Soybean and Corn Fungicide Efficacy Sheets Available

April 22, 2015 in Corn, Corn Disease Management, Soybean, Soybean Disease Management

Our ratings for soybean and corn fungicides are now available.  To access these sheets click the links below:

Soybean Fungicide efficacy table_2015_final (3)

CDWG Fungicide efficacy table_2015_final (2)

We determine these relative ratings based off of the results of local efficacy trials.  We (plant pathologists) from around the nation then discuss our results and compile them to form these rating sheets.

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Review and history of Cucurbit Downy Mildew

April 18, 2015 in Vegetables

Downy mildew of cucurbits is a serious disease for vegetable growers in the Midatlantic.  The epidemic in 2004 changed the way we manage this disease.  The downy mildew picture continues to change, and we continue to learn more about this pathogen and its management.  A recent article published in the journal Plant Disease gives an excellent overview of the history of this disease and the current knowledge status.  The article can be found by clicking this link:  CDMReviewpdis-09-14-0990-fe

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2015 wheat fungicide table now available

April 13, 2015 in Barley diseases, Wheat, Wheat Diseases

Each year our national wheat pathology working group gathers and publishs an updated list of fungicides for small grains.  We utilize our local data to determine the relative performance of products on specific diseases.  This year’s list is changed somewhat from last years.  Please note the footnote on fungicide resistance in leaf blotches at the bottom of the table.

The table can be accessed by clicking the following link: NCERA 184 Wheat fungicide table 2015_V3

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New work on tillage and fungicides for Phomopsis and Purple Seed Stain in soybean

April 3, 2015 in Soybean, Soybean Disease Management, Soybean diseases

Phomopsis seed decay (PSD) and purple seed stain (PSS) are two seed-borne diseases that can impact soybean quality.   PSD-infested seeds are often lightweight and show reduced germination, whereas PSS infected stain often develops a purple discoloration.  PSS also can result in leaf blighting and seedling death in some instances.   Therefore, both PSD and PSS can reduce value of soybean grown for seed or sent overseas.  Management of these diseases often is achieved by planting clean, certified seed, crop rotation, deep tillage to bury infested residue,  and in very limited situations, fungicide applications between R3 and R5.  Many growers are switching to no-till or conservation-tillage systems, which may influence the severity and incidence of soybean diseases such as PSS and PSD and also impact disease management.  Unfortunately, there simply isn’t much out there in terms of replicated, applied research in this area.

Researchers at The University of Tennessee conducted trials over a 4 year span that looked at the impact of tillage and fungicides on PSD or PSS.  However, the use of a fungicide reduced PSD in tilled but not no-tilled settings.  In addition,the application of Headline at either R3 or R5 resulted in greater levels of PSS across tillage treatments.  Their results were recently published in the journal Crop Protection.

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2015 small grains disease outlook

March 28, 2015 in Barley, Barley diseases, Wheat, Wheat Diseases

For the second year in a row, we are dealing with the aftermath of a cold, prolonged winter.  In addition, a wet end to the summer resulted in much of the small grains being planted later than normal.  How might this impact the 2015 diseases and what should you be looking for?

Barley yellow dwarf virus (BYDV) is unlikely to show up in any significant amount.  This virus is spread by several species of aphid, and severity and intensity is related to the amount of aphid activity early in the season.  Late plantings coupled with a cold, prolonged winter make it highly unlikely to see much of this disease in 2015.  BYDV symptoms will be most evident around heading, and manifest as discolored flag leaves, stunted plants, and deformed heads.

Other cool season viral diseases that prefer wet soils, such as Wheat Spindle Streak Virus may be more pronounced in fields where this virus has appeared in the past.  Look for stunted, plants before Feekes 8.  Stunted plants often occur in low lying areas of the field , but may also be found throughout the field in some instances.  Viruses can only be confirmed through special tests such as PCR or ELISA.

A cool , delayed spring means that our crop is a behind.  The cool temperatures in the south have resulted in flare ups of Stripe rust.  Stripe rust needs to blow up to our region from southern areas, and the combination of a high inoculum load in the south, cool temperatures, and a delayed crop increase the chance that we might see a bit of this disease in 2015.  Keep an eye out for this disease as under the right conditions flare ups can cause some significant reductions in yield.  Click here for a detailed factsheet from KSU on stripe rust.

 

 

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Glyphosate application does not increase Soybean Sudden Death Syndrome

March 9, 2015 in Soybean, Soybean Disease Management, Soybean diseases

Sudden death syndrome (SDS) is a soilborne disease of soybeans caused by the fungus Fusarium virguliforme.  This disease infects soybeans during the seedling stage during prolonged periods of cool, moist weather, resulting in root rot.  Rains at the reproductive stage of growth cause the fungus to deeply colonize the roots and produce a toxin, resulting in the characteristic interveinal necrosis.

A leaf with interveinal chlorosis characteristic of SDS

A leaf with interveinal chlorosis characteristic of SDS Photo by N. Kleczewski

If you are lucky, you will see blue growth around the soil line, which is indicative of SDS.

Blue growth (within circle) on the roots or soil line indicates the presence of SDS.  Photo by N. Kleczewski

Blue growth (within circle) on the roots or soil line indicates the presence of SDS. Photo by N. Kleczewski

 

SDS has become a yield-limiting disease in high input fields in the Midwest, and is present at low levels in the mid-Atlantic.  Glyphosate-resistant soybeans are commonly planted because they facilitate weed management.   Over 90% of soybeans planted in the United States contain glyphosate resistance.  There have been reports of glyphosate related issues with diseases in soybeans, including SDS, with some studies showing an increase in disease, and others indicating a reduction of disease when glyphosate is used.

A paper recently published in Plant Disease  examined the effects of glyphosate on SDS severity, grain yield, and plant nutrition in studies conducted across five states in the US  and one site in Ontario, Canada from 2011-2013.  What did they find?  There were no effects of herbicide on disease, and treatments with glyphosate tended to yield more than treatments with non-glyphosate containing herbicides.  In addition, there were no effects of glyphosate on plant nutrition.   For additional information follow THIS LINK

Reference: Kandel, Y. R., Bradley, C. A., Wise, K. A., Chilvers, M. I., Tenuta, A. U., Davis, V. M., Esker, P. D., Smith, D. L., Licht, M.A., and Mueller, D. S. 2015. Effect of glyphosate application on sudden death syndrome of glyphosate-resistantsoybean under field conditions. Plant Dis. 99:347-354.
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UD Nematode Assay Service 2015

March 7, 2015 in Soybean, Soybean Disease Management, Vegetables

The University of Delaware realizes the importance of a local nematode assay service to our growers. However, changes in staff and resources have required us to change when and how this service is offered. To maximize resources, predictive soil nematode assays will only be conducted by the service from April 1- May 1, 2015 and from October 1-November 1, 2015Soybean cyst nematode (SCN) egg assays, the most accurate means of assessing SCN, will be available throughout the season.

Fields with issues during the growing season (troubleshooting samples) will be accepted as needed; however, Dr. Nathan Kleczewski must be contacted prior to submitting troubleshooting samples at nkleczew@udel.edu or 302-300-6962.  Remember that the service only accepts commercial vegetable and field crop samples from within Delaware.

The UD Nematology fee schedule can be found here:  https://commerce.cashnet.com/cashnetc/selfserve/BrowseCatalog.aspx

 

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Fungicides and potency

March 3, 2015 in Barley diseases, Corn Disease Management, Soybean Disease Management, Wheat Diseases

Fungicide selection can be a challenging process, and growers often need to take into account many factors in deciding on a product.  Disease history, variety susceptibility, cost, and performance are important factors that go into the overall equation for selecting a product.  One statement you may hear sounds something like this:

“I’m going with Product X because it has more of triazole1 than Product Y, which has a lower amount of triazole 2 for this price”.

Let’s change that statement around, but this time let’s say the individual is in the demolition business.  “I’m going with black powder over plastique because I get less plastique for this price.”

That statement is true, but the amount of powder needed to do the same job as a given amount of plastique is much greater.  Thus, the comparison doesn’t really make sense.

The same goes for our fungicides.  Potency can vary significantly within a fungicide class.  Thus you may only need to go out at a 6 oz rate for one product to achieve the same level of disease suppression that you may achieve at a 10 oz rate for another product.  In addition, the inactive ingredients play vital roles in the performance of fungicides.  Premixes are another issue, as sometimes synergism occurs-the activity of the actives in a mixture are greater than what would be expected if they were applied solo.  Keep this in mind going into the field season.

 

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Nematode Management and Nimitz Training Offered

February 25, 2015 in Vegetables

Location: University of Delaware, Carvel Research and Education Center,
16483 County Seat Highway, Georgetown, DE 19947
Time: 8:30 a.m. – 12 p.m.

Date: April 20th, 2015

Registration: Please call Karen Adams at (302) 856-2585 ext. 540 to register

Vydate will be in short supply for at least 2015, and growers have few options for root knot nematode management in vegetables. This technical session will cover fumigant options for nematode management and training in the use of Nimitz, a new contact nematicide offered by Adama®. Speakers will include Dr. David Langston from Virginia Tech, and Pablo Navia Gine, Innovation Technical Leader at Adama®. Participation will be limited to the first 90 registrants.  Food will be provided.

Nathan Kleczewski – Extension Plant Pathologist UD and

Kate Everts – Extension Vegetable Pathologist UD and UMD

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Vydate to be limited in supply in 2015

February 11, 2015 in Vegetables

You may have heard that the Vydate plant in Texas has closed temporarily.  Consequently, expect this product to be limited during the growing season.  This is unfortunate news as Vydate is a fairly economical means to suppress root knot nematodes in many vegetable crops.

Unfortunately we do not have many alternatives.  Liquid fumigants such as Telone II can work, but often are not economical.  I mentioned a new product from Adama called Nimitz.  This is a synthetic, contact nematcide that acts on the nematode cuticle.  The data I have seen shows that it performs fairly well, but there are some issues with stunting and phytotoxicity.  According to Adama the product can be applied preplant either as a broadcast or banded application.  The product is then worked into the ground and allowed to set for 14 days.  During this period, two typical irrigation cycles should be run to 1) allow the product to move deeper into the soil profile and 2) dilute the product.  A final concentration of 1ppm is what you are shooting for with this method.  Another key is to apply the product when temperatures are above 65 degrees F.  This ensures that the nematode population is active and more likely to encounter the product in the soil.  I have also heard from some colleagues in the South that stunting and phytoxicity may increase in cooler conditions.  Adama does offer training sessions on Nimitz to consultants and growers to familiarize them with proper use of the product.

Unfortunately not many people have experience with Nimitz, particularly in this area.  Hopefully we can get a look at it and some other pipeline products in the upcoming season.  In the meantime, realize that there may be a shortage in Vydate this year and adjust your programs accordingly.

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