Vegetarian Newsletter

A Vegetable Crops Extension Publication
University of Florida
Institute of Food and Agricultural Sciences
Cooperative Extension Service

Vegetarian 00-12
December 2000

WB01645_.gif (935 bytes)Index Page

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WB01647_.gif (256 bytes) VEGETABLE CROPS CALENDAR

WB01647a.gif (256 bytes) COMMERCIAL VEGETABLES

WB01647b.gif (256 bytes) VEGETABLE GARDENING

List of Extension Vegetable Crops Specialists

(Note: Anyone is free to use the information in this newsletter. Whenever possible, please give credit to the authors. The purpose of trade names in this publication is solely for the purpose of providing information and does not necessarily constitute a recommendation of the product.)

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Twenty-sixth Annual Watermelon/Cucurbit Meetings. January 11, 2001.  Jackson County Ag. Office Complex Auditorium, 2741 Pennsylvania Avenue, Marianna, and at the Washington County Agriculture Center on Highway 90, Chipley. For further information or special accomodations for handicapped persons, please contact either the Jackson County Extension Office (Charles Brasher) at 850-482-9620, or the Washington County Extension Office (Andy Andreasen) at 850-638-6180.
2001 FL107 In-Services:
Feb. 13: Strawberry in-service training. GCREC-Dover. Contact: John Duval.
March 5-8: Florida Postharvest Industry Tour. Contact: Steve Sargent.
April 23-25: Beneficials and Biorationals for Vegetable Pest Management. Contact: Susan Webb.

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Utilizing the Plant’s Natural Defense Systems: Induced Systemic Resistance (ISR) or Systemic Acquired Resistance (SAR)

Protecting plants from disease is frequently discussed using the terminology of war, such as "winning the battle" against plant disease. New weapons emerge periodically in the age-old battle against plant diseases. The arsenal now includes such diverse weapons as novel genes transferred via biotechnology, new fungicidal chemistry such as the strobilurin compounds, and compounds that activate a plant’s own defense system. The plant’s defensive reaction is the topic of this article.

Plants do not have an immune system such as humans and animals posses, but plants definitely have an immediate, complex, induced defense response against pest and pathogen invaders. This response was recognized as early as 1933 and first termed "acquired physiological immunity." Other terms used to describe this response are "induced systemic resistance" and, the term we use here, "systemic acquired resistance".

The plant SAR has several distinguishing characteristics. First, it is an induced or activated plant reaction of host defense mechanisms in response to stimuli such as an invading bacterium. The plant reaction is both localized at the site of the invasion and is also transferred systemically to other tissue not in direct contact with the invader. Although the response is induced by a particular agent, the reaction is non-specific and can provide resistance to a wide variety of organisms, such as fungi, bacteria and viruses. The response involves turning on plant SAR genes that result in both biochemical and cytological changes within the plant cell. The SAR reaction can last for several weeks after activation, so that the plant is resistant to future invaders.

The SAR response is exploited for disease control by applying an inducer to activate the plant’s SAR and turning it on prior to attack by some pathogen. The plant, in a sense, is armed and waiting. The SAR response can be broken down into three stages. First is the application of an inducer. The inducer can be a pathogen, synthetic chemical, and metabolic products such as a protein of either the host or pathogen.

The second part of the response involves activation of a plant signaling pathway that alerts the plant of the inducer’s presence. Again, there are several plant pathways that the inducer can activate. The salicylic acid (= aspirin) pathway is probably the most well known plant signaling pathway for SAR, but at least four other signaling systems are known. The take-home message is that not all SAR inducers or the signaling pathways they activate are the same. This means that an inducer may work well or not at all depending on the plant host. As an example, a product may work well on tomato but not on bell pepper.

The last component of the SAR is the actual biological and cytological plant cell changes made after the activation of the SAR genes.

Agrichemical companies capitalize on the plant’s own natural defenses by marketing inducers of the SAR. These products by themselves do not have any toxicity to pests. Some of the products currently available are Messenger™, Actigard™, and KeyPlex DP™. The obvious conclusion from this is that plants treated with these products may have reduced disease incidence and or severity. This does seem to be the fact; however, in our trials, the disease suppression sometimes is not enough to be noticed by the naked eye. These products will most likely have to be used in conjunction with other fungicidal or bactericidal chemicals. In one SWFREC trial, clear differences in downy mildew severity were noted between watermelons treated with both an SAR inducer and fungicide compared to plants that were treated with a fungicide alone. The most tangible benefit from these products may be the enhanced side effects of increased plant vigor and early yield. This slight edge may be just what’s needed to keep profitability in the post-methyl bromide era. Producers using these products should keep track of early yield and overall yield compared to non-treated plants to determine if the product gives an economical bonus.

We are currently testing several SAR inducers for their effect on plant vigor and control of bacterial spot and root-knot nematode in tomato in both controlled greenhouse studies and in the field. Preliminary results indicate that there are differences in the tomato plant’s response to some compounds, and we have seen both disease and plant growth enhancement occur. By the end of these trials, we hope to have a better understanding of what to expect in the performance of a broad spectrum of SAR products.

(Pamela Roberts and Vavrina, Vegetarian 00-12)

Is Inorganic Growing in Your Future?

The Natural Foods Merchandiser reports that organic sales have risen 20% or more for nine consecutive years. Produce has lead the way with 25% to 33% gains nationwide. Why are people buying organically produced produce? Lots of reasons for choosing organic products are given. Many people say organically grown foods taste better. One of the main reasons shoppers give for buying organic food is avoiding chemicals. When organic products are bought, farmers do use environmentally friendly methods which keep chemicals out of the soil, water, and air.

Food industry leaders such as General Mills, Heinz, Gerber, Gallo, Dale, M&M/Mars, and Tanimura and Antle have noted the organic industry by either buying an organic company or having organic SKU available. They are putting their company in a position to take advantage of the opportunity in organic produce sales. In this growing market, is there an opportunity for you as a producer?

In the organic produce world a grower needs to plan ahead, learn how to produce a consistent quality crop, start small and find a buyer or outlet. In the west and northeast, a new market opportunity has emerged. Many of the organic growers are looking to purchase organic transplants rather than producing their own. There may be a market need in your area for organic transplants for vegetables, herbs, and/or cut flowers. Growers nationwide need organic certified transplants. The only known producer of certified transplants serving the New England and Mid-Atlantic states has nearly 200 customers supplied from his 12,000 square foot greenhouse located in Maryland. In the West, organic transplants are easier to buy and a much higher volume are being produced. Most customers are longtime and local within a three state area. Is there a need or market in the southeast? If interested, there are special considerations. Growing organic transplants takes careful, attentive growing. If a disease becomes a problem, there are no fungicides to bail you out. Growers need to be certified. Many commercial soil mixes contain wetting agents which may not be allowed by organic certifiers. Organic fertilizers can include fish emulsion, fish meal, blood meal, rock phosphate, greensand, and compost. Ongoing fertilization is usually done with fish/kelp soluble fertilizers. Some organic fertilizers have a tendency to settle and may clog emitters during irrigation. A fountain pump and no-clog emitters should keep the solution mixed. Also pH and salt levels can run high and need to be checked. Plant pests usually are not major problems in transplant production. Aphids can be controlled with Neemix, Impede, or insecticidal soaps.

The future for organic produce is expected to continue to grow. Many think it will not be linked to whether consumers can afford the extra cost of organic, but will be a life style choice for safety and nutrition.

Organic information sources:

www.Floridaplants.com/FOG

www.AMS.USDA.GOV/NOP/INDEX.htm

www.Fl-ag.com/develop/organics.htm

www.attra.org/attra-pub/plugs.htm#web

www.growingformarket.com

www.ota.com

(White, Vegetarian 00-12)

Carfentrazone (Aim) Labeled for Use in Sweet Corn

Aim (carfentrazone-ethyl) has received labeling for use in corn (all types) to control a wide range of actively growing broadleaf weeds from 30 days before planting, to emerged corn up to the 8-leaf collar growth stage. Several of the weeds controlled are: common lambsquarter (up to 3 inches), iveyleaf and pitted morning glories (2-3 true leaves), black nightshade (up to 4 inches) and redroot pigweed (up to 4 inches). The use rate is 1/3 ounces of product (0.008 lb ai) per acre. The use of nonionic surfactant at 0.25% v/v is recommended. Crop oil concentrate also may be used, but may increase leaf speckling on the treated corn leaves.

The manufacturer (FMC) states that not all sweet corn varieties have been tested, and the use of Aim herbicide on sweet corn is the responsibility of the grower.

In limited trials in Florida, leaf burn did occur on the older leaves of sweet corn when applied over the top. This was more evident when applied to corn older and taller than the labeled height. No yield reduction was seen due to the leaf burn, however. Aim may be tank mixed with several herbicides, to enhance control of many weeds. Carefully read the label before use.

(Stall, Vegetarian 00-12)

Some New and Exciting Fungicide Labeling
for Plant Disease Control in Vegetables

Attaining new pesticide labeling for essential needs is at an all time slow pace. It might best be described as being in the "slow to stop gear." Thus, any new labeling is usually welcomed by those interested in providing safe and healthy vegetables. Two products, Actigard 50 WG and Quadris 2.08 FL, have attained labeling that should provide benefits for farmers.

Actigard 50 WG provides a new mechanism for plant disease control. This product induces systemic aquired resistance (SAR) within the plant by activating specific biochemical pathways. This is not a new concept; the newness of this product relates to the commercial exploitation of this phenomenon. Traditional fungicides provide chemical protection on the outside of the plant or within the plant, but they are generally not considered as activators of chemical processes within the plant that impair the infection process caused by fungi, bacteria, or viruses.

Actigard has attained national labeling for control of bacterial spot and bacterial speck in tomato. One must read the label carefully because the use pattern is not typical of most plant protection chemicals. For example, in order to allow the product to perform to its maximum without delaying the onset of the earliest harvest in tomato, the spray concentration must not exceed 1/3, 1/2, & 3/4 oz. (of product, not a.i.) for spray rates per acre of 30-50, 60-70, and 70-100 gpa of water, respectively. The lower spray volumes are to be used on the plants when they are small. While the label provides rates in relation to product/spray volume, the maximum rate allowed per spray is 3/4 oz./acre and the maximum rate/crop/season is 4 ozs./acre.

Although I am not thrilled with this type of label (i.e. providing rates for spray volumes confounded with land areas), Novartis (soon to be Syngenta) is trying to prevent growers from using too high a spray concentration, particularly when the plants are small, which may delay the onset of harvest. Also, rate per spray volume, rather than rate per acre, is apparently the way the growers wanted to have this product labeled. Further confusion exists with the statement on the label: "Use the higher rate over time, even if the volume does not increase. If gallonage at any particular application is higher than in the example, increase Actigard accordingly, i.e., keep the concentration the same but do not exceed 3/4 oz./100 gals. concentration." One interpretation of this statement is that more than 3/4 oz./acre can be used if the spray volume is over 100 gpa of spray. Yet, earlier in the label it is clearly stated that 3/4 oz/acre is the highest label rate. Mixing these two parameters (volume and land area) for the purpose of calculating spray loads by different people will be interesting; I envision interpretation by different individuals to vary. A maximum of six applications/crop/season can me made on tomato.

Actigard 50 WG is also labeled on spinach, but this use is for Texas. The labeling of Actigard on tobacco is on a national basis and that use pattern is clearly presented on the label. Actigard has a 30 day plant back restriction except for the crops for which it is labeled. The PHI on tomato is 14 days and it is labeled for field use only. It is not to be applied via chemigation.

The second product with new labeling is Quadris 2.08 FL which was developed by Zeneca and will be part of the Sygenta product line when the merger of Novartis and Zeneca is complete. Quadris has been on the market for several years. For vegetables, it was initially labeled on tomato and later labeling for a few other crops was established. Recently, a highly expanded label allows for use on over 90 different vegetable crops, including many of the herbs. The label is clearly written and provides information on how to utilize this product with good stewardship for resistance management. The mode of action of this product is specific and thus resistant (insensitive) strains of target pests are likely to occur.

The label for Quadris provides use patterns and restrictions for use of this product as treatment for designated foliar diseases and designated soilborne diseases. Although this composite use pattern is not a new concept for fungicides, it provides for some interesting possibilities for suppression of certain soilborne diseases in vegetables. Will this use be a substitute for methyl bromide + chloropicrin? The answer is clearly no.

To access the newest chemical recommendations for vegetables, as well as many other bits of information related to plant diseases and their control, go to the web site http://plantpath.ifas.ufl.edu and then click on Extension Publications. I would recommend that County Extension faculty bookmark this site for easy referencing on plant diseases in the future.

(Tom Kucharek, professor, Plant Pathology Department, Vegetarian 00-12)


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Cool-Season Vegetables for Florida Gardens

The cool-season vegetables are those of which the primary parts eaten are the vegetative parts– roots, leaves, buds, or immature flower parts. That is a general rule, for there are exceptions: sweet potato roots and New Zealand spinach tops are warm-season, while pods of English peas and broad beans are cool-season vegetables.

Here are some major ways cool-season vegetables differ from the warm season vegetables (generally, not always):

1.   They are cold hardy or frost-tolerant.
2.   Seeds germinate at cooler soil temperatures.
3.   Root systems are more shallow.
4.   Plant size is smaller.
5.   They respond more to nitrogen fertilizer.
6.   They must be watered more frequently.
7.   Some are susceptible to pre-mature seed stalk development.
8.   Most are stored at or near 32 degrees F (except potato); sweet corn is a warm-season exception that is also stored at 32 F. Many warm-season vegetables suffer chilling injury between 32 and 50 F.
9.   Some seeds like lettuce and celery are favored by light at germination.
10. For asparagus, very cold temperatures are required for dormancy and re-growth.

List of Cool-season Vegetables:

Artichoke, globe

Chard, Swiss

Kohlrabi

Shallot

Artichoke, Jerusalem

Chicory

Leek

Spinach

Asparagus

Chinese cabbage

Lettuce

Turnips

Bean, broad

Chive

Mustard

Watercress

Beet

Collard

Onion

 

Broccoli

Corn salad

Parsley

 

Brussels sprouts

Cress

Parsnip

 

Cabbage

Dandelion

Pea English

 

Cardoon

Endive

Potato

 

Carrot

Florence fennel

Radish

 

Cauliflower

Garlic

Rhubarb

 

Celery

Horse-radish

Rutabaga

 

Celeriac

Kale

Salsify

 

Planting Dates for Cool-season Vegetables in North Florida

Some of these crops can be planted as temperatures approach the proper range. Cool-season crops grown in the spring must have time to mature before temps are too warm. In the fall, they can be started in warm weather if they mature when it is cooler. However, if seeds are germinated in the garden, they must have cool enough soil temperatures for sprouting properly.

There is a fairly wide range of soil temperatures for seed germination, from about 40-80 for lettuce to 60-105 for turnip, 50-70 for parsnip, 50-85 for parsley and watermelon is 70-95. Gardeners should follow the suggested planting dates in the Florida Planting Guides - Stephens.

(Stephens, Vegetarian 00-12)

Extension Vegetable Crops Specialists

Daniel J. Cantliffe
Professor and Chairman, Horticultural Sciences Department
Mark A. Ritenour
Assistant Professor, postharvest

Timothy E. Crocker
Professor, deciduous fruits and nuts, strawberry

Ronald W. Rice
Assistant Professor, nutrition
John Duval
Assistant Professor, strawberry
Steven A. Sargent
Professor, postharvest
Chad Hutchinson
Assistant Professor, vegetable production
Eric Simonne
Assistant Professor and Editor, vegetable nutrition
Elizabeth M. Lamb
Assistant Professor, production
William M. Stall
Professor, weed control
Yuncong Li
Assistant Professor, soils
James M. Stephens
Professor, vegetable gardening
Donald N. Maynard
Professor, varieties
Charles S. Vavrina
Associate Professor, transplants
Stephen M. Olson
Professor, small farms
James M. White
Associate Professor, organic farming


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