September 2000
Edited by
Frank J. Dainello, Ph.D.
Extension Horticulturist - Commercial Vegetable Crops
The Texas A&M University System
College Station, Texas 77843-2134
Edited by
You may click on any of the following articles, or scroll down.Upcoming Events
New Rust May Hit Corn
Study Reveals Little Risk From Manure Use
To Be REALLY Safe, Let's Ban Everything
Dow Response to New Restrictions on Chlorpyrifos Products
Bug Against Bug
Statewide Watermelon Trial Summary
Upcoming Events Sweet-corn growers who plant rust-resistant hybrids to control common rust should be prepared to scout fields and apply fungicides in 2000, because a new race of the rust fungus (Puccinia sorghi) probably will be widespread in North American this season. Sweet-corn hybrids with Rp (resistance to Puccinia) could be infected wherever this race occurs.
Texas Plant Protection Conference
December 4, 5, and 6, College Station, Texas
For additional information, contact
Pat Miller at (519) 959-2118National Spinach Conference and Tour
December 14, 15, and 16, San Antonio, Texas
For additional information, see web site at:
http://aggie-horticulture.tamu.edu/PLANTanswers/publications/spinach/index.html
or call Larry Stein at (830) 278-9151
New Rust May Hit Corn This article by Jerald Pataky originally appeared in "Flagleaf," the newsletter of the Harris Moran Seed Company
New Race of Rust
The race of P. sorghi is a strain of the fungus that infects corn with the Rp1D gene for resistance. For the past 20 years, Rp has controlled common rust on sweet corn in North America. Nearly 150 commercial sweet-corn hybrids have Rp genes. Rp prevents P. sorghi from producing spores. More than 25 different Rp genes occur in corn, but most Rp sweet-corn hybrids have the gene Rp1D.Although the new race may have arisen from a natural mutation, it is more likely that this race was introduced to Mexico or Central America from South America, Hawaii, or southern Africa, where races of P. sorghi that infect corn with the Rp1D gene have occurred for several years. The pattern of Rp genes that are effective and ineffective against the new North American race is similar to the pattern observed for Hawaiian and South American races of rust.
If the new race did not come from Central America or Mexico, it may have been introduced from Hawaii or South America. Spores of other rust fungi have been collected in jet streams of the upper atmosphere. The coffee rust fungus probably spread from Africa to South America in jet streams associated with unusual weather patterns.
Will It Make Landfall?
It is impossible to know for certain if the new race will be widespread in North America this year, but it is very likely. Once introduced, the new race should survive in Central America or Mexico, even if it is not detected there. The new race may only be an extremely small percentage of the population of rust urediniospores that are disseminated in the U.S.; however, when the new race infects a field of Rp1D corn, it will be the only strain capable of reproducing on those plants. Because each rust pustule produces about 5,000 urediniospores, the new race will quickly become the predominant race in that field, and it will spread to other fields.Thus, by mid to late August, the new race is likely to spread throughout North America if it survives in Central America or Mexico. If the new race is not established in Mexico or Central America, Rp hybrids should not be infected in 2000.
Susceptibility of Rp Hybrids
The reaction of Rp hybrids to the new race will depend on the background of the hybrid. Hybrids should be moderately resistant if their inbred lines were moderately resistant prior to being converted to Rp. Hybrids should be highly susceptible if their inbred lines were highly susceptible prior to being converted to Rp.Rust reactions cannot be determined for hybrids developed from inbred lines for which the background reactions are unknown.
Fungicides and Common Rust
Currently-labeled fungicides are effective against the new strain of rust. Whether fungicides are necessary to control the new race of rust on Rp hybrids depends on the rust reaction of the hybrid being grown, the growth stage at which plants are initially infected, weather conditions, and economics.Fungicides will be essential until hybrids with different rust resistance are available. Several Rp genes are effective against the new race, including: Rp1E, Rp1G, Rp1I, Rp1K, and possibly Rp1C, Rp1L, and Rp1N. Also, several 'compound genes', which combine two or more Rp genes, are effective against the new race; they are Rp1GI, Rp1GDJ, Rp1JFC, Rp1G5JC, and Rp1G5JD.
Hybrids with effective individual or compound Rp genes should be available in a few years because several advanced breeding lines carry these sources of resistance. Also, high levels of partial or general resistance should be effective against the new race.
A few hybrids are available with adequate levels of partial resistance to prevent severe rust infection. Others may be developed in response to the new race, although breeding for partial resistance is usually much more difficult, expensive, and slower than converting inbreds to Rp resistance.
More Mutants Coming?
New races of pathogens develop in response to selection pressures placed on pathogen populations by host resistance. In other words, plants and their pathogens are constantly co-evolving. When breeders and pathologists incorporate new resistance in adapted hybrids, and growers plant these hybrids over large acreage to control diseases, pathogens adapt to survive.In the case of the new race of rust in North America, the pathogen probably adapted very little. Instead, a strain of the fungus that had adapted previously to Rp1D probably was introduced to an area where it had not occurred before. If other Rp genes are used to control rust in sweet corn, this probably will occur again, but hopefully, other sources of Rp resistance will be effective in North America for as long as Rp1D was.
Some sweet-corn producers have benefited from Rp1D for nearly a decade, and others have used this resistance effectively for nearly 20 years. General resistance (i.e., high levels of partial resistance) should remain effective much longer than Rp, because it is more difficult for P. sorghi to adapt to selection pressures from this form of resistance. However, partial resistance will not be available as soon as, or in as many hybrids as, Rp.
Be Prepared
Stay informed. Know what type of Rp is in the hybrids you grow. Know the background reactions of Rp hybrids, if that information is available. Know which fungicides are available to control rust on sweet corn, and read their label for proper use.During the growing season, try to learn if the new race of rust has occurred elsewhere in North America, particularly in areas near you. If it has, scout fields for rust on seedlings of Rp hybrids that have moderate-to-susceptible backgrounds.
Study Reveals Little Risk
from Manure UseBy David S. Jones
This 'Grower Gram' appeared in "The Grower," June-July 2000.The use of manure is an old practice in the Salinas Valley of California for maintaining organic matter and soil tilth. Kurt Schulbach and Richard Smith, University of California Cooperative Extension farm advisors for Monterey County, evaluated the levels of microbial contamination in fall-applied manure, and the potential of those materials to contaminate lettuce subsequently grown in the spring.
In 1998 and 1999, 10 and 13 fields were monitored, respectively. Twenty-three to 40 percent of the manure sampled (both steer and chicken) was contaminated with Escherichia coli. Over the two-year study, no E. coli bacteria was found in the soil or on the lettuce at harvest in 1998 or 1999. The lack of survival of E. coli from contaminated manure in the soil is not surprising, based on prior research evaluating waste-water applications to soil that showed relatively short survival times of bacterial human pathogens in soil.
After two years of study, it appears that the risk from the use of manure contaminated with E. coli is small to nonexistent. Given the relatively high percent of manure samples with E. coli contamination, a potentially greater risk exists from locating manure piles and manure-spreading operations upwind from, or adjacent to, fields at harvest, where dust from manure piles can blow over and contaminate the fresh product.
The anxiety over the contamination issue has caused buyers to request that growers reduce or eliminate their reliance on the use of manures as a soil amendment. As a result, 42 percent of the companies surveyed in this study in 1999 decided to eliminate the use of manure, and are using composted manures and/or yard trimmings or grape pomace to alleviate concerns and risk of microbial contamination of lettuce.
To Be Really Safe, Let's Ban Everything By Dr. Elizabeth M. Whelan
President and Science Advocate for the
American Council on Science and Health (ACSH)
While Americans blithely go about their business, an insidious and irrational flight from technology is taking place, all in the name of 'public health'. In recent weeks, two safe and useful products have been taken away from consumers, despite the conclusions that the approved use of these products is safe. To make matters worse, some manufacturers of these rejected technologies are joining forces with some extreme environmentalist groups and the U.S. Environmental Protection Agency (EPA) to protect us from hazards that do not exist.
Recently, ACSH criticized 3M's withdrawal (prompted by pressure from the EPA) of its unique fabric protector Scotchgard. The product will soon disappear from the supermarket shelves, not because there is any evidence it is unsafe, but because trace levels of some of the product's chemical components have been persistent in human blood samples and in the environment. These trace levels of chemicals in the blood have not been deemed harmful, but their mere detection was enough to be fatal to Scotchgard.
The EPA has also announced its ban of Dursban, one of the most common ingredients in home, lawn, and garden bug killers. This compound is found in familiar household pesticide sprays such as Raid and Black Flag roach and ant killer. EPA administrator Carol Browner defends her decision to ban this useful product by claiming that Dursban causes damage in the brains of newborn rats. She further argues that both children and adults have been harmed from the use of these products. These sprays can indeed, when misused, be toxic, and misuse and accidental ingestion of the products could cause serious health hazards. Yet, Ms. Browner presents no evidence that the approved and intended use of Dursban products poses any health problems at all.
Thus, the 3M Scotchgard episode and Dursban sequel illustrate an emerging -- and unscientific -- code for 'protecting public health', as follows.
#1. Ban the product if you can find traces of any chemical components persisting in the body or the environment. Scientists know that the ability to merely measure the presence of a chemical that is potentially harmful does not indicate that human health is in jeopardy. Furthermore, it is well known that human blood contains traces of nearly all the myriad natural and synthetic chemicals to which we are exposed daily.
#2. If it causes health problems in rodents, ban it. Yet repeated laboratory-animal studies using extremely high levels of naturally occurring chemicals (in food, water, and air) can cause toxic effects, cancer, and reproductive damage. For example, the naturally-occurring chemicals hydrazines, found in mushrooms, are carcinogenic in rodents. Arsenic and solanine, natural components of potatoes, can be highly toxic to humans and animals in high doses, but are harmless in the trace levels found in spuds.
#3. If the product is abused or misused, ban it, even for its rational, approved use. Yet common pharmaceuticals, cosmetics, cleaning agents -- and even table salt -- can cause injury and death if misused or accidentally ingested. In the case of a small child, even small amounts of such ingested material can pose a grave risk. Are we pursuing such a degree of safety in our society that we are willing to discard any and all useful technology where no valid evidence of a health threat with intended use exists? And what negative consequences might we face from the purging of these allegedly hazardous materials?
That 'household hint' guru, Heloise, recently appeared on the Today Show, suggesting primitive ways of protecting our clothes from stains, now that Scotchgard will be gone. But what her comments made clear is that there are no good alternatives to Scotchgard available, and that means higher costs for all of us to replace blighted clothes and furniture. And with Dursban gone (most likely to be joined in the graveyard of chemicals by pesticides with similar properties), we have lost even more of our tools in fighting off the asthma-inducing effects of cockroaches and other pests.
The most troubling aspect of this insidious threat is that consumers seem unaware that we are on a slippery slope, with almost any useful and safe consumer product now vulnerable to strident cries to 'be safe rather than sorry' to 'protect the children'. And, to make matters worse, some manufacturers seem to be willing to fold up their tents and move on rather than stand up for the science-based conviction that their products are safe.
Dow Response to New Restrictions
on Chlorpyrifos Products By Garry Hamlin of Dow AgroSciencesThe U.S. Environmental Protection Agency announced new restrictions on chlorpyrifos products at a June 8 technical briefing held in Washington, D.C. At that technical briefing, the Agency announced its revised risk-assessment for chlorpyrifos products under the U. S. Food Quality Protection Act of 1996.
It is a stated goal of the Clinton administration to reduce potential exposures to pesticides in the U.S., especially potential exposures to children. In its ongoing implementation of the Food Quality Protection Act, the EPA has demonstrated that it intends to apply standards far more restrictive than those historically established by the scientific community, and accepted by the EPA and other regulatory organizations around the world.
Although the Food Quality Protection Act has fundamentally changed the way in which pesticides are regulated in the U.S., the safety of chlorpyrifos products hasn't changed. We stand behind the safety of these products for all of their labeled uses.
Several major print and broadcast news vehicles have seriously mis-characterized the safety of our product Dursban insecticides by claiming that the EPA intends to 'ban' Dursban products because a recent study allegedly found that the product caused 'brain damage' in fetal rats. There is no scientific evidence that the labeled use of Dursban products causes adverse effects, even in particularly sensitive persons such as children.
These blatant misrepresentations have originated with activists, who fail to note that the dose at which these alleged effects occurred in laboratory animals is equivalent to an estimated human exposure to more than 500 applications of this product throughout your home in one day. This would be the equivalent of having your home treated every three minutes, 24 hours a day, seven days a week, at a cost of more than $17,000 per day.
Regarding these alleged effects, which activists are now misrepresenting as 'brain damage', the EPA has said that it 'cannot directly link health significance' of these responses in rats to people. Further, according to the Washington Post, the EPA has determined that Dursban products 'pose no imminent threat to public health' and that, consequently, the Agency 'won't order a recall of products containing it'.
Chlorpyrifos products have been on the market for more than 30 years. More than 3,600 studies and reports have been conducted examining critical aspects of chlorpyrifos products as they relate to health and safety.
Taken together, these reports and studies show that currently labeled uses of chlorpyrifos products provide wide margins of safety for both adults and children. No pest control product has been more thoroughly studied.
Chlorpyrifos is used to protect virtually every major crop grown in the U.S. from insect damage. It has been used in and around millions of homes each year to safeguard families and pets from dangerous pests like cockroaches, ticks, fleas, termites, spiders, and fire ants.
Bug Against Bug: Most of the successes in greenhouse biological control have occurred in the Netherlands and the United Kingdom, mainly because these countries, together, contain more than half of the world's greenhouse acreage. An important event occurred in the Netherlands when Koppert (1967), a cucumber grower, entered the natural-enemy business.
Production, Distribution, and Quality Control
of Biological Control OrganismsThis article by Cathy Thomas
Integrated Pest Management Program
Pennsylvania Department of Agriculture,
appeared in the"Vegetable and Small Fruit Gazette," August 2000, Volume 4, Number 8.
Koppert is currently the international market leader in the field of biological crop protection. Large-scale production of natural enemies, such as Encarsia formosa and Aphidius colemani, takes place in the main facility located in the Netherlands. In addition to Kopperts, there are several other large producers, such as Biobest (Belgium) - a leader in bumblebee pollination and biocontrol producer; Novartis BCM (England and California) - a division of Novartis Crop Protection and Applied Bio-Nomics Ltd. - Canada's largest producer of biological controls. There are also some small companies in the U. S. that specialize in the production of predatory mites, lacewings, and trichogramma parasitoids.
Distributors for these biocontrol producers are found throughout the U.S. and Canada. For example, International Technology Services (ITS), Lafayette, Colorado, is the U.S. distributor for Biobest Biologicals. Together with the technical support staff at Biobest, they have a full-time entomologist to answer pest-control and pollination questions. A list of distributors in the U.S. can be found at
which is the web site of the Association of Natural Bio-control Producers. Most distributors require orders to be placed by Thursday (since they must be shipped from Europe or Canada) for delivery the following Wednesday. Products are delivered directly to your farm or greenhouse via UPS, Airborne, or FedEx. Insist on guaranteed live delivery and overnight express only.
The large natural-enemy producers screen for quality, and use expiration dates. Check biocontrol shipments for this date, and be cautious of suppliers who do not put dates on the material. A non-reputable supplier could have material that is weeks old and not viable. When biocontrols arrive at your operation, check for viability. Predatory mites can be monitored by shaking material onto a white sheet of paper and observing movement.
Parasitoids, such as Aphidius colemani, are shipped in bottles. Within 24 hours after placement in the greenhouse, check bottles for parasitoid emergence. If you observe high mortality of parasitoids, call your distributor immediately. During warm-weather months, biocontrols should be shipped with cooling material. Inform employees that you will be receiving biocontrols, so that they can be stored in a cool area if you cannot distribute them immediately.
Web sites to explore are:
http://www.bugsandbees.com
and
http://www.ipmlabs.com
Jill Stavenhagen, Web Site Design
J-STAVENHAGEN@TAMU.EDU
Produced by Extension Horticulture
Texas A&M University
HFSB 225
College Station, Texas 77843-2134
(979) 845-5341
fax: (979) 845-8906
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