Broad-spectrum fungicides for vegetables

Check out these broad-spectrum fungicide options available for use on multiple vegetable crops.

Chlorothalonil (Bravo/Echo/Equus) is a FRAC M5 fungicide that is well known for its ease of use as a stand-alone product or tank mix partner for protecting against a range of pathogens of vegetable crops. Some examples of uses of chlorothalonil fungicide for disease control includes Alternaria leaf blight and fruit rot on tomato, late blight of tomato, Anthracnose ripe fruit rot of tomato, Cercospora and/or Septoria leaf and petiole blight of celery, Alternaria and Cercospora leaf and petiole blight of carrot, purple spot of asparagus, purple blotch in onions, garlic, and leeks, and Alternaria blight of cucumbers, squash, pumpkins, and melons. In addition to these disease examples, chlorothalonil has been important as a tank-mix partner for fungicides targeting downy mildew. Due to its multiple modes of action, this product can be used repeatedly and sequentially.

It appears that chlorothalonil-based fungicides may be in short supply this year and changes in fungicide programs may be needed. Luckily, other fungicides are available and can be selected to ensure that vegetable crops remain protected. Michigan State University Extension recommends paying attention to FRAC codes when deciding on an alternative broad-spectrum fungicide.

Mancozeb, available as Manzate or Dithane, is a broad-spectrum FRAC M3 fungicide that acts similarly as chlorothalonil.  It can be used to fill in many of the gaps that could pose a problem due to the short supply of chlorothalonil. Unfortunately, the mancozeb label lacks some crop registrations including Brussels sprouts, carrots, cauliflower, celery, and leeks.  Also, the pre-harvest interval for mancozeb is a relatively long 5 days, which can make it difficult to use on quick-growing and multi-pick crops such a cucumbers, zucchini, and summer squash. Due to its multiple modes of action, this product can be used repeatedly and sequentially, but some formulations only allow a maximum of four applications to asparagus, and eight to vine crops.

Switch is a broad-spectrum, locally-systemic fungicide and is a combination of fludioxonil (FRAC 9) and cyprodinil (FRAC 12). It has activity against Alternaria leaf blight in carrots, Alternaria leaf spot in broccoli, Brussels sprouts, cabbage, and cauliflower, crater rot in celery, and purple blotch in onions. It has comparable pre-harvest intervals to chlorothalonil. It could be a good alternative to chlorothalonil in cole crops, carrots, celery, and onions. Its label is limited to leafy and root/tuber vegetables. After two applications of Switch, rotate to a fungicide representing another FRAC code before using it again

Scala is a broad-spectrum systemic fungicide made from pyrimethanil (FRAC 9). It lacks labeling for cole crops, vine crops, and asparagus. However, it could make a good alternative for purple blotch control in garlic, leeks, and onions. It has a similar post-harvest interval as chlorothalonil.

Tanos is a broad-spectrum, locally-systemic and contact fungicide that is a combination of famoxadone (FRAC 11) and cymoxanil (FRAC 27).  It is helpful for Alternaria control and has been used as a tank mix partner with downy mildew specific fungicides. It is not labeled for asparagus, broccoli, Brussels sprouts, cabbage, carrots, cauliflower, or celery. It can be used for all of the vine crops, tomatoes, peppers, onions, garlic, and leeks. The pre-harvest interval is shorter than mancozeb products in most cases, but still three days longer than chlorothalonil products for vine crops, tomatoes, and peppers. Products in FRAC 11 have a high risk of pathogen resistance if they are used repeatedly. Always rotate to another FRAC code between applications of Tanos in a spray program.

Pristine is a broad-spectrum, locally-systemic and translaminar fungicide that is a combination of a strobilurin (FRAC 11) and a carboxamide (FRAC 7). Currently, it is not labeled for asparagus, cole crops, tomatoes, peppers, and potatoes. It can be used in place of Bravo for Alternaria leaf blight in vine crops and carrots, Alternaria leaf spot in celery, and purple blotch in garlic, leeks, and onions. The pre-harvest interval is similar to chlorothalonil and has a maximum application cap of four applications per year in vine crops, and six applications per year in onions, garlic, and leeks. Only two applications of Pristine are allowed each year in celery. Always rotate away from FRAC 11 products between applications of Pristine in a spray program.

Quadris/Heritage, Cabrio/Headline, or Flint/Gem are broad-spectrum, locally-systemic FRAC 11 fungicides. These strobilurin-based fungicides are labeled for most vegetable crops, with a 0-day pre-harvest interval in most cases. These products have a good history of working well on a variety of fungal diseases. However, FRAC 11 strobilurins have a high potential for generating resistant pathogens with repeated use. To conserve the use of strobilurins and delay the development of resistance, current labels limit the number of sequential applications permitted in any given year. For most crops, only two sequential applications are allowed with Quadris/Heritage, one sequential application with Cabrio/Headline, and four maximum applications with Flint/Gem.

Table 1. Comparison of broad-spectrum fungicides for the most common vegetables grown in Michigan (view pdf to print or read)

Asparagus

Broccoli

Brussels Sprouts

Cabbage

Carrots

Cauliflower

Celery

Cucumber

Garlic

Leeks

Melons

Onions

Potatoes

Pumpkins

Squash

Tomatoes

Active Ingredient

Trade Names

REI hours

FRAC codes

PHI days

Chlorothalonil

Bravo, Equus, Echo

12

M5

190

7

7

7

0

7

7

0

7

14

0

7/14

7

0

0

0

Azoxystrobin

Quadris, Heritage

4

11

100

0

0

0

0

0

0

1

0

0

1

0

14

1

1

0

Pyraclostrobin

Cabrio, Headline

12

11

0

0

0

0

0

0

0

7

7

0

7

3

0

0

0

Mancozeb

Manzate, Dithane

24

M3

180

7

7

5

7

5

7

3

5

5

5

Famoxadone + cymoxanil

Tanos

12

11 + 27

3

1

1

3

1

14

3

3

3

Cyprodinil + fludioxonil

Switch

12

9 + 12

7

7

7

7

7

0

7

Pyrimethanil

Scala

12

9

7

7

7

7

1

Boscalid + pyraclostrobin

Pristine

12

7 + 11

0

0

0

7

7

0

7

0

0

Trifloxystrobin

Flint, Gem

12

11

180

7

7

0

0

7

0

0

3

Source: MSUE publication E312.

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