Transcript Monitoring Risk for Bitter Rot and Apple Scab

Monitoring Risk for Bitter
Rot and Apple Scab
Kirk Broders
Matt Wallhead
Assistant Professor
Dept. of Biological Sciences, COLSA
University of New Hampshire
PhD Candidate
Dept. of Biological Sciences, COLSA
University of New Hampshire
Venturia inaequalis epidemiology
V. inaequalis has coevolved
to eject spores at same
time as the tree flowers
“The catch” – ascospores
will not eject until a
significant rain event
Old model used degree day
accumulation from 50%
Mac green tip
Weather patterns were
more consistent year to
year
RIMpro (Relative Infection Measure)
http://www.rimpro.be/USA/
Germinating
spores
Infections
Discharged
ascospores
Wetness
Kickback
Infection period
Rain
Inoculum
Fungicide
+
4
4
Total # of Sprays During Primary Scab
Season
Unsprayed
Captan
Captan
KBC+S
Calendar- according to according to
Based
RIMpro
RIMpro
0
8
5
9*
*KBC+S costs ~50% less than Captan
# of lesions/leaf (8.14.2013)
6
5
4
3
2
1
0
UTC
Captan
CalenderBased
Captan
RIMpro
KBC+S
RIMpro
5
Bitter rot & Glomerella leaf spot
• Increased frequency in 2011 &
2012
• Historically, a bigger problem in
the southern and mid-Atlantic
states
• Same organism causing leaf and
fruit lesions?
• Where is the inoculum coming
from?
–
–
–
–
Infected leaves?
Latent infections?
Other orchards
Other crops (strawberry, cherry,
blueberry, etc)
Inoculations
Differences in virulence & resistance
Average % Disease 6-Weeks Post-Harvest
60
UTC
50
Regalia
40
Timorex
30
Captan
20
10
0
Mac
Macoun
A
B
Mutsu
C
Cortland
AB
9
Phylogenetic analysis of
Colletotrichum from apple in
New Hampshire
• All 20 isolates were C.
fioriniae
• Included leaf and fruit
strains
• C. fioriniae is likely made up
of two distinct species
Implications
• What we knew about C. acutatum and C.
gloeosporioides may not hold true for C.
fioriniae
• What is the distribution of C. fioriniae in NE &
NA?
• Is C. fioriniae the dominant species in NE?
• Is there variability in virulence?
• When does infection occur?
Apple Blossom Inoculation Study
• Investigate the rates of Bitter Rot infection in apple
trees inoculated at blossom with Colletotrichum
• 83% of fruit on trees inoculated at flower developed
bitter rot
• 5% of fruit on trees that were not inoculated
developed bitter rot
12
Future Plans
• Second year of RIMPro
• Second year of Apple blossom inoculations
• Colletotrichum on fruit in the Northeast
– Fungicide sensitivity and virulence
– Host specificity and genetic diversity