Bitter Rot of Apple in the Mid-Atlantic United States: Causal Species and Evaluation of the Impacts of Regional Weather Patterns and Cultivar Susceptibility

Abstract

Apple growers in the Mid-Atlantic region of the United States have been reporting an increase in losses to bitter rot of apple and are requesting up-to-date management recommendations. Management is complicated by variations in apple cultivar susceptibility, temperature and rainfall, and biology of the Colletotrichum species that cause bitter rot. Over 500 apples with bitter rot were obtained from 38 orchards across the Mid-Atlantic and the causal species identified as C. fioriniae and C. nymphaeae of the C. acutatum species complex and C. chrysophilum, C. noveboracense, C. siamense, C. fructicola, C. henanense, and C. gloeosporioides sensu stricto of the C. gloeosporioides species complex, the latter two being first reports. Species with faster in vitro growth rates at higher temperatures were more abundant in warmer regions of the Mid-Atlantic, while those with slower growth rates at higher temperatures were more abundant in cooler regions. Regional bloom dates are earlier and weather data shows a gradual warming trend that likely influenced, but was not necessarily the main cause of the recent increase in bitter rot in the region. A grower survey of apple cultivar susceptibility showed high variation, with the increase in acres planted to the highly susceptible cultivar ‘Honeycrisp’ broadly corresponding to the increase in reports of bitter rot. These results form a basis for future studies on the biology and ecology of the Colletotrichum species responsible, and suggest that integrated bitter rot management must begin with selection of less-susceptible apple cultivars.

Diversity of Leaf Fungal Endophytes from Two Coffea arabica Varieties and Antagonism towards Coffee Leaf Rust

“…Refs. [67][68][69][70][71][72][73][74][75][76][77][78][79][80][81][82][83][84][85][86] are cited in the Supplementary Materials.…”

“…Refs. [ 67 , 68 , 69 , 70 , 71 , 72 , 73 , 74 , 75 , 76 , 77 , 78 , 79 , 80 , 81 , 82 , 83 , 84 , 85 , 86 ] are cited in the Supplementary Materials.…”

New Species-Specific Real-Time PCR Assays for Colletotrichum Species Causing Bitter Rot of Apple

“…This complex disease is caused by multiple fungal species in the genus Colletotrichum. There are three species complexes within Colletotrichum with pathogens infecting apple and pear fruits as follows: (1) acutatum species complex (CASC), (2) gloeosporioides species complex (CGSC), and (3) boninense species complex [9][10][11]. Over the last 8 years, efforts in the Mid-Atlantic U.S.A. have led to identifying the following nine species as causal agents of apple bitter rot: C. chrysophilum, C. fructicola, C. noveboracense, C. siamense, C. theobromicola, C. henanense and C. gloeosporioides sensu stricto (s.s.) from CGSC, and C. fioriniae and C. nymphaeae from CASC.…”

“…Accurate and rapid identification of the Colletotrichum species causing apple bitter rot is vital for Malus resistance breeding [23,24]. It is also essential for the development of effective control strategies while minimizing risks for single-site fungicides resistance in these pathogens [5,11,25,26]. Furthermore, fast detection of the Colletotrichum spp.…”

Ingestion of fungicides reduces net energy gain and microbiome diversity of the solitary mason bee

“…Before and during owering, apple orchards are typically sprayed with fungicides with varying modes of action (contact and systemic) to treat diseases such as apple scab, bitter rot, brown rot, and powdery mildew (9,10). Historically, unlike insecticides, fungicides were assumed harmless to pollinators; hence, they were recommended to growers during owering.…”