The measurement and modelling of losses of cucurbits to Tephritid fruit flies

Losses of cucurbit fruits to Tephritid fruit flies are often assessed as the infestation percentage of mature fruit at harvest, but this way of appraisal may underestimate losses, as attacks on pre-mature fruit that are lost before ripening reduce the mean mass of surviving fruit also. An alternative approach is proposed, which improves accuracy by incorporating the effects of losses of pre-mature fruit. This approach entails computation of an aggregate loss by combining infestation levels in four cohorts of fruit, assuming different rates of compensation by the plant for losses in each cohort. Using data from different sites in India, this "by cohort, compensated" model obtained significantly less variability, among replicates of identically-treated plots, than the mature-fruit-only model, and a pattern of losses comparable to those obtained by incorporating reductions in surviving-fruit mass. The model is more accurate and realistic than the assessment of mature fruit only