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ARS Home » Southeast Area » Byron, Georgia » Fruit and Tree Nut Research » Research » Publications at this Location » Publication #320979
Title: Reasons for inconsistent citrus canker control

Author
item GRAHAM, JAMES - University Of Florida
item Bock, Clive

Submitted to: Citrus Industry
Publication Type: Trade Journal
Publication Acceptance Date: 2/23/2015
Publication Date: 4/1/2015
Publication URL: http://www.citrusindustry.net/
Citation: Graham, J.H., Bock, C.H. 2015. Reasons for inconsistent citrus canker control. Citrus Industry. Vol 98: 22-25.

Interpretive Summary: Trade journal.

Technical Abstract: Crop losses from citrus canker in 2014 for Hamlin due to premature fruit drop, or for grapefruit from unacceptable severity of fruit lesions, were highly variable due to periodic rains that in certain locations were coincident with grapefruit flushes in February-March or with early Hamlin fruit development in late April-early May. Experiments in 2014 investigated i) the efficacy of windbreaks, ii) the interaction with HLB, iii) canker control in Hamlins, and iv) integrated management of canker with systemic acquired resistance (SAR). Grapefruit blocks surrounded by a 20-30 ft tall Corymbia torelliana windbreaks again confirmed they do an excellent job of reducing not only incidence but severity of canker lesions. As expected distance from the windbreak determines the level of control. The closer the proximity of the windbreak to the grove edge, the better the performance of the windbreak. As HLB greatly disrupts cycles of flowering, fruit set and foliar flushing, canker has been observed to be either reduced or exacerbated depending on the amount of inoculum present and horticultural management, as was the case in these experiments. In young Hamlin groves where trees have not formed hedgerows, early season spray timing in relation to fruit size and application of formulations with sufficient metallic copper was crucial to protect the fruit until mid-summer. Fruit infected before July generally dropped prematurely. After midsummer, smaller lesions did not develop to a sufficiently large size to trigger fruit drop, so further protection of fruit is unnecessary, even though canker inoculum continues to build up on the leaves. HLB was a serious issue in this canker experiment. With respect to SARs, four drenches of Actigard® at 60 day intervals between April and October produced better control of foliar and fruit disease than the copper program alone in grapefruit. Additional information regarding insect and disease management recommendations consult the Florida Citrus Pest Management Guide (http://www.crec.ifas.ufl.edu/extension/pest/.