Field and Garden: Fall is best for dandelion control

If you are bothered by dandelions in your lawn, now is the time to act.

As the weather cools, dandelions begin channeling energy to their roots in preparation for winter.

Herbicides applied at this time will also travel to the roots, effectively killing the plants.

The best herbicides for broadleaf weeds like dandelions are Trimec formulations, which contain a blend of 2,4-D, mecoprop, and dicamba.

Rather than treating the entire lawn, it’s more efficient to spot-treat weeds or problem areas. This saves money and reduces exposure to harmful chemicals.

Be cautious of spray drift, as it can damage nearby trees, shrubs and flowers. Avoid spraying when wind speeds exceed 5 miles per hour, and always follow label directions for safe and effective use.

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Here are some recent questions that I have received:

Q: We have a lot of rust in our lawn. Is it going to permanently damage our grass?

Rust is a fungal infection that commonly occurs in late summer and early fall.

When rust is widespread, your lawn may take on a yellowish to reddish-orange hue, and you might notice the fungus collecting on your shoes as you walk across the grass.

The fungus doesn’t kill the grass but can weaken it, making it more vulnerable to other issues.

Rust is most often seen in lawns that are stressed, whether drought stress or lack of nitrogen.

The best way to control rust is by encouraging healthy lawn growth through proper fertilization and mowing practices.

Do not irrigate in the evening or at night because extended periods of dampness favor the disease.

Fungicides are usually not needed or recommended for homeowners.

Q: Why were my onions mushy when I harvested them?

The symptoms you described sound like bacterial soft rot, which often goes unnoticed until harvest.

The pathogen typically spreads from the neck down into the bulb, causing the tissue to become water-soaked and eventually break down into pulp, often accompanied by a distinctive rotten smell.

It’s best to avoid planting onions in this area for a couple of years. Onions already have a naturally weak root system, so ensuring good drainage is essential for their health.

Q: What’s wrong with my quaking aspen tree? The leaves are turning black and falling off.

Leaf diseases have been widespread in many tree species this spring and summer, with weather conditions favoring anthracnose in ash trees, apple scab in crab apples, and rust in cottonwoods.

To identify the exact disease affecting your tree, we’d need to send leaf samples to the NDSU Plant Diagnostic Lab. However, the recommendation is typically the same regardless of the disease: it’s too late in the season for fungicides to be effective.

Instead, focus on good sanitation – rake up fallen leaves to help prevent reinfection next year.

The good news is, if your tree is otherwise healthy, it should recover well by next season.