Leaf Blotch is fungal
disease spread by spores from various Alternaria species such as A.
mali and A. alternata. The disease overwinters on fallen leaves before
the primary infection period in the late spring which is followed by
further secondary outbreaks through the summer. On leaves the disease
symptoms begin as brown spots about 5mm across before turning grey
while fruit lesions appear as small, dark pimples. Severe infections
can cause leaf fall of up to 50% defoliation by mid-summer and cause a
reduction in fruit yield and quality. Captan-based protectants can be
used especially in regions with hot, wet summer climates which help
the disease to thrive.
Pear Brown Spot
A disease of growing importance in pear is Brown Spot which is caused
by the fungus Stemphylium vesicarium.
The fungus infects leaves, fruits and twigs and causes necrosis and
fruit rot appearing as brown spots on the skin. Severe damage to pear
crops has been seen in southern Europe but it has also been identified
as an emerging and serious problem in orchards in northern Europe -
particularly in the Netherlands and Belgium.
Fungicides such as Captan-based products can be applied as a
preventative measure but there is no curative action so again
vigilance for the emerging disease is paramount.
Apple Powdery Mildew
The powdery mildew fungus Podosphaera leucotricha is one of the most
important diseases in commercial apples - reducing yield and quality.
The mycelium overwinters in buds and the primary mildew appears on
pink blossom or shoot tips at petal fall. As the spring and summer
seasons progress mildew spreads to growing shoots. This secondary
phase can infect leaves and produce sporing mildew colonies in less
than a week.
Control becomes increasingly difficult as the primary mildew colony
spreads so strategies depend on routine spraying and careful
monitoring. Monitoring is essential to establish the disease level
before matching the amount of active ingredient applied and spray interval.
Where more than 2% of blossoms or shoots are covered in the primary
phase, action should be taken. For the secondary phase, with under 10%
mildewed shoots it may be possible to reduce fungicide inputs if the
weather is hot and dry and fungal growth is slow.
Systemic Fungicides such as Bupirimate can provide curative and