At the request of the American Cranberry Growers’ Association and the New
Jersey State Agricultural Experiment Station, Shear began to investigate diseases
of the cranberry in 1901. Continuous plantings for many years in the Middle
Atlantic and some New England states, especially in the old cranberry bogs of
New Jersey, had created conditions favorable for the development and dispersal
of several fungal pathogens that were becoming of increasing economic concern
for growers (13). One of the first objectives of Shear’s research was to sort out
the confusing etiology of cranberry diseases. His mycological skills took cen-
ter stage. Growers, for instance, had used the term “scald” to refer to a single
disease. Shear’s mycological studies, however, demonstrated for the first time
that instead of one disease, “scald” actually included three distinct and destruc-
tive diseases of the fruit—scald, rot, and anthracnose—caused by three different
fungal pathogens, Guignardia vaccinii Shear, Acanthorhynchus vaccinii Shear,
and Glomerella rufomaculans vaccinii Shear. Shear also discovered the etiology
of a fourth major fungal disease of cranberry caused by Exobasidium oxycocci,
which he called “hypertrophy” (15). Shear’s life history studies revealed much
about these fungi with respect to various spore forms, growth requirements, and
reproduction.
With this knowledge about the causal pathogens in hand, Shear soon turned his attention to control. He collected and studied data on the effects of water supply, so crucial to cranberry culture, the benefits of the destruction of dead vines, and the possibilities of resistant cultivars. His major focus, however, was on chemical treatment, particularly with respect to the much-heralded copper sulfate and lime compound known as the Bordeaux mixture. Since the introduction of copper spray compounds in the mid-1880s, a revolution had occurred in the chemical control of certain plant diseases (8). His field experiments centered on preparation of the mixture, methods of application, as well as the frequency and timing of sprays. His work showed that the addition of resin-fishoil soap to the Bordeaux aided significantly in leaf coverage and adherence. Shear also demonstrated that at least five applications of Bordeaux mixture should be made during the season and that the interval between applications should not exceed 15 days. Results from his 1905 field trials indicated that with five applications, only 2.36% of sprayed fruit was destroyed at harvest compared with 92% of unsprayed fruit (14, 15).
Shear had provided information on fundamental biology of important cranberry pathogens and effective control strategies. For his studies of cranberry diseases, he received a PhD degree from George Washington University in 1906. He also had won the affection of the cranberry growers. When the American Cranberry Growers’ Association celebrated its 40th Anniversary in 1909, organizers insisted that “as the man who worked out our most difficult problems, it is eminently fitting that you should be one of our honored guests” (9).
With this knowledge about the causal pathogens in hand, Shear soon turned his attention to control. He collected and studied data on the effects of water supply, so crucial to cranberry culture, the benefits of the destruction of dead vines, and the possibilities of resistant cultivars. His major focus, however, was on chemical treatment, particularly with respect to the much-heralded copper sulfate and lime compound known as the Bordeaux mixture. Since the introduction of copper spray compounds in the mid-1880s, a revolution had occurred in the chemical control of certain plant diseases (8). His field experiments centered on preparation of the mixture, methods of application, as well as the frequency and timing of sprays. His work showed that the addition of resin-fishoil soap to the Bordeaux aided significantly in leaf coverage and adherence. Shear also demonstrated that at least five applications of Bordeaux mixture should be made during the season and that the interval between applications should not exceed 15 days. Results from his 1905 field trials indicated that with five applications, only 2.36% of sprayed fruit was destroyed at harvest compared with 92% of unsprayed fruit (14, 15).
Shear had provided information on fundamental biology of important cranberry pathogens and effective control strategies. For his studies of cranberry diseases, he received a PhD degree from George Washington University in 1906. He also had won the affection of the cranberry growers. When the American Cranberry Growers’ Association celebrated its 40th Anniversary in 1909, organizers insisted that “as the man who worked out our most difficult problems, it is eminently fitting that you should be one of our honored guests” (9).
No comments:
Post a Comment