Basil Downy Mildew

Sporulation of Peronospora behlbarii, causal agent of basil downy mildew.

Basil downy mildew is a new disease that has been causing headaches for growers in the eastern US for the past two seasons. Basil downy mildew was reported in South Florida in October 2007. This disease has the potential to be very destructive to basil producers. European producers have been dealing with the disease since 2001. The disease is thought to have been introduced in the US from infected seed from Europe

The first confirmed case of the disease in NC occurred last summer in Chatham County. Agriculture agent, Debbie Roos, did a great post on the diseases with wonderful pictures last August.

The disease has been found in several locations in WNC this year. This is surprising because we have been so hot and dry and downy mildew pathogens tend to like cooler temperatures and wet and humid conditions. Apparently, basil downy mildew is the exception - it likes moderate to warm temperatures!

Basil downy mildew is so devastating because the discoloration of the leaves makes the basil unmarketable. Eventually the leaves will become black or necrotic and die completely.

Slight yellowing of basil plants that are infected with Peronospora behlbarii, causal agent of basil downy mildew.

Discoloration of basil leaf caused by downy mildew.

The basil downy mildew pathogen, Peronospora belbahrii, is spread by contaminated seed, marketing infected plants or leaves and wind-borne spores. This pathogen also infects other plants of the Lamiacea family which inculdes basil, sages, and mints. The spores of the pathogen are abundant on the underside of the leaf.

Discoloration of basil leaf caused by downy mildew, P. behlbarii.

Notice the fuzzy growth on the underside of the leaf. This was the first tip that what we were dealing with was downy mildew. Also, note the black dying tissue.

Dark sporulation of the pathogen P. behlbarii that causes downy mildew on basil on the underside of the leaf.

This disease can often be mistaken for sunburn on basil leaves, which I have also noted this year.

Sunburned basil leaves.

There is a similar downy mildew pathogen that infects coleus, but this pathogen has been shown to be genetically different than the pathogen on basil and the ornamental hosts are no longer considered alternative hosts to the basil disease. To read more about the specifics of basil downy mildew, visit Cornell Plant Pathologist Dr. Meg McGrath's on-line factsheet Basil Downy Mildew - A New Disease to Prepare For.

Management of basil downy mildew requires an integrated approach. Using seed that is not contaminated with the pathogen, selecting less susceptible varieties and applying fungicides are the primary practices. Management should also include increasing airflow through the plant canopy in order to minimize leaf wetness and humidity in order to suppress the disease. This is especially true in greenhouses. Dr. McGrath outlines management steps, including variety trials from New Jersey, in her factsheet.

Fungicides used for downy mildew on basil include OMRI-approved Actinovate and OxiDate, which are labeled for use. Many other conventional fungicides do not yet have the label required to control this disease on basil, with the exception of K-Phite and ProPhyte. It is expected that this will change in the near future. Fungicides should be applied frequently and prior to first symptoms if possible in order to control downy mildew on basil effectively. This is of course tricky, especially in areas without history of the disease.

If you suspect that you have downy mildew on your basil, visit your local NC Cooperative Extension office for help identifying and reporting the disease.

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!

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!*

Asparagus Disease

Recently, an organic asparagus grower brought in some diseased ferns. The grower was going to mow off the ferns and burn them, but wanted to identify the problem first to make sure that was the correct thing to do and to minimize problems next year.

It wasn't hard to find the reddish, circular lesions on the stems and discolored needles.

Lesion on asparagus stem.

Discoloration of asparagus fern.

Some of the lesion were older and inside of them, dark black fungal structures were present.


My initial thought was that it had to be either Cercospora blight(Cercospora asparagi) or Purple Spot (Stemphylium vesicarium). The NCSU factsheet on Commercial Asparagus Production mentioned Cercospora blight as a problem in NC, but did not mention Purple Spot.

After looking under the scope, I didn't find any spores that looked like the ones produced by Stemphylium vesicarium, but I did see some other, very elongated spores that almost looked like leaf hairs. Sorry I didn't take a picture, but here is a link to another Cercospora species' spores.

After doing a little more research I found an APSnet Feature Article on Economically Important Asparagus Diseases in the United States. This article stated that Cercospora blight and Purple Spot are easily confused, so I decided to send it into the NCSU Plant Disease and Insect Clinic.

During the next few days, the lesions got larger and coalesced.

Luckily for me, Dr. Averre, whose pictures were included in the above article, was available to do the diagnosis! He identified that the problem was, in fact, Cercospora blight.

There are no known sources of resistance to Cercospora blight, though Jersey Gem does have tolerance to Cercospora. As a result, management must include an integrated approach of sanitation and fungicide applications. Fall removal or burial of the year's fern residue can delay the onset of disease development. This was just what the grower was going to do! Heavily infected ferns should be removed.

Cultural management techniques that reduces leaf wetness are very important for the management of Cercospora blight. These techniques include:

• Using drip or furrow irrigation to decrease leaf moisture. If overhead irrigation must be used, it should be scheduled so that the foliage has time to dry before nightfall.
• Increasing row spacing. This will improve air circulation within the planting.
• Plant asaparagus in areas with good air movement to encourage leaf drying.

To learn more about asparagus production in NC, review the horticulture leaflet Commercial Asparagus Production.

Also, Oklahoma State University has a nice factsheet on Cercospora blight of asparagus.

Downy Mildew: Hops

Hops are a new crop to western North Carolina. As with all new crops, it is going to take some time to figure the ins and outs of hops production. We are learning from our current hops growers about when and how to harvest, yield per bine, how to dry the hops cones, what varieties work well for WNC and how to control mites, leafhoppers and other pests.

In addition, as you all know, WNC is very humid and sometimes wet! As a result, we struggle with the control of plant diseases. Hops are no exception. Upon my last visit to the hops yard, I found some leaves exhibiting symptoms that had me concerned. I had discovered what I initially thought was downy mildew, caused by the fungal-like organism, Pseudoperonospora humuli, on some lower hops leaves.

Downy mildew causes angular lesions, bound by leaf veins.
Note: the large circular lesion is not caused by downy mildew

Underside of leaf infected by P. humuli

Underside of leaf infected by P. humuli

Upon inspection using my hand lens, I was able to confirm that there was downy mildew sporangia emerging on the underside of the leaf surface. Because I love learning about plant diseases, I had to take a closer look using a dissecting microscope (about 20-45x magnification).

The fuzzy growth of P. humuli on the underside of the leaf surface.

Sporangia (spores) and sporangiophores of P. humuli on underside of hops leaf.

Sporangia (spores) and sporangiophores of P. humuli on underside of hops leaf. You can really see the football/lemon shaped spores at this magnification.

After the dissecting microscope, I had to take a closer look at the sporangia and sporangiophores using the light microscope. Check out these beautiful pictures of P. humuli up close and personal (200-600x magnification)!

Football/lemon shaped sporangia and dichotomously branched sporangiophores (note the pointy ends upon which the sporangia are borne).

Another picture of the sporangia and sponrangiophores of P. humuli.

P. humuli sporangia. Note the small raised bump at one end of the sporangia. This is the papilla and is characteristic and diagnostic of this pathogen.

Strategies for the Management of Hops Downy Mildew
To manage downy mildew of hops it will take an integrative approach using some or all of the following strategies.

• Host Resistance. One of the most effective management strategies for hops downy mildew is to plant resistant varieties. There is no variety that is immune to downy mildew, but 'Fuggle', 'Cascade', 'Newport' and 'US Tettnang' are resistant. 'Centennial', 'Willamette', 'Chinook', 'Liberty', 'Cascade', 'Bullion' and 'Brewer's Gold' are tolerant. 'Late Cluster', 'Galena', 'Horizon' and 'Nugget' are susceptible. Interestingly, many of the varieties that are resistant to downy mildew are susceptible to powdery mildew and vice versa. For a complete listing of varieties inlcuding disease susceptibility, pedigree and chemical characteristic, see the Compendium of Hop Diseases and Pests edited by Walter Mahaffee, Sarah Pethybridge and David Gent. This book is a must have for a hops producer!

• Disease Free Stock. It is always important to purchase disease free plant stock! Ask your supplier.
  

• Pruning. P. humuli overwinters in dormant crowns and buds of hops. During the winter and spring, P. humuli may spread into developing buds and cause the new shoots to be systemically infected. Pruning helps to reduce downy mildew levels in already infected plantings. Pruning hops yards as late as possible in the spring can help to reduce the amount of downy mildew in the yard, however if you do it too late you may reduce yield by dealying training.
  

• Manage Moisture. Moisture on the leaves favors disease development, so using practices that reduce leaf moisture will also help to manage the disease. Avoid overhead irrigation.
  

• Reduce Inoculum. Stripping diseased leaves after training may help reduce disease in the upper plant canopy.

• Early Harvest. Early harvest may be beneficial in minimizing cone infection. Downy mildew favors the cool, wet weather that occurs late season in WNC.
  

• Timely Fungicide Application. Many hops growers rely on fungicide use for downy mildew control. Because P. humuli produces so many spores (progeny), it is impoprtant to employ tactics to prevent fungicide resistance. To read more about fungicides for the management of downy mildew of hops visit Oregon State Extension's Factsheet. Some organic fungicides include copper products and Sonata (Bacillus pumulis strain QST 2808).

If you suspect you have downy mildew in your hops yard. Let me know, I will do my best to help you confirm it and come up with a strategy for control.

I would like to thank Dr. Kelly Ivors and Landis and Dreama for letting me use their awesome microscopes and camera to take these incredible pictures!!

Late Blight Confirmed on Tomatoes In Henderson County

Late blight was confirmed in the plant pathology lab today at the research station in Mills River. The sample came from a field in Henderson County. Reports of the disease will most likely start popping up all over WNC.

Review my last post on Late Blight and Dr. Kelly Ivors Factsheet on Tomato Late Blight for details on the pathogen.

Conventional growers are advised to use a chlorothalonil product or Revus Top (mandidpropamid + difenoconazole) if late blight is not detected in the planting as a protectant. If late blight is confirmed in your planting, a combination of Presidio (fluopicolide) tank mixed with chlorothalonil is recommended. Other effecacious products labeled for late blight on tomato include: Curzate (cymoxanil) and Tanos (famoxadone + cymoxanil).

Organic growers are urged to use preventative sprays to manage late blight because the disease can progress very quickly. Do not wait to see disease to treat! Recommended control involves: Copper + Serenade (Bacillus subtilis QST 713, labeled for late blight suppression only) alternated with Copper + Sonata (Bacillus pumulis QST 2808).

Good luck!

Downy Mildew Confirmed in Henderson County!

Downy mildew has been confirmed at 2 locations in Henderson County, NC.

• July 20 - The first incidence of cucurbit downy mildew in WNC was reported from the Mountain Horticultural Crops Research Station in Mills River. The hosts were butternut squash and cucumber. Disease incidence and severity is very low at that site.

• July 24 - Cucurbit downy mildew was confirmed this morning in Zirconia (just south of Hendersonville, NC). This was a larger planting, about 8 acres. Spaghetti squash is the most severely diseased, about 65% of plants are showing early (top picture) - more advanced (second picture) symptoms. Sporulation (noticeable on the underside of the leaf) was very heavy on the spaghetti squash (third picture). Cucumber (cv. Jackson) is also affected, though less severely overall (bottom picture). The summer squash (cv. Destiny III) is showing only very early and mild symptoms.

Moral of the story, cucurbit downy mildew is in WNC and growers need to start treating now!

Review a previous post for control recommendations.

Visit the Cucurbit Downy Mildew Forecasting site for more updates.

If you feel you have downy mildew on your cucurbits, bring a sample to your local county cooperative extension office for positive identification. It is important that the outbreaks get reported to the forecasting site.

Cucurbit Downy Mildew- Moderate Risk for WNC

Downy mildew (Pseudoperonospora cubensis) has been threatening cucurbits in NC since early June. There have been no reports of downy mildew on cucurbits in WNC and we have been lucky to have been considered at LOW RISK for chance of infection, until now...

The Cucurbit Downy Mildew Forecasts for today and tomorrow show WNC as having a MODERATE RISK for infection. A MODERATE RISK means that there is a 40-60% chance for cucurbits growing in areas along the course of the trajectory (or trajectories, in the case of multiple sources) to be infected by the pathogen and develop downy mildew. To read about how this is calculated refer to the Downy Mildew Forecasting site.

The trajectories that may effect WNC can be seen below.





As you can see there is the potential of spore deposition in WNC from multiple sources. If the weather continues to include cloudy skies and the potential of rain (to wash the spores from the sky) growers should begin to take action to protect their cucurbit crops.

The following products* have proven very effective for the conventional control of downy mildew of cucurbits:

Presidio 4F (fluopicolide)
Ranman 400 CS (cyazofamid)- must use with non-ionic surfactant
Gavel 75DF (zoxamide + mancozeb)
Curzate 60DF (cymoxanil)

Chlorothalonil and mancozeb products can be sprayed as protectants, but when downy mildew is detected in a field growers need to take a more aggressive approach. *The label on some of these products require that they be tank mixed with a fungicide of a different mode of action. Chlorothalonil and mancozeb products make excellent mixing partners.

A sample spray program might look like this:

Curzate 60DF (3.2 oz/acre) + Manzate Pro-Stick 75DG (3 lb/acre) alternated with Previcur Flex 6F (1.2 pt/acre) + Manzate Pro-Stick 75DG (3 lb/acre)

OR

Presidio 4F (3 fl oz/acre) + Bravo Weather Stik 6SC (2 pt/acre) alternated with Gavel 75DF (1.5 lb/acre)

These treatments can be rotated on a 7-day schedule when downy mildew pressure is great.

ORGANIC GROWERS have a chance to combat downy mildew if they begin applications now before the onset of symptoms. If you wait until infection has established in your planting, spraying will not be effective. The same is true in conventional systems. Some OMRI-listed products that are labeled for the management of downy mildew in cucurbits include: copper, neem, biofungicides (ex. Serenade), peroxides (ex. OxiDate), and bicarbonates (ex. Kaligreen).

I have had a lot of experience with this disease, as my master's thesis was focused on the control of downy mildew on cucurbits. Our research showed that most organic fungicides were NOT effective at controlling downy mildew on cucumber. Once the disease develops and conditions are favorable, it is nearly impossible to control it.

Your best option as an organic grower is to use a copper product. Spray early in the morning to avoid phytotoxicity that may develop in the heat of the afternoon. Spraying copper prior to disease development or at very early onset (very few, mild symptoms), may help suppress the disease, but will not offer 100% control under favorable conditions (cool, wet and humid weather).

If you suspect that you have downy mildew on your cucurbits, please contact your local cooperative extension office. It is very important that these cases are documented and reported to the forecasting site in a timely manner.

To read more about this disease or to view some pictures, visit the blog post from 5 June and the NCSU Factsheet.

In addition, look for updates in the latest NCSU Pest News.

***As always, follow the product label for instructions!***

Tomato Late Blight

Let me first start off by saying Late Blight of Tomato HAS NOT BEEN FOUND IN WNC, yet. But, it has been confirmed very close by in Northern Georgia.

Late blight of tomato is caused by Phytophthora infestans, the same pathogen that wiped out the potatoes in the Irish Potato Famine of the 1840s. P. infestans is an oomycete organism, a group that is also known as the water molds. The pathogen enjoys cool, wet weather conditions. P. infestans spreads and kills a plant very quickly, especially in ideal conditions. Spores of the pathogen are easily disseminated from infected areas to other areas via wind currents, these spores are protected by cloudy conditions.

Symptoms of late blight appear as large, olive green to brown spots on leaves. You may see a fuzzy, white fungal growth on the underside of the leaves. Symptoms also appear as brown or black lesions on the stems and fruit.

To see some excellent pictures of late blight, visit Cornell's Long Island Horticulture and Extension Center's site and the NCSU Factsheet on Tomato Late Blight.

Late Blight is often confused with Early Blight. Unfortunately, these diseases have similar names, but the symptomology and causal organisms couldn't be more different. If you see bulls-eye lesions on leaves starting on the bottom leaves, you are most likely dealing with Early Blight, a fungal disease, caused by Alternaria solani. Revisit my post Early Blight of Tomatoes for pictures and additional information. Compare symptoms of Early Blight with the pictures of Late Blight from Cornell's link above. Cheryl Smith at UNH has also put together an excellent resource comparing the 2 diseases.

If you think you have Late Blight of Tomato, please contact your local extension office to have it positively diagnosed.

Late blight has been all over the news because of its early arrival in the Northeastern US, which has been experiencing cool and wet weather as of late. The disease doesn't usually occur in that region until late-July or August. This year it is believed that the pathogen hitch-hiked on transplants to retail stores and then to home gardens. It is believed that the disease appeared as early as mid-June.

To read more about the problem in the Northeast visit the following sites/article:

UMass Extension "Late Blight Alert for Potatoes and Tomatoes"

American Vegetable Grower "Late Blight on Potatoes, Tomatoes Confirmed in Northeast" - contains information on management as well

Providence Journal "Irish Potato Famine Fungus Strain Hits R.I. Crops"

Downy Mildew: Cabbage

Today I went to a field of cabbage, a nice change from all of the time I have been spending in tomato and pepper fields. I noticed that the lower leaves had some spots that were yellow and turning necrotic. When I turned the leaf over I notice that familiar fungal growth- downy mildew.

Symptoms of downy mildew on cabbage include irregular shaped lesions that vary in size and are sunken and whitish-gray (image, left). The tissue around the lesions will turn yellow. When you flip the leaf over, a fluffy, white, downy growth is evident (image, below). One can distinguish downy mildew from powdery mildew because only downy mildew will sporulate (reproduce new spores) on the bottom side of the leaf.

Downy mildew on cabbage is caused by Peronospora parasitica. This organism causes downy mildew on vegetables in the Brassicacea family such as broccoli, cauliflower and radishes, and is different from the organism that causes downy mildew on cucurbits (Pseudoperonospora cubensis). P. parasitica, like most downy mildews, thrives in cool, wet weather (temps. 50-60 degrees F) though it can tolerate cooler and warmer temperatures.

P. parasitica forms two types of spores, oospores and sporangia. Oospores are the overwintering, resistant spores that can survive in the soil (not shown). The other spore type are sporangia. Sporangia are large (relatively speaking for a microscopic organism), round spores that are born on tree-looking structures known as sporangiophores (images left and right). These sporangia are disseminated by wind or rain splash. Isn't this organism beautiful (I know, I know... a face only a plant pathologist could love). Making a successful slide is difficult because P. parasitica is quite delicate. You will notice that some areas of the image to the left are out of focus, this is because P. parasitica is 3-D and taking a 1-D image doesn't do it justice.

Downy mildew can be introduced into a field through transplants, so make sure that your transplants are disease free. Also, if you notice that you have diseased plants, do not dump these plants in a cull pile in the field because they have the potential of infecting the non-diseased plants. Try to eliminate brassica weeds and rotating the field with non-brassica vegetables might help.

There are no downy mildew resistant cabbage cultivars, however there are a few effective fungicides for the control of downy mildew on cabbage. A new fungicide from Syngenta, Revus (mandipropamid) has shown excellent efficacy for controlling this disease. Also, ProPhyt (potassium phosphite) + Manex (maneb) can be used to control the disease.
Reduced efficacy of Ridomil Gold and Bravo has been shown in NC (Adams et al., 2007, Plant Disease Management Reports 2:V119. DOI:10.1094/PDMR02).

As always refer to manufacturers' recommendations on the fungicide label.

**Special thanks to Kelly Ivors and Dreams Milks who assisted with the pictures of P. parasitica.**
*Much of this information was gathered from Univ. of FL Plant Pathology Fact Sheet 33 (Tom Kucharek) available on-line.*

Bramble Fungicide Sprays

As a result of the rain last week and the possibility of more rain from Gustav, Hanna and Ike, blackberry and raspberry growers should think about disease control options. Dr. Gina Fernandez of the horticulure department at NCSU was kind enough to pass along some information from Plant Pathologists Dr. Phil Brannen (UGA) and Dr. Turner Sutton (NCSU).

From Phil Brannen big issues for FLORICANE fruiting types:
1. Pruning wounds and cane blight. Dr. Brannen recommends suspending pruning until dry conditions are predicted for several days. Applications of Prisitine or another broad-spectrum fungicide to pruning wounds after each day of pruning is recommended.
2. Leaf spots. Leaf spots will also likely develop and early defoliation due to pathogens like Septoria and others is possible, so a preventative spray ahead of heavy sustained rains may be helpful. A broad-spectrum material, like Prisitine, would be good for control of these pathogens with application 24-h prior to rains being the ideal.
3. Orange cane blotch. Dr. Brannen suggests the consideration of copper application both ahead of and following the storms in order to suppress orange cane blotch. Copper materials are not great, but they are still the best products available for the algal disease.
4. Phytophthora. If winds are severe, tearing of roots and the entry of Phytophthora is possible. Application of ProPhyt or other Phosphonate materials are recommended. Where possible, drip-applied Ridomil Gold either before or after the rain can be used.

From Turner Sutton big issues for PRIMOCANE fruiting raspberries and blackberries:
"Anyone with fruit needs to spray asap if they haven't already. (As soon as it stopped raining would have been an ideal time)."
1. Botrytis and other fruit rots. CaptEvate (a broad-spectrum fungicide with a 3-day phi) may be a good choice than a botrytis-specific fungicide. Alternatively, Captan + a botrytis fungicide can be applied (check the phi).
2. Leaf spots. Monitor leaves of primocanes closely (at least weekly) for leaf spots or rusts. You do not want to lose a lot of leaves before frost to predispose then to winter injury. If rust is not a problem, Captan is okay and is the least expensive.
3. Phytophthora. Phytophthora is typically not a problem until the soils cool in late Sept/Oct, unless you are in very heavy wet soils. Sutton also recommends a phosphite foliar spray at this time.
*Thanks to Dr. Fernandez, Dr. Sutton and Dr. Brannen for this great information. As always, follow manufacturers' guidelines on the fungicide label.*

Early Blight of Tomatoes

One of the first disease problems I have encountered in WNC is Early Blight on tomatoes. Early blight is caused by Alternaria solani, a fungal pathogen. Traditionally, symptoms of Early Blight appear as spots on the foliage. These spots have concentric circles and look like a "bull's eye" (image, right- click on image to enlarge). These symptoms first appear on older leaves of the tomato plant.

In addition, Early Blight can actually affect the stems of the tomato plants (image, below). This condition is known as "collar rot". Notice that the stem lesion begins where the plastic begins, not at the soil line. Concentric circles may also be seen in the stem lesions. Early Blight attacking stems can be an severe problem, especially in fields that are not fumigated, as plants will not be able to survive stem girdling.

In order to control A. solani and other important pathogens of tomato, prevention is key. Dr. Kelly Ivors and Dr. Frank Louws, both of the Department of Plant Pathology at NCSU have put together a comprehensive Foliar Fungicide Spray Guide for Tomatoes in NC. This is program is a holistic approach to tomato disease control and followed by many WNC tomato growers.

Other fungicides that are very effective for Early Blight on tomato are the strobilurin fungicides, azoxystrobin (Amistar, Quadris) and pyraclostrobin (Cabrio). *Strobilurin fungicides must be rotated with a fungicide that is not in FRAC group 11.* Other fungicides with good efficacy towards Early Blight are boscalid (Endura), mancozeb (Dithane, Manzate, Penncozeb, Manex II) and maneb (Manex, Maneb).
Efficacy data obtained from Southeastern Vegetable Extension Workers 2008 Vegetable Crop Handbook. Always follow application guidelines on the fungicide label!