Flowering, pollination and fruit set
update
Simon Newett, DAF, Nambour, Qld
For the individual grower alternate
and irregular bearing have negative
effects on income and cash flow.
At the industry level it creates
headaches for planning marketing
and research.
Today’s talk
1. Define alternate & irregular bearing
2. Explain the basics of the unique
avocado flowering process
3. Provide some results from last years
flowering & fruitset study
4. Outline some steps to reduce irregular
bearing
Alternate bearing
HASS
30
25
t/ha
20
15
10
5
0
2002
2003
2004
2005
2006
2007
Year
2008
2009
2010
2011
Alternate bearing
1. Associated with late harvesting
2. Identified by “see-saw” yields and
very weak flowering in the “off” year
3. More likely once yields reach about 15
+ t/ha
Alternate bearing is currently not a
widespread issue in Australia
Irregular bearing
A major issue in
Australia
HASS
40.0
35.0
30.0
t/ha
25.0
20.0
15.0
10.0
5.0
0.0
2006
2007
2008
2009
2010
2011
2012^
Year
?
Hot dry winds
desiccated flowers
(dust storm)
Cold temps
at flowering
Farming is a gamble!
For an average sized tree on typical spacing . . .
•1,000,000 flowers
•If 1 in every 2,700 flowers sets a fruit and retains it
through to harvest = 15 t/ha
•If you can improve the odds to 1 in 2,000 you will
increase the yield to 20 t/ha and at $30/tray you will
net an extra $27,000/ha!
How do you improve the odds?
You have little control over the weather but
there are steps you can take to improve
the chances of:
• Pollination
• Fruitset, and
• Fruit retention
Many factors lead to irregular
bearing but what happens at
flowering can have a dramatic
effect
Basic requirements for fruitset
1. Flowers! (weak flowering = alternate bearing)
2. Overlap of male and female flower stages
3. Insect pollinators to transfer pollen
4. Warm temperatures – three consecutive days
over 10ºC for Hass (a ‘pollination event’)
5. Absence of other environmental stresses
(e.g. too hot, wet or windy, or humidity too low)
“Dichogamy”
Avocados have unique flower opening behaviour Each flower opens twice over 24 hr period:
1st as functionally female
2nd as functionally male
This favours cross pollination, increasing diversity in
the species - an evolutionary advantage allowing it a better chance to adapt and compete.
Flowering pattern of a single flower: ‘A’ type
e.g. Hass
Male 1.
Female 1
Afternoon
Morning
Day 1
Night
Morning
Day 2
Afternoon
Avocado flowering pattern in: ‘A’ type
- the net effect of multiple flowers
e.g. Hass
Female
Male
6 am
8 am
Morning
10 am
Midday
Time of day
2 pm
4 pm
6 pm
Afternoon
Overlap of male and female flower stage
• Erratic changes in temperature (common in
spring) throw out the timing of male and female
flower stages and can result in good overlap
• However, cold weather can result in no overlap
• ‘B’ type varieties are more sensitive to cold
temperatures and the female stage may be
omitted altogether
Flowering pattern of a single flower: ‘B’ type
e.g. Edranol
Male
Female
Afternoon
Morning
Day 1
Night
Morning
Day 2
Afternoon
Use of ‘pollinizers’
• Inter-planting varieties of the opposite flower
type e.g. using Edranol (‘B’ type) in a block of
Hass (‘A’ type)
• Pollinizers increase the odds of getting a set
especially in marginal conditions
• Expect it to be beneficial in some years but not
others
• Of course, flowering times of Hass and the
pollinator(s) need to match
The overlap of male & female flower stages if
‘A’ & ‘B’ types within the same block
Improving the odds!
Female
A e.g. Hass
Male
Female
B e.g. Edranol
Male
6 am
8 am
Morning
10 am
Midday
Time of day
2 pm
4 pm
6 pm
Afternoon
‘A’ and ‘B’ flower types
Each avocado variety has either an ‘A’ type or a
‘B’ type flowering pattern.
A type
Gwen
Hass
Pinkerton
Reed
Wurtz
B type
Bacon
Edranol
Ettinger
Fuerte
Sharwil
Shepard
Zutano
Last year we started to have a closer
look at the flowering and fruitset
process under Australian conditions
What was done in the 2015 season
• 28 farms participated across Australia
• Data loggers installed to measure temperature &
humidity over flowering period
• Growers/team members took observations on:
– Weather events that might interfere (rain, wind, hail …)
– Flowering dates of each variety including pollinizers
– Times of day male and female flower stages were open
– Insect pollinator activity
– Fruitset (appearance of pinhead fruit)
Some results from 2015 flowering
season . . .
8 to 10 days
8 to 10 days
9 to 11 days
2mm fruit
18 Oct
2mm fruit
24 Oct
3mm fruit
28 Oct
31/10/2015
29/10/2015
27/10/2015
25/10/2015
23/10/2015
21/10/2015
19/10/2015
17/10/2015
15/10/2015
13/10/2015
11/10/2015
9/10/2015
7/10/2015
5/10/2015
3/10/2015
1/10/2015
29/09/2015
27/09/2015
25/09/2015
23/09/2015
21/09/2015
19/09/2015
17/09/2015
15/09/2015
13/09/2015
11/09/2015
STEPHEN PERUCH, KULNURA
40.0 °C
35.0 °C
30.0 °C
25.0 °C
20.0 °C
15.0 °C
Min
oC °C
1010.0
Max
5.0 °C
0.0 °C
PERUCH: snap shot - potential for cross pollination
Date
Hass
Hass
5 Oct
100%
8 Oct
100% 8am
11 Oct
100% 8am
8am
100% 4:30pm
14 Oct
16 Oct
Edranol
Comments
100% 8am
38°C
90% 4:30pm
100% 8am
Cool morning
100% 8am
Rain overnight
70%
1pm
100% 1pm
18 Oct
50% 1pm
50%
1pm
100% 1pm
24 Oct
80%
20%
9am
End of flowers
28 Oct
10% 1pm
9am
End of flowers
90%
1pm
?
ROBINVALE, VICTORIA
Peter McIntosh
Times when minimum temperatures warm
enough for fruitset (McIntosh, Robinvale)
Too hot and/or dry
DATE
Min C
Max C
Min humidity
1/10/2015
2.4 °C
28.2 °C
17.1 %RH
2/10/2015
5.2 °C
33.4 °C
12.1 %RH
3/10/2015
10.4 °C
34.8 °C
11.0 %RH
4/10/2015
15.8 °C
37.9 °C
7.9 %RH
5/10/2015
11.5 °C
37.6 °C
9.0 %RH
6/10/2015
14.6 °C
37.6 °C
8.6 %RH
7/10/2015
11.3 °C
22.8 °C
23.6 %RH
8/10/2015
8.8 °C
30.4 °C
25.7 %RH
9/10/2015
12.8 °C
37.2 °C
13.7 %RH
10/10/2015
19.7 °C
34.3 °C
21.4 %RH
11/10/2015
13.5 °C
31.9 °C
18.5 %RH
12/10/2015
11.1 °C
23.4 °C
30.7 %RH
13/10/2015
6.5 °C
24.4 °C
24.5 %RH
14/10/2015
5.5 °C
32.1 °C
15/10/2015
7.8 °C
37.5 °C
DATE
Min C
Max C
Min humidity
27/10/2015
6.4 °C
29.3 °C
29.2 %RH
28/10/2015
15.3 °C
28.5 °C
33.3 %RH
29/10/2015
12.3 °C
33.1 °C
17.3 %RH
30/10/2015
19.0 °C
34.8 °C
22.4 %RH
31/10/2015
18.5 °C
35.7 °C
20.3 %RH
1/11/2015
14.3 °C
26.9 °C
39.4 %RH
2/11/2015
12.5 °C
27.3 °C
32.8 %RH
3/11/2015
10.7 °C
29.0 °C
27.8 %RH
4/11/2015
16.4 °C
28.8 °C
41.9 %RH
5/11/2015
16.9 °C
25.0 °C
54.3 %RH
6/11/2015
13.7 °C
25.1 °C
51.8 %RH
12.8 %RH
7/11/2015
10.2 °C
27.2 °C
21.0 %RH
10.1 %RH
8/11/2015
7.2 °C
31.6 °C
12.1 %RH
9/11/2015
9.6 °C
36.2 °C
16.4 %RH
Only about 5 pollination events in the whole season
PETER MCINTOSH, ROBINVALE
3 – 7 Oct
Humidity
(green line)
Temperature
(blue line)
38 C
9 – 12 Oct
10°C
> 10°C
28 Oct – 7 Nov
23 Aug
1 Sep
Flower
intensity, score
out of 10
Pollinator
activity, score
out of 5
27 Sep
20 Oct
2 3
Very low
humidity &
very hot days
2 2
21 Nov
5
Hass flowering
425
6
Edranol flowering
22
2
Pollinator activity in Hass #
12 2
2
Pollinator activity in Edranol #
2
8 days
2mm fruit
19 Oct
# …. honey bees, native bees, flies, ants, lady beetle.
About 14 to 21days
10 mm fruit
23 Nov
An anomaly last year which remains
to be fully explained . . .
TOUCHWOOD ORCHARD, MT BINGA,
SOUTH QUEENSLAND
Andrew & Judy Veal
VEAL, MT BINGA TEMPS & HUMIDITIES 2015
°C Max
°C Min
Humidity Min
11/09/2015
7.4 °C
20.0 °C
52.3 %RH
12/09/2015
7.9 °C
23.1 °C
40.7 %RH
13/09/2015
7.1 °C
23.6 °C
0.0 %RH
14/09/2015
5.4 °C
23.2 °C
0.0 %RH
15/09/2015
5.5 °C
26.1 °C
0.0 %RH
16/09/2015
10.0 °C
29.1 °C
0.0 %RH
17/09/2015
9.2 °C
22.8 °C
0.0 %RH
18/09/2015
5.6 °C
20.9 °C
41.4 %RH
19/09/2015
8.4 °C
22.5 °C
38.7 %RH
20/09/2015
7.6 °C
23.6 °C
0.0 %RH
21/09/2015
9.6 °C
23.4 °C
0.0 %RH
22/09/2015
9.2 °C
27.2 °C
0.0 %RH
23/09/2015
6.8 °C
20.8 °C
23.8 %RH
24/09/2015
0.6 °C
21.5 °C
0.0 %RH
25/09/2015
-0.2 °C
21.6 °C
0.0 %RH
26/09/2015
5.3 °C
22.7 °C
0.0 %RH
27/09/2015
4.8 °C
20.8 °C
0.0 %RH
28/09/2015
3.8 °C
26.7 °C
0.0 %RH
29/09/2015
11.6 °C
24.7 °C
38.5 %RH
30/09/2015
11.9 °C
25.9 °C
35.1 %RH
1/10/2015
10.3 °C
26.8 °C
0.0 %RH
2/10/2015
6.0 °C
27.3 °C
0.0 %RH
3/10/2015
5.4 °C
27.3 °C
0.0 %RH
4/10/2015
5.4 °C
30.2 °C
0.0 %RH
5/10/2015
6.2 °C
32.9 °C
0.0 %RH
6/10/2015
4.8 °C
30.7 °C
0.0 %RH
7/10/2015
4.4 °C
31.1 °C
15.7 %RH
Times when minimum temperatures warm
enough for fruitset (Veal, Mt Binga, SQ)
continued . . .
.
8/10/2015
9/10/2015
10/10/2015
11/10/2015
12/10/2015
13/10/2015
14/10/2015
15/10/2015
16/10/2015
17/10/2015
18/10/2015
19/10/2015
20/10/2015
21/10/2015
22/10/2015
23/10/2015
24/10/2015
25/10/2015
26/10/2015
27/10/2015
28/10/2015
°C Min
°C Max Humidity Min
13.4 °C
14.0 °C
11.1 °C
6.4 °C
12.3 °C
13.3 °C
13.8 °C
14.5 °C
10.1 °C
8.5 °C
7.7 °C
9.6 °C
10.5 °C
6.2 °C
13.8 °C
9.3 °C
14.0 °C
15.4 °C
14.9 °C
14.4 °C
14.8 °C
24.2 °C
23.0 °C
23.9 °C
26.3 °C
29.6 °C
30.4 °C
24.2 °C
26.0 °C
26.4 °C
28.9 °C
27.0 °C
25.4 °C
26.5 °C
29.5 °C
30.6 °C
29.1 °C
22.3 °C
27.3 °C
29.4 °C
30.7 °C
17.8 °C
0.0 %RH
0.0 %RH
0.0 %RH
0.0 %RH
28.2 %RH
0.0 %RH
0.0 %RH
0.0 %RH
0.0 %RH
0.0 %RH
1.7 %RH
0.0 %RH
0.0 %RH
0.0 %RH
0.0 %RH
0.0 %RH
0.0 %RH
0.0 %RH
0.0 %RH
0.0 %RH
0.0 %RH
10oC
29th Sep
to 1st Oct
8th to
10th Oct
12th to
16th Oct
24th Oct on
2mm fruit
This orchard block had not had a crop for four years due to hail and frost,
so stored carbohydrate levels would have been very high going into flowering
last year.
This may have somehow allowed pollination and fruitset to occur
at lower temperatures.
Humidity (green line)
Temperature (blue line)
TOUCHWOOD, MT BINGA (Andrew and Judy Veal)
Collecting information again this year,
will be interesting to see differences
between the seasons . . .
Remember - farming is a gamble!
. . . adopt practices to improve
your odds
Practices to improve flowering, pollination
& fruitset
1. Don’t harvest late
2. Prune to allow light penetration into canopy
3. Introduce plenty of bees (10 hives/ha?) and
encourage other pollinating insects
4. Interplant pollinizing varieties (e.g. ‘Edranol’ for
‘Hass’)
5. Consider using PGRs at flowering on healthy trees
Other practices to reduce irregular bearing
Use monitoring to . . .
1. Manage root rot, & other diseases and pests
2. Be fastidious about soil moisture
3. Adopt effective nutrition practices especially:• Boron sprays at flowering
• Feed nitrogen according to crop load to sustain
current crop and to maintain a healthy canopy
(‘factory’) of leaves but avoid too much
nitrogen to prevent excessive vegetative growth
ACKNOWLEDGEMENTS
The project has been funded by Horticulture Innovation Australia
Limited using the avocado levy and funds from the Australian
Government. The Queensland Government has also co-funded the
project through the Department of Agriculture and Fisheries.