CAULIFLOWER MOSAIC VIRUS IN CRUCIFEROUS CROPS
Cauliflower mosaic virus (CaMV) is present at low levels in many areas on the Central Coast. Each year I am made aware of a few fields in which the problem is occurring.
The virus has several strains known variously as cabbage virus B, Chinese cabbage virus, and broccoli mosaic virus. Symptoms include stunting, a leaf mottle, and warty overgrowths along the leaf veins on the undersurface. The most notable and common to all hosts symptom is vein clearing. The stunting, mottle and wartiness do not occur on all hosts, and these three symptoms may not occur together. On some hosts (ex. cabbage and Chinese cabbage) a black stipple often develops in storage. The stipple will be throughout the head. These necrotic flecks are similar to those caused by turnip mosaic virus but are smaller. This symptom expression is referred to as pepper spot or fly speck and should be differentiated from the physiological flecking in Napa caused by adverse environmental conditions or bad storage and handling conditions. Physiological flecking in Napa usually does not occur throughout the head but is confined to the outer (older) leaves, initially.
All members of the cabbage family (Brassicaceae) are hosts for CaMV virus which is aphid-transmitted. It is not seedborne. After aphid transmission symptoms of infection usually show in 9 - 10 days. CaMV also has a number of weed hosts. All are cruciferous, such as mustard, penny cress, shepherd's purse, charlock, and chickweed.
Management is difficult. Cruciferous weed control in and around seedling growing sites, and in and around production fields is the first line of defense. Aphid control in the standing crop may reduce in-field-spread, but will not stop CaMV introduction to the field from surrounding wild hosts. Some work has been done in cabbage to introduce resistance.
Badger Ballhead, Penn State Ballhead, Eastern Ballhead, Green Winter, Hybelle, Sanibel, Ace High, Storage Green, Hybrid 15, Hybrid H, Rio Verde, Greenboy and Blue Jacket are varieties that show some resistance to fly speck/pepper spot symptom expression. This variety list comes from a 1986 reference, so its applicability to currently in use cultivars may be in question.
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BATS ARE APPARENTLY WORTH THEIR WEIGHT IN PESTICIDES
More and more studies are indicating that bats can significantly reduce insect numbers in croplands. Research has shown that a mature bat can eliminate 1,000 mosquito-sized insects per hour. The studies also show that in cropland environments Mexican free-tailed bats eat adult moths of armyworms, corn earworms, cutworms and codling moths. Stinkbugs, cucumber beetles, and leafhoppers are also fair game. Mexican free-tails are one of the common bats in California.
The research also shows that if you "build them, they will come." Them meaning bat houses.
If you have interest in experimenting with this old/new technology, contact my office at 805/934-6240. We have instructions on How to Build a Bat House. Also suggestions as to where the houses should be placed to make them safe for bats and from people.
Bat Conservation International (BCI) has two Web sites where more information is available:
rrooney@batcon.org and
www.batcon.org/bhra/index.html
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RISK MANAGEMENT PROGRAMS FOR SPECIALTY CROPS
The USDA has for years had a crop subsidy program for grains, cotton, and oil seeds. The department has recently come under pressure to expand this program to include all other crops (called Specialty Crops).
The University of California and others have been contracted to develop guidelines for risk management programs for specialty crops. During the next month or so 30,000 California farmers growing specialty crops will receive a survey document. This survey document will ask you for information, which will be used to develop risk management tools.
I encourage you to take some time and respond to this survey, either "for" or "against." If you do not respond, your voice will not be heard. Your input is needed. The development of "risk management tools" for specialty crops could have a huge impact on the way farming is conducted in the future.
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FERTILIZER "STARTER" SOLUTIONS FOR TRANSPLANT ESTABLISHMENT
by Tim Hartz, Extension Vegetable Specialist, Department of Vegetable Crops, UCD
 The use of transplants is expanding in the California vegetable industry; even in processing tomato production transplaning is becoming a reasonably common practice. Under some environmental condition plant losses in transplanted fields can be serious. In investigating the problem, the issue of appropriate use of starter fertilizer solution came up and prompted me to write this review.
Historically, starter fertilizer solutions (applied to the root zone at transplanting) were used to supply the short-term nutritional needs of transplants until the root system was established and could draw nutrients from a large soil volume. NPK fertilizers with high P content are generally used. Typical applications range from 3 to 10 ounces (75-300 ml) of solution per plant. The concentration of fertilizer in the solution is geared to the N content, with concentrations usually between 500-1000 PPM N. This level is high enough to support immediate plant needs, but low enough that the salinity level of the solution is not dangerously high. The salinity issue is directly tied to the N level because the NH4+ and NO3+ ions are very osmotically active (have a high "salt index").
In an informal survey of transplant tomato operations, it appears that starter rates are much higher. Rates of 8-24-0 as high as 10 gallons per acre in 400 gallons total volume seem to be widespread. This amount of fertilizer is certainly beyond immediate plant needs; the only justification for this practice is to take the place of a banded fertilizer application, thus saving an equipment pass. The problem is that the salinity level of this solution is very high (EC greater than 10 mmhos/cm); N concentration exceeds 2500 ppm.
Is this practice detrimental? I think that depends on several factors. If the soil is reasonably moist, and irrigation is applied soon after transplanting, the starter is probably diluted enough to minimize any salt problem. However, if the soil is reasonably dry and irrigation is delayed for several days after transplanting, the root zone salinity could restrict root development; a nutrient solution this concentrated would reduce soil matrix potential at least 3 bars, the equivalent of removing more than 70% of available soil moisture. In warm, dry weather serious moisture stress could develop.
Unfortunately, I can find no hard field data on transplant establishment with very high starter fertilizer rates. If asked for a recommendation, I would suggest limiting N concentration to approximately 1000 PPM. This is equivalent to about 1 gallon of 8-24-0 per 100 gallons of water. If this amount requires an additional banded application of P fertilizer, I would consider that an acceptable tradeoff for minimizing transplant stress.
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BEST PRACTICES FOR PROMOTING FOOD SAFETY IN ORGANIC PRODUCTION: WATER QUALITY
by Shantana George, Postgraduate Researcher. From materials developed by Trevor Suslow, Extension Specialist, Department of Vegetable Crops, UC Davis
 With the introduction of the President’s 1997 Food Safety Initiative, the national "From Farm to Table" program was instituted. This program drew attention to the ways growers can help manage food safety risks on their farms.
As organically-grown fruits and vegetables become more successful in the marketplace, organic farmers should continue to give attention to the issue of microbial food safety. The following guidelines on water use can help organic farmers manage and reduce microbial risks.
- Be sure that high-quality water is used for all operations where the water comes into contact with the edible portion of the plant.
- As the possibility increases for water to make direct contact with fruit, it becomes easier for water contamination to be transferred. Some growers find it useful to divide farm operations into agricultural and postharvest operations. This helps to divert the highest quality water to the later stages of food production.
- Be sure irrigation water does not contaminate produce. While no comprehensive microbial standards for agricultural water have been established, state regulations require that reclaimed water used for irrigation does not exceed 2.2 total coliforms per 100 ml. World Health Organization (WHO) guidelines specify less than 1,000 fecal coliforms per 100 ml of water as acceptable. We recommend that these limits be used as guides until more definitive data is available.
- Contact between irrigation water and edible plant parts should be minimized. This may include favoring drip or furrow irrigation instead of sprinkler irrigation. If overhead irrigation must be used, the grower should use water with less than 2.2 E. coli per 100 ml water. Minimizing contact between plants and water when contact isn’t necessary acts as a safety barrier to cross-contamination between irrigation water (which is often reclaimed water or surface water) and produce.
- Protect the water source. Factors such as run-off, flooding, and animal waste may cause contamination in the water supply. Diversion berms and buffer areas may help protect the water source from contaminants brought in by run-off and flooding. Nearby animal production may pose risks to water quality due to high volumes of animal waste production. Water contamination from animal waste has been shown to be involved in outbreaks of E. coli O157:H7. The use of fences or gates may help keep animals out.
- Maintain and repair wells regularly. This includes having well casings inspected regularly and repaired as needed. Growers who rely on wells for their water source should have wells inspected and their water tested annually by a water quality expert.
- The grower should be aware of his/her certifying agency’s guidelines for water disinfectants. Organic operations may not permit the same levels of chlorine for sanitizing irrigation equipment or for water disinfection that conventional growers use. California Certified Organic Farmers allow a maximum of 50 parts per million of chlorine to come into initial contact with edible produce. They also stipulate that the flush water from irrigation equipment may not contain more than 4 parts per million of chlorine, the maximum for drinking water. Each organic certifying agency has its own guidelines; consult with your agency for specifics.
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