Wet weather complicates risks of garden problems

By: Brian Louwers | C&G Newspapers | Published July 2, 2019

 Leaf spot is easy to diagnose from the yellowing leaves with brown spots  that typically begin on the bottom of the plant and spread up.

Leaf spot is easy to diagnose from the yellowing leaves with brown spots that typically begin on the bottom of the plant and spread up.

Photo by Brian Louwers

 Delays in planting can result in plant nutritional deficiencies. Even plants  bought from a garden center can lose phosphorous when planting is delayed by cool,  wet weather. The end result can be seen in tomato plants with purple leaves.

Delays in planting can result in plant nutritional deficiencies. Even plants bought from a garden center can lose phosphorous when planting is delayed by cool, wet weather. The end result can be seen in tomato plants with purple leaves.

Photo provided by Ben Phillips

METRO DETROIT — Soggy. In a word, that describes the weather we’ve experienced this spring and early summer.

With wet weather more the rule than the exception in recent years, home vegetable growers can plan ahead with eyes equally set on the sky, the thermometer and their plants to prevent potential problems and take action once the telltale signs of disease or temperature-related growing issues are recognized.

“It’s been a tough spring,” said Ben Phillips, a vegetable extension educator for the Michigan State University Extension office in Saginaw County. “It’s been the hardest spring people can remember in terms of commercial production. I’m sure gardeners are experiencing similar frustration, with a little less riding on the line.”

One of the biggest problems thus far has been weather-related delays in the growing season. Simply put, all the rain has kept many growers from putting plants in the ground.

“There are some consequences of that,” Phillips said. “We’ve been seeing a lot of peppers that already have flower buds on them, and they’re much too short to have flowers on them right now.”

Philips said pepper plants should be at least a foot tall before they start flowering and that if the process reaches fruition any sooner, the plants will stop growing taller. That means decreased yields over the summer.

“If gardeners have time and interest, they can go and try to remove those flower buds or flowers, and that will kick the plants back into their vegetative state, at least for a short time,” Phillips said.

When you’re doing that, Phillips suggests adding fertilizer — specifically nitrogen, in granular or liquid form — to replace what’s being washed out by heavy rains. He suggests granular urea, which will add only nitrogen in a form that’s readily usable to the plant, as opposed to composted manure, which, while it’s good to use as well, releases nitrogen more slowly throughout the season.

Delays in planting can also result in other plant nutritional deficiencies. Even plants bought from a garden center can lose valuable phosphorous when planting is delayed by cool, wet weather. The end result can be seen in tomato plants with purple leaves.

While tomato growers likely won’t face any increase in some conditions, including blossom end rot, as a result of the wet weather, they could face challenges from fungal or bacterial diseases that thrive in rain-splash conditions.

“If you still haven’t planted any transplants, it’s a good idea to inspect them for leaf spot,” Phillips said.

Leaf spot is easy to diagnose from the yellowing leaves with brown spots that typically begin on the bottom of the plant and spread up.

“When it’s dry, you can pick those leaves off and destroy them to reduce that effect,” Phillips said.

Besides choosing varieties more tolerant to disease, over-the-counter fungicidal or bactericidal products are your best bet for staving off the potentially devastating effects of leaf spot and similar conditions.

“The best ones contain copper in some form,” Phillips said. That includes copper hydroxide and copper oxychloride.

“Copper is a bacterial defense mechanism,” Phillips added. “If you don’t want to spray, you can just try to get the aeration as good as you can, and pick off those leaves when it’s dry. Don’t go out there when it’s still wet.”

Keeping enough space between plants to allow adequate airflow is important. Only touching the dry leaves minimizes the risk of cross contamination with the soil, tomato stakes and cages, and even other plants that you touch with contaminated hands.

Phillips identified two “weekend killers” that he said could wreak havoc on the crops of unwary gardeners who try to steal away for just a couple of days of rest and relaxation: late blight and downy mildew.

“The conditions are great for those two, but they don’t exist here yet (this year). Those diseases only happen if the pathogens are around,” Phillips said.

Downy mildew moves north on the wind each year and hasn’t yet arrived in metro Detroit.

Late blight affects tomatoes and potatoes. It can overwinter in surviving potato plants.

“Once it gets cooking, it does spread by wind, just like downy mildew,” Phillips said. “The main difference between those two is that late blight can overwinter here. It can start early. Downy mildew can’t overwinter. It has to blow up from the south. It takes longer to get here.”

The MSU Extension has a variety of resources available for growers at all levels.

“To some extent, unless you have a drainage system, there’s not a lot you can do to control there being excessive water,” said Lori Imboden, a consumer horticulture educator with the MSU Extension office in Oakland County. “In a drought, you can always go out and water. But you can’t un-water.

“You’ll want to keep an eye out for diseases. When the humidity is there, there can be a little more risk,” Imboden said.

The MSU Extension staffs a gardening hotline, available 9 a.m.-noon and 1-4 p.m. Mondays through Fridays. There is also an online “Ask an Expert” tool available at www.canr.msu.edu/outreach/ask-an-expert where gardeners can get answers and even upload photos.