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Garden Help Desk: Check seed packets for disease-resistant varieties

By Meredith Seaver use Extension Services - | Mar 27, 2021
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Not every plant disease can be managed with disease-resistant varieties, but home gardeners will find that there are also many vegetable varieties that do have disease resistance.

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Not every plant disease can be managed with disease-resistant varieties, but home gardeners will find that there are also many vegetable varieties that do have disease resistance.

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Look at the corners of your pesticide label for a tab or symbol that tells you there is more information inside the label.

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You might not see "PPE" on the label, but if you should be using protective equipment, the label will tell you.

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It's common for pesticide labels to have more than one page. Open and read the entire label and follow the directions.

We’re looking at two related questions today about seed catalogs, vegetable varieties and disease resistance.

Question: Where can I find disease-resistant seeds of my favorite tomato and pepper varieties?

Question: Why do some vegetables in seed catalogs have letters or numbers after their names? Do they make a difference?

Letters, numbers and symbols after the names of vegetables can mean a few different things. They may indicate resistance to specific diseases, a variety’s hybrid status or some special characteristic of a variety — it was bred for growing in containers or is suited for greenhouse production. Seed catalogs usually have a page with a chart or guide explaining their abbreviations or symbols.

When it comes to the letters at the end of a variety name, those could represent disease resistance. For example, a squash plant with resistance to powdery mildew could have the initials PM after the name or a pepper plant with TSWV after the name would have some resistance to tomato spotted wilt virus. Some seed companies mention disease resistance or other special characteristics in the variety description instead of using symbols or letters after the variety names.

Growing a disease-resistant variety can make a difference for gardeners that have had problems with specific plant diseases. Fungicide applications might be needed less often, or not at all. Insecticides to prevent the transmission of plant viruses by aphids, thrips or leafhoppers could be used less often. Resistance doesn’t necessarily mean immunity. Most resistant varieties aren’t immune, but they may be less affected by the disease, continue to be productive even though they have the disease or be much slower to decline because of the infection.

There are many fungal, viral and bacterial plant diseases that we see here. Unfortunately, there aren’t resistant varieties available for most of them. For example, there are some pepper varieties that are resistant to tomato spotted wilt virus or tobacco mosaic virus but there are no varieties that are resistant to curly top virus.

Disease resistance isn’t the result of a seed treatment that one seed company chooses to use while another company doesn’t. Resistance is a genetic characteristic specific to that variety, the result of careful plant selection, plant breeding and field testing. It can’t be added to the seeds of plants that don’t already have that characteristic.

Gardeners usually have to choose between their favorite varieties and resistant varieties. However, different seed companies offer different varieties, so checking in several catalogs may help you find a variety you like that also has some resistance to the disease you’ve had problems with.

Cornell University has lists of disease-resistant vegetable varieties, organized by vegetable category. If you’re serious about finding some nice resistant varieties, look through the list. You’ll find links to the lists here https://www.vegetables.cornell.edu/pest-management/disease-factsheets/disease-resistant-vegetable-varieties/. You might find new varieties that you like just a well as your current favorites.

Question: My weed killer spray doesn’t say anything about PPE. What should I do?

First, read the label again carefully. Most pesticides (herbicides, insecticides, fungicides, etc.) have labels with multiple pages. Make sure you’ve opened the label and read the entire thing. Look for the PPE (Personal Protective Equipment) information inside. If you still don’t see any PPE information, at least wear latex or nitrile gloves if you don’t have any chemical resistant gloves.

I generally choose to also wear long pants, long sleeves, old shoes and socks when I’m going to spray something; a little extra PPE is always better than not enough. If I’m going to do something messy, like spraying dormant oil on a tree, I’ll also put on a washable hat. I stick with old clothes so that stains aren’t a worry. Once I’m done spraying anything, everything goes into the washer and gets washed separately from the rest of the laundry.

While you’re reading your herbicide label, look carefully for information about the temperature guidelines. Most herbicides have lower temperature limits, and it may be too early in the season to use the product you have. You don’t want to waste your money and put extra chemicals out into the environment by spraying your product if we haven’t been having warm enough temperatures yet for your product to be effective.

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