Developed by The University of Georgia, College of Agricultural and Environmental Sciences; The University of Florida, Institute of Food and Agricultural Sciences; Auburn University, College of Agriculture
Many factors combine to influence the risk of losses to Tomato Spotted Wilt Virus. Some factors are more important than others, but no single factor can be used as a reliable TSWV control measure. Research data and on-farm observations indicate that when combinations of factors are considered, an individual field’s risk of losses due to TSWV can be estimated.
There is no way to predict with total accuracy how much TSWV will occur in a given situation or how the disease will affect yield, but by identifying high-risk situations, growers can avoid those production practices that are conducive to major yield losses.
The Peanut Disease Risk Index, known as Peanut Rx, was developed as a tool to evaluate risk associated with individual peanut production situations.
When high-risk situations are identified, growers should consider making modifications (i.e. variety, planting date, seeding rate, etc.) to reduce the level of risk. Using preventative measures to reduce risk of TSWV losses is the only way to control the disease.
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Risk levels are relative. If this index predicts a low level of risk, you could expect that field to be less likely to suffer major losses due to TSWV than a field that is rated with a higher level of risk. However, a low index value does not imply that a field is immune from TSWV losses and losses due to TSWV vary from year to year.
For each of the following factors that can influence the incidence of TSWV or fungal disease, identify the option that best describes the situation for an individual field. An option must be selected for each risk factor, unless the information is “unknown.” A score of “0” for any variable does not imply “no risk,” but that this practice does not increase the risk of disease as compared to the alternative. Add the numbers associated with each choice to obtain an overall risk index value. Compare that number to the risk scale provided and identify the projected level of risk.
Planting ‘Windows’ to Attain Low Risk for Spotted Wilt
If planting date were the only factor affecting spotted wilt severity, growers would have no flexibility in when they planted. Fortunately, other factors are involved and by choosing other low-risk options, growers can expand their planting date window. Remember, the goal is to have a total risk index value of 65 or less, regardless of which combination of production practices works best for you. The following table demonstrates how the planting date window expands as other risk factors go down. For example, where a grower achieves a good stand, uses strip tillage and twin rows, and Thimet, but does not use Classic, he may plant a “10” or “15” point variety at ANY time in the season and still be at “Low” risk for spotted wilt.