The Influence of Host Leaves on Germination of the Asexual Spores of Sphaerotheca Macularis (Wallr. Ex. Fr.) Cooke

Although the conidia of Sphaerotheca macularis need high moisture levels (above 90% relative humidity (R.H.)) to germinate satisfactorily on glass surfaces, they are able to germinate on host leaves under very dry conditions. The effects of some fractions, extracted from strawberry leaf surfaces, revealed that none of these fractions have a stimulating or an inhibitory influence on germination of these spores on glass surfaces at 98% R.H. The R.H. of strawberry leaf was measured and its influence on germination of these spores discussed.