ISHS Acta Horticulturae 309: XV International Symposium on Fruit Tree Diseases
ABSENCE OF DECLINE-LIKE SYMPTOMS IN ENGLISH PEAR TREES PROTECTED FROM EARLY SEASON POPULATIONS OF CACOPSYLLA PYRICOLA |
| Authors: | C.M. Guise, D.L. Davies |
| Abstract:
Parry's disease (PD) is a widespread disease of English pears and is associated with infection with mycoplasma-like organisms (MLOs) transmitted by the pear psyllid Cacopsylla pyricola. The disease has many similarities to pear decline and is characterised by premature reddening of the foliage in autumn and reduced vigour with sparse foliage the following spring. For two consecutive years, trees of the cv. Conference with quince rootstocks were protected from C. pyricola by nylon mesh cages between March and July. A proportion of the protected trees developed premature reddening symptoms and MLO infection by autumn, but none of the trees developed the damaging spring symptoms the following year. By comparison, 78% of trees that were unprotected developed spring symptoms during the period of the experiment. The results strongly indicate that an important component of the epidemiology of PD in English pear orchards is the size of C. pyricola populations and the time over which they are actively feeding on pears. | |
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