Foliar diseases: Citrus Canker and Citrus Black Spot

Transcription

1 Foliar diseases: Citrus Canker and Citrus Black Spot Megan M. Dewdney Associate Professor of Plant Pathology and Extension Specialist University of Florida, IFAS Citrus Research and Education Center

2 CITRUS CANKER Some slides adapted from E. Johnson

3 Fruit susceptibility to canker o Orange fruit are most susceptible from 3/8 in. diameter until fruit reach ~1.5 in. dia. o Rains in April, May, and June promote early season infection o Rind becomes much more resistant for fruit > 1.5 in. dia. o Rind susceptible throughout entire fruit growth period o Early bloom may affect timing of susceptible fruit size

4 Copper sprays at 21 day intervals protect fruit beginning at 3/8 in.: Spray volume and tractor speed important for fruit coverage

5 Why a 21-day interval? ocopper residue is significantly reduced by rain washing ocopper does not move once dried ocopper residue is cracked by fruit growth As the fruit grows, copper must be reapplied to continually cover the fruit as it becomes larger

6 Alternative way for application timing o Time application based on residue levels Citrus copper application scheduler Available on Agroclimate or through FAWN

7 Proper Application of Copper ouse label rate recommended for a disease obe cautious in hot weather (> 94 F; 34 C) Phytotoxicity occurs more easily in hot weather opotential for phytotoxicity can be reduced with greater water volume per acre Complex tank mixes, oil applications, and nutritional materials contribute to phytotoxicity owith aerial applications get inadequate penetration of canopy for control, best method is with an air blast sprayer

8 Field Trials o Evaluate copper sprays in relation to early season rains for control of fruit infection and drop in young fruiting Hamlins In a south central Florida citrus grove o Compare soluble and fixed copper formulations for efficacy 2011, 2014, and 2015

9 Timing and weather matters o Need to watch early season weather forecasts for rain o Effects of being too late In 2011, 9 sprays began 15 April (too late) to 27 Sept attempting to reduce impact of early epidemic Fruit canker 2011 Fruit Drop 2011 Fruit with lesions 2011 Fruit drop 2011 Canker lesion incidence (%) 120 old lesions young lesions Kocide Kocide b b b b Kocide NuCop 50 WP 2.0 Nordox 75G 3.0 Cuprofix Ultra Kentan DF 2.62 b b b b Badge X Americop 40 DF 2.5 Magna-Bon 50 Magna-Bon 20 Treatment b ab ab a ab UTC 1 UTC 2 Canker fruit drop (%) cde de de Kocide Kocide e bcde cde cde Kocide NuCop 50 WP 2.0 Nordox 75G 3.0 Cuprofix Ultra Kentan DF 2.62 Badge X Americop 40 DF 2.5 Treatment bcde bcde abcd bcde a Magna-Bon 50 Magna-Bon 20 UTC 1 UTC 2 ab

10 Dry spring o Limited early season infection In 2014, rain below average when fruit most susceptible size old lesions new lesions Fruit canker 2014 Fruit drop 2014 Fruit with lesions 2014 Fruit drop Canker lesion incidence Kocide Kocide Nordox 75 WG 1.33 Nordox 75 WG 2.66 ChampION 30 WDG 3.0 NuCop 50HB 2.0 NuCop 30HB 3.0 Quimetal CO 1.4 Treatment Quimetal CH 3.0 Badge X Magna-Bon 37 UTC 1 UTC 2 No. canker fruit drop Kocide Kocide Nordox 75 WG 1.33 Nordox 75 WG 2.66 ChampION 30 WDG 3.0 NuCop 50HB 2.0 NuCop 30HB 3.0 Quimetal CO 1.4 Treatment Quimetal CH 3.0 Badge X Magna-Bon 37 UTC 1 UTC 2

11 Well timed application owell timed applications can mitigate unfavorable rainfall patterns 2015, April rain greater than average when fruit at most susceptible stage 70 Fruit with Fruit lesions canker Fruit Fruit drop Canker lesion incidence (%) bc Nordox 75 WG 1.33 NuCop 30HB 2.5 ChampION 30 WDG old lesions new lesions bc bc bc NuCop 30HB 1.0 NuCop 30HB 1.75 bc bc Quimetal CH 3.0 Quimetal CO 1.4 c bc ab a Kocide UTC 1 UTC 2 No. canker fruit drop c Nordox 75 WG 1.33 bc c c bc a bc bc bc ChampION 30 WDG NuCop 30HB 2.5 NuCop 30HB 1.75 NuCop 30HB 1.0 Quimetal CO 1.4 Quimetal CH 3.0 Kocide UTC 1 ab UTC 2 Treatment Treatment

12 Effect of inoculum carry over oapril rains induced early season fruit drop Not canker inoculum carry over from previous season oearly bloom this season Initiate program once fruit reach 3/8 in. dia. May be in mid- to late-march Rainfall (mm) Fruit dropped/tree due to canker April May June July Aug Sept Oct Nov 0 Cu treated Untreated Cu treated Untreated Month Treatment

13 How does Irma change things? oon all trees, hurricane force winds force bacteria past any barriers Considerable mature leaf infection (even Valencia) and stem lesions Particularly bad in young blocks, especially if high canker in surrounding blocks ostem lesions found on twigs with green bark Quite visible still and advisable to prune out in young blocks while still dry

14 How does Irma change things? Cont. Will contribute years of inoculum; leaves only supply significant inoculum for a few months ofor non-bearing and young blocks, Actigard recommended Copper does not control stem or leaf lesions Will help to suppress inoculum

15 Conclusions on Application Timing o Spray timing before rains in late-march to early-april critical for fruit protection once 3/8 in. dia. o Inoculum from infected leaves and stems from previous season always present in spring Stem lesions more problematic Irma has amplified inoculum this spring and in future

16 Conclusions on Application Timing o Early fruit infection leading to fruit drop depends on late March-April rains coinciding with most susceptible fruit stage o In June-July, infections of fruit > 1.5 in. result in smaller lesions that do not induce premature drop If for juice production, these are less of a concern

17 NEW MATERIALS UNDER DEVELOPMENT In collaboration with: Evan Johnson and Swadesh Santra, UCF

18 Multiple new products under development o Core-shell Copper Reduced copper based on surface area o Fixed-Quat Quaternary ammonia immobilized to keep bactericidal activity and prevent phytotoxicity o Zinkicide Zinc-based nanomaterial using plant metabolizable ingredients o Tested in grapefruit trial because of susceptibility

19 2014 Grapefruit canker trial o Equivalent efficacy to copper Core-shell copper Fixed-Quat o Zinkicide control exceeded Cu and Cu/Zn Canker incidence (%) Nordox 75G 2.66 lb/a Nordox 30/ lb/a b c c cd d Nordox 30/ lb/a Zinkicide SG4 Zinkicide SG6 Fixed Quat 2X Fixed Quat 1X CS-CuSiNPs Treatment c bc c a UTC

20 2015 Grapefruit canker trial o Equivalent efficacy to copper Core-shell copper Fixed quat o Zinkicide control matched commercial Cu/Zn at same rate of Zn

21 2017 Grapefruit canker trial o Oh Irma! Nearly 100% incidence in UTC o All treatments significantly better than UTC Nothing gave satisfactory control Canker incidence (%) 100 A Nordox 75WG (1.0 lb/a) BC BC BC CDE DEF F EF Nordox 30/30 (0.45 lb/a) Nordox 45 WG (0.5 lb/a) Zinkicide -TMN-113 (SG-4; 0.5 lb/a) Zinkicide-TMN 110 (SG-6; 0.5 lb/a) Zinkicide-TMN 113 (SG-4; 1.0 lb/a) Zinkicide-TMN 110 (SG-6; 1.0 lb/a) Treatment UTC

22 Conclusions o Provide Copper equivalent or better efficacy o Reduce metal or Cu applied to the field o Provide rotation alternatives to Cu Resistance management o Licensing and registration for commercial availability underway Time to available product is difficult to predict o Hurricane force winds break any form of control

23 CITRUS BLACK SPOT

24 Spores of importance o Only one spore type present in Florida Only splash dispersed conidia present Every other location with disease has two: ascospores and conidia o Known to be abundant in the leaf litter Present in high numbers all year When in canopy, tend to move down more than splash up Rain splash likely moves spores into lower canopy from leaf litter

25 Large Scale Field Trial o 20 year-old Valencia o 3 treatments Urea (40 lb/acre) Soil-set (1.3 fl oz/acre) a compost accelerator Untreated control o Applied with herbicide booms at 50 gal/acre in a 10 ft strip o Three rows treated per rep, middle row evaluated for disease

26 Disease Incidence o Data taken spring following treatment o Disease incidence lower in 2015, 2016 post-trt for Soil-set but not 2017 Blue = urea Orange = Soil-set Gray = UTC

27 Disease Severity o Soil-set consistently had the lowest disease severity

28 Summary o Disease incidence consistently increased over the four years of the trial o Despite conidia being only spore type present, enhanced leaf litter management improved disease management o Soilset had the greatest reduction in disease incidence and severity Urea did not have the same effect

29 Black spot program o Fungicide applications should start mid- April to early-may Dependent on April rainfall o Monthly applications until September of fungicide o Alternate copper (full rate of chosen product) with a strobilurin, a premix, or Enable

30 Black spot program cont. Preferable to alternate among modes of action Strobs are Abound, Gem, Headline Premixes are Pristine (SDHI), Amistar Top (DMI), and Priaxor (SDHI) and contain a strobilurin o Coverage is key so at least 125 gal/acre and slow!

31 Acknowledgments o Tracey Hobbs o Etelvina Aguilar o Katia Rodrigues o Monty Myers o Funding sources: Any Questions?