603-2618
jpsmth@clemson.edu

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G. Final points

 > Plant ryegrass before you punch holes for plants. The recommended seeding rate for ryegrass broadcast for strawberry plasticulture production is only 25 lbs. You are only covering half of the area with seed, so this rate would be equivalent to 50 lbs per acre.) Heavier seeding rates will result in very thick and luxuriant stand that often have to be sprayed twice to get it to lay down.

> If growers cannot set up their drip irrigation system prior to or right after planting, then Ridomil can be incorporated into the beds when beds are being formed.

> Ridomil Gold acts against Phytophthora inside the plant and not in the soil. The focus of Ridomil application should be on supplying a sufficient reservoir of fungicide to the plants so that the fungicide can be taken up as early as possible after planting and so that this uptake can continue for as long as possible.

I’m off to harvesting grapes again tomorrow, but will be able to get questions, comments on the road with my handy Verizon hotspot!

Have a great afternoon!

Barclay

p.s. in the next issue I will be going into much more depth on correct planting techniques for plugs, bare-roots and cut-offs

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—

Dr. E. Barclay Poling, Professor Emeritus/Extension Strawberry Specialist
919-418-9687 (Cell)
919-515-2505 (Fax)
barclay_poling@ncsu.edu
//strawberries.ces.ncsu.edu/author/strawberries/