[nafex] Apricot Protection

Dan Nave nave1 at comcast.net
Thu Mar 22 23:15:55 EDT 2012

In the NAFEX Apricot Interest Group newsletters, Bob Purvis has written about a product that has the 
ability to give some protection to apricot blossoms and immature fruit. I have taken the liberty of 
excerpting some of this for the group.  See below.


NAFEX APRICOT INTEREST GROUP** November 10, 2005   Newsletter #8

Agro-K products show promise in frost control.*Agro-K is a Minneapolis-based corporation that 
manufactures a number of different foliar and soil nutrient products for use by fruit and vegetable 
growers.Agro-K had a growers' meeting in March 2005 which I found valuable in terms of acquiring 
information useful to my orchard.There were a number of both conventional and organic fruit and 
vegetable growers present who have been using their products.Given the difficulty that apricot 
growers face with late frosts, I was pleased to find that they have one product that has shown value 
in protecting blossoms from frost:KDL (abbreviation for Potassium (chemical symbol is K) 
Dextro-Lac), makeup is 0-0-24.Agro-K potassium products are derived from potassium carbonate and in 
one case, from potassium sulfate.The manufacturing process combines potassium with sugars (dextrose, 
lactose) and other carbohydrate molecules to make a product that is quickly absorbed, readily 
available, and easily utilized by the plant.The brochure also states that "KDL contains a unique 
activating component designed to enhance the mobilization of potassium within the plant."

The brochure describing KDL's effects on frost protection states the following:

"_How can KDL help protect or minimize frost damage?_

"During spring, as plants begin to grow new green tissue, the demand for nitrogen is at its 
greatest.At this stage the nitrogen to potassium ratio favors nitrogen.During the fall, as fruit 
ripens and plants begin to "harden off" and prepare for winter, the demand for potassium is at its 
greatest.At this stage, the potassium to nitrogen ratio favors potassium.

"In the spring, when soil is still wet and cold, roots may not operate as efficiently as during the 
summer.In addition to climatic conditions, soil type, pH, etc. can also affect uptake of 
nutrients.These factors, combined with the natural increased demand for nitrogen, may predispose the 
plant to low or deficient levels of potassium.Potassium is an important element in cell wall 
turgor.Having tender new tissue growth with a high nitrogen to potassium ratio creates 
susceptibility for frost damage.

"Applying KDL immediately before an expected frost can help increase potassium and sugar levels 
within the plant and temporarily put the plant into a more 'winterized' or hardened mode, where its 
tissue is better able to survive cold temperatures without damage.In general, KDL provides 
approximately 5 degrees Fahrenheit of production.If KDL is applied prior to a frost and temperatures 
dip below 27F, some damage may occur."

"_When to apply KDL_

"KDL should be applied within 36 hours before a frost is expected.The recommended rate is 1 
gallon/acre.If frosts are expected to occur on two or more successive nights and daytime 
temperatures are expected to remain low (below 55F), KDL does not need to be reapplied.However, if a 
frost is followed by two or more days of good weather (daytime temperatures 65F or greater), the 
plant will metabolize the potassium quickly.If a second frost is predicted after two or more days of 
good weather, for maximum protection, KDL should be re-applied at 1 gal/acre."

The rate for application with backpack sprayers is 4 oz/gallon, and the recommended amount of water 
to use per acre with 1 gallon of KDL is 30-50 gallons.The cost of a gallon of KDL is $17.25 plus 
shipping f.o.b. Minneapolis.KDL is also recommended for application to apricots 4 weeks and 2 weeks 
before harvest to raise the sugar content of the fruit.

NAFEX APRICOT INTEREST GROUP REPORTJanuary 16, 2012   Newsletter #14

*KDL update.*I've used potassium dextrose-lactose (KDL), a foliar spray product produced by Agro-K 
Corp. in Minneapolis, for seven years, both in MN and here in ID.I learned more in 2011 about best 
use of this product, valuable in protecting apricot blossoms and fruitlets during frost events in 
the spring and helpful in improving sugar content when applied 4 and 2 weeks before harvest.

The current price of KDL is $22/gallon, plus UPS shipping charges from Minneapolis to your 
location.Chapman Mayo, one of the principals at Agro-K, said to use absolutely no more than 3 
oz/gallon, and 2 to 2.5 oz/gallon water may be even better.KDL causes phytotoxicity on young leaves 
and blossoms primarily if it is applied to the point of run-off, where this alkaline product sits 
and dries on the leaf tips.As in past years, I followed the policy of adding household vinegar 1:1 
to KDL before mixing the two with water.My two sprays of KDL (the first was on apricots at full 
bloom, April 8, 2011; the second at petal-fall, April 22) were both at a rate of 3 oz/gallon of 
water with 3 oz vinegar/gallon of water to neutralize its alkalinity.There was absolutely no damage 
at these rates to the blossoms or new leaves on my apricots.

Use of 4 oz/gallon on foliage and fruits in late June, however, resulted in marking of fruits on 
apricot and especially pear, and significant and rapid damage to pear foliage.If you spray with KDL 
apply it as a mist, or the finest droplets your sprayer can produce.Potassium is very mobile in 
leaves, according to Chapman.AIG member Barry Todd (Littleton, CO), who also grows ultra-large 
pumpkins competitively, said that KDL is used extensively by pumpkin growers also to help size their 

On 3/22/2012 1:08 PM, Jay Cutts wrote:
 > It seems like that far north apricots would be real long shot. Here in
 > NM they rarely set fruit because of late frosts. Maybe once in 7 years.
 > Of course further north your spring might not be as warm as ours.
 > I've never figured out a practical method for protecting tree flowers
 > from late frost. I once set my temperature alarm so that if the
 > temperature was going to go below freezing (usually 5:30 or 6 am) it
 > would wake me up. My plan was to spray water on the trees. But when I
 > got out there, the hose was already frozen solid!!
 > Regards,
 > Jay
 > Jay Cutts
 > Director, Cutts Graduate Reviews
 > Lead Author, Barron's Test Prep Publications
 > (505)-281-0684
 > 10 am to 10 pm Mt Time, 7 days
 > On 3/22/2012 11:54 AM, Caren Kirk wrote:
 >>    Following Steve's e-mail about early pruning due to excessively warm
 >> weather I am starting to freak out about the apricot I planted last
 >> spring. Being that it's the first winter here and then with this yo-yo
 >> temperatures, does anyone have any suggestions on how to protect the
 >> blossoms. I'm a long way from that right now, the buds haven't even
 >> begun to swell yet but it won't be long with this warm weather and I
 >> like to be prepared!
 >> Any advice appreciated.
 >> Caren Kirk
 >> St. Jerome, QC

More information about the nafex mailing list