Etiology and management of recent outbreaks of pepper anthracnose in Florida.

摘要

In the last 4 to 6 years, anthracnose has become an increasingly serious disease on immature, green pepper fruit in Florida. This contrasts with earlier reports of anthracnose as strictly a ripe-rot disease of mature, colored pepper fruit. The species of Colletotrichum associated with anthracnose on both immature and ripe pepper in Florida were identified. Based on reactions with PCR-specific primers, 28 of 50 isolates associated with anthracnose lesions from Florida were identified as C. acutatum, including 22 of 22 recovered from immature, green fruit. Six of the C. acutatum isolates were associated with typical lesions on ripe, colored fruit, but only in fields where lesions on green fruit were also observed. In contrast, all 17 isolates identified by PCR as C. gloeosporioides were recovered from lesions found only on ripe, colored fruit from fields where no lesions on green fruit were initially observed. No isolates were identified as C. capsici or C. coccodes. Isolates of C. gloeosporioides grew up to twice as fast in vitro as isolates of C. acutatum, suggesting a way to tentatively differentiate pepper isolates without PCR testing. In addition, C. gloeosporioides produced conidia that were slightly larger than those produced by C. acutatum.In field and laboratory pathogenicity tests, anthracnose isolate HB05 recovered from bell pepper was not pathogenic on tomato or strawberry when artificially inoculated on ripe and unripe fruit in the field. However, anthracnose lesions did form on detached, wounded fruit of all three crops in the laboratory. This result suggests that laboratory wound-inoculation studies might not be a reliable method to determine the natural host range of Colletotrichum spp. on various crops in the field.Three fungicide field trials were conducted on pepper ('Revolution') artificially inoculated with an isolate of C. acutatum recovered from pepper (HB05) to evaluate azoxystrobin (Quadris 250SC), famoxadone plus cymoxanil (Tanos 50WG), copper hydroxide (Kocide 2000), mancozeb (Manzate 75WG), acibenzolar-S-methyl (Actigard 50WG), and fludioxanil plus cyprodinil (Switch 50WG) for control of pepper anthracnose. In one of the three trials, difenoconazole (Inspire 250EC) was included. All treatments provided significant control of anthracnose symptoms on fruit in comparison to the untreated control. Overall, azoxystrobin, fludioxanil plus cyprodinil, difenoconazole, and mancozeb provided the highest amount of uninfected, healthy fruit per plot, while famoxadone plus cymoxanil, copper hydroxide, and acibenzolar-S-methyl provided the least amount of healthy fruit per plot among all of the treatments. The name "early anthracnose" is proposed for the disease on immature, green fruit caused by C. acutatum.