By Steve Reiners, Professor and Chair, Horticulture Section, School of Integrative Plant Science, Cornell University, Cornell AgriTech.
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July 20, 2021

This season sure changed quickly.  A month ago, we were relatively dry, and hoping for some rain from every passing cloud.  Now, some of us have received between five and ten inches of rain over the last three weeks.  And our vegetable gardens are showing the result.

There’s an old saying among farmers:”A dry year will scare you to death.But a wet year will starve you to death.”  A farmer, especially a vegetable farmer with access to irrigation, will always choose a dry year.  You can always turn on a faucet.  You just can’t stop the rain.

Too much rain can hit you on many fronts.  Wet leaves and high humidity encourage more plant diseases.  Saturated soils are low in oxygen.  Roots, just like you and me, need oxygen to survive.  Deprived of oxygen, roots temporarily dieback, especially the fine feeder roots responsible for nutrient and water uptake.  All this rain leaches away fertilizers and nutrients, causing nutrient deficiencies once soils dry out and air moves back in.  And all those weeds just keep growing.

For those of you gardening on raised beds, things are not as bad.  And I’m not talking about fancy, three-foot high, wood framed beds.  Even a raised bed formed from mounding soil a few inches high can make a huge difference.  Too late to do this now but remember this when preparing the garden next spring.

Diseases and pests aplenty

Let’s start with diseases.  Some diseases are already present in your soil.  Some will blow into your area on airborne spores.  So, there are lots of diseases that are lurking.  But if the weather was dry, some of them might not be too bad.  Wet weather provides ideal conditions for many diseases to thrive. 

For tomato growers worried about Late Blight, I have good news.  There have been no reports of the disease in New York or anywhere in the country as of this writing.  Yes, conditions seem to be perfect for it. But if it’s not present, no worries.

It’s tempting to run out to the garden as soon as the rain stops and check your plants.  But be patient and let the foliage dry first.  You can easily spread bacterial diseases by touching one wet, infected leaf and moving down the row touching others.

Hopefully you didn’t plant your veggies too close together.  We always talk about having good air circulation so leaves can dry out.  That has never been more important than right now.  You can’t change the spacing now, but you can get rid of tall weeds that are blocking air movement. And the good news is that weeds will pull a lot easier when the soil is wet.

There are chemicals that you can use for disease management.  An organic option would be copper, which is available in most garden centers.  For those willing to use a synthetic fungicide, materials containing ‘Daconil’ can be very effective is slowing fungal infections. 

If using any material, follow the label directions completely.  If it says use a teaspoon in one gallon of water, use a teaspoon in one gallon of water.  More is not better.  You will likely need to apply multiple times through the season.  And make sure you spray both the tops and bottoms of leaves.

If you are willing to use chemicals, look for materials that are labeled for disease control and for the crops that you have in your garden.  You don’t need a material that contains insecticides.  One bit of good news in a wet year is that insect problems are usually lessened.  So don’t apply chemicals you don’t need.

Although too late this year, think about using varieties with greater disease resistance when planting in 2022.  That is the easiest and safest way to control many diseases.

Slugs and snails also thrive when it’s wet. So be prepared to deal with them.  There are poison baits that can be used. But try other techniques first.  Pie plates filled with beer attracts slugs which climb in and drown.  Or put a wooden plank on the ground in the morning.  Slugs will be attracted to the dark, moist area during the day.  Then just slough off the pests into a bucket of soapy water in the afternoon. 

Add needed nutrients

Chances are your plants are yellowing, most likely from a nutrient deficiency.  Nitrogen is easily leached out of the root zone after heavy rains, especially in sandy soils with low organic matter. So, it’s time to sidedress.  You could throw some compost down next to each plant or along the row, but this wet year calls for a quicker response.

The plants need nutrients now and quickly.  That shovelful of compost might be fine in a normal year as it will slowly feed the plant over a few weeks’ time.  This summer, use a fertilizer that will be quickly available.  Yes, soluble synthetic fertilizers like Miracle-Gro provide that quick shot of fertilizer.  But organic gardeners can get similar quick action by using something like fish emulsion or blood meal. 

As with the fungicides, follow the label directions on the fertilizer container.  Although the bulk of nutrients are picked up by the roots, you can sometimes get a quick greening up of plants by wetting the foliage with a nutrient solution.  Check the fertilizer label to see if they have specific recommendations for foliar feeding. 

Sidedress the plants as soon as you can.  And it wouldn’t hurt to apply the same amount of fertilizer in 2 to 3 weeks.  At that time, try putting a teaspoon of Epsom salt in a gallon of water and sprinkling the plants.  Epsom salt is magnesium sulfate and both nutrients are essential for plant growth.  And even in a normal year, most plants, especially tomatoes, will show a magnesium deficiency.

So don’t give up.  It looks like the weather pattern is beginning to change this week with dryer, sunnier conditions on tap.  If you can get them over this stress, there is still hope for a productive season.