Effect of root and butt rot uncertainty on optimal harvest schedules and expected incomes at the stand level

• Key message Root and rot (RBR) caused byHeterobasidion parviporumNiemelä & Korhonen andHeterobasidion annosum(Fr.) Bref. damages Fennoscandian spruce stands. In case the rot infection and its severity are unknown, the mere risk of infection should seldom affect the harvest timing. When it does, the gains by harvesting earlier are minimal. • Context It has been suggested that stands infected by RBR should be harvested earlier than the healthy ones. Yet, we must decide on harvest timing decisions without reliable information on the infection. • Aims We studied if harvesting earlier pays off under RBR uncertainty. • Methods We structured the uncertainty with a decision tree and calculated the optimal rotations based on expected net present values. We compared rotation lengths to those of healthy stands and calculated gains from earlier harvesting. • Results The inclusion of RBR-related uncertainty in the model changed the rotation length of only 14–23% of the stands. The average reduction was 1.3–4.7 years. Yet, the gain from harvesting earlier was too low to be considered. • Conclusion In the absence of information on the extent and severity of RBR, it seldom pays off to advance harvests. The value growth in healthy trees tends to compensate for the value reduction due to rot.

Technologies for Forecasting Tree Fruit Load and Harvest Timing—From Ground, Sky and Time

The management and marketing of fruit requires data on expected numbers, size, quality and timing. Current practice estimates orchard fruit load based on the qualitative assessment of fruit number per tree and historical orchard yield, or manually counting a subsample of trees. This review considers technological aids assisting these estimates, in terms of: (i) improving sampling strategies by the number of units to be counted and their selection; (ii) machine vision for the direct measurement of fruit number and size on the canopy; (iii) aerial or satellite imagery for the acquisition of information on tree structural parameters and spectral indices, with the indirect assessment of fruit load; (iv) models extrapolating historical yield data with knowledge of tree management and climate parameters, and (v) technologies relevant to the estimation of harvest timing such as heat units and the proximal sensing of fruit maturity attributes. Machine vision is currently dominating research outputs on fruit load estimation, while the improvement of sampling strategies has potential for a widespread impact. Techniques based on tree parameters and modeling offer scalability, but tree crops are complicated (perennialism). The use of machine vision for flowering estimates, fruit sizing, external quality evaluation is also considered. The potential synergies between technologies are highlighted.

Influence of Harvesting Season on Morphological and Sensory Quality, Bioactive Compounds and Antioxidant Activity of Three Late-Season Orange Cultivars ‘Barberina’, ‘Valencia Midknight’ and ‘Valencia Delta Seedless’

The genus Citrus amounts to one of the most relevant fruit crops in the world. This work assays overall fruit quality information in order to ascertain the optimal harvest timing of three late-season orange cultivars (‘Barberina’, ‘Valencia Midknight’ and ‘Valencia Delta Seedless’) during two consecutive growing seasons. Thus, morphological and physicochemical parameters, organic acids, polyphenolic content and antioxidant activity (ABTS and DPPH) were analyzed. ‘Barberina’ yielded the highest morphological (large and heavy fruits, albeit with lower fruit color index) and physicochemical (high juice content and intermediate but optimal acidity) fruit quality, with April providing the optimal harvest timing. By contrast, ‘Valencia Delta Seedless’ offered the smallest fruits, while ‘Valencia Midknight’ reported the lowest physicochemical juice quality (low juice content and earlier sensory depreciation). Nevertheless, both ‘Valencia Delta Seedless’ and ‘Valencia Midknight’ had higher functional quality than ‘Barberina’, which could be interesting for the industry in terms of obtaining higher added value products. Thus, ‘Valencia Midknight’ fruits recorded the highest organic acids concentration, especially in citric acid, while ‘Valencia Delta Seedless’ fruits showed the highest antioxidant activity and ascorbic acid concentration. In addition, while March-April emerged as the optimal harvest timing in terms of the highest organic acids concentration and antioxidant activity, it was February the optimal harvest timing for polyphenols content. Finally, the 2017/2018 growing season proposed better response of color index, density, polyphenols and antioxidants, but lower results of total organic acids.