With rainy weather, watch for slugs, plant diseases in Western New York

wet peonies from Donna Brok
Photo courtesy Donna Brok, who publishes the blog Garden Walk, Garden Talk

With all this rain in Western New York, it looks more like April than June. John Farfaglia, extension educator with Cornell Cooperative Extension in Niagara County, said some gardeners have water ponding in their yards, and yesterday he saw someone’s riding lawn mower stuck in the mud.

We had a dry spring in Western New York, but so far this month we’ve had about twice the average amount of rain we would get during that period.

This weather poses some challenges. You may have problems with slugs and plant diseases, and you may have to fertilize more.

Slugs and snails

This wet weather provides ideal breeding conditions for slugs and snails, Farfaglia said.

“They love chewing on a multitude of tender garden plants,” he said, including hostas and annuals.

There are a number of things you can try to control them.

photo of snail from garden by Donna Brok
Photo courtesy Donna Brok, who publishes the blog Garden Walk, Garden Talk

Bait is one of the more reliable methods, he said.

There are two kinds of slug bait. The conventional bait is a typical pesticide and probably should not be used near pets and children. The iron-containing bait or iron phosphate bait is safer to use around pets and children, he said.

If you want to avoid the use of chemicals, you can try picking the slugs off your plants by hand.

Another method is to set out saucers of beer. The slugs are attracted to the beer and drown in it.

You can also buy bait stations, which are circular plastic objects that contain beer. Slugs crawl in the small openings and drown in the beer.

Farfaglia also mentioned a couple of home remedies you might try. Some gardeners set crushed egg shells around their plants. The idea is that the abrasive surface might deter the pests.

Some gardeners shake salt or vinegar directly onto the slugs, which dissolves the slugs. If you find slugs grouped together, you can get rid of many slugs at once. However, salt isn’t good for the plants, he said. Vinegar can also harm plants– Vinegar is used as a weed killer and can burn the leaves of plants.

A reader asked whether we should expect other types of garden pests, such as cutworms, to become more abundant because of the rain. The answer is no, the wet weather won’t nurture other pests that might bother your plants, he said.

What gardeners should watch out for, Farfaglia said, is plant diseases.

Plant diseases

Plant diseases are much more likely than pests to be an issue with the rainy weather, Farfaglia said. Here are some examples:

  • Apple scab fungus can affect ornamental apple trees. The leaves get spots, turn yellow and shed in June or July.
  • Powdery mildew can affect lilacs, phlox, squash, pumpkin and many other plants. It looks like a white film on the leaves.
  • Black spot can affect roses.
  • Late blight can affect tomatoes later in the season.

These diseases like areas that have less sun and less air circulation. If you have a pocket garden on the side of your house, it’s more likely that your plants will be affected. Farfaglia suggested evaluating the plants you have in an area like that. If your plants are prone to these kinds of diseases, you may want to replace them with other plants.

You can also watch for disease and treat your plants at the first signs of disease. Some people use baking soda as a natural, fairly safe fungicide, he said.

There are also fungicides that you can buy. However, before you start spraying your plants with fungicide, make sure that your plant actually has a fungal disease. You can do this by contacting your your county’s Cooperative Extension office. You may be able to email a photo of your affected plant to them to help in the diagnosis.

You can also place some affected leaves in a clear plastic bag and take it to a garden center that has professionals on staff. They’ll be able to tell you what’s wrong with your plant and guide you to the correct treatment. Please check out the garden centers that support this magazine.


Another question from a reader was whether she should fertilize during this excessive rainfall or whether the plants were too stressed.

“With all this rainfall, the nutrients in the soil, particularly nitrogen, gets washed away, so you need to replenish it,” Farfaglia said. “The more rain we have, the more frequently fertilization is needed.”

Weather forecast

maple leaves in rain
Photo courtesy Donna Brok, who publishes the blog, Garden Walk, Garden Talk

Everyone wants to know whether this wet weather will continue through the summer or whether the dry conditions we experienced last year will return, and there are folks who try to make long-range forecasts. Almanacs attempt to predict weather for entire seasons a year in advance, and we commonly come across 10-day forecasts. Unfortunately, the almanacs are so vague that they’re not very useful, and the 10-day forecasts are no more accurate than if you had simply looked at the climate data– the average temperatures and precipitation for that date.

Our short-term weather forecasts have become much more reliable in recent decades, but we still can’t make a weather forecast that is accurate nine days or more into the future, according to Nate Silver in  The Signal and the Noise.

Even our short-term forecasts have uncertainty in them. The forecasts don’t tell us that it will rain or won’t rain tomorrow; they tell us what the odds are that it will rain. If the forecast is accurate, when there’s a 20 percent chance of rain, it should rain 20 percent of the time. If there’s an 80 percent chance of rain, it should rain 80 percent of the time– 20 percent of the time it won’t rain.

You can read an article adapted from The Signal and the Noise here, but that article isn’t as interesting as the book. I suggest you read the book.

When I asked Farfaglia if he had any predictions on how the weather would play out for the rest of the summer, he laughed.

“The best forecast is that the weather is likely to be very changeable,” he said.

8 Comments on “With rainy weather, watch for slugs, plant diseases in Western New York

  1. I use a mixture of plain, NOT lemon-scented, ammonia and water, which I mix together in gallon jugs and then spray on the slugs and snails. I live in a very swampy area and I have been fighting them for years. It is time-consuming and at first I felt horrible when I saw the slugs disintegrating before my very eyes, but I had to get over it. I had 5 slugs hanging off a ripe tomato in my garden once (the last one I bothered having). My cats come in the house with snails and slugs hanging off their fur or caught inside it. If I could afford to move, I would have years ago.
    You mix the ammonia through trial and error as to how much ammonia is effective. The lemon stuff does not work unless it’s almost half and half. You can spray the snails, but you have to make sure it gets onto the soft body parts under the shell. Otherwise they will fall off the plants and you think they’re dead, but after awhile they recover and climb back. With the snails, I go around holding a flat, wide container in one hand and knock them off the plants with the other into the container. Sometimes there are hundreds of them when I’m done, but I can go around again an hour later and get just as many. Then I cover them with the ammonia and water and wait a couple minutes, then throw them into the woods nearby. I also use Sluggo.
    At certain times of the day, the slugs mate. If you see one in the grass, look around because there is at least one more close by on its way to that one.
    I won’t harm a tiger slug, though. Watching them mate in the middle of the night is an absolutely beautiful, almost holy experience.
    I won’t kill the slugs while they are in the grass mating, either, because it just doesn’t seem right. But I finally decided it’s them or me. I didn’t want to put down diatomaceous earth because I have cats and I read that if they got it on their paws and licked it they could get very ill.

  2. John Farfaglia says that even though there are no obvious signs of slugs, the damage may still be slugs. Recheck in the evening with a flashlight to see if you can see slugs. He doesn’t know of anything else that is a common feeder on hostas, especially at this time of the year. Besides, hostas are tough. Injury to leaves doesn’t look good, but you’re not going to lose the hostas because of it.

  3. John says you could do either. In wet years, he usually prefers the dry fertilizer because you’re not adding more water to already saturated soil.

  4. Hosta, in a very dense garden, are developing holes in their leaves. No sign of slugs. What could be causing this and what kind of spray should I use?

  5. Great information and “signs to watch for” in the garden! If the wet weather continues, should we apply dry (granular) fertilizer or can we apply a liquid fertilizer?

  6. For years I’ve lightly surrounded my hostas with a layer of sand before they leafed. Haven’t had a problem a problem since I started.

  7. John always has great and knowledgable advice. I pick the slugs off by hand. Tried the beer and it does not effectively drown they reliably. I am glad to read we are having twice the rain for this time of year. Much rain was needed. Unfortunately, with the good of rain, also comes the bad in plant disease.

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