Cooperative Extension Service
The University of Georgia College of Agricultural and Environmental Sciences
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	2004
	Georgia Plant Disease Loss Estimates
	Compiled by: Mila J. Pearce Extension Plant Pathologist

Introduction
2004 Plant Disease Clinic Annual Summary
Apple
Blueberry
Bunch Grape
Corn
Cotton
Muscadine Grape
Ornamentals
Peach
Peanut
Pecan
Soybean
Strawberry
Tobacco
Turf
Vegetables
Wheat
Summary of Total Losses Due to Disease Damage and Cost of Control

It is estimated that 2004 plant disease losses, including control costs, amounted to approximately $558.92 million. The value of the crops used in this estimate was approximately $5472.65 billion, resulting in a 10.21 percent total disease loss across all crops included in this summary.

The estimated values for most crops used to compute these disease losses are summarized in: Georgia Agricultural Statistics Service, Georgia Farm Report Vol. 04, No. 4 and the 2004 Georgia Farm Gate Value Report (AR-05-01). Estimates for tobacco are based on Market News Service figures for growers' net sales and do not include warehouse resales. Some estimates for grapes, ornamentals, and turf rely on specialists' knowledge of the industry and industry sources for information.

The Following Members of the University of Georgia Department of Plant Pathology
Made Direct Contribution to this Publication:

2004 PLANT DISEASE CLINIC ANNUAL SUMMARY

Extension Plant Pathology maintains three clinics as educational resources for county extension agricultural faculty to use to aid their clients in diagnosing and correcting disease-related plant problems. Plant samples are submitted directly to the county extension faculty who, at their discretion, forward samples to the appropriate clinic. Commercial fruits, legume forage crops, forestry, Christmas tree, and commercial ornamental greenhouse, nursery, and landscape samples are sent to the Plant Disease Clinic in Athens. Diagnoses of and control recommendations for commercial samples of field crops, grain forages, pecans and vegetables are handled by the Plant Disease Clinic at the Rural Development Center in Tifton, Georgia. Commercial turf and all non-commercial homeowner plant samples are sent to the Plant Disease and Homeowner IPM Clinics in Griffin for disease diagnoses and recommendations. Diagnoses and educational recommendations are returned to the county faculty. The clinics maintain a computerized database of samples and their diagnoses, as well as a reference library for use by extension agents, specialists, researchers, and students.

APPLE

Apples had a moderate to high disease pressure in 2004. This was partly due to wet, warm conditions during bloom, as fire blight was prevalent if antibiotic sprays were not applied. In addition, fire blight was even more prevalent as post-bloom shoot blight. The disease was so prevalent that antibiotic-resistance testing was conducted, but resistant bacteria were not found – indicating that the environment or inoculum buildup from 2003 was responsible. As usual, bitter rot was a major issue; fungicides for bitter rot were not effective enough when wet conditions were observed, and rainy weather sometimes made fungicide application difficult. There is still a strong need for more efficacious fungicides for control of bitter rot and other summer rot diseases. In addition, though not yet observed, we are concerned that streptomycin antibiotic resistance may yet become an issue; currently, streptomycin is the only effective antibiotic for fire blight. If we lose this antibiotic due to resistance, apple production will be much more difficult. Cost of control included increased pesticide use for fire blight as well as increased pruning costs as a result of fire blight and summer rot control measures.

BLUEBERRY

In 2004, mummy berry (both primary shoot blight and mummified fruit) was observed at very high levels, largely due to wet conditions and/or poor fungicide programs. Botrytis blight was prevalent when fungicides were not utilized during bloom. In southern highbush cultivars, problems due to foliar diseases and dieback were also observed, but the use of fungicides helped to reduce these diseases when utilized. Rust was also much more prevalent than normal. In general, disease pressure was high due to wet conditions.

BUNCH GRAPE

Disease pressure was low to moderate among bunch grape vineyards in 2004, due largely to dryer conditions throughout the maturation period and during harvest. Disease pressure was greatly reduced over that observed in 2003, and wine produced from the 2004 crop should be excellent. Pathological issues, foliage diseases and rots resulted in minor losses in 2004. Where adequate spray programs were maintained, nearly 0 percent losses were observed in many cases. The degree of loss was directly correlated with the accuracy and intensity of the fungicidal spray program. Where used correctly, fungicides and spray programs were very effective in disease control.

CORN

In 2004, corn was planted on 335,000 acres and harvested from 280,000 acres in Georgia. The average yield in 2004 was 130 Bu/A. The 2004 crop was valued at $80,080,000. Much of the corn crop was harvested prior to the arrival of tropical storms late in the season. Had harvest not been well underway, the damage to the corn crop from these storms could have been phenomenal. Southern corn leaf blight was of minor importance in 2004. Southern rust, which was very important in 2003, was inconsequential in 2004. Rainfall was less abundant during the growing season in 2004 than in 2003. Therefore, aflatoxin levels increased slightly for the 2004 crop. The true importance of damage from nematodes, e.g. stubby root and southern root-knot nematodes, is becoming more apparent as growers and county agents become more familiar with the symptoms.

COTTON

Torrential rainfall from multiple tropical storms and hurricanes as harvest approached in 2004 had devasting effects on many growers and helped to increase the severity of boll rot. Cotton was planted on 1.29 million acres in 2004 and harvested from an estimated 1.20 million acres. The average yield was 675 lb/A for a total production of 1.8 million bales. The crop was valued at $406,080,000.

Hardlock of cotton occurs when the lint forms properly yet fails to "fluff" when the bolls open and cannot be harvested effectively with a spindle-picker. There are multiple causes for hardlock of cotton, including boll maturity, environmental conditions, and damage from insects, especially stinkbugs. Researchers at the University of Florida believe that another factor involved with this malady may be the fungal pathogen Fusarium moniliforme; research efforts continue to verify this. In some test plots assessed in 2003, as many as 35 percent of the bolls could be considered "hardlocked." Until the cause of this condition is completely understood, hardlock will not appear in our disease loss estimates.

Losses to nematodes, primarily southern root-knot nematode, continue to be important problems for cotton growers in the state. Until growers are able to practice effective crop rotation and increase the number of years between cotton crops in a field, the losses and damage from parasitic nematodes will continue to increase unless growers use nematicides effectively.

MUSCADINE GRAPE

Minimal disease pressure was observed in most muscadine vineyards. When rots were observed, Macrophoma rot was the predominant disease observed. Black rot was observed on leaves, but this did not translate to fruit rots. Moisture levels were sufficient enough to reduce vine stress while not being in excess. Conditions may have helped to reduce vine stress, which had been causing vine losses due to secondary dieback diseases.

ORNAMENTALS

The 2004 farm gate value for ornamentals horticulture (excluding turf) was estimated at $516.13 million. Landscape, re-wholesale and retail (service) industries are estimated to account for an additional $800 million for a total ornamental industry estimated value of $1.31 billion. The disease losses provided are only for ornamental production and exclude the service industries as value and disease losses are difficult to assess in these areas. This is a major change from disease loss estimates in previous years. Typically, root rot diseases account for the largest percentage of disease loss in ornamentals. However, the introduction of Phytophthora ramorum, cause of sudden oak death and ramorum blight, into primarily retail ornamental nurseries resulted in significant losses due to destruction of infected and adjacent plants. Leaf rusts, downy mildews and needle blight on Leyland cypress continue to increase in occurrence cost of control due to additional fungicide inputs and labor costs. This combined with wet conditions in 2004 contributed to an overall increase in percent reduction in crop value compared to 2003.

PEACH

Due to dry conditions throughout much of the season in the major production regions, peach production in 2004 experienced very low disease pressures. Brown rot pressure was especially low, with in-field losses of 1 percent in most areas. Also in 2004, we confirmed resistance of the brown rot fungus to the DMI fungicides that are generally used for control. This resistance will increase the cost of control in the future due to the required use of more expensive fungicides. Scab was also minimal. The same was true of bacterial spot, which was virtually nonexistent; the good control of bacterial spot can be largely attributed to producer acceptance and utilization of more advanced spray programs and weather-monitoring systems. Problems with Armillaria root rot and phony peach were observed. Armillaria continues to be a major, expanding problem in re-plant peach production. In addition, some losses were incurred from nematodes and crown gall. Cost of control included cost of pesticides, equipment and labor. Costs associated with certain cultural practices (flail mowing to reduce gummosis, detailed pruning for control of Phomopsis shoot blight) are directly related to disease control and were, therefore, considered in the assessment.

PEANUT

In 2004, peanut was planted on an estimated 620,000 acres and harvested from approximately 610,000 acres. With ample rainfall, improved varieties, and effective disease management programs, peanut farmers achieved the highest average yield per acre on record. Yields in 2004 averaged 3,000 lb/A, for a total production of 1.83 billion pounds, valued at $347,000,000. Growing conditions for the crop were fair throughout much of the season; however, the end of the season was marred by multiple tropical storms and hurricanes. The most important result of these storms was that the torrential rainfall fueled fungal disease epidemics, delayed growers from making timely fungicide applications, and delayed harvest in many instances. Many growers still successfully managed fungal diseases, both foliar and soilborne, despite inclement weather. Losses from leaf spot diseases were increased in 2004 from 2003, primarily because of rainfall and also the increased incidence of late leaf spot in the state. Losses from Rhizoctonia limb rot also increased from 2003 due to wet weather and delays in fungicide applications and harvest. The losses associated with white mold also increased slightly; severity of Cylindrocladium black rot (CBR) was similar to 2003. Although still of relatively minor concern, a few fields in southwestern Georgia were particularly hard-hit by Diplodia collar rot. Losses from tomato spotted wilt were increased in 2004 from 2003 and were estimated to be approximately 4 percent. Grower use of more resistant varieties and the University of Georgia's Spotted Wilt Index helped to keep the severity of this important disease lower than it might have been. Where the losses to this disease were severe in individual fields around the state, the cause could likely be related back to planting date, poor plant stand, and/or choice of variety.

PECAN

The 2004 season will be remembered for the series of hurricanes and tropical storms that moved through Georgia late in the growing season. Rains during June and July resulted in fairly high disease pressure at most locations. Loss potential was variable, ranging from 15 to 80 percent.¹

SOYBEAN

In 2004, soybean was planted on approximately 280,000 acres and harvested from an estimated 270,000 acres. Average yields in 2004 were 31 bu/A, which is fairly high by state standards. The total soybean production for Georgia in 2004 was valued at $44,361,000. The percent losses to most diseases appeared similar between 2003 and 2004. Frogeye leaf spot and downy mildew were common in 2004. Many growers were interested in spraying fungicides to control frogeye leaf spot though few actually did. Nematodes remain an important problem of soybeans in Georgia, especially in fields rotated with corn and cotton.

STRAWBERRY

Disease pressure was not severe in 2004 since rainfall was not as prevalent as that observed in 2003. Angular leaf spot was minimally observed. Anthracnose and Botrytis (gray mold) diseases were also not prevalent throughout the state, due once again to drier conditions during bloom and throughout fruit development. However, plug plants were found to have anthracnose at the time of transplanting, and some producers did not produce strawberries as a result. Overall, it was a very good year for strawberry production. There is some concern that the strobilurin fungicides, which are heavily and virtually exclusively utilized for control of anthracnose, may be developing resistance. There is a strong need for fungicides with different modes of action if we are to continue strawberry production in Georgia.

TOBACCO

Spotted wilt returned in 2004 to cause the second highest loss recorded. Losses were particularly severe in a 40-mile wide band running along U.S. Highway 1. Several farmers plowed up their tobacco for insurance. Losses were somewhat less in the Douglas-Hazelhurst-Nashville triangle due in part to a heavy spotted wilt loss history inducing a higher percentage of growers to use what control measures are available. Blue mold was not reported in 2004. Black shank increased in frequency and severity on the newer resistant varieties (NC-71, NC-72, NC-297, Sp-168, etc.). It is increasingly clear that these varieties rapidly select for race 1 of the pathogen to which they have no resistance. Target spot occurred late and caused very little damage. Growers in increasing numbers are not using nematicide, which is reflected in an overall decline in cost of control.

TURF

It is estimated that there are 1.80 million acres of turf with the maintenance value of $1.65 billion in Georgia. In 2004, soilborne diseases are present wherever turf is grown and were responsible for much of the disease losses. Rhizoctonia spp. was the most prevalent pathogen on turfgrass. Increased incidence of Gaunannomyces spp. and Pythium spp. was observed in 2004. In 2004, a steady increase of Magnoportha poae (summer patch) and Opiosphaerella spp. (spring dead spot) was observed. Foliar diseases continue to be problematic in 2004. Sclerotinia homoecarpa was present throughout the state in several turfgrass species. During the summer, Curvularia spp. and incidences of Sclerophthora macrospora (downy mildew) were registered in 2004. Nematodes have been attributed to increased damage and promoting stress on turfgrass. Mixed infections of nematodes and Pythium were common in 2004.

VEGETABLES

About 200,000 acres of vegetables are grown in Georgia in 2004 worth a total of ca. $725 million. Overall, most crops suffered fewer losses in the spring. Although low disease pressure was observed in the spring, low produce prices reduced the value per acre. In the fall, however, the hurricanes predisposed many crops to disease and may have actually brought some diseases into the state. Prices on produce reached record highs in the fall due to production shortfalls caused by hurricanes. Snap beans suffered losses in the fall to brown rot caused by Pseudomonas syringae. Fall cucurbits were damaged by downy mildew that was found to be resistant to strobilurins. Fall pepper crops were ravaged by anthracnose (Colletotrichum acutatum) and bacterial spot (Xanthomonas campestris pv. vesicatoria).

WHEAT

Barley Yellow Dwarf Virus (BYDV) was variable throughout the state with low amounts observed in South Georgia. From the Piedmont and north, the damage was severe; this was mostly due to intense aphid activity experienced during the mild fall-early winter. Sporadic wheat samples with symptoms resembling wheat spindle streak mosaic virus were observed in 2004. Rusts caused only low amounts of damage to wheat during 2004 due to planting of resistant cultivars and the use of fungicides to control other foliar diseases such as powdery mildew. Fusarium foot rot and take-all were sporadically found in South Georgia and may have contributed to the early decline of some fields. Powdery mildew incidence was moderate, causing minimal damage. Weather conditions and early spray of fungicides helped to avoid an epidemic. Glume blotch on heads and leaves (Stagnospora) was at some of the lowest levels in years. An important piece of the disease management strategies was the use of disease resistant cultivars in 2003. Wheat was harvested from 250,000 acres.

SUMMARY OF TOTAL LOSSES DUE TO DISEASE DAMAGE AND COST
OF CONTROL IN GEORGIA - 2004

ATTENTION!

• Observe all directions, restrictions and precautions on pesticide labels. It is dangerous, wasteful and illegal to do otherwise.
• Store all pesticides in original containers with labels intact and behind locked doors. "KEEP PESTICIDES OUT OF REACH OF CHILDREN."
• Use pesticides at correct label dosage and intervals to avoid illegal residues or injury to plant and animals.
• Apply pesticides carefully to avoid drift or contamination of non-target areas.
• Surplus pesticides and containers should be disposed of in accordance with label instructions so that contamination of water and other hazards will not result.
• Follow directions on the pesticide label regarding restrictions as required by State and Federal Laws and Regulations.
• Avoid any action that may threaten an Endangered Species or its habitat. Your County Extension Agent can inform you of Endangered Species in your area, help you identify them and through the Fish and Wildlife Service Office identify actions that may threaten Endangered Species or their habitat.

Trade names are used only for information.

Special Bulletin 41-07/June, 2005

The University of Georgia and Ft. Valley State University, the U.S. Department of Agriculture and counties of the state cooperating. The Cooperative Extension Service, the University of Georgia College of Agricultural and Environmental Sciences offers educational programs, assistance and materials to all people without regard to race, color, national origin, age, gender or disability.

An Equal Opportunity Employer/Affirmative Action Organization Committed to a Diverse Work Force

Issued in furtherance of Cooperative Extension work, Acts of May 8 and June 30, 1914, The University of Georgia College of Agricultural and Environmental Sciences and the U.S. Department of Agriculture cooperating.

Josef M. Broder, Interim Dean and Director