Compiled by Phillip W. Pratt, Area Extension Plant Pathology Specialist, Oklahoma Cooperative Extension Service, Oklahoma State University, Muskogee, OK 74401
Since 1974, soybean disease loss estimates for the Southern United States have been published in the Southern Soybean Disease Workers Proceedings. Summaries of the results from 1977 (5), 1985 and 1986 (2), 1987, (3), 1988 and 1991 (4), 1992 to 1993 (7), 1994 (9) have been published. A summary of the results from 1974 to 1994 has also been published (6).
The loss estimates for 1996 published here were solicited from: Bill Gazaway in Alabama, Clifford Coker in Arkansas, Robert Mulrooney in Delaware, Tom Kucharek in Florida, Boyd Padgett in Georgia, Don Hershman in Kentucky, Ken Whitam in Louisiana, Arvydas Grybauskas in Maryland, Joe Fox in Mississippi, Allen Wrather in Missouri, Steve Koenning in North Carolina, Phil Pratt in Oklahoma, Charles Drye in South Carolina, Melvin Newman in Tennessee, Joseph Krausz in Texas, and Patrick Phipps in Virginia. Various methods were used to obtain the disease losses, and most individuals used more than one. The methods used were: field surveys, plant disease diagnostic clinic samples, variety trials, questionnaires to Cooperative Extension staff, research plots, grower demonstrations, private crop consultant reports, and foliar fungicide trials. The actual production figures for each state were supplied by the state crop reporting service. Production losses were based on estimates of yield in the absence of disease.
In the southern states, the 1996 average soybean yield and the acreage increased over what was reported in 1995 (8). In 1996, 575.8 million bushels were harvested from 17.418 million acres in 16 southern states. The overall average for the 16 reporting states was 30.4 bushels/a. The overall average reported in 1995 was 26.3 bu/a (8). The total acres harvested, average yield in bushels per acre, and total production in each state are presented in Table 1.
Percentage loss estimates from each state are specific as to causal organism or the common name of the disease (Table 2). The total average percent disease loss for 1996 is 8.66%. This is the lowest total average percent soybean disease loss ever reported by SSDW (Figure 1). The lowest total percent loss reported during the 21-year period between 1974 and 1994 was 9.05% in 1994 (6). In 1995 the total percent loss was reported as 9.14% (8). In 1996 Texas reported the greatest loss at 14.70%, and Virginia reported the least at 1.31%.
The estimated reduction of soybean yields is specific as to the causal organism or the common name of the disease (Table 3). The estimated reduction in soybean yield due to diseases during 1996 was greatest in Missouri with 14.673 million bushels and least in Florida with 0.149 million bushels. The total reduction in soybean yield due to diseases in the 16 southern states was 58.217 million bushels in 1996. The estimated value of this loss was $378,410,500 (based on $6.50/bu).
The most destructive soybean disease in 1996 was the soybean cyst nematode that caused 30.1% (17.536 million bushels) of the total yield loss reported by the states participating in this survey. The second most destructive disease was charcoal rot that caused 14.9% of the total yield loss (8.687 million bushels). The least reported diseases were Brown stem rot and Sclerotinia stem rot. Each of these diseases caused and estimated 0.02% of the total yield loss (0.009 million bushels). In 1996 the average percent loss for all recorded diseases was below the 22-year average for each disease except for sudden death syndrome (Figure 1).
In 1996, diseases continued to cause significant loss in soybean production throughout the 16 southern states that participated in this disease loss estimate. It is essential that Extension and University research continue their efforts to discover methods to control these diseases and to educate soybean producers concerning the best methods to prevent yield loss due to soybean diseases.
Table 1. Soybean production for 16 southern states in 1996.
| State | Acres harvested | Yield/acre (bu) | Total production (bu)
|
| Alabama | 315,000 | 31 | 9,765,000
|
| Arkansas | 3,800,000 | 32 | 115,200,000
|
| Delaware | 215,000 | 32 | 6,880,000
|
| Florida | 33,000 | 30 | 990,000
|
| Georgia | 400,000 | 27 | 10,800,000
|
| Kentucky | 1,180,000 | 38 | 44,840,000
|
| Louisiana | 1,020,000 | 33 | 33,660,000
|
| Maryland | 480,000 | 34 | 16,320,000
|
| Mississippi | 2,000,000 | 31 | 62,000,000
|
| Missouri | 4,050,000 | 39 | 157,950,000
|
| North Carolina | 1,200,000 | 29 | 34,800,000
|
| Oklahoma | 285,000 | 24 | 6,840,000
|
| South Carolina | 540,000 | 26 | 14,040,000
|
| Tennessee | 1,150,000 | 32 | 36,800,000
|
| Texas | 270,000 | 30 | 8,100,000
|
| Virginia | 480,000 | 35 | 16,800,000
|
| Total | 17,418,000 | Avg. = 31.4 | 575,785,000
|
