  Forecasts and future beliefs play a critical role in the harvest labor hiring
planning, especially when errors in them entails fixing previous made
decisions, which can carry extra costs or losses. In this article, we study the
effect that errors in the forecast/belief can have in the wine grape harvest
planning process and the losses of the product. Errors are reflected in the
prediction of yields and in the estimation of rain transition probabilities
have on the value and losses of product. Also, using a multi-stage stochastic
optimization model we can study the effect that second stage decisions have on
the ability fix the planning decisions, reduce product losses and generate
value. In a first step, we develop a multi-stage stochastic model which
considers grape growth uncertainty given a belief in future events. The model
decisions variables are: hiring, firing and maintaining harvest labor through
periods, and also the harvested quantities in each period and block. Once the
model defines the plan for the coming epoch, some decisions are implemented and
a deviation in the forecast is revealed and the decision maker can adjust
future decisions and beliefs. Results indicate that the effect of the errors in
yield determination is not symmetrical; underestimations of the yields have a
more significant negative effect on the objective function, while
overestimation does not. Flexibility to revise hiring decisions does not make a
significant difference if the yields are overestimated. The model significantly
reduces losses of the better-quality grapes, since they correspond to a
significant proportion of the income and account for the largest portion of
income loss. Last, grapes that have an early improvement of their quality give
the decision-maker an extra level of flexibility to adjust the harvesting plan.
