Asian Soybean Rust Invades U.S. Crops, Aerial Could Be the Fix
By Lindsay Barber, NAAA Manager of Communications
Article appeared in March/April 2005 Issue of Agricultural Aviation

This past year, Asian soybean rust blew into the United States via one of the several hurricanes late in the year. Officials believe spores of the disease may have been carried here from South America. As of December 1, 2004, soybean rust has appeared in Alabama, Arkansas, Florida, Georgia, Louisiana, Mississippi, Missouri, South Carolina and Tennessee.

Background
Asian soybean rust was first found in Japan in 1902. It has also been found in several other countries including, Asia, Australia, Africa, China, Korea and it was discovered in South America in 2000.

Experts predict the disease will be more devastating in the southern portion of the U.S. because general weather conditions allow it to survive over the winter months.

According to the American Soybean Association (ASA), as soybean plants mature and set pods, infection may progress rapidly under favorable environmental conditions to cause high rates of infection in the middle and upper leaves of the plant. Soybean rust thrives on moisture, high humidity and moderate temperatures. Clouds of spores may be observed within and above canopies of highly infected fields. Fields with high infection rates may begin to look yellow or brown.

According to the U.S. Department of Agriculture (USDA) soybean rust is a fungus, which is spread primarily by windborne spores capable of being transported over long distances. If there are winds, or someone is simply walking through a rust-infested field, spores will be released and carried through the air.

Although the disease is devastating to soybean crops, there is no threat to the food supply. Soybean rust is the type of disease that needs to be caught within the first few days to avoid a reduction in soybean crops. The rust can reduce soybean yields by as much as 80% in an individual field.

During the crop year 2001-2002, the rust arrived in Brazil. According to Alan McCracken, an independent consultant in the area of aircraft application of agrochemicals “It has caused serious crop losses, in the area of 3.5 million tons of soybeans during the year 2002-2003. The economic loss was estimated at $1.2 billion and some experts suggest that during the recent crop year, the production loss was over 4.5 million tons and this loss may have been as high as $2 billion.”

Symptoms
According to the USDA, producers need to watch for symptoms of the fungus such as small lesions on the lower leaves of the infected plant that increase in size and change from gray to tan or reddish brown on the undersides of the leaves. Lesions are most common on leaves but may occur on petioles, stems, and pods.

Tan lesions, when mature, consist of small pustules surrounded by slightly discolored necrotic area with masses of tan spores on the lower leaf surface. Reddish brown lesions have a larger reddish brown necrotic area, with a limited number of pustules and few visible spores on the lower leaf surface. Once pod set begins on soybean, infection can spread rapidly to the middle and upper leaves of the plant.

Treatment
Soybean rust can be managed with the judicious use of fungicides. However, early detection is required for the most effective management of soybean rust. Monitoring soybean fields and adjacent areas is recommended throughout the growing season.
Fungicide applications can reduce yield loss, depending on the plant developmental stage, time when soybean rust is detected, and fungicide application method.

In Brazil, the majority of areas are sprayed by aircraft with excellent results in most cases using various application techniques as follows:
a) Conventional application with water at 2 – 3 gallons per acre. Small nozzles are used with high pressure to produce small droplets to give the necessary penetration.
b) Low volume 0.75 – 1.2 gallons per acre. Using a mixture of fungicide + emulsifier + vegetable oil + water using rotary atomizers for improved droplet spectrum with smaller droplets.
c) Ultra Low Volume: 0.25 gallons per acre. Using a mixture of fungicide + vegetable oil. Several operators are using this system also with rotary atomizers.

NAAA Action
On January 13th, Paul Liemandt, the President of the Association of American Pesticide Control Officials (AAPCO) and Manager, Environmental Response and Enforcement Section of the Minnesota Department of Agriculture, sent a letter to AAPCO members to organize approved reciprocity agreements between State Lead Pesticide Regulatory Agencies (SLAs) in anticipation of the soybean rust outbreak.

The National Agricultural Aviation Association (NAAA) Executive Director Andrew Moore spoke with Liemandt about the urgency for reciprocity agreements. The mobility and availability of pesticide applicators licensed via reciprocity, aerial and ground, depends on proper and prompt licensing, with proven competency and certification/licensing done earlier and elsewhere.

The letter urges SLAs to examine their current in-place reciprocity agreements now, make sure those agreements are current and explore additional agreements in anticipation of what may be an unprecedented need for pesticide applicators over a large portion of the U.S. for the soybean rust.

NAAA has many different mechanisms in place to ensure aerial application is available to treat soybean rust. NAAA posts a pilot/operator database on its website under the membership section at www.agaviation.org. Pilots can submit forms if they are looking for work and operators can post job listings that they have work available.

Aerial applicators tend to gravitate towards work. For example, during the early summer, pilots from other states may come to the Mississippi Delta to spray rice fields and during August, they may go to another area of the country to spray for an aphid outbreak. Pilots and operators should take the time to get licensed in other states where outbreaks of soybean rust might be expected. The NAAA Membership Directory is a good place to start because it lists the contact information of all 50 state pesticide control officials. You can make contacts to find out regulations and other information from those individuals.

If you are not a member of the NAAA, now is the time to join. If you are looking for work, you’ll only be posted on the pilot/operator database if you are a member. You also only receive a copy of the 2005 Membership Directory if you are a member.

Other Asian Soybean Rust Hosts
A complicating factor for pest detection and control are the large number of legume hosts that can harbor soybean rust. One widespread host for the rust in the U.S. is kudzu. There are a variety of other important hosts that have shown varying degrees of susceptibility to soybean rust; including yellow sweet clover, vetch, medic, lupine, green and kidney bean, lima and butter bean and cowpea or black-eyed pea.

Government Action
APHIS has organized a Soybean Rust Detection Assessment Team to determine the nature and extent of infection. Because soybean rust is spread via wind currents, quarantining the area will not be effective to contain the disease. In preparation for the possible introduction of the disease, APHIS had been working with industry groups and its sister agencies, Agricultural Research Service (ARS) and Cooperative State Research, Education and Extension Service, to educate soybean producers nationwide on how to identify the disease and report suspected finds.

According to McCracken, a large number of agronomists in Brazil have been trained to assist farmers in identifying the disease and a number of chemical companies have implemented training programs, which include support for the aerial applicators to ensure a high quality of spraying. The secret has been selection of the necessary small droplets to ensure good coverage.

More information on soybean rust can be found at:
• APHIS - http://www.aphis.usda.gov/ppq/ep/soybean_rust/
• American Soybean Assn. - http://www.soygrowers.com/rust/default.htm
• Plant Health Initiative - http://www.planthealth.info/rust/rust.htm
• Your State University Ag Extensions

Information provided by:
• Animal and Plant Health Inspection Service (APHIS) of the U.S. Department of Agriculture (USDA).
• American Soybean Association
• Alan McCracken is an agricultural engineer and independent consultant in the area of aircraft application of agrochemicals. He has currently been involved in helping with the control of Asian Soybean Rust in Brazil and Argentina. He provides the following services: assistance in testing application parameters for chemicals, application techniques to improve performance of products and operating efficiency and trouble shooting to identify why chemicals did not perform as expected. For more information, you can contact Mr. McCracken at McCrackenAlan@aol.com.