Posts Tagged ‘fungicides’

Cucurbit Downy Mildew Fungicide Decisions

Friday, May 11th, 2012

Kate Everts, Vegetable Pathologist, University of Delaware and University of Maryland;

Downy mildew on cucurbits has been a problem on Delmarva beginning in early July for the last few years. Good fungicides for management are available. However, last year in my trials, one of these fungicides, Presidio, was not as effective as expected. Looking ahead to your spray program, be careful not to rely on one fungicide class. It is difficult to know which fungicides will be effective here, because our population does not overwinter and is reintroduced from the South each year. Therefore use excellent resistance management practices to avoid allowing the pathogen to develop resistance and to improve the efficacy of your fungicide management program.

Fungicide Resistance management guidelines by crop are available online and hard copies are available in Delaware at the county Extension offices.

More Vegetable Fungicide Updates for 2012

Thursday, April 5th, 2012

Kate Everts, Vegetable Pathologist, University of Delaware and University of Maryland;

I wrote last week about some new and recent fungicide registrations of interest to vegetable growers. Two additional registrations occurred in the last week.

  • · Luna Experience has now received a label for use on watermelon in both DE and MD. Diseases on the label include gummy stem blight, anthracnose, and powdery mildew.
  • · Meteor is a new fungicide from United Phosphorus, Inc., with the active ingredient of iprodione. It is labeled for beans (white and grey mold), broccoli, carrots, Chinese mustard, bulb dry onions, garlic and lettuce (drop and bottom rot). See label for more details. There are other fungicides that are labeled for similar diseases on vegetables with the same active ingredient, such as Rovral.

Vegetable Fungicide Updates for 2012

Thursday, March 29th, 2012

Kate Everts, Vegetable Pathologist, University of Delaware and University of Maryland;

The following is a very brief overview of recent fungicide registrations and new updates that may be of use to vegetable growers in 2012. This is not meant to be a comprehensive list. Also, I have not run research trials for most of these product uses, and therefore cannot say anything about efficacy in comparison to other products. Remember to follow all label directions carefully. Before use, check each label for rates, information on resistance management, tank mix incompatibilities and other information.

  • · Prophyte and some other phosphorous acid fungicides are available for use on bean cottony leak (Pythium cottony leak).
  • · Quintec now has a Section 2ee label for the suppression of bacterial leaf spot on pepper in some states in the mid-Atlantic (including DE and MD, but not PA).
  • · Both chlorothalonil and Manzate Pro Stick labels have added anthracnose fruit rot on pepper.
  • · The Ranman label now includes spinach white rust as well as club root and downy mildew of cole crops (brassicas).
  • · Quilt Xcel and Stratego YLD are labeled for sweet corn rust.
  • · A new OMRI approved copper, Nordox, has a broad label that includes many vegetables and use in the greenhouse on some crops.
  • · Quash fungicide is labeled on potato and sweet potato for many diseases including early blight and white mold.
  • · A label expansion for Cabrio lists management of stem rots caused by Rhizoctonia and Sclerotinia and Southern blight (Sclerotium rolfsii) on tomato, pepper and eggplant.
  • · Fontelis has received a label for many vegetables including brassicas (Alternaria, gray mold, powdery mildew, Sclerotinia); tomato and other fruiting vegetables (early blight, gray mold, powdery mildew, Septoria leaf spot, etc.); Leafy vegetables (Alternaria, Cercospora, Septoria, etc.); Legume crops (Alternaria, anthracnose, Ascochyta, Botrytis, etc.); and some root vegetables (early blight, Cercospora leaf spot, Sclerotium rolfsii, etc.)
  • · Luna Experience has received a label for use on watermelon in DE and the label is pending in MD. Diseases on the label include gummy stem blight, anthracnose, and powdery mildew.

Sweet Corn Fungicide Label Updates

Friday, March 2nd, 2012

Bob Mulrooney, Extension Plant Pathologist;

A few new fungicide combinations are now labeled for sweet corn as well as field corn. Stratego YLD is a new combination of trifloxystrobin plus Proline (prothioconazole). Headline AMP is a combination of pyraclostrobin and Caramba (metconazole) and Quilt Xcel is a higher concentration of Quadris (azoxystrobin) plus Tilt (propiconazole). They will provide excellent control of Northern corn leaf blight, gray leaf spot, and rust if used as directed on the label.

Gavel 75DF from Gowan Company LLC Now Labeled for Pumpkin and Winter Squash

Thursday, August 4th, 2011

Bob Mulrooney, Extension Plant Pathologist;

Gavel has been labeled for use on pumpkin and winter squash for the control of Alternaria leaf spot, Cercospora leaf spot, downy mildew and Phytophthora fruit and stem rot. This is in addition to labels for use on cucumber, cantaloupe, summer squash and watermelon. Gavel is not recommended for downy mildew control on cucumbers but is recommended for control on pumpkin and winter squash as well as watermelon and cantaloupe. Remember that Gavel contains mancozeb, so some cantaloupe varieties might be sensitive. Go to to see updated label.

The Deadline to Remove Tolerance of Maneb Extended Until December 21, 2012

Thursday, August 4th, 2011

Bob Mulrooney, Extension Plant Pathologist;

via Gene MacAvoy, University of Florida

The U.S. Environmental Protection Agency has taken into consideration written comments submitted by FFVA and others and agreed to delay the expiration of tolerances for the fungicide product maneb. Among its comments, FFVA reminded EPA that existing stocks of maneb may remain in growers’ inventories and that a premature revocation of tolerances could generate complications such as disposal obstacles if all components were not carefully considered before a final decision. Therefore, to allow sufficient time for existing stocks that may remain in the channels of trade to be used and subsequent marketing of affected commodities, tolerances for maneb on food uses such as succulent beans, broccoli, cabbage, cauliflower, celery, collards, sweet corn, cucumbers, eggplant, endive, kale, lettuce, melons, mustard greens, papaya, peppers, potatoes, squash, tomatoes and turnips, will now not expire until Dec. 31, 2012.

Grower’s Guide to Understanding the DMI or SI Fungicides

Friday, June 10th, 2011

Bob Mulrooney, Extension Plant Pathologist;

The following article by Andy Wyenandt, Ph.D., Specialist in Vegetable Pathology at Rutgers University is particularly timely since many vegetable growers are spraying fungicides to prevent many foliar diseases at this time of year especially on vine crops where DMI or SI fungicides are used very frequently.

The DMI (DeMethylation Inhibitors) or Sterol biosynthesis Inhibiting (SI’s) fungicides belong to FRAC code 3, which include the triazoles and imidazoles. Some of these fungicides are commonly known as Tilt (propiconazole), Rally (myclobutanil), Folicur (tebuconazole), and Procure (triflumizole). SIs work by inhibiting the biosynthesis of ergosterol, which is a major component of the plasma membrane of certain fungi and needed for fungal growth.

Resistance by fungi to the SI fungicides has been characterized and is generally known to be controlled by the accumulation of several independent mutations, or what is known as ‘continuous selection’ or ‘shifting’, in the fungus. Such that, in any given field population the sensitivity to the SI fungicide by the fungus may range from extremely high (highly sensitive, i.e. will be controlled by fungicide) to moderate (partially sensitive) or low (mostly resistant to fungicide). This type of resistance is also known as quantitative resistance. With quantitative resistance there are different levels of resistance to the fungicide due to independent mutations, which is unlike the target mutations that occur in qualitative resistance associated with the QoI fungicides (FRAC code 11).

Because different levels of resistance to the SI fungicide may exist in the field, the fungal population may behave differently to different rates of the SI fungicide being applied. If that is the case, it is suggested that using a higher rate of a SI fungicide, may improve control when lower rates have failed. For example, let’s say that a powdery mildew population on pumpkin has 25% high, 50% moderate, and 25% low sensitivity to a SI fungicide. If fungicide is applied at the low rate, only 25% of the population (highly sensitive) may be controlled. Whereas, if the high rate was used 75% of population may have been controlled.

The main point is that if low rates of SI fungicides have been used and control seems to be weakening, bumping to a higher rate may improve control. Unfortunately, it is difficult to determine what proportion of the powdery mildew population is sensitive or not sensitive by looking at the field until you have begun spraying. The best advice, if you are using low rates and think those rates are not working like you feel the rate should be bumped up to the high rate the next time the fungicide is sprayed, and if the high rate doesn’t work, it may be safe to assume the fungal population has grown mostly resistant. Importantly, if the high rate fails, whether you bumped up to a high rate or started with one, and control does not seem adequate, do not continue to use the fungicide.

Recognizing if and when fungicide chemistries are failing and when fungicide resistance is developing is critical to producing successful crops and why scouting on a regular basis, at least before and after each fungicide application, is important. Regular scouting can help reduce unwarranted and ineffective fungicide applications and help reduce wasted costs. Remember to always tank mix SI fungicides with protectant (M) fungicides (i.e., chlorothalonil) to help reduce the chances for fungicide resistance developing. Always apply SI fungicides according to label rates and resistant management recommendations and always be aware of the fungicide rates you are applying.


Grower’s Guide to Understanding the Protectant Fungicides (FRAC Codes M1 – M9)

Friday, May 20th, 2011

Bob Mulrooney, Extension Plant Pathologist;

The following article is excerpted from Rutgers Plant and Pest Advisory Newsletter and is a good refresher on fungicide basics. It was written by Andy Wyenandt, Ph.D., Specialist in Vegetable Pathology, Rutgers University

Protectant (or contact) fungicides, such as copper (FRAC code M1) and sulfur (M2), the dithiocarbamates (mancozeb, FRAC code M3) and chlorothalonil (M5) belong to FRAC groups which have a low chance for fungicide resistance to develop. Protectant fungicides typically offer broad spectrum control for many different pathogens. So, why wouldn’t fungi develop resistance to protectant fungicides? Protectant fungicides are used all the time, often in a weekly manner throughout much of the growing season. The answer is in their modes-of-action (MOA). Protectant fungicides have MOA’s that affect (i.e., prevent) fungal development in different manners. In inorganic compounds, sulfur (M2) prevents fungal growth (i.e., spore germination) by disrupting electron transport in the mitochondria. Coppers (M1), on the other hand, cause non-specific denaturation of proteins. Chlorothalonil (M5) inactivates amino acids, proteins and enzymes by combining with thiol (sulfur) groups. In all cases, a protectant fungicide’s chemistry disrupts fungal growth and development either non-specifically or in multiple manners. Because of this, there is a much lower chance for fungi to develop resistance to them.

Protectant fungicides are contact fungicides, meaning they must be present on the leaf surface prior to the arrival of the fungus and must then come into direct contact with the fungus. Protectant fungicides can be redistributed on the leaf surface with rainfall or overhead irrigation, but can also be washed off by too much of either! Remember, that with protectant fungicides, any new growth is unprotected until the next protectant fungicide is applied, in other words, protectant fungicides are not systemic and do not have translaminar activity like some of the newer chemistries. Protectant fungicides should be tank-mixed with fungicides with higher risks for resistance development. Protectant fungicides used in this manner will help slow (or reduce the chances for) fungicide resistance development on your farm. In any case, it’s best to always follow the label and tank mix protectant fungicides with those fungicides with a high-risk for resistance development when required to do so.


Label Additions for Presidio

Friday, May 6th, 2011

Bob Mulrooney, Extension Plant Pathologist;

Valent USA just reported that brassica leafy vegetables, root and tuber vegetables, potatoes and carrots have been added to the Presidio label. The other good news is that the rotation interval for wheat has been reduced from 18 months to 30 days. Hopefully this will be the beginning of the reduction of the other rotational intervals for other crops that follow cucurbits that have limited its use for downy mildew control in pickling cucumbers particularly. The supplemental label is available online here: Presidio is an excellent fungicide for cucurbit downy mildew control and will be another excellent fungicide for control of late blight and pink rot on white potatoes.


Mancozeb Label Updates

Friday, April 8th, 2011

Bob Mulrooney, Extension Plant Pathologist;

Good news on the fungicide front. Tolerances were established for mancozeb to replace some of the uses that maneb was labeled for. Maneb is no longer being manufactured. This has led to the first labels of mancozeb for use on broccoli, peppers, cabbage and leaf and head lettuce. Manzate Pro-Stick from UPI has a supplemental label for these uses, pending state approvals. I am sure the other manufacturers of mancozeb will have labels shortly. See the linked label for details: This label expansion was needed especially for control of anthracnose on peppers. These additions are not in the 2011 Commercial Vegetable Recommendations so you need to be aware of that.