Troubleshooting

I am having a lot of trouble getting my rhododendron leaves to become infected and having discussed the issues with a group of scientists working on Phytophthoras I have come up with a list of ideas which may be the reason for this:

1. The plants are dormant and have suberised for the winter and so their innate immunity afforded by their thick cuticle is especially effective.
2. The plants have been wounded by me cutting leaves from them for previous experiments and this has elicited systemic aquired resistance to infection.
3. The plants at the farm are irrigated by water which has been treated and this may be inhibiting the infectivity of the plants.

To test these theories I will carry out a number of small scale experiments using detached leaves to determine if there is an effect of wounding the plants or if there is a difference in infectivity year round or how the irrigation is affecting the plants.