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Ask a Master Gardener Oak seedlings and herbicide damage to veggies

Ask a Master Gardener Oak seedlings and herbicide damage to veggies

June 10th, 2018 by James Quinn, Regional Horticulture Specialist, MU Extension in Life & Entertainment

<p>Submitted</p><p>In general, the lobes on seedling pin oaks aren&#8217;t as deep as on a more developed tree, and the points aren&#8217;t as sharp.</p>

Q: We have a bunch of oak seedling popping up under our pin oak. We want to grow more trees from them. Are they the same, because the leaves on these seedlings look different? (see photo)

A: The seedling leaves are different for pin oak than when it is a small tree, not to mention a mature one. Here is a link to a MDC page on pin oak and it shows some seedling pictures nature.mdc.mo.gov/discover-nature/field-guide/pin-oak. You'll see some match yours quite closely.

On the lobes being less pointy, they may be influenced by light exposure and maybe air flow. So at first the lobes are less distinctive and gradually increase. They might be more lobed if not in such a shady area. Given they are right under your large tree, I think it is safe to assume they are pin oak seedlings.

Q: Are the Japanese beetles out yet? Someone said they heard they were, but I haven't seen any. Would now be a good time to treat plants you want to protect?

A: We put our trap up on June 1 and as of June 5 none have arrived. However, two other locations in the state have reported a very tiny catch, Columbia and Nevada. So, they probably are popping up here and there around Jefferson City. Rain and humid weather will surely bring them on, so yes, now is an excellent time to treat desirable plants (that they eat) with an insecticide. When spraying plants that are in flower, spray in the evening to avoid harming bees and other pollinators. Any systemic drench products should be used in ASAP and watered in quickly. Those products take about a week to move into the foliage of shrubs like roses.

Q: All my tomatoes started having their growth twisting up, especially on the tips. Someone said it might be herbicide. How might this have happened?

A: Accidental herbicide damage to vegetables can be difficult to sort out, but tomatoes are the "canary in the coalmine," so to speak, due to being the most sensitive. When all the plants do this at the same time, it definitely is the most likely culprit. We can look at a plant sample for specific changes in the leaves to confirm. Regarding your question, here are typical ways that damage occurs:

When adjacent to lawns, use of "Weed and Feed" or similar products (often put on as a dried granules) or spraying of weeds in the lawn.

Grass clippings from lawns that have had a herbicide applied to them, which are used as mulch around vegetables. Lawn clippings should be OK after three weeks of any herbicide applied.

Contamination in a sprayer that is used around the garden. We always advise two sprayers for gardeners, one for herbicides and another for insecticides and fungicides. These latter products are considered protectants so never should harm plants. Trace residues of herbicides in a fungicide or insecticide applied directly onto a plant is quite damaging.

Weed killers that are solely glyphostate (the active ingredient of the well-known herbicide 'Round-up') are commonly used for spot spraying. But if that sprayer was used previously to spray 2,4-D or some other lawn herbicide, it can have traces in it and is more likely to damage tomatoes nearby any spot spraying.

Any brush killers used in the area.

Roadside spraying by crews responsible for that activity, or farmers who might have sprayed a pasture/hayfield or field crops nearby.

Lastly (and sadly), manure from cattle or horses can contain traces of certain herbicides. This happens when the herbicides have been applied to pastures or hay which they consume. It is active even after sitting in a stagnant pile for several years or been composted, as it is exposure to sunlight that breaks the active ingredient down. This has become increasingly common to get a few reports on each year and is challenging to rule out or verify.