Browsing by Author "McDonald, Sharon Angella"

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    Epidemiology, Aphid Vectors, Impact and Management of Tobacco Etch Potyvirus in Hot Peppers in Jamaica
    McDonald, Sharon Angella (Virginia Tech, 2001-02-22)
    Production of hot peppers, Capsicum spp., in Jamaica is constrained by the aphid-transmitted potyviruses, tobacco etch virus (TEV) and potato virus Y (PVY). The virus epidemiology was not understood and no effective virus management system existed for these viruses. This study sought to identify possible management strategies for aphid-transmitted viruses of hot peppers in Jamaica, using TEV and Capsicum chinense, var. 'Scotch Bonnet' and 'West Indian Red', as models. Field spread of TEV to pepper was mainly by secondary spread from primary infections. Secondary infections were spatially correlated to primary infections for up to 25 meters. Natural infections of TEV were associated with aphid flight activity. Over 30 species of aphids were collected on pepper farms in St. Catherine parish. These aphids included five known vectors of TEV, Aphis gossypii Glover, A. craccivora Koch, A. spiraecola Patch, Lipaphis erysimi Hille Ris Lambers and M. persicae (Sulzer), and 12 new records for Jamaica, Aphis amaranthi Holman, Brachycaudus helichrysi (Kaltenbach),Capitophorus hippophaes (Walker), Geopemphigus floccosus (Moreira), Hysteroneura setariae (Thomas), Lipaphis erysimi Hille Ris Lambers, Rhopalosiphum padi (Linnaeus), Schizaphis graminum (Rondani), Schizaphis rotundiventris (Signoret), Trichosiphonaphis poligoni (van der Goot), Uroleucon ambrosiae complex (Thomas) and Uroleucon pseudoambrosiae (Olive). A. amaranthi and U. ambrosiae were associated with TEV spread. Weeds on and near farms influenced the abundance and species of aphids captured. West Indian Red pepper showed tolerance to TEV. Scotch Bonnet pepper yield reduction was greater if plants were infected with TEV during the vegetative stage through flower initiation rather than after the start of fruit set. Stylet oil and reflective mulch used together delayed the incidence of TEV in pepper plots for over two months. TEV management programs should aim to delay the virus from infecting peppers during the first two months after transplanting. A risk analysis is proposed for management of TEV and other aphid-borne viruses.
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    Infestation Patterns of the Coconut Mite, Eriophyes guerreronis (Keifer) (Acari: Eriophyidae), on Coconuts and Resulting Yield Loss in Eastern Jamaica
    McDonald, Sharon Angella (Virginia Tech, 1997-07-09)
    Coconut mite populations and levels of damage to 2-, 4- and 10-month old Maypan and Red Malayan Dwarf nuts in Low and High Rainfall Zones of eastern Jamaica were evaluated. Damage due to the coconut mite was assessed by quantifying scarring of the nut surface, size reduction and copra yield. It was found that coconut mite populations were the same in the two rainfall zones but differed between Maypan and Red Malayan Dwarf varieties. More Maypan nuts were infested with coconut mites than Red Malayan Dwarf nuts. More 2-month old Red Malayan Dwarf nuts were attacked than 2-month old Maypan nuts while more 10-month old Maypan nuts were colonized than 10-month old Red Malayan Dwarf nuts. In both varieties, a greater percentage of 4-month old nuts had > 1,000 coconut mites than 2- and 10-month old nuts. Nuts in the Low Rainfall Zone had greater percentage of coconut mite damage than nuts in the High Rainfall Zone. Damage was more severe on Red Malayan Dwarf than on the Maypan nuts. The water content of Red Malayan Dwarf nuts declined with increased coconut mite damage but no relationship was found between the water content of Maypan nuts and coconut mite damage. Nut size and copra yield declined significantly with increased coconut mite damage. Total copra yield loss was only about 3% in Maypan and 6% in Red Malayan Dwarf nuts because most of the nuts had < 30% surface area damage.