Dialing in on the Downy: Dealing with Basil Downy Mildew in your Greenhouse

Dialing in on the Downy: 

Dealing with Basil Downy Mildew in your Greenhouse

By Dr. Natalie Bumgarner

http://hyg.ipm.illinois.edu/article/php?id=467

Some basic facts on basil downy mildew

Basil downy mildew (Peronospora belbahrii) is a disease that is rapidly getting the attention of many of hydroponic greenhouse growers. Over the last couple months, we have heard from growers in several states who are now facing this disease. So, I want to take an opportunity in this blog to introduce growers to the threat and present some information as well as sites for further research. Knowledge and preparation are some of the best steps to prevent or mitigate losses in our greenhouse

basil crops.

In the continental US, reports of basil downy mildew were first confirmed in late 2007 and the disease has been widely distributed from 2008 onward. Significant crop losses in both outdoor and greenhouse production have been reported since that time for a couple reasons. First, a new disease situation can be a challenge because growers are less prepared for the appearance of a relatively new disease and the development of chemical or other control measures likely are not complete from a broad industry perspective. Secondly, any infection on the leaf can result in unmarketable crop due to appearance and rapid deterioration after harvest, so losses can mount quickly. 

Tracking its spread

Basil downy mildew can be spread through seeds or airborne spores, so the disease can affect crops from multiple sources. Work is underway to develop and implement accurate tests to identify the pathogen on seeds and enable sale of disease-free basil seeds. This will be crucial to more effective control of the pathogen in the future, but growers must also be vigilant in terms of the threat from airborne spores. The pathogen can overwinter in warm areas (such as southern Fl) and can be distributed through airstreams as the growing season progresses. This means that the incidence and frequency of infection often moves northward during the late spring and summer months. Monitoring and reporting programs are available for growers to be better aware of when outdoor or greenhouse crops in their area have been reported with basil downy mildew. The first site listed in the additional information section at the end of this blog has info on the monitoring program. 

Recognizing the signs

Early symptoms can mirror nutrient deficiency, so it is important to check for fungal growth under the leaf, which can develop only 2 to 3 days after infection.

The stages of impact

The image on the left illustrates early stage infection while the plant on the right has a more severe infestation that  render the entire plant unmarketable in addition to producing spores that will likely infect nearby plants. Impacts in a greenhouse can be severe as the pathogen can spread quickly under greenhouse temperature and humidity ranges because they are conducive to rapid multiplication. 

Preventing disease

Preventative steps fall into two main categories for growers. The first occurs in seed and cultivar selection. As discussed earlier, disease free seed is going to become increasingly available in the future. Additionally, it has been demonstrated in various tests that sweet basil (Ocimum basilicum) is the most susceptible to basil downy mildew. Red leaf basil as well as Thai basil and the lemon and lime basils have generally been shown to be more resistant than sweet basil.

The second important element in preventing the disease is controlling the environment in your greenhouse to minimize conditions that lead to the reproduction and spread of the disease. It will be crucial in the prevention and control of the disease to reduce leaf wetness by maintaining lower relative humidity and increasing air flow in the greenhouse. Such steps can include maintaining slightly higher temperatures to reduce relative humidity, increased lighting (or decreased shading), as well as increasing air circulation through addition of fans or some other method. 

Control options

First step- Assess the extent of infection

The important first step in addressing basil downy mildew is to determine the severity of infection. In some cases, removing the most affected plant material from the greenhouse may be needed as remediation of affected tissue is challenging. Infected plants often are completely unmarketable and may pose more risk than reward if left in the greenhouse. In some instances, the removal of a few plants may be adequate if the disease is caught in the early stages. How much of the crop with mild to moderate infection that should be removed is kind of a judgment call, but this is not known as an easy disease issue to control. Another step that can help if the older plants are highly infected is starting new seedlings in a separate area where the inoculum cannot

spread to them from the older plants while you are spraying to control the disease

Second step- Decide on a control approach

Spray and chemical options: There are not as many weapons as we might like in terms of spray materials for use in greenhouses for basil downy mildew, but there are a few tools at our disposal. Another thing to keep in mind is that these controls have been shown to be more effective as a preventative, so spraying to prevent infection on the plants that are still healthy is one of the most important goals.
In the organically certifiable or softer category, there are hydrogen dioxide products (Oxidate), biologicals (Actinovate) as well as potassium bicarbonate (Milstop) products. These are labeled for use in greenhouses and on downy mildew, but in tests have not generally been the most effective materials for controlling active infections.
In terms of conventional fungicides, some products that have been listed as most effective and labeled for greenhouse use are cyazofamid (trade name Ranman), phosphanates (trade names such as ProPhyt, Fosphite, and Fungi-Phite) and others detailed in the additional resources. It is best to alternate use of chemicals to try and prevent pathogen resistance. Further information of specific chemical products and 

tests of their relative efficacy are available at many of the sites listed in the additional resources section

Third step- Watch the disease closely and keep on top of the spray schedule 

Remember, this disease is most effectively prevented rather than controlled. So, there is a need to spray both for control and prevention under conditions that are most conducive to the disease. One thing to keep in mind as you implement your control plan is that a backpack sprayer  is going to be difficult to get adequate leaf coverage because the underside of the leaf is where the pathogen is most present. If frequent spraying is needed, it is worth considering acquiring  some type of air assisted mist blower or high pressure cold fogger.

Arming ourselves with information, remaining vigilant in environmental control and scouting and acting quickly if disease is found are all key in managing the risk of basil downy mildew in our greenhouse crops. 

Additional information

http://vegetablemdonline.ppath.cornell.edu/NewsArticles/BasilDowny.html
http://edis.ifas.ufl.edu/pp271
http://hyg.ipm.illinois.edu/article.php?id=467
http://www.greatplainsgrowers.org/2012%20program/Powerpoints/MeganKennellyVegDiseaseHeadlines.pdf
http://extension.umass.edu/vegetable/articles/downy-mildew-basil

Spring to Summer Romaine Lettuce Trial

Spring to Summer Romaine Lettuce Trial

Romaine in NFT production in Ohio

By: Dr. Natalie Bumgarner

Introduction

Romaine lettuce can sometimes be a challenging lettuce crop to produce in the greenhouse due to its susceptibility to tipburn and related quality deterioration. However, there often appears to be a solid market for high quality, locally produced, romaine. In addition to environmental challenges, romaine cultivars specifically bred and developed for controlled environment production are less common than bibb cultivars. This trial was designed to evaluate a selection of romaine lettuce cultivars through a range of spring and summer conditions to evaluate their potential for greenhouse growers in the Midwest and northeast. 

Methods and Management

Primed and pelleted seeds were seeded by hand in pre-moistened 1” x 1” x 1 ½” rockwool cubes. Seeds were germinated in clear water in seeding trays, and were transferred to the nursery and nutrient solution 4 to 7 days after seeding. Seedlings were produced in flowing nutrient solution in the nursery for  approximately an additional week before transplanting (Run 1 and 2 were provided supplemental lighting during the seedling phase). After transplanting, lettuce plants were grown out in the channel for approximately four weeks prior to harvest. The nutrient solution was continually cycled through the Fertroller where automatic pH and EC adjustments met programmed solution set points. The pH was maintained at 5.8 by the addition of dilute sulfuric acid. EC was maintained at 1.6 to 1.8 (lower light levels = higher EC) by the addition of concentrated fertilizer solution and source water. 

* It is important to note that these trials were carried out over set periods of time and harvests were made regardless of plant readiness for sale because clear comparisons were the main goal. In a commercial operation, more (or less) time may have been give these heads to reach a consistent saleable size and crop quality. 

Transplants 2 weeks after seeding

Some thoughts on the trial

In these data, there are a few items that are important to consider and understand about this trial.

1)  The first important fact to glean from these numbers is that the performance of the cultivars was fairly consistent, even though there were large variations across runs.  Green Forest and Salvius tended to be the higher yielding cultivars (in all runs except #2, discussed below) while Helvius was intermediate and Maximus and Counter were the two lower yielding cultivars in most trials. It is useful for growers to see that across both spring and summer conditions, these trends were fairly consistent. The yield trends could be influenced by the growth habits of these plants. Green Forest and Salvius were usually taller plants that were open longer while Helvius tended to form a head a little earlier. Maximus was a very open cultivar in most of our trials while Counter formed a smaller head. Cultivar choices should be made both on yield potential but also the plant form suitable for markets. 

2) Nutrient solution conditions  may have been a key factor.

 In viewing these numbers, there are a couple of key items to keep in mind. During the middle of May, we had an issue with our source water here at CropKing. The softener that we were relying upon was not functioning properly and the plants were receiving higher than optimum levels of sodium. This solution issue likely led to reduced growth and increased tipburn in run 2. Our new reverse osmosis system was installed on May 21st to correct these issues. However,  we then had a chlorine spike in our municipal water source that created some root damage and plant stress on June  13th. (Source water may need to be the topic of  a blog post in the near future!)  So, it was likely not until the 4th run that impacts of the improved source water quality can be observed. Keep in mind, though, that higher summer light and temperature were likely also a source of the higher yields in run 4. Temperature in Ohio was quite moderate for most of June and July and these crops were grown without a shade cloth on the greenhouse to take full advantage of available light. As with most contributors to plant growth, light, temperature and the impact of other stresses often cannot be completely separated in greenhouse work. 

3) There were some differences in quality across the runs and the cultivars. Specific  data on plant quality was not collected in this study in a way that allows statistical comparisons. However, it should be noted that Counter had some heads with tipburn in all 4 runs (see below). Tipburn was observed mainly in Counter in Run 1 and in all cultivars in Run 2, while tipburn levels in all cultivars were reduced in runs 3 and 4.  

A picture is worth a thousand words..

Counter Run 1

Counter Run 4

Green Forest Run 1

Green Forest Run 4

Salvius Run 4

Helvius Run 4

Helvius Run 1

Salvius Run 1

The attraction of opposites: Using both soil and soilless production to enhance diversified vegetable and fruit operations - Part 2

The attraction of opposites: Using both soil and soilless production to enhance diversified vegetable and fruit operations - Part 2

Peach Hill Orchard, Martinsburg, PA-

On this mid-summer morning in central Pennsylvania, it turned out that tomatoes were not the first thing on Ammon Martin’s mind. While Ammon and his son Dave were certainly willing to discuss their greenhouse hydroponic tomato production with me, he explained with a smile that right now it was peach picking season. So, it was going to be the orchard that would consume much of their time over the next few days. This simple explanation very clearly illustrates both the opportunities and challenges that greet diversified direct marketers like the Martins, who have owned and operated Peach Hill Orchard, in Martinsburg, PA for over two decades.

Ammon started his production over twenty years ago with fruit trees and vegetables. To widen his season and therefore marketing window, he began growing tomatoes in high tunnels. However, the management and production in soil with unheated structures contained more yearly and seasonal variability than he desired. In order to have more control over his growing environment and therefore his crop productivity, he installed a CropKing hydroponic greenhouse about 20 years ago. Beefsteak tomatoes were their most important hydroponic crop, but European cucumbers were grown as well to add variety to the early spring produce selection. Along with hydroponic production, the Martin’s also produced bedding plants, vegetable transplants and hanging baskets in adjacent, but separate greenhouses. These protected environments were combined with both field vegetables and fruits for a wide diversity of crops to market.

For many years, they sold these varied crops through a small roadside stand at their dairy farm in addition to selling through the local flower and produce auctions. To enhance their direct-marketing ability and establish a year-round business, they built a permanent farm market about five years ago that was certainly well stocked with both produce and customers on the morning I visited. Various fruit crops and vegetables, along with meats and cheeses, provide consistent selection for all seasons. The hydroponic tomato crop, though, still played a key role in providing spring and early summer fresh produce to attract customers. However, as the summer season progressed each year, field vegetable crops, sweet corn, and the fruit trees consumed more and more time. To address the labor needs of their diverse operation, Ammon simply decided to end their hydroponic crop in late July of each year to focus on other farm responsibilities. The hydroponic tomatoes, along with a few cucumbers, are produced and sold in the months of March through July. Field vegetables, fruit, and cider then become the focus of Peach Hill Orchard.

Over time, the Martin’s found they were direct marketing essentially all of their produce and rarely needed to sell at the produce auction. In fact, they even discontinued growing bedding plants and hanging baskets because they found those markets were more crowded. Growing hydroponic and field vegetables and fruit for their market, it turned out, was a more profitable use of their time. This past year, they even added a small CropKing nutrient film system to grow hydroponic lettuce for their customers in the spring. Peach Hill Orchard, now run by Ammon along with his son Dave, demonstrates the potential of coordinating traditional fruit and vegetable production in soil with greenhouse hydroponic crops. This crop combination provides the Martin’s an opportunity to provide a diverse and high quality selection of produce to their customers throughout the seasons- and it certainly seems to be working!  

The attraction of opposites: Using both soil and soilless production to enhance diversified vegetable and fruit operations - Part 1

The attraction of opposites: Using both soil and soilless production to enhance diversified vegetable and fruit operations - Part 1

By Dr. Natalie Bumgarner

For horticultural crop producers, the balance between specialization and diversification on their farms must be continually managed. These days, the concept of diversification does not just apply to the types of vegetables planted in the field or varieties of trees in the orchard. Horticultural growers around the country have a wide variety of growing systems available to them to enhance the selection of crops they market and the seasons in which they are able to harvest and sell. Visiting with some of these experienced and diverse growers is really the best illustration of the potential of diversification. For me, a summer day spent traveling across central Pennsylvania certainly did reveal some intriguing paths to diversification.

Yarnick’s Farm and Market, Indiana, PA

As I followed the small, winding road through rolling Pennsylvania hills, there was no danger of missing Yarnick’s because all first-time visitors are guided by a road sign. As I approached the farm, greenhouses filled the valley and clearly illustrated diversification in action. Dan and Lynette Yarnick have been building and expanding the business for over 30 years, and their son Joey has also come on board to lead the farm into the next generation of diversification. The current farm market, which was certainly bustling, was built more than half a dozen years ago and is the direct-marketing portion of the Yarnick’s business. In the market, Lynette retails a variety of vegetables and fruits, along with their own Black Angus beef and many other food and gift items. In addition to supplying the farm market, Yarnick produce is marketed through SuperValu supply chains, Giant Eagles grocery stores and Eat ‘n Park restaurants.

It all started back in 1981 when Dan read a short article on hydroponic tomatoes in the Farm Journal. Although the farm was currently focused on dairy cattle and agronomic crops, Dan was intrigued by the possibilities of vegetable production that was not all tied to the season. From this first experience with tomatoes in a hydroponic greenhouse over 30 years ago, Yarnik’s farm has grown to about 300 acres in vegetable production. With this many acres under production, obviously the soil-grown portion of the crop has expanded. Yarnick’s field crops range from cabbage, leaf lettuce, candy onions, watermelon, cantaloupe, and zucchini to a large and well-known crop of sweet corn. Season extension practices, such as the use of row covers, enable Yarnick’s to expand the production season of their soil-grown vegetable crops. However, the hydroponic greenhouses have multiplied over the years as well and still play a very important role in the business. Currently, Dan is producing many varieties of hydroponic tomatoes- both modern and heirloom beefsteak and cherry varieties- along with peppers, cucumbers, eggplants, green beans, and even some giant radishes in spring.

Over the years, Dan has developed a hydroponic growing system that fits his needs as well as the palettes of his customers. He now grows in peat bags rather than the perlite or rockwool system that many hydroponic growers use because he prefers the way peat allows him to manage moisture and fruit quality. This hydroponic tomato crop is typically seeded in December to enable 10 months of production from March until November. Along with Dan’s tomatoes, Lynette also produces hydroponic lettuce and herbs in the living produce section of the market. Here, customers, who range from individuals to restaurant chefs can select and harvest their own fresh produce. A visit to Yarnick’s Farm Market demonstrates that diversity and freshness are much more than catch phrases at Yarnicks, and they look forward to continuing the fine tradition and the “Charm of Yarnick’s Farm”. 

Investigating iceberg lettuce in the hydroponic greenhouse – 2013 Trial, Part 1

Investigating iceberg lettuce in the hydroponic greenhouse – 

2013 Trial, Part 1
 By Natalie Bumgarner, Horticulturist
CropKing, Inc. Lodi OH

Why isn’t there hydroponic greenhouse iceberg lettuce?

Lettuce is the 2^nd most popular vegetable in the US (second only to potato), and head lettuce is certainly the most recognizable type. So, it is not uncommon for us to hear the question “Why don’t you produce iceberg lettuce in the greenhouse?”  There are, in fact, several key reasons iceberg lettuce is not commonly grown in vegetable greenhouses in the United States. They are listed below and loosely ranked by importance, but these reasons may vary depending on production area and market. 

 

1)  Market potential and price

One of the most important reasons that we do not see head lettuce in the greenhouse is because the economics of the market are not always encouraging. Nearly all of US head lettuce is produced in California (spring through fall) and Arizona (winter). Huge expanses of open field production are dedicated to lettuce production in some of the most productive cropping areas in the world. Soil and climate factors make these regions quite appropriate for head lettuce production and the scale of production also contributes to competitive advantages. For example, recent terminal market data reported that head lettuce cartons (approximately two dozen 2 lb. heads of lettuce) are selling for $11.00 to $17.00. These prices illustrate that greenhouse producers are unlikely and unwilling to produce head lettuce at prices that could be competitive with field production.  An additional facet to this topic of markets is that recent per capita consumption of head lettuce has been flat or on the slight decline as other leafy vegetables have become more popular.

Iceberg lettuce typical in California open field  production. Specific cultivars are slotted in specific times of year for production regions of CA and AZ across the entire year.

 2) Production time

Typically in the open field, head lettuce matures in 70 to 80 days in the summer and up to 130 days in winter or lower light and temperature seasons. Of course one of the benefits of greenhouse production is the potential for faster growth rates and reduced production times. To date, in summer greenhouse production in OH, we have harvested our iceberg lettuce approximately 55 to 60 days after seeding. However, the total weight of our lettuce may not equal field packed cartons. This production time contrasts with a bibb production schedule in the greenhouse which might produce a crop in 40 to 50 days. 

3) Nutrition

As consumers become conscious of the nutrient and antioxidant levels in their food, they continue to become more discerning in food purchases. Due to underlying genetics, plant growth form and a few other factors, iceberg lettuce is not the most nutrient dense leafy green vegetable. The table below (From USDA National Nutrient Database for Standard Reference Release 24 ) gives average nutrient information for the most common types of lettuce. Remember that these are averages from primarily soil grown crops from around the country, so they do not represent the exact profile of product from individual greenhouses or cultivars. Nevertheless, this table does support the generally held perception that iceberg lettuce contains fewer nutrients per serving that other lettuces and certainly other leafy greens. However, keep in mind that iceberg lettuce from greenhouses has been less often evaluated than that from the open field.   

4)    Customer Preference and Perception

This potential reason for the lack of iceberg lettuce in US greenhouses is linked with the nutrition topic discussed above. Most greenhouse lettuce producers are growing and marketing their crop as a premium product. This means that the quality of the crop is crucial, but the perception of the crop is also important. Iceberg lettuce is often viewed by many discerning consumers as inferior in taste, visual appeal, and nutrition to the bibb, romaine and leaf lettuces. There is also little attraction based on novelty or distinctiveness. These views mean that many of the most profitable potential customers for hydroponic greenhouse producers may be less interested in iceberg than other leafy crops. However, if greenhouse producers were able to market a product with comparable attributes (crisp, multiple servings per head, etc) and improved taste, freshness, or nutrition, these perceptions and preferences could change.

5)    Adaptability of cultivars and environments 

Much of greenhouse lettuce production (especially bibb) utilizes cultivars that were specifically bred and developed for greenhouse environments. These cultivars can generally be depended upon to perform consistently across seasons and even geographic areas. When investigating types of lettuce, like iceberg, that are less often produced in greenhouses, preferable cultivars and knowledge of how they may perform is limited.

Additionally, iceberg lettuce often requires specific environmental conditions to produce the tight head consumers are accustomed to- without bolting or becoming bitter. So, even though we can control temperatures closely in greenhouses, producers may not be able to exactly emulate conditions that are common in field iceberg production. There may be more seasonal constraints of light and temperature on iceberg production in many US greenhouses than we experience in producing other types of lettuce.   

So, why would we be interested?

After spending the time to try and elucidate why iceberg is rarely produced in hydroponic greenhouses, you are probably asking what would possibly be the attraction. While I will be the first to admit that greenhouse iceberg is unlikely to become a US market force in the near future, there are some reasons for investigation.

First, familiarity is not always a negative. Some consumers will always be attracted to what they know best and producers should always be ready to fill small market niches if they are possible and profitable- especially if they can provide a product with superior quality. 

Secondly, we at CropKing deal with producers not only in the US, but also internationally. Market demands and dynamics may differ considerably in these areas. For instance, in the Caribbean islands where imports are expensive and often of poor quality, iceberg may be both desired by consumers and potentially profitable for greenhouse growers.

 Thirdly, it is always important to investigate potential crops and understand both the benefits and drawbacks to their cultivation to assist current and future producers- essentially, we need to have solid backing to the answers that we give growers.

Goals and Early Observations

Main Objectives

•      Produce 5 iceberg cultivars in spring and summer greenhouse environments in OH

•      Evaluate yield as well as broad metrics of internal and external quality

•      Evaluate production timing and suitability for the CropKing NFT system

After one run, we observed

•      Head lettuce production was possible

•      Head weight and density may not be the same as field iceberg

•      Not all cultivars appeared to be well suited to our conditions because some bolting and tipburn occurred

•      Anecdotally, the taste of the produce was encouraging 

Additional Sources

•http://anrcatalog.ucdavis.edu/pdf/7215.pdf
•http://151.121.3.194/cat/?shortcut=terminalMarket
•http://www.agmrc.org/commodities__products/vegetables/lettuce-profile/