Agriculture Reference
In-Depth Information
Fig. 5.19.
The infection cycle for
Botrytis allii
, the cause of neck rot in stored onions.
In warm regions where onions are grown,
A. niger
can be found on onion
seeds and sets, on onion foliage and on many kinds of organic debris in soil. The
disease can be transmitted by seed, and the hotter the climate where seeds are
produced the higher tends to be the percentage of infected seed (Maude, 2006).
In trials in Sudan, dusting of seeds with the fungicide benomyl was effective for
reducing bulb infection in soils where onions had not previously been grown,
but in locations regularly used for onion production other sources of infection
made seed treatment less effective (Hayden
et al
., 1994). Fungicidal dips and
dusting of bulbs with calcium carbonate reduce black mould, as can treatment
with hydrogen peroxide (Afek and Orenstein, 2003). The growth of the fungus
is slow at temperatures below 15°C and at low humidities.
Aspergillus fumigatus
and
A. alliaceus
have also been reported as causing
disease on onion bulbs subjected to high temperature in store.
