Insecticide Spray Damage

roger_foxtrotJuly 17, 2006

Hi Folks. New to this forum but have gardened all my life. I decided to try some heirloom tomatoes this year and put out 40 different ones, more than I usually plant but read the yield is less that of hybrids.

Anyway, I noticed whiteflies in a number of my plants this past Saturday, and decided to spray for them. I've used Malathion for them in the past, so I went and got a new bottle and since I already had some Sevin mixed in my sprayer from spraying my beans a couple of weeks ago and didn't want to waste it, I just mixed in the Malathion with the Sevin and began spraying very late that evening.

Today (Monday) I go out to tie them up some more and noticed that a good deal of the new growth and leaves have turned brown, like they were burned from the spray. Not all my tomatoes were so affected, but most were. Looks like a lot of the newer flowers were burned as well.

Has anyone experienced this before? I'm looking for advice, not a condemnation of my choice to use chemical pesticides.

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dilbert(z5 IL)

"new bottle"

Read the label. Usually, liquid formulations contain "petrolium distillate." It is like spraying your plants with emulsified gasoline.

1. Switch to a wettable powder.

2. Use a good surfactant made for plant sprays to distribute the spray evenly. If you don't, large beads of spray will dry leaving a concentrated residue which will turn into brown dead spots.

    Bookmark   July 18, 2006 at 10:44AM
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torquill(z9/sunset15 CA)

Both of those are chemicals that can burn plants if the concentration is wrong; they may also have interacted in a nasty fashion. The rule of thumb is to never mix sprays unless they say specifically that they can be combined, or unless they are both gentle foliar feeds.

The damage is finite, and they should grow out of it shortly. Do take care not to spray in the heat of the day, either; do it when the day is cool and relatively windless, like early morning or evening.

--Alison

    Bookmark   July 21, 2006 at 12:02AM
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azkayla(Z7b Northern AZ)

I just sprayed my six plants with malathion a few days ago, and have one plant with newest growth (leaves, stems, flowers) that have brown lesions, particularly at the base of the leaves and the tips of the growth, looks sort of like late blight (see photos on problem solver 2), but I don't think it's late blight. I too think I've burned the foliage with the chemical. And I think a couple of real hot days in the mid-high 90's exacerbated the plant's reaction. Strange though that none of the other 5 plants have any of these lesions. I overreacted to hornworms and decided to use the malathion on an impulse. Wish I hadn't. Found out later that other, much less toxic substances can do the same job. Not happy to hear of your similar experience, but am relieved to hear that my problem is very likely the same as yours, with the cause being chemical reaction rather than disease. Also, this is my second year growing heirloom tomatoes, and I have found that they are really very resilient overall, and I expect that they will recover from this setback. I'm just going to watch the plant closely, particularly the new growth.

Hope this helps.

    Bookmark   July 26, 2006 at 11:26AM
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