Downy Mildew on Hops Present in WNC

This week I have been visiting with our WNC hops growers. To my dismay, I found the dreaded downy mildew, Pseduoperonospora humuli, in two of the yards.

We saw the beginnings of this problem late last season on the hop cones. See my post from September 2008 on downy mildew of hops.

When determining if you have downy mildew in your hops yard, look for pale green to yellow newly emerged spikes that appear stunted.

Note the pale green, stunted spikes of this hops plant.

A closer look at the pale green to yellow new spike. Note the shorten internodes and miniature leaves.

Another shot of the infected, newly emerged shoot. Take note of the curled and brown lower leaves.

A close up of the browning, curled leaves on the hops shoot. The leaf looks dirty, but those are actually millions of downy mildew sporangia!

A hops leaf exhibiting foliar symptoms of downy mildew.

The underside of the downy mildew infected leaf. Note the fuzzy spores.

The worst downy mildew infection that I noted was on 'Nugget'. 'Nugget' is considered to be susceptible to downy mildew. Interestingly, in the hops yard where downy mildew was found on 'Nugget', it appeared to be the most vigorous variety.
**Update May 21**
Some sources report that 'Nugget' is resistant to downy mildew, while others report it is susceptible.

Downy mildew was also found to be prevalent on 'Centennial' which is considered to be tolerant to downy mildew.

One of the best management strategies for the control of downy mildew on hops is to remove primary basal spikes and to heavily prune and strip leaves. This is important in order to prevent downy mildew from moving up the bines and eventually infecting the cones. Pruning and thinning also helps to reduce moisture and humidity in the lower part of the canopy which is favorable for disease development.

Hops yard with lower leaves stripped up to 3 feet.

Because we are expecting wet weather in the next few days here in WNC, action needs to be taken quickly to prevent the spread of disease to other bines. The first step is to prune and thin the bines.

In addition, the application of fungicides is recommended as soon as the wet weather is over or before if product is rainfast. For a complete list of fungicides (conventional and organic) used to control downy mildew on hops, visit the Oregon State University Downy Mildew Fact Sheet. Before you apply any pesticide make sure you follow the specific label directions and make sure that the product is labeled for downy mildew on hops in NC.

*UPDATE*

Organic Fungicides Labeled for Management of Downy Mildew of Hops in NC:

• Sporatec (rosemary oil, clove oil and thyme oil)
• Copper products (look for OMRI label)
• Sonata (Bacillus pumulis strain QST 2808)
  

Conventional Fungicides Labeled for Management of Downy Mildew of Hops in NC (not a complete list):

• Curzate (cymoxanil) - must be tank mixed with a fungicide of different mode of action, such as copper
  
• Tanos (cymoxanil + famoxadone) - must be tank mixed with a fungicide of different mode of action, such as copper
• Acrobat and Forum (dimethomorph) - must be tank mixed with a fungicide of different mode of action
• Fosphite and other phosphorous acid products
• Legion (Aluminum tris)
  

The best approach would be to incorporate a few of these products in order to slow down the possibility of fungicide resistance. Again, always follow the directions on the label - it's the law!

Hops Pest: Eastern Comma Butterfly

A few weeks ago a number of our local hops producers were noticing large holes in some of their hops leaves. Upon closer inspection, they found spiky, white caterpillars feeding on the leaves.

Larva of Eastern comma butterfly found on hops in WNC (picture courtesy of R. Pelczar).

The entomologists at NCSU agreed that the caterpillars are larvae of the Eastern comma butterfly, Polygonia comma.

Larva of Eastern comma butterfly found on hops in WNC (picture courtesy of R. Pelczar).

Hosts:
Hosts plants of the Eastern comma butterfly are American elms, hackberry, nettles, false nettles and other members of the Urticacea. But, perhaps the favorite food of the Eastern comma butterfly is hops.

Beginning in the early 1900's, the Eastern comma butterfly was referred to as the "hop merchant" because hops farmers would predict the future price of hops based on the variation in the silver and gold spots on the pupae.

Larvae:
The larvae ranges in color from white to green-brown to black and are typically just over 1 inch long. The spikes also range in color from black to white with black tips. The larvae rest on the underside of leaves and make nests by silking together the sides of the leaf. The larvae rest during the day and feed at night.

Eastern comma butterfly larva. (Picture courtesy of Echoview Farm).

Eggs:
The eggs are green with vertical ridges and are laid singly or in stacks. I was lucky to find these (sorry they are not the greatest pics)!

Eggs of Eastern comma butterfly on underside of hops leaf.

Close-up of the eggs of Eastern comma butterfly. Notice the vertical ridges.

Pupae:
Pupae are variable in color but always have prominent ventral gold or silver spots.

Adults:
The adult is an orange and brown butterfly with a wingspan of 1.75 to 2 inches. With its wings folded it looks like a dead leaf.

Life Cycle:
There are two generations per year for Eastern comma butterflies. During the summer, the new butterflies are inactive during the hot period and then become active again in the fall. The fall brood of adult butterflies overwinter and start the cycle again in the spring.

Management:
The feeding damage caused by the Eastern comma butterfly larvae ranged in the individual hops yards here in WNC. One grower experienced quite a bit of initial damage, but was able to prevent further destruction by hand-picking the caterpillars.

Growers at another farm reported shaking the bines to knock off the caterpillars and then destroying them. This appeared to work well and little damage has since been noted. This grower also applied BT (Bacillus thuringiensis, a bacterial biological control material that is labeled for Lepidopteran pests) and reported that it was effective.

Hopefully, the Eastern comma butterfly will not be a problem for our hops growers in the future. At least now we know what the pest is and how to control it.

Thanks to all the folks who helped in the identification of the larvae and for the great growers for sharing their experience and their wonderful pictures!

To learn more, read the University of Florida's fact sheet on the Eastern Comma Butterfly.

Local Hops Producers Featured in Raleigh N&O

Congratulations to two of our local WNC hops producers, Julie Jensen and Van Burnette, who were featured in the Raleigh News & Observer Story "Brewers Have High Hopes for NC Hops".

In addition, we have a lot to be thankful for with all the hard work that NCSU researchers, Dr. Jeanine Davis, Dr. Deanna Osmond and Rob Austin are doing to help our hops industry grow!

Congratulations everyone!

Here is a sidebar from the on-line article entitled, "Beer in the Mountains":

The four farms working with N.C. State University to explore the possibility of commercial hops growing are all clustered around Asheville, and that's no coincidence: The mountain city is gaining national attention as an attraction for craft-beer lovers, and would be an obvious market for the bitter flowers.

Last year Asheville was voted "Beer City USA" in an online poll, sharing the top honor with a much better-known brewing city, Portland, Ore.

Also in 2009, eight brewing operations in the city and four nearby formed the Asheville Brewers Alliance.

"Any day of the week, you can have your choice of probably 80 Asheville-made beers," said Tony Kiss, who covers beer like a sport for the Asheville Citizen-Times.

A tour called the Brews Cruise takes tourists on a circuit of local brewing operations and the city now boasts five annual beer festivals. All 3,500 tickets for the fall Brewgrass Festival were snapped up in less than a day when they went on sale Wednesday.

With all this beer action, Black Mountain farmer Van Burnette said hops growers like him not only could supply local brewers with their most crucial ingredient, but also could become part of a critical mass of attractions for the beer-related tourism.

Blackberry Rusts

I have been spending a lot of time lately in the blackberry fields of Henderson County. This is a really great crop to work with and our growers are excellent. It is a relatively new crop for the county, but over the past few years our growers have planted about 87 acres of blackberries. Most of the varieties that we are cultivating are floricane-fruiting varieties developed from the Arkansas breeding program, including Natchez, Navaho and Ouachita.

One of the things we are learning is all of the disease and insect issues that we are going to experience. I have observed two rust diseases on blackberries so far this season and would advise all growers to be scouting for these problems.

Section of Natchez planting with an obvious problem.

The first disease I observed was causing a problem only in Natchez. It is cane and leaf rust. The infected section of plants had some rust problems late last season. The grower has heavily pruned out infected canes and applied products for management.

The causal agent of cane and leaf rust is the fungus Kuehneola uredinis. Cane and leaf rust is first seen in late spring on infect floricanes. The large yellow-orange spores of the pathogen split the bark. At this point, we have not observed any rust on the leaves.

Vibrant yellow rust spores emerging from cracked bark.

Bark cracking in multiple spots on Natchez cane, exposing rust spores.

Pustule of K. uredinis breaking the bark on Natchez.

Control of cane and leaf rust involves cultural and chemical control. The first step is to remove heavily diseased canes and dispose of them in order to reduce inoculum (spores). Highly susceptible varieties or areas with a history of this problem require chemical control. Products used to control cane and leaf rust are copper, myclobutanil (Rally), pyraclostrobin (Cabrio) and pyraclostrobin + boscalid (Pristine).

Next rust problem...

At first glance there is no problem with these Navaho blackberries, right?

Upon closer inspection, there is an obvious orangey problem. The leaves are also slightly yellowish.

Notice the orange pustules on the underside of the leaves. The leaves also appear pale green.

This problem is orange rust on the variety Navaho. Orange Rust is the most important rust problem in the eastern United States and a limiting factor in the northeast. It is a systemic rust, meaning that it lives throughout the infected plant.

Symptoms of orange rust can be seen in the spring as new growth appears. The young shoots are spindly and the new leaves are often mishapen, stunted and pale green to yellowish. The first spot on the leaves will be a subtle black speck on the upper leaf surface that is caused by the mycleium of the pathogen growing in leaf tissues. In a few weeks, the orange rust spores can be seen on the bottom of the leaf surface.

The infected leaves are stunted, have a slightly yellow hue and the ends are curled.

Close up of the orange-blister like aecia and many orange aeciospores [Aecia = Geek talk for a cuplike structure containing the rust spores (aeciospores)].

There are two forms of orange rust. The form on black raspberry is caused by a fungus known as Arthuriomyces peckianus, while the form more common on blackberry is known as Gymnoconia nitens. Orange rust is not known to kill plants, but it causes reduction in vegetative growth and fruit production. Infected plants rarely recover.

Navaho is susceptible to orange rust. Orange rust has not been observed on Natchez or Ouachita and is seldom a problem on Chester or Hull in North Carolina. Orange rust can also be observed on our wild caneberries. Cornell University has a good factsheet on orange rust.

Control of orange rust includes picking resistant varieties, removing heavily infected canes and plants and applying fungicides. Fungicides (Rally, Pristine or Cabrio) are applied in the spring before pustules are formed on the lower leaf surface. Often the wild blackberries are used as indicators of when to spray. Sprays are applied on 10- to 14- day intervals until the mean temperature remains above 77 degrees F.

I do not have specific organic recommendations available for either of these disease, but the use of resistant varieties, removal of diseased plants (including wild brambles if possible) and diligent scouting will do a lot of good. In addition, here is a great ATTRA publication on the Organic Culture of Brambles.

Henderson County Father and Son Team Featured in Times-News

I would like to take this opportunity to congratulate some local growers.

Stepp's Plants, etc. is a great local farm in Henderson County that is run by father and son team Larry Stepp Sr. and Larry Stepp Jr. The pair have a great dynamic and it is a joy to talk and learn with them. The Stepps grow a wide variety of small fruits, asparagus, diverse vegetables, bedding plants and hanging baskets.

Recently, the duo was featured in the Hendersonville Times-News. They even shot a video (below).



To read the entire article, visit "Son Leaves Corporate World to Join Dad in a New Farming Venture".

You can find Stepp's Plants, etc on Facebook.
Visit Stepp's Plants, etc! Stepp's Plants, etc and other local farms will be part of ASAP's Family Farm Tour on June 26 and 27!

Congratulations!

Herbicide Carryover: Bioassay Results

About a month ago I reported on a farmer who had received manure that was contaminated with the herbicide picloram and applied it to his vegetable production fields. We conducted a bioassay on the contaminated land to see if the soil was safe to plant. Last week we assessed the results of the test.

The first site we tested was "Moses". This field had been contaminated by the manure, however the manure was only applied in a small amount in each of the holes where tomatoes were planted. From the test, it looks like this site should be safe for planting this year.
Side note - The greenhouse where the seedlings were located was very hot, so some of the "crispy" edges are more than likely due to the temperature because some of the control plants also were affected.

Beans are sprouting in soil that was contaminated with manure containing the herbicide picloram.

Control test using soil that was not contaminated.

Next up was the field we called "Fred". Manure was applied to this entire field. The field appears to be unsuitable for vegetable production at this time. The grower will not be producing on this plot this season.

Bean seedlings did not emerge from the soil collected from field "Fred".

Control soil taken from part of field where no manure was applied. Seedlings look pretty good.

We were also concerned about the field below "Fred". There were a few spots where the grower's Austrian winter peas did not emerge. So we tested these areas to see if runoff from "Fred" was the reason. Looks like that field should be okay.

Bean bioassay of soil taken from a field below "Fred" where some water runoff from "Fred" flows.

The final plot that was tested was a field that is located next to the growers house. This field had the most manure applied and there was no soil available to test as a control. As you can see, this soil appears to be unsuitable for vegetable production.

No bean seedling emerged from the soil taken at the home site. This plot had the most manure applied to it.

Overall, we were not surprised by the results. All of our seedlings from the control plots emerged successfully. The seedlings planted in soil from the field with the least amount of manure applied ("Moses") emerged and there appeared to be no damage. The grower is planning on producing vegetables in this field this season. Luckily, the grower did not lease field "Fred" this season due to other reasons.

The most unfortunate situation is the field that is located next to the house. The grower will continue to work this land to allow for the elements, sun, rain, etc to break down the herbicide. He is considering growing a less susceptible crop in this field, such as corn or a grass cover crop.

To read more about the bioassay and herbicides that may be a problem in manure, read Dr. Jeanine Davis's article "Herbicide Carryover in Hay, Manure, Compost and Grass Clippings".

**UPDATE May 2010**
New Herbicide Carryover publication available!

Don't Bring in Problems with Transplants!

Healthy vegetable transplants in a local greenhouse.

This is the time of year when commercial growers and homeowners alike are preparing for transplanting of vegetable crops.

Warning: Don't bring diseases into your garden or field on transplants!

Purchasing and planting diseased plants into your garden or production field can cause big headaches and major problems later in the season.

Be sure to inspect transplants before you purchase them, especially from home garden centers! Often diseased vegetable starts find their way onto retailers' shelves.

Last year, there was a major problem with late blight on tomato transplants that were purchased from some garden centers. Though this was not a problem in North Carolina, the lesson is still an important one: Do not purchase any plants that have visible signs of disease including lesions, spots, specks, wilts, discoloration, etc!

Some disease problems to look out for are bacterial spot on tomatoes and peppers, damping-off on many different vegetable crops and late blight on tomato and potato.

In addition, always make sure your transplants have nice, healthy, white root growth. Pull a few plants out and inspect their root system. Also, handle your transplants with care. If you pinch the tender stem of a transplant too tightly, you could damage it and invite pathogens in for attack.

Pepper transplants which became diseased by Alternaria spp. after improper handling.

Dr. Mary Hausbeck from Michigan State University has just published an on-line report for greenhouse producers entitled: Transplant Diseases: Identification and Control. This publication includes conventional control measure for greenhouse producers that produce transplants, but it also includes some good identification tips for everyone purchasing or producing vegetable transplants.

*Special thanks to Dr. Kelly Ivors for reminding me about this important topic!*