The effects of direct harvesting and drying systems on the incidence and control of neck rot (Botrytis allii) in onions

Abstract

Direct harvesting, with mechanical removal of the foliage (topping), of onion crops followed by post‐harvest drying at ambient temperatures (c. 18°C) resulted in an increase in the incidence of onion neck rot (Botrytis allii). The disease was substantially reduced if topped onions were dried at 30°C with an airflow of 425 m3 air/h/tonne. The treatment was most effective if the crop was removed from the field for drying within 48 h of topping thus avoiding severe infection of the damaged green tissues of the necks of onions.

Effects of low temperature on mycelial growth and spore germination of Botrytis allii in culture and on its pathogenicity to stored garlic bulbs

“…Obviously, it is valuable to study low temperature biology and pathogenicity of storage pathogens, in particular temperatures near freezing point, such as -2 and 4 C which are currently used to store garlic bulbs in Israel (Philosoph-Hadas et ai, 1993) and in Italy (Anonymous, 1994). However, up to now, little has been known about the effects of low temperatures on growth, germination and pathogenicity of the organisms causing decay in stored garlic bulbs, except for that research concerned with B. allii of bulb onions (Maude & Presly, 1977;Ali A Shabrawy, 1979;Kritzman, 1983;Maude et at., 1984).…”

Effect of temperature of production of Botrytis allii conidia on their pathogenicity to harvested white onion bulbs

“…Mechanical topping of onion foliage, leaving a truncated cylinder of green leaf base (neck), which is not properly dried, could also provide an ideal infection point for B. allii (Maude et al, 1984). Mechanical wounds caused during handling produce other infection sites for B. allii in the bulbs (Isenberg, 1955;Smith et al, 1982).…”

Onions, Shallots and Garlic

“…Fairly crude field storage in clamps or heaps was common in Europe and the United States for long-storing onions at that period. However, methods changed greatly during the next two decades, as scientists and growers experimented with better ways to control environmental conditions during drying, curing and longterm storage (Maude et al 1984). At the same time, the biology and epidemiology of many storage diseases were also elucidated, and treatments developed led to marked improvements in onion storage life.…”

“…Extension literature produced in the 1970s and 1980s (e.g. Maude et al 1984) established a framework for the 'direct harvest' methods which are still being refined today in temperate countries where large-scale storage is practised (O'Connor 2002).…”