to Spray? Read the Label! by Don Urbanus
Some customers came into our store recently with mulberry leaves that
looked like they took a carnival ride – you know, one that flips you upside down
and spins you around. I immediately diagnosed it as herbicide damage but they
insisted that they had never sprayed it with anything. They had whacked the
branches way back that winter and this spring the leaves came out all distorted.
Was it some new disease?
Many questions later, except for a new sidewalk nearby, nothing
exceptional had happened in the area. I emailed a picture to three different
experts in the horticultural field to ask their opinion. All said herbicide
damage to which I concurred.
So my original diagnosis still stood. Somehow the tree had been
damaged by herbicide from somewhere. A little light bulb popped up in the
customer’s mind as she remembered her neighbor boasting about
how proud he was
of his “concoction” of weed killers that really did a number on weeds. He also
liked to be helpful when they were gone and occasionally was the “good neighbor”
by spraying weeds for them. We both figured that there must be some connection
Phytotoxicity is the term used when plants get damaged by chemicals –
not just herbicides. It can occur even when the right amount is applied but at
the wrong time – like in windy or very hot conditions. Mixing chemicals together
can make the final solution even more toxic than the original – which was
probably the case with the good neighbor.
Phytotoxicity can occur when:
A material is properly
applied directly to the plant during adverse environmental conditions.
A material is applied
A spray, dust, or
vapor drifts from the target crop to a sensitive crop.
A runoff carries a
chemical to a sensitive crop.
accumulate in the soil or on the plant.
I had my own lesson in phytotoxicity years ago
when one of my sprayers that I used to spray for insects and disease wasn’t
working. I carefully washed and rinsed out my sprayer I used for weeds and
proceeded to spray my roses for mildew, which any good rose grower knows you
have treat quickly. The roses started looking a bit odd and my rose salesman,
who just happened to pop in, suggested that it looked like herbicide damage.
Oops. I never did that again.
Some people often get chemicals mixed up.
Herbicides, insecticides, fungicides -what’s the difference? Often people come
into the store holding a diseased leaf that they had sprayed an insecticide on
and wondered why it wasn’t getting better.
Years ago my ex brother-in-law decided to spray
around his mother-in-law’s house for bugs with something he found in the shed.
His pregnant wife was sleeping inside with the air conditioner running. He
proceeded to kill everything in his path and whatever he was using was sucked
into the house. His wife woke up coughing and proceeded to get toxemia and
almost died when they had to do a caesarian delivery. Like I said. He is my ex
On a local Facebook gardening page, a friend
posted a weird looking picture of fig leaves and another of a healthy bunch.
Although there were dozens of guesses, it looked like herbicide damage to me.
Again, it seemed to be another case of a rampaging husband who got a little
careless where or how he sprayed the weeds.
I am amazed how many people don’t actually read
the label. They’ve spent millions of dollars doing hundreds of tests so that you
can use that particular chemical and then people don’t read it! And there is the
old adage, if a little is good – a lot must be better! Also, the label has a
danger level warning on it. It will either say “Caution”, “Warning”, or
“Danger.” There aren’t too many labels anymore with the latter two warnings.
Most chemicals are pretty safe these days but people can still muck it up.
Although he was serious, the most humorous
customer we had wanted the “atomic bomb” solution. He wanted one thing that
would kill everything! He wanted to kill snails, caterpillars, flies, spiders,
borers, flying bugs, crawling bugs, buggy bugs. And he wanted to know why we had
all these mamby pamby chemicals.
There is a reason why some chemicals have been
taken off the market and, even organics sprays, are very specific. We don’t want
collateral damage – either dead fish or animals, damaged plants, or the wrong
things dead like beneficial insects such as lady bugs or bees. For instance, by
not spraying when you have flowers or spraying in the evening, bees are not
affected by most chemicals. Please read the label. Timing is just as important
as the correct dose when it comes to chemicals.