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limits on pesticides

Posted by thecityman 7a/6b (My Page) on
Thu, May 22, 14 at 22:13

I have a (I think) simple question: most of the fruit tree sprays I have seen and used have something in the instructions saying not to exceed some number of sprays per season (bonide says 3). Is that because it might harm the tree or is it to protect human health? I strongly suspect the latter, but I wanted to be sure. I confess that I've sprayed my trees more than the limits call for (not by much). I have a few trees that seem to be struggling, and I just wanted to be sure it isn't because of my spraying them too much. In terms of my own exposure, please understand that my trees are all small and I'll only get a small amount of fruit this whole year. I also will be eating it myself (no kids) and I am cutting back already. I know it is a poison and I should and will be more careful. I'd still be interested in any thoughts about the health dangers of spraying too much (say, every 10-14 days) but I'd especially be interested in whether that might affect tree health. thanks.


Follow-Up Postings:

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RE: limits on pesticides

I believe the issue is most often about residue levels in food, for which the government sets very high standards. It is my opinion that the risks of pesticides on human health when used responsibly is wildly and irresponsibly exaggerated on a regular basis in the media as a whole- an issue often discussed on this forum.

I have seen a couple of studies of very large groups of farmers licensed and engaged in pesticide application. Most of these farmers presumably pulled mist blowers in open tractors to spray their fields or orchards. This means they spent the growing season living much of the time in a fog of fresh pesticides. Careful evaluation of their health and mortality showed them to be the beneficiaries of significantly longer and healthier lives than the general population.

Understand that these farmers ranged from the young to the elderly and many had been extensively exposed to pesticides long since taken off the market because they are considered too dangerous.

This isn't to say that risks don't exist, and the farmers did suffer higher rates of some forms of cancer than the general public. Also fetuses and young children are probably much more sensitive to and at risk from the danger of exposure. But the fact that these groups of farmers absorbed exposures hundreds of times that of someone like you, spraying a few trees with a wand and backpack sprayer suggests you should be far more concerned with getting enough exercise and eating lots of vegetables and fruit.

It is still important, IMO, to limit the sprays to the least amounts possible with only needed materials in the mix. Bonide pre-mix formulations don't fill this bill at all and I suggest you search this forum for information about best spray materials if you are currently using a pre-mix.

You also need to learn what you are spraying for and limit the sprays to what is needed to get sound fruit.

The link is to the summary of a study taken by the U. S. dept of health. If you want the details you can e-mail me for it- I paid for the download.

If you search for it, there is a similar study that was done by the Canadian government that showed similar results.

Here is a link that might be useful: relative health of pesticide users


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RE: limits on pesticides

  • Posted by olpea zone 6 KS (My Page) on
    Fri, May 23, 14 at 11:21

In the case of commercial pesticides, in some cases the label limits the amount of sprays to reduce the risk of pesticide resistance of the target pest. In other words, spraying one product repeatedly can increase risk of resistance.

In terms of the amount of active ingredient (a.i.) allowed annually, I think each pesticide is considered on a case by case basis.

Food residue level could be the limiting factor in the amount of a.i. applied annually, but I think more often the impact on the environment is the limiting factor.

As an example, captan has a zero pre-harvest interval, meaning theoretically the fruit could be eaten as soon as the spray dried, yet there are seasonal limits to the amount of captan that can be applied annually.

Pesticides used on lawns also have seasonal limits. Again I think the main consideration is the environment. According to the U.S. Fish and Wildlife Service, "Homeowners use up to 10 times more chemical pesticides per acre on their lawns than farmers use on crops, and they spend more per acre, on average, to maintain their lawns than farmers spend per agricultural acre." This is from their Division of Environmental Contaminants.

Likewise, pesticides like imidicloprid have annual limits/acre on the amount of pesticide used when treating ornamentals (like ash trees).

As Hman points out, EPA sets the guidelines for maximum residue levels of pesticide in food. They use a very science driven and complicated model to protect the public. Again as Hman mentions, they do consider more sensitive groups, like pregnant women and infants, when setting tolerance levels. Most max. residue levels are in the low single digit ppm range. Most people don't realize how little pesticide exposure that is.

There are some pesticides which have long half-lives and could violate max. residue levels on food crops if used repeatedly (I'm thinking of some of the neonics here.) However, in most cases, pesticides used on food are designed to break down quickly to avoid residue issues.

Mustang Max can be used 8 or 9 times on some fruit crops. The EPA relies on the short degradation period of pyrethroids, and fairly lengthy Pre-Harvest Interval, to avoid illegal residues. I think the limit on the sprays has to do with the environment, or insect resistance in this case.

The topic about applicators, which Hman brings up, has always interested me. I have read summaries of studies indicating the same results. Namely, applicators (i.e. farmers) live longer lives than the general public and have less incidence of overall cancer (although have higher incidence of some specific cancers).

This has always surprised me, partly because I've been conditioned to think pesticides are extremely dangerous (When they are mentioned in news or movies, it's always mentioned in that context. Benefits are never mentioned.)

What's truly surprising is that farmers have such a risky occupation and have such high exposure to pesticides, one would expect cancer and death rates higher.

In the past, when these studies were done, the chemicals used were much more toxic, despite the fact most farmers used almost no personal protective equipment. PTO and tractor accidents were much more frequent. Farmers also generally cared for livestock as well as crops. Livestock are also dangerous (I know of one farmer who was crushed to death by his horse, while herding cattle). Additionally, farmers were out in the sun all day (without sunscreen). They also did the bulk of their maintenance exposing them to dangerous or suspect chemicals, like oil, grease, diesel fuel, welding fumes, agricultural dust, etc.

If deaths due to occupational risk of accidents and non-pesticide chemical exposure were removed, incidence of of cancer/death rates would be even lower. This is a strong indication to me, the EPA has layers of redundancy built into the extremely low pesticide tolerance levels allowed on food.


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RE: limits on pesticides

But you won't be readin 'bout that in the NY Times (and it's my paper).


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RE: limits on pesticides

  • Posted by olpea zone 6 KS (My Page) on
    Fri, May 23, 14 at 18:31

The disproportionate focus is in the newspapers and in our everyday thinking is somewhat amusing. I recall you've posted about people reproaching the use of pesticides while smoking a cigarette.

Recently, I came across the same situation. I never challenged the assertions of the smoker, but the duplicity was obvious to me. What's even funnier is when people insist on smoking organic tobacco. In my mind, that's akin to swallowing a camel, while straining out the gnat.

This post was edited by olpea on Fri, May 23, 14 at 22:16


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RE: limits on pesticides

The expertise (and willingness to share it) in this forum blows my mind. I also must admit that I was especially glad to see that 2 of the people I've benefited from the most In the past year responded, so thanks to you both for those detailed, on point, extremely helpful and informative posts. Harvestman, just so you know, I have a post you sent me back in the winter with a recommended spray routine still tacked up in my home office and I've followed it ever since, including the dormant oil, immunox, and Triazide. I have, however, increased frequency of the Triazide slightly, and also added a bonide treatment or 2 in between your suggested triazide schedule. I did this because I could clearly see that my peaches and plum trees were still being hit hard by insects. I added bonide instead of just increasing Triazide because I saw articles/posts saying exactly what you all just stated in this thread-that too much use of the same product could lead to resistance. I'm clearly unqualified to be enhancing your recommendations in my own, but maybe it helped. I am still loosing some peaches, though. I cut several open today and I still am not 100% certain if the critters in my peaches are OFM or PC. I've looked hard for the little legs I'm told to look for, but they are just to small for me to tell. The little maggot looking things do sort of seem to be crawling, but when I turn them over I don't see legs. They do have brown heads. Either way, though, isn't treatment for THOSE TWO about the same? I also must confess that I think part of the reason I have bugs in spite of my spray is that I may not have got complete coverage of one old, tall peach tree.
Anyway, thanks again for both of your help!


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RE: limits on pesticides

Your problem is almost certainly not resistance. One issue I suspect with Triazide is that it doesn't come with an expiration date and yet has a shelf life of only two years. You have to wonder about shelf rotation or any other situation that would lead to purchasing a stale batch.

If you have any plants covered with a labeled target species that you can test the effectiveness of your product on, I suggest you do that.

A limitation I have when giving advice to home growers is that I buy my products from an agricultural supplier. The pyrethroid I use is dated with the time it leaves the factory. I did test a bottle of Triazide and it lost potency a year after I purchased the product from Lowes.

I will need to mention this issue in a revised version.

You are not going to develop resistant insects in a single season and probably not in the lifetime of a small stand of fruit trees. Commercial growers need to be very mindful of this issue- home growers, not so much, IMO.


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RE: limits on pesticides

You very well may have just solved my mystery. The triazide I have been using all season was purchased in early spring of LAST YEAR (2013). Since it was purchased so early last year (at Lowes), it seems very likely that it could have been on the shelf at Lowes from the prior season....which would make it 2 years old or more at this point. I've been trying to convince myself that I just hadn't got full coverage on some trees, especially tall ones, but I found that hard to believe and it also didn't explain why I had some problems with my short trees too, and I'm sure I soak them every time. I had also started to wonder about resistance, but now you say that's very unlikely. So old Triazide could absolutely be my problem! Maybe this will help others here as well.....sounds like we need to be very, very sure that our Triazide is fresh. Seems like they should put dates on the bottles if they know time is the enemy of its effectiveness, but I guess that could result in disposal of lots of outdated product they would rather sell. (cynical?) Thanks, H-man.


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RE: limits on pesticides

Wow, that is funny- almost an identical experience. Mine was purchased in early April from Lowes and it worked fine the first season but lost potency by the second.

Sure, post it. Triazide, One Year Only!


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