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Wednesday, May 31, 2017

Pyrethrum Doesn't Kill Thrips

Q. I was advised to spray my nectarines and peaches with a garden pesticide containing pyrethrum to kill thrips. Would you still eat the fruit once this chemical has been applied? And if I spray it, will the fruit not be deformed?
Thrip damage to netarine.

A. If the label for this pesticide does not have fruit trees or gardens on the label, then it should not be used for that purpose. This is a legal response, not a technical response to your question.
            Nectarines, not peaches, are deformed and scarred mostly because of the feeding damage on the skin of the fruit by Western flower thrips. These insects are tiny but when there are hundreds of them all feeding on the skin of one nectarine, they rip and tear at this so badly that the fruit becomes deformed and scarred horribly. Killing off the thrips prevents fruit deformity and scarring.
            Strangely enough, thrips damage does not occur on peaches so they will not have to be sprayed. Evidently the hair on the peach skin is enough to interfere with the feeding damage by these extremely small, flying insects.
            By the way, thrips are so primitive they don’t have wings like most insects. They have “sticks” that come out of their body with hairs on them. They are very poor flyers and can’t travel very far.
/Thrip. Not my picture but don't remember where I got it.
            On the label of the pesticide it tells you how many days you must wait before picking fruit. This is called the “Re-Entry Period” or “Days before Harvest”.
Years ago I had to find out if the damage was because of thrips so I put this fine mesh insect netting around an apricot tree. The fruit was not damaged. It was due to thrips.
            There is a lot of science that goes into that label. It’s not guesswork. It does not mean that the pesticide is totally gone. It means that a reasonable amount of the pesticide has been degraded by our weather and the EPA has deemed it “safe to eat” if the fruit is washed before eating.
            As far as the insecticide goes, it is called a synthetic pyrethroid and does a good job killing most insects including those in the home. However, on thrips it does not do a great job. Spinosad is much better to use and organic to boot.
Doesn't say it in the common name but this contains spinosad.
            But Spinosad is lethal to bees so spray only when there are no flowers present in the tree or beneath it and bees have gone home for the day. This will be at dusk. Rotate this spray with Neem oil and soap sprays.

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