Definition - What does Threshold mean?
At any point, a vine will have insects and pests on it, and the vineyard’s threshold is the amount or density of pests that must accrue before action is taken to remove them. Threshold varies dependent on the type of pest, type of vine, season, and required action. There is also an economic threshold to consider before action is taken and can be utilized by comparing the value of the crop versus treatment costs.
WineFrog explains Threshold
Thresholds provide a numerical amount of measure to determine if the density of insects or pests within in a vineyard warrant action taken against them. If below the threshold, insects are usually not dramatically harmful to the vines, are left alone or a short-term, safer pest control products are used. Vineyard managers also must consider the type of insect, as some pests have higher thresholds than other less invasive or destructive pests. If pest density on the plant or within the soils are above the threshold point, there are many ways to reduce the pest population, which includes biological pesticides and chemical control practices.
For vineyard management there is also economic thresholds to consider before starting a pest control or vine treatment plan. For vines with high value, the economic threshold will be much lower than for lower value vines, as most owners want to intervene earlier for high value crops. Vineyard managers also consider what time the infestation occurs during the season; it would be more economically sound to invest in treatments early in the season rather than after pruning when winter seasons eliminate many pests naturally.