Strawberry Plasticulture - September 18, 2002 Vol. 3 No. 56
In this issue:
-1. General update & greetings from Orlando!
-2. Backpack calibration for Quadris + Captan spraying of Plug Plants
-3. Plant-back periods - YOU MUST ADHERE TO FUMIGANT LABEL
-1. General update: Greetings from hot and humid Orlando! I am participating in an IR-4 Food Use Workshop in which pest control needs of minor crop growers (including strawberries) are assessed for research in 2003. There are a number of exciting new products and chemistries under discussion. For example, Dr. David Monks, Weed Scientist, NC State, was involved yesterday in discussions about a new herbicide that could provide nutsedge control in strawberries. Research with this product will be undertaken by David at Clayton Central Crops as well as on 1 or more farms to assess its pest control performance. In another year, he and other weed scientists from the US and Canada will meet to share the results of their studies, and then set research priorities after an open dialogue about this product. If it receives a Priority A, all efforts will be made to submit results of research to EPA within 30 months of the experimental start date. Today, Dr. Ken Sorensen is here with his colleagues in Entomology from other Universities, including Dan Horton, UGA and Donn Johnson, U of Arkasnas, going through some very interesting products that may help us out in our efforts to better manage 2-spotted spider mites. Tomorrow, the program focus shifts to the Disease Management workgroup.
Anthracnse. Speaking of Disease Management, there are 2 September Advisories now up on Berry Agent that focus on anthracnose management issues in plug plants:
http://intra.ces.ncsu.edu/depts/hort/berrydoc/sept14/index.htm
http://intra.ces.ncsu.edu/depts/hort/berrydoc/sept16/index.htm
Please continue to send any suspicious looking plugs to the clinic
for positive diagnosis.
If a grower has a hotspot in the greenhouse (go to sept 16 advisory on
web to see some of these photos), contact your local Cooperative Extension
Agent and send samples to the Plant Disease and Insect Clinic according
to the clinic instructions (http://www.ces.ncsu.edu/depts/ent/clinic/Submit/submit.htm).
Once it arrives
there, Dr. Louws will diagnose the samples (do not send samples directly
to Frank)
Weather: I have heard that most growers "beat the rainy weather" and have successfully fumigated before the rains from Tropical Depression Hanna. Here is an email from VA Beach:
We feel fortunate to have finished bedding with good moisture on 9/7/02. Much of the time since then has been too wet. I know at least one local grower hasn't bedded yet; others were "late."
We're on track for planting about 9/25 or 26." Tom & Anne Baker, Brookdale Farm
Clayton. We are also "late" in getting our fumigation
done at Clayton, but we are hoping to get it done this Friday (Sept 20)?
Just before I flew out for the meeting here, I took the shot in Figure
1 which shows are very wet beds and lots more clouds threatening to further
delay fumigation and planting! We like to plant at Clayton by October
3-5, that may not happen if more rains head our way before Friday - the
first day we may "possibly" be able to fumigate this week!
Fig.1. "Copious rains" over last weekend continued into Monday (Sept. 16), and this field could possibly be ready by Friday Sept 20, provided no more rains come our way. On Thursday (Sept 19) we are going to take a light tractor with some sweeps to open up the furrows (at the surface) and try to accelerate drying of the aisles in this way - this is the wettest area (beds are fine).
Fig. 2. The "story" behind these poor looking plugs goes back to some shipping injury (partially chilled in transit). The cold injury is actually identical to what we see after a freeze in late winter - note the "blackish" bands that somewhat "glossy" bands that are evident in two leaf blades in the front center of this photo. Botrytis appears to be "at work" in the yellowing and brownish tissues also seen in this photo - Sept. 13, Lee Co.)
-2. Backpack calibration
In applying Quadris + Captan to small areas (greenhouse, outdoor pad with plug trays) it is very important to: 1) follow label instructions on safety and product use rates (which are commonly given on per acre basis); 2) know the square footage requiring treatment (the areas for plug tray rooting are only a fraction of an acre - for example, a 20 ft x 220 ft greenhouse floor area = 4,400 square feet is approximately 1/10th acre; and 3) calibrate your backpack before making any chemical application. It will just take a few minutes of your time to calibrate your backpack sprayer, and by following these steps you will apply Quadris and captan at the proper rates to be effective and economical. Using more chemical than needed is wasteful and may violate the labeled rates; not using enough results in ineffective control and wasted expense for materials and labor.
No. 1 - Area Requiring Treatment. Make a careful measurement of the area that needs coverage - do this right now. And, then make a note of the square footage. A grower I saw on Monday had a 20 ft x 220 ft greenhouse = 4400 sq ft.
No. 2 - Calibration of your backpack sprayer.
Determine how much area you actually cover with 1 gallon of "clear
water." Alternatively, you can also fill the sprayer up, and determine
the total area covered by a full sprayer. Its just a little easier to
stop at 1 gallon, and measure the area covered. Remember, no chemical
at this point. Some growers will cover more area with a gallon of water,
and other less. It is a function of walking speed and sprayer pressure.
This application is not a drench, and a normal walking pace is recommended.
Example: You may have use 1 gallon to spray an area of plug trays that
is 20 ft wide x 30 ft in length, so multiply 20 x 25 = 500 square feet/gallon.
For your information, this is equivalent to an application of 87 gallons
per acre (1 gal/500 sq ft).
No. 3 - Calculate amount of product needed for your area of
coverage
In this step we simply take the per acre product rates and "adjust
them" in proportion to the area needing coverage.
Per Acre Rates (based on this amount of product treating 43,560
sq ft):
Quadris - 12.4 oz
Captan - 4 lb (64 oz)
Amount of product for your coverage area:
a) Coverage area: 4400 sq ft (20 x 220 ft greenhouse)
b) Divide your coverage area by the number of square feet in an acre:
4,400 sq ft divided by 43,560 = 0.10101 (use this factor below)
c) Calculate exact amounts of product:
Quadris: 12.4 oz (per acre rate) x 0.10101 = 1.25 oz
Captan 50 W: 64 oz x 0.10101 = 6.46 oz (~ 6 ½ oz)
This means that for an area of 4400 sq ft, you need to apply 1.25 oz of Quadris +6 ½ oz captan. The next step is important to make sure you don't over or under-apply these amounts of product for 4400 sq ft.
No. 4 - Divide your total square footage by the square footage to spray 1 gallon
Square footage for treatment: 4400
Square footage covered by 1 gallon from backpack: 500
Divide: 4400/600 = 8.8 gallons of spray will be needed to cover
4400 sq ft
No. 5 - Mixing and applying
Your backpack may hold 3 gallons, and to apply 8.8 gallons of solution,
you will need to fill your backpack three times to cover 4400 sq ft. You
can next make up a stock tank of solution in which you measure out 8.8
gallons of water, and then mix in the correct amounts of Quadris and captan
(1.25 oz. Quadris + 6.5 oz captan). It is probably best to make this solution
up fresh each time you spray instead of making larger quantities for future
applications. Use proper safety equipment and care in handling and pouring
these chemical solutions. Under circumstances of high anthracnose pressure,
it may be necessary to treat plug trays a second time in 7 days.
Table 1 is based on a 12.4 oz/A rate for Quadris, and shows in Column 1 the actual area to be treated (sq ft); Column 2 is the amount of Quadris that needs to be applied to the area in Col. 1 (e.g. if you have 2000 sq ft, then 0.57 oz Quadris should be applied to this area); Columns 3, 4 and 5 indicate total gallonage needed to cover the area shown in Column 1, based on whether you are using a backpack that is applying 1 gallon of water to 600 sq ft (COL 3), 500 sq ft (COL 4), or 400 sq ft (COL 5). You will also note the per acre amounts (gallons) associated with these three columns (600 sq ft/gal = 72.6 gal/A; 500 sq ft/gal = 87.12 gal/A; and 400 sq ft/gal = 108 gal/A. I include thislast bit of information because growers may wish to know this relationship between their backpack spraying and field spraying.
Table 1. Quadris rates based on 12.4 oz/A
Table 2 (below) has similar information for Captan 50 W. It is recommended that Quadris should be tank mixed with Captan for greatest effectiveness against anthrannose.
Table 2. Captan 50W rates based on 4 lb (64 oz)/A
Table 3. Elevate 50 WDG rates based on 1.5 lb (24 oz)/A
-3. . Plant-back periods - YOU MUST ADHERE TO FUMIGANT LABEL
Remember that methyl bromide + chloropicrin (67% + 33%) requires a 2 week
waiting period to allow the fumigant to dissipate from the soil. Transplanting
in less than 2 weeks can be ruinous to your crop! I just learned of a
grower who set after 9 days (not 14) and it is possible he will see phytotoxicity!
Have a good weekend!
E. Barclay Poling
Professor and Extension Specialist (Strawberries)
NC Cooperative Extension Service
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