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Anna, Teacher, writer, biologist
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We have an old Conference Pear Tree For the last two years a sort of canker has developed

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We have an old Conference Pear Tree
For the last two years a sort of canker has developed on the leaf. It is yellw / orange on the upper side of the leaf and it has what looks like an egg cluster on the underside. Any ideas on how to get rid of this for next season.


I apologize that no one has responded to your question sooner. Different experts come on at various times. I just logged on and saw your question. If you still need help, some additional information will help me to answer your question.

Is the thing which appears like an egg cluster light brown in color?

Do you - or your neighbors- have any juniper trees?

Thank you.


Customer: replied 4 years ago.

Yes, light XXXXX, XXXXX't know about any juniper trees near by.


Thank you. Do these photos look like what you're seeing?


Customer: replied 4 years ago.

Yes this is exactly the problem. Almost every leaf was infected.

We did not get any fruit this season but a very large crop last season. I don't think that we were alone with this, in that we had an early warm session and then a late frost in spring.

Customer: replied 4 years ago.

The first photo with the raised clusters looks like our problem

Thank you for getting back to me. First of all, the lack of any crop at all was probably due to the late frost. The disease infecting your tree is called Pear Trellis Rust. It is a fungal infection that is common throughout continental Europe and has now spread to the UK and North America, as well. It can cause developing fruit to mummify, but doesn't prevent the fruit from appearing in the first place. It is complicated and difficult to control, as it requires the cooperation of a whole neighborhood. The fungus has two life stages. One of them requires juniper trees. That stage looks like an orange jelly-like mass. It doesn't harm the juniper trees - they remain healthy and keep growing. In early spring these masses release spores that are carried by the wind to pear trees, where they begin the second stage of their lives. The leaves are infected and the first sign is tiny orange spots. Throughout the summer they become larger. In the fall, the projections on the underside of the leaves appear. They mature and release spores that are carried by wind to juniper trees. The whole cycle begins again. If you click on this link, you'll get a download that explains the disease in detail:

I'm sorry to ahve to bring you bad news, but in most cases there is little you can do about it. Some growers report that the common fungicides sold in garden centers slow down the infection enough to get a crop, but official sources say the fungicides are ineffective. Other growers pluck off the first leaves they see with spots in the spring and continue to do that throughout the season. However, when every leaf is affected, that isn't practical. If the leaves can be destroyed in the early fall before the spores are released, it may break the cycle temporarily by decreasing the spores available to infect the junipers.

In regions where pear-growing is important, people have cooperated to remove all the juniper trees in the area, but in residential neighborhoods, people are not happy to remove a healthy juniper tree. Even if they are, the spores can be carried long distances on the wind, and after a few years, the fungus will be present again.

Unfortunately, the only practical steps to take are to destroy the leaves before the spores are released, rake up all debris under the tree and destroy it, and in the spring, try suing a fungicide regularly throughout the growing season. The Royal Horticultural society is researching the problem and would like pear growers to submit information to help them track the problem. If you want to help out, here's a link:

If you have more questions, let me know by clicking on REPLY. I'm sorry to give you bad news.


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