Postbloom Fruit Drop Megan M. Dewdney Associate Professor of Plant Pathology and Extension Specialist University of Florida, IFAS Citrus Research and Education Center
Symptoms
Post-bloom fruit drop disease cycle Colletotrichum acutatum
Disease cycle highlights o Fungus survives on leaf surfaces, twigs, and buttons in specialized structures o Structures germinate and form new spores with moisture and petal extracts o Spores are dispersed to new flowers via rain splash o Germinate with moisture in 12-24 hours, infect in 24-48 hours New symptoms and spores in 4 to 5 days
Control options o Remove declining trees to reduce inoculum Prune out HLB-affected branches if only 1 or 2 per tree? o Fungicides Strobilurin containing fungicides Abound, Gem, Headline, Quadris Top, Pristine, Priaxor Best combined with Ferbam Strict label limits for these fungicides for resistance management o 2015-2016 trial data with newer pre-mix fungicides Pristine, Priaxor, and Quadris Top o Low volume ground and aerial applications are options
Low volume rates* Product Ground Aerial Abound Quadris Top Headline Pristine Ferbam No restrictions listed 10 GPA (15 GPA recommended) 10 GPA (recommended) 10 GPA (recommended) No restrictions listed No restrictions 5 GPA (10 GPA recommended) 10 GPA 10 GPA Prohibited *Provided as a guide. Always verify what is written on the label.
2015 TRIAL RESULTS
Trial details o Navel oranges in Polk City area Heavily infected with HLB Off-season bloom on most trees o Prior to applications ratings taken Buttons - Not significant Open flowers Not significant Infected flowers o Applications made on recommendation of PFD model Could not apply more than once a week
Buttons in 0.25m 2 /tree side Feb 10-20 th, 2015 18 16 Buttons on Navel Oranges 2015 Number of fruit 14 12 10 8 6 Not significant 4 2 0 BA243+COHERE Abound+Ferbam Abound Control Headline Pristine Quadris Top+COHERE Companion+TKO Headline+Ferbam
Infected flowers in 0.25m 2 /tree side Feb 23-March 13, 2015 25 a Navel Oranges 2015 20 Number of infected flowers 15 10 5 b bc bc bc bc bc c d 0 Control Companion+TKO BA243+COHERE Abound Quadris Top+COHERE Headline Pristine Abound+Ferbam Headline+Ferbam
PFD Trial 2015 - Navels Product Rate/acre Control (UTC) -- Quadris Top and Cohere 15.4 fl oz + 16 fl oz Abound 15.5 fl oz Pristine 18.5 oz BA243 and Cohere 6 fl oz Headline 15 fl oz Abound and Ferbam 15.5 fl oz + 6 lb Headline and Ferbam 15 fl oz + 6 lb Companion and TKO 32 oz + 64 fl oz Treatment Dates: Feb 25 th, March 4 th, 16 th, and 24 th
Buttons in 0.25m 2 /tree side April 15, 2015 60 a Number of infected flowers 50 40 30 20 a b b Buttons after treatments on Navel Oranges 2015 b b bc bc c 10 0 Control Companion+TKO Headline Abound+Ferbam BA243+COHERE Abound Quadris Top+COHERE Pristine Headline+Ferbam
Number of fruit per tree June 12-23, 2015 250 200 a a ab ab ab ab Navel Oranges 2015 Number of fruit 150 100 b 50 c c 0 Pristine Headline+Ferbam Abound Abound+Ferbam Headline BA243+COHERE Quadris Top+COHERE Control Companion+TKO
Conclusions o No difference in the number of buttons prior to trial initiation o There were significantly different numbers of infected flowers but did not change outcome o Most treatments significantly better than UTC o Few statistical differences among strobilurin containing fungicides
2016 TRIAL RESULTS
Trial details o Navel oranges in Polk City area Heavily infected with HLB Off-season bloom on most trees Trees hedged in January Consequence much of bloom concentrated at the middle to end of March More uniform than previous year Trees selected for uniform disease pressure HLB and PFD o Applications made on recommendation of PFD model o Applications on March 16 and 22
Buttons in 0.25m 2 /tree side April 20 th, 2016 Number of old buttons per tree side (0.25 m 2 ) 4 3 2 1 0 Priaxor + Cohere Pristine UTC Abound + Ferbam Quadris Top + Activator 90 Navel Old Buttons Polk City 2016 Ferbam 4 Ferbam 5 Headline Topsin M Quadris Top + Abound + Activator 90 Headline + Ferbam Abound + Activator 90 Fungicide treatment No significant difference
PFD trials 2016 Navels Product Active Ingredient Rate/acre Quadris Top Activator 90 Azoxystrobin + difenoconazole 15.4 fl oz. 0.25% v/v Quadris Top Abound Activator 90 Azoxystrobin + difenoconazole Azoxystrobin 15.4 fl oz. 3.2 fl oz. 0.25% v/v Abound Activator 90 Azoxystrobin 15.5 fl oz. 0.25% v/v Abound Ferbam Azoxystrobin Ferbam 15.5 fl oz. 6 lb Headline Pyraclostrobin 15 fl oz. Headline Pyraclostrobin 15 fl oz. Ferbam Ferbam 6 lb Pristine Pyraclostrobin + boscalid 18.5 oz. Priaxor Pyraclostrobin + fluxapyroxad 6 fl oz. Cohere 16 fl oz. Topsin M Thiophanate-methyl 2.0 lb Ferbam Granuflo Ferbam 4 lb Ferbam Granuflo Ferbam 5 lb Untreated control -- --
Buttons in 0.25m 2 /tree side April 20 th, 2016 Number of new buttons per tree side (0.25 m 2 ) 40 35 30 25 20 15 10 5 0 A AB UTC Quadris Top + Activator 90 ABC ABC Navel New Buttons Polk City 2016 BCD BCD B-E Headline Ferbam 4 Ferbam 5 Pristine Priaxor + Cohere Topsin M Abound + Activator 90 Quadris Top + Abound + Activator 90 Fungicide treatment C-F D-G EFG FG G Abound + Ferbam Headline + Ferbam
Number of fruit per tree side June 24-28 th, 2016 100 90 80 A AB AB AB AB AB Navel Fruit Polk City 2016 Number of fruit per tree 70 60 50 40 30 BC CD DE E E 20 F 10 0 Headline + Ferbam Pristine Abound + Ferbam Priaxor + Cohere Headline Topsin M Quadris Top + Abound + Activator 90 Fungicide treatment Ferbam 5 Ferbam 4 Quadris Top + Activator 90 Abound + Activator 90 UTC
Conclusions o No difference in the number of buttons prior to trial initiation o The number of buttons from 2016 infection, does not always match fruit counts o All treatments significantly better than UTC o Topsin M did not perform better than strobilurin containing fungicides o Ferbam is best when mixed with other fungicides Similar conclusion to Pete Timmer s work in 1990s o Will be looking at pre-harvest fruit drop
Trial details o Valencia oranges in Fort Meade area Infected with HLB but relatively healthy Off-season bloom on most trees Trees in block were slow to bloom compared to others in area Trees selected for uniform disease pressure HLB and PFD o Applications made on recommendation of PFD model o Applications on March 17, 23, and April 1
Buttons in 0.25m 2 /tree side May 27 th, 2016 Number of old buttons per tree side (0.25 m 2 ) 3 2 1 0 Topguard 5 Rhyme 5 Topguard + Ferbam Valencia Old Buttons Fort Meade 2016 UTC Luna Sensation 7 Rhyme 7 Fungicide treatment No significant difference Topguard 8 Quadris Top Luna Sensation 5
PFD trials 2016 Valencia Product Active Ingredient Rate/acre Rhyme 2.08 SC Flutriafol 5 oz. Rhyme 2.08 SC Flutriafol 7 oz. Topguard EQ Flutriafol + azoxystrobin 5 oz. 4.3SC Topguard EQ Flutriafol + azoxystrobin 8 oz. 4.3SC Topguard EQ 4.3SC Flutriafol + azoxystrobin Ferbam 5 oz. 5 lb Ferbam Quadris Top Azoxystrobin + 15.4 fl oz. difenoconazole Luna Sensation Trifloxystrobin + 5 oz. fluopyram Luna Sensation Trifloxystrobin + fluopyram 7 oz. Untreated control -- --
Buttons in 0.25m 2 /tree side May 27 th, 2016 Number of new buttons per tree side (0.25 m 2 ) 105 100 95 90 85 80 75 70 65 60 55 50 45 40 35 30 25 20 15 10 5 0 A Rhyme 7 AB Valencia New Buttons Fort Meade 2016 BC C C UTC Rhyme 5 Luna Sensation 7 Topguard 5 C Luna Sensation 5 Fungicide treatment D D F Topguard 8 Quadris Top Topguard + Ferbam
Number of fruit per tree side June 30 th -July 1 st, 2016 200 180 A AB ABC Valencia Fruit Fort Meade 2016 Number of fruit per tree side 160 140 120 100 80 60 40 BCD CD D DE E F 20 0 Topguard + Ferbam Topguard 8 Quadris Top Luna Sensation 5 Topguard 5 Luna Sensation 7 Fungicide treatment Rhyme 7 Rhyme 5 UTC
Conclusions o No difference in the number of buttons prior to trial initiation o The number of buttons for 2016 followed similar trend as fruit o All treatments significantly better than UTC o The addition of ferbam to Topguard treatment significantly improved performance o Three best treatments all contained a mixture of strobilurin and DMI fungicides
Luna Sensation timing o Three stages of bloom o One application o Were the flowers protected? Pinhead Popcorn Open
Luna Sensation application by flower stage Buttons/branch Number of calyces per branch 9 8 7 6 5 4 3 2 A B Valencia new buttons Fort Meade 2016 1 C 0 Open Popcorn Flower stage Pinhead
Luna Sensation application by flower stage Fruit 90 80 Valencia Fruit Fort Meade 2016 No significant difference Number of fruit per tree side 70 60 50 40 30 20 10 0 Open Pinhead Fungicide treatment Popcorn
Conclusions o Application made later than desired May have influenced fruit data as many untagged flowers in another stage o Luna Sensation applied at pinhead appeared to give best protection Based on button data o Did not appear to protect open flowers o Need to modify experiment to get better fruit data Have fruit data per branch but mostly zeros
AERIAL VERSUS GROUND
Trial details for 2016 o Valencia oranges in Ona area Infected with HLB Off-season bloom on most trees 5 trees selected for uniform disease pressure to make measurements HLB and PFD o Applications made weekly by grower preference o Fixed wing aircraft and Curtec o Applications on March 3 rd, 11 th, 18 th, and 24 th
Aerial versus ground application trial o 10 gal/acre by air o 21 gal/acre by ground o 40 acre blocks Product Active Ingredient Rate/acre Control (UTC) -- -- Quadris Top Difenoconazole + azoxystrobin 15.4 fl oz Abound Azoxystrobin 15.5 fl oz Headline Pyraclostrobin 15 fl oz Gem Trifloxystrobin 3.8 fl oz
Number of Buttons Number of Buttons Buttons in 0.25m 2 /tree side May 13 th, 2016 200 175 150 125 100 75 50 25 0 Last season s buttons a a Current season s buttons 200 a 175 150 125 b 100 75 50 25 0 aerial ground ground aerial Application type Application type
Number of Buttons Buttons in 0.25m 2 /tree May 13 th, 2016 250 225 200 175 150 125 100 75 50 25 0 a ab Gem Grower* Abound UTC Quadris Top Application type *2 Applications of Abound on March 3 rd and 11th by Curtec only By fungicide treatment b b b b Headline
Number of Fruit Number of fruit per tree July 6th, 2016 200 a 175 150 125 b 100 75 50 25 0 ground aerial Application type
Number of Buttons Number of fruit per tree side July 6th, 2016 300 a 275 250 ab 225 200 175 150 125 100 75 50 25 0 headline Quadris Top *2 Applications of Abound on March 3 rd and 11th by Curtec only By fungicide treatment bc c c d Abound Gem UTC grower* Application type
Conclusions o Curtec applications had more buttons than aerial in trial o The significantly more buttons were found with Gem than UTC o Curtec applications had more fruit per tree than aerial Better coverage of trees o Headline and Quadris Top had significantly more fruit than UTC
Summary o Application timing still critical! More important that product Can waste time and money if with no attention to timing o Need to be proactive for PFD Regular scouting for symptoms Train employees to recognize buttons and flower symptoms Need to be able to react quickly if necessary o Some promising results in field trials Are these products economical for effect? Will be working with Ariel Singerman to determine most economical
Acknowledgements o Those who did much of the work Tracey Hobbs, Etelvina Aguilar, Collin Solomon- Lewis o Partially funded by CRDF