This post is in continuation to my previous post on Apple Diseases:Holistic Management of Apple Scab. Here we are going to discuss about
Monitored spray control
Monitored Spray control:
Among two different monitored spray strategies (curative and eradicative) as developed and tried in the orchards, the curative sprays with well timed application of Ergosterol-biosynthesis-inhibiting (EBI) fungicides even after 72 and 96 hour of the predicted infection periods is not only more effective but also economical for control the disease with three lesser sprays.
Monitored Spray control:
Among two different monitored spray strategies (curative and eradicative) as developed and tried in the orchards, the curative sprays with well timed application of Ergosterol-biosynthesis-inhibiting (EBI) fungicides even after 72 and 96 hour of the predicted infection periods is not only more effective but also economical for control the disease with three lesser sprays.
Av Temp
(oC)
|
Minimum
wetness (hr)
|
Scab
appear (days)
|
|
Ascospores
|
Conidia
|
||
17.2-23.8
|
9.0
|
5.9
|
9
|
13.8-11.0
|
11.0
|
7.5
|
15
|
10.5-8.5
|
15.0
|
9.8
|
17
|
The monitored spray
programme developed for Indian conditions at Regional Horticultural Research and
Training Station, Mashobra, Shimla for the control of spring and summer scab
conditions is described below. This strategy is recommended to orchard areas
where scab is present.
First Spray:
At green tip stage if scab during last
three years was present and temperature after rains remained above 10oC.
The spray strategy to control primary scab must include high residue fungicides
for better protective action for longer duration. The strong bio-efficacy of
dodine, mancozeb, dithianon, and captan is established on apple parts. The residues of these fungicides are persistent, stable and re-distributive on the
foliage and remain effective against primary infection up to 36 days. Hence recommended at green tip stage as
first spray under monitored control program in Himachal Pradesh.
Second Spray:
Second spray at pink
bud stage is recommended to give protective coverage
on plant parts to control primary
scab infection during the long flowering session.
However, according to monitored spray strategy, this spray is considered to be optional and should be given only if
first spray is not given or continuous wet conditions prevailed after the
first spray. The fungicides recommended at this
stage are both protective as well as curative. However, it is also observed
that at high altitude locations (above 6500 ft) where primary infection
generally initiates after pink bud stage the first spray at green tip stage is
inappropriate. Benzimidazole and EBI fungicides having protective/ curative and
broad-spectrum mode of action is recommended for such locations at pink bud
stage (as first spray) to control invisible infection caused by apple scab,
canker fungi, powdery mildew, core rot and leaf blotch. However, the sensitive
flowering stage is avoided for any spray as might obstruct the
cross-pollination process.
Criteria for sprays:
In addition to its
anti-fungal properties it also help in improving fruit set and can be used
safely during bloom.
Third Spray:
Third spray at petal fall stage is
very essential to protect the newly emerged fruit-lets against primary scab and
powdery mildew infections. Moreover, the earlier sprays given either through
first spray or at pink bud stage are found ineffective all through the long
flowering period of apple. The brands of benzimidazole and EBI are recommended
at this stage also having both protective curative and anti-sporulant actions.
This group of fungicides is effective to other summer diseases as well and also
acts as anti-senescent and increased fruit set.
Fruit Development Spray:
At fruit development stage the actual monitored spray strategy implies
where curative fungicide sprays are recommended after the infection period
instead of routine sprays. There
are three options of sprays and type of fungicides use according to the
prevailing weather and scab conditions in the orchards.
Most effective option of curative (EBI)
fungicides is to kill the fungus in host tissues after the infection has
occurred. However, the fruit development sprays can be extended for longer
duration or discontinue in case there is no visible scab on leaves and fruits
out of primary infection. This can also be ascertained by the overall scab
records in the last three years and no primary symptoms have appeared till date
in the current period.
Dormant
spray:
Dormant sprays of 5 per cent urea a foliar nitrogenous
fertilizer at leaves shedding stage and followed by a spray of Bordeaux mixture
(1%) are most effective IDM strategy used to eradicate the most overwintering
pathogen/diseases on apples.
In coming posts I shall be discussing about the cankers.
