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Spraying Fail... Lesson learned

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Bobp

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Earlier this year we had a sudden explosion of a nasty little fruit fly called the spotted wing drosophila. SWD....

I had already been following the recommended treatment program. Or so I thought...

I received a call from my harvest superintendent, also known as, my wife, saying that there was an explosive amount, and we were seeing a heavier than normal amount of softs/bad berries...

When I got home from work, I assessed the situation, set up the sprayer, and once the yard light came on i hit the half of the feild with the next product in my rotation. Thinking that this would get em licked, I went to bed....
It didn't work.
I fought this explosion for two weeks... Lost several hundred pounds of product...

I was talking with another grower...One of those decades long family fruit farmers who doesn't mind my questions....Who also happens to own a big farmers market and is one of my good customers, who began asking me questions about my issue..
I was using all the right tools... Tools that others we're using with success..

The last question was where are you getting your spray water...From my Rural Water hydrant of course??? Then he hit me with it...Our area gets its water from a large local lake, with water which is heavily mineralized... The water athority adjusts the PH to about 8..... Yup....8.... Can you guess where 'Most' AG chemicals need the PH to be to function as designed???? About a 6!!!

Needless to say a 5$ test kit and a cup of vinegar to my 50 gallon sprayer water made the difference...The formally ineffective products now worked miracles.... Imagine that... Using it as designed works.... Lol

Some lessons come hard... I'll tell you I read every lable.... Think I understand.... But I never quite grasped the importance of PH.....

So if you can learn from my fail.... This long story was worth it...

And I'd love to say that I've learned my lesson..I'll read every small detail from.now on.... But Mr Murphy says my complacency will likley kick me in the knee again someday...

Good luck and read the details. Especially if you're trying to use the organic approved materials which have marginal effectiveness to start with!
 
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RonObvious

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This is interesting to me because we have high pH water too. In our case we raise the pH of our well water by adding soda ash to the water stream. We have a lot of iron and manganese and the higher pH helps remove it. pH of 8 is really not that high, actually. Plenty of people have higher than that. Can I ask what kind of pesticide you were spraying? Might be time to get a rain barrel. I started using rainwater as much as possible in the garden because of the high sodium in our well water from the soda ash. Our vines are only in their first year so I haven't had to spray them yet, but I'm glad you posted this because I'll remember in the back of my mind to use rainwater for them too.
 

Bobp

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My understanding is that the ground water is very low PH and they raise it intentionally for maintenace issues.

Rain water can have Ph issues at times I think... I'd still test it..
In this case we used a rotation of biferen, Malathion, mustang max.

It would also be difficult to keep up with rain water collection and keep enough to have enough freshly available.

I'm thinking that I'll order AG powdered citric acid for pH Control. It's cheaper and easier on equipment.
 

Bobp

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Interesting read on pH and chemicals.

Has a grower ever come up to you and complained that the insecticide you sold him or that you custom applied for him didn't do a good job of controlling his insect problem? You probably attributed the reduction or lack of control to either a bad batch of chemical, or poor application, or pest resistance, or, maybe the farmer just didn't know what he was talking about. But, how many of you ever bothered to check the pH of the water prior to mixing the chemical?

If you look closely at the pesticide label, chances are you will find a statement cautioning you against mixing the pesticide with alkaline materials such as lime or lime sulfur. The reason for this is that many pesticides, particularly the organophosphate insecticides, undergo a chemical reaction in the presence of alkaline materials which destroys their effectiveness. This reaction is called alkaline hydrolysis and occurs when the pesticide is mixed with alkaline water; water with a pH greater than 7. The more alkaline the water, the more rapid the breakdown of the pesticides.

Lime and lime sulfur are often mentioned on pesticide labels because they are sometimes added to spray tanks. However, they are not the only materials that provide sufficient alkalinity for this reaction to occur. Caustic soda, caustic potash, soda ash, magnesia or dolomitic lime, liquid ammonia--all of these provide alkaline conditions in which susceptible pesticides can readily be hydrolyzed to inactive organic compounds.

It has been shown recently that in many areas of the U.S., water supplies have sufficient natural alkalinity to cause hydrolysis of certain pesticides. This means that a pesticide may begin to break down as soon as it is added to the tank. In practical terms, this means that the degree of pest control may be somewhat less than desirable, or even nonexistent, because a certain amount of the active ingredient will be decomposed to an inactive form before it ever reaches the plant and the pest. And if a spray rig is allowd to stand several hours or overnight before spraying out the contents of the tank, as much as 50% or more of the active ingredient may be decomposed.

Chemistry of Alkaline Hydrolysis

To better understand the phenomenon of alkaline hydrolysis, let's take a brief look at the chemistry using one of the organophosphate insecticides as an example.

Trichlorfon (Dylox, Proxol):

The phosphorous atom sort of divides the compound into two parts. Organophosphate insecticides are effective when the two parts of the chemical are together. When the parts are separated the OP pesticides are generally ineffective.

As you already know, water is made up of H and O . . . 2 parts H, one part 0 = H20. You also find charged particles or ions in water; both H+ and OH, and depending on where the water comes from, there may be an abundance of either H+ in the water, or an abundance of OH ions. The more H+ in the water, the greater the acidity; the greater the OH, the more alkaline the water.

This may seem rather elementary to all of you, but I feel it is necessary to understand the chemistry of water in order to understand alkaline hydrolysis.

The OH ion reacts readily with the OP molecule and breaks the molecule into two parts. The more alkaline the water (more OH), the more rapid the breakdown. This is what happens to most of the OP and carbamate pesticides in the presence of alkaline water; the rate of breakdown varies according to the alkalinity and the temperature of the water, and the length of time the spray mix sits in the tank.

[ Diagram Of Dylox Molecule In Two Parts Shown Here (couldn't find original illustration) ]

pH of Natural Water Sources

If the pH of your spray water is higher than 7.5, it is alkaline enough to affect some pesticides. The next few tables show the pH ranges reported for natural water sources in different areas of the U.S. A pH of 7.5-8.5 is common in many areas of the U.S. and in many surface and ground water sources in Pennsylvania. There have been reports that 5% of the natural water supplies in the U.S. have a pH higher than 9.0.

pH - Rivers in the U.S.
Potomac (MD, PA, WV) 7.8-8.4 Ohio (OH, IN, KY) 7.0-9.0
Delaware (PA, NJ) 7.4-7.6 Colorado (CA, AZ) 7.7-8.5
Hillsborough (FL) 7.1-8.2 Snake (ID) 7.6-8.4
Little (MA) 6.2-6.5 Rio Grande (CO, NM,
Arkansas (AR, OK, KS, CO) 7.4-8.6 (TX) 7.3-9.0
Missouri (NE, KS, MO) 7.8-8.5 Brazos, Trinity,
Mississippi (MN, WI, Colorado, Guadalupe
IL, MO) 7.6-8.9 (TX) 7.2-8.5
pH - Great Lakes
Lake Michigan (MI, IN
IL, WI) 7.5-8.5
Lake Ontario (NY) 7.9-8.3
Which Pesticides Are Affected by Alkaline Water?

Although there is a great deal of variability, in general we find that insecticides are affected more severely by alkaline water than fungicides and herbicides. And, we find among the insecticides that the OP and carbamates are decomposed much more rapidly than the chlorinated hydrocarbons.

Many manufacturers provide information on the rate at which their products hydrolyze. This rate is usually expressed as 'half-life' or the 'time it takes for 50% hydrolysis or breakdown to occur'. With trichlorfon or DYLOX, for example, the time for 50% hydrolysis at pH 8.0 is but 63 minutes; at pH 7.0 50 % breakdown occurs in 386 minutes. and at pH 6, 80 hours.

This means that if the pH of your spray water is 8 and one hour elapses between the time you add the insecticide to your spray tank and the spray dries on the foliage, 50% of the active ingredient has already decomposed. But if your water has a pH of 6, it is not likely that you will lose any significant activity during the process of application.

Let's take a look at a few more examples:

Carbaryl (Sevin) Imidan
pH Half-life pH Half-life (20 degrees C)
6 100-150 days 4.0 15 days
7 24-30 days 7.0 1 day
8 2-3 days 8.3 4 hours
9 1 day 10.0 1 min.
Lower the pH in Your Spray Tank

If your water supply is alkaline, especially if the pH is 8 or greater, and you are using a pesticide that is sensitive to hydrolysis, you should lower the pH of the water in the spray tank. A pH in the range 4-6 is recommended for most pesticide sprays. You can adjust your spray solutions to the 4-6 pH range by the use of adjuvants that are marketed as buffering agents. Examples are:

Buffer-X (Kalo Lab.)
Nutrient Buffer Spray
0-8-0 Zn Fe
0-16-9 Zn
10-12-0 Zn
8-8-2 Zn Mn
Spray-Aide (Miller)
Sorba-Spray(s) (Leffingwell) -- 6 different products
Unite (Hopkins)
A question that is sometimes asked is whether acidification increases the residual time of the pesticide on the plant, thus affecting such factors as re-entry time and pre-harvest intervals. Residue tests on foliage sprayed with acidified and unacidified parathion sprays have failed to show any differences in the rate of degradation of the parathion. This would be expected since the pH of the foliage runs around 7.

There are a few pesticide materials which should not be acidified under any circumstances. Sprays containing fixed copper fungicides (including Bordeaux mixture, copper oxide, basic copper sulfate, copper hydroxide, etc.) and lime or lime sulfur should not be acidified. But, if the product label tells you to avoid alkaline materials, chances are good that the spray mixture will benefit by adjusting the pH to 6 or slightly lower.

The major benefit from acidification is obtained during the time the pesticide is in the spray tank; that is, from the time the pesticide is added to the water in the tank to the time the spray has dried on the foliage. If your water source is alkaline, addition of a buffering agent to the spray preparation is an easy and economical way to guarantee maximum results from your pesticide applications.

pH HYDROLYSIS RATE 50%
TRADE NAME COMMON NAME HYDROLYZED IN
Dylox trichlorfon 8.0 6.3 minutes
7.0 6.4 hours
6.0 3.7 days
Guthion azinphos-methyl 9.0 12 hours
7.0 20 days
5.0 17.3 days
Carzol formetanate 9.0 3 hours
7.0 14 hours
5.0 17.3 days
Imidan -- 8.3 Less than 4 hours
7.0 Less than 12 hours
4.5 13 days
Dimecron phosphamidon 10.0 30 hours
7.0 13.5 days
4.0 74 days
Sevin carbaryl 9.0 24 hours
8.0 2-3 days
7.0 24-30 days
6.0 100-150 days
Gardona tetrachlorvinphos 10.5 80 hours
7.0 44 days
3.0 54 days
Phosdrin mevinphos 11.0 1.4 hours
7.0 35 days
DiSyston disulfoton 9.0 7.2 hours
5.0 60 hours
-- EPN 10.0 8.2 hours
6.0 More than 1 year
-- Parathion (Note: 11.0 170 minutes
Methyl Parathion 10.0 29 hours
hydrolyzes 7.0 120 days
several times 5.0 690 days
faster than
Parathion.)
-- TEPP 10.0 21 minutes
9.0 3.5 hours
6.0 6.8 hours
Lannate methomyl At a pH of 9.1, loses 5.0% of its
effectiveness in 6 hrs. at a
rate of 8 oz. per 100 gal.
water. Stable in slightly acid
solutions.
-- malathion Hydrolyzes rapidly at a pH above
7.0 and below pH 3.0.
Dibrom naled Hydrolyzes 90-100% in 48 hours in
alkaline conditions.
DeFend, Cygon dimethoate Unstable in alkaline media.
Stability is at a maximum at pH
values between 4 and 7.
Benlate benomyl Less soluble in alkaline
solutions.

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RonObvious

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That's really good information - thanks for sharing. What makes you choose citric acid as a buffer? Logically, it does indeed sound like a good option because it's all just C, O, and H (as opposed to, say, HCl, which contains chlorine). Is that your line of thinking as well, or did you read it as a recommendation?
 

Bobp

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Citric acid, to start with is easier on equipment, cheaper, not volotile with much of anything, and safer.... AND it's what a couple of the bigger growers I know use...

Google spray water PH there's tons of reading on it.
 

RonObvious

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Thanks again - I'm definitely tucking this info away in my head for future reference. :b
 

dbeck

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What are you spraying for the spotted wing drosophila?
 
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