Fungal storage rots like blue mould, grey mould, bull’s eye rot, bitter rot and brown rot destroy large amounts of the harvested apple crop around the world. Application of fungicides is nowadays severely restricted in many countries and production systems, and these problems are therefore likely to increase. Considerable variation among apple cultivars in resistance/susceptibility has been reported, suggesting that efficient defence mechanisms can be selected for and used in plant breeding. These are, however, likely to vary between pathogens, since some fungi are mainly wound-mediated while others attack through lenticels or by infecting blossoms. Since mature fruits are considerably more susceptible than immature fruits, mechanisms involving fruit-ripening processes are likely to play an important role. Significant associations have been detected between the susceptibility to rots in harvested fruit and various fruit maturation-related traits like ripening time, fruit firmness at harvest and rate of fruit softening during storage, as well as fruit biochemical contents like acidity, sugars and polyphenols. Some sources of resistance to blue mould have been described, but more research is needed on the development of spore inoculation methods that produce reproducible data and can be used for large screenings, especially for lenticel-infecting fungi.

In an organic apple orchard, standard mechanical cultivation was compared with four different orchard floor management systems (OFMS): acetic acid (V), living mulch (L), a sandwich system during the growing season (SSS), and a sandwich system during the whole year (SSW). The effects of these OFMS on weed management, soil conditions, tree growth, tree yield, fruit quality, and fruit storage potential in a cool climate were evaluated. Acetic acid treatment showed good weed suppression without any amendatory effect on soil conditions, fruit quality, or tree performance. The L and SSS systems increased soil respiration, decreased tree vigor, and improved fruit quality, but had no sufficient influence on weed competition and thus decreased fruit yield. Only SSW gave better weed control, higher soil respiration, and acceptable tree growth with no yield reduction. Fruit from this system also showed better quality at harvest than fruit from other OFMS and maintained this good quality during storage. A 6-week weed-free period from late May to mid-July gave the highest apple yield in two OFMS (SSW and V).

A series of pre- and post-harvest experiments were conducted to enhance apple tree productivity and improve fruit quality and storage life by altering production system and post-harvest treatments in an organic orchard. Increasing the light distribution and carbohydrate uptake (summer pruning and covering the orchard ground with reflective textile) improved tree productivity, fruit color, content of anthocyanin, ascorbic acid, and total phenolic compounds and reduced incidence of fungal storage diseases. Optimal harvesting time could be determined from the starch index in some cultivars, whereas the Streif index [firmness (soluble solids concentration × starch hydrolysis score) ⁻¹ ] was more accurate for other cultivars. In yet others, titratable acidity and flesh firmness also produced important information. By contrast, soluble solids concentration and skin color are not useful as a result of their sensitivity to weather conditions and light intensity. Post-harvest fruit treatment with hot water (46 °C for 120 seconds) decreased fungal decay during storage in two cultivars, whereas spraying the fruit with 10% ethanol decreased fungal decay in all investigated cultivars. Optimization of storage conditions [cultivar-specific controlled atmosphere (CA) and ultra-low oxygen (ULO) storage procedures] maintained fruit quality and reduced the amount of fungal decay.

Reducing food losses in apple production is becoming increasingly important, as the effects of climate change constitute a challenge to food production. Improving methods for determining fruit maturity at harvest leading to the longest storability is crucial, thereby facing more unpredictable seasonal weather conditions. In addition, the increasing temperature is affecting common maturity indices differently; thus, present practice may not be valid. In this study, a non-destructive, time-efficient method was used, tentatively indicating maturity. This study was performed during three climate-diverse years, reflecting more irregular climate conditions. Mid- to late-season cultivars ‘Frida’, ‘Ingrid Marie’, ‘Rubinstar’, and ‘Elise’ were harvested at different pre-determined I_AD (index of absorbance difference) intervals and stored for five months. Correlations between I_AD values at harvest and total losses after storage were found for all cultivars and years, while only a few correlations related to firmness after storage were found. Although a strong effect of year was related to correlations between I_AD and different quality parameters, no noticeably general differences could be found between the exceptionally warm year in comparison to the other investigated years. I_AD, as a maturity index, thus, seems to be resilient to changing temperatures and can be used as a complementary maturity index.