Overspray

Overspray, also known as drift or carryover, occurs when someone else’s herbicide reaches your plants. It rarely ends well, and it can make for strained relations.


And sometimes you do it to yourself! Those pesky weeds coming up through the patio blocks or on pathways are such a pain to dig out. One quick spray and you're done, right? Wrong. But, there is a slightly easier way, so read on!


Very often, overspray is accidental. A quick breeze appears, temperatures shift, or a happy canine comes on scene. In other cases, overspray is the result of thoughtlessness, ignorance, or even vandalism. From your point of view, it makes no sense. One day, your plants are thriving. The next day, something is definitely wrong. 

Symptoms of herbicide damage

The symptoms of herbicide damage vary, depending on the type of chemical being used. Broadleaf weed killers cause leaves to twist and cup, and new leaves are narrower than normal. Also, the roots of annuals will come to the surface. These herbicides will, as advertised, cause grasses to yellow and die. Non-selective herbicide overspray will cause chlorosis, poor health, and dieback, if not rapid death. Other symptoms of herbicide overspray include leaves turning purple, stem dieback, and leaf mottling and spotting. These symptoms can indicate other problems, too, so it can be difficult to diagnose overspray.


How overspray occurs
Sometimes the best indicator of a problem is having seen your neighbor applying chemicals the day before. Many herbicides are applied as a spray. This means that vapor can spread to areas where it is not wanted, especially if there is a breeze, low humidity, or high temperatures. According to UCANR, herbicides can travel for miles on the wind. And those convenient handheld spray bottles look safe, don’t they? But, when you squeeze that handle, it is all too easy for the spray to bounce off your intended target, the soil, or your shoe, and land someplace else. That contaminated shoe can now carry the herbicide to new plants. After the intended application is complete, the soil around treated plants also contains herbicides. This soil can be kicked, carried on the sole of a shoe, in gardening tools, or on a breeze to places where herbicides are not wanted.


Preventing overspray
There are several ways you can prevent overspray from damaging or killing plants you never meant to harm:

• ALWAYS FOLLOW PACKAGE DIRECTIONS EXACTLY. EVERY TIME. NO MATTER WHAT.
• Communicate with neighbors about what chemicals are being used, when, and how.
• Identify plants that are most sensitive to overspray and use herbicides that are less damaging (or none at all) in those areas.
• Leave buffer zones between treated and untreated areas.
• Do not apply herbicides while wind is blowing.
• Do not spray when big temperature swings are expected. This can cause thermals that carry chemicals the same way wind does.
• Use low-pressure nozzles to reduce the number of tiny droplets that are more likely to travel.

Treating victims of overspray

Large perennials can often be saved from the effects of overspray, if it is caught soon enough, because the chemicals move more slowly through the vascular tissue of these larger plants. Leaves that have come in contact with an herbicide should be removed, to halt the spread of the chemical. Plants should be hosed off and watered well. Of course, the water that comes off the plant will contain herbicides, which can then spread to new locations. [Oh, what a tangled web we weave…] Anyway, watering the plant thoroughly will help to dilute the chemicals. These plants will require special care for at least a year. Left untreated, they will eventually die. Tender annuals and edibles should be removed from the garden and disposed of in the trash (not the compost pile). Even though you might be able to keep these plants alive, do you really want those herbicides in your food?


Finally, keep in mind that you can be held legally liable for damage caused by overspray, even if it was unintentional.


As for those pesky sidewalk weeds, grab a sharp knife or screw driver and cut them off at ground level. Then, pour a liberal amount of vinegar over the area. It may not kill the root completely, but it will take the plant a lot longer to come back, if it does at all.