I doubt PLC is resistant to copper. It's more likely a matter of timing and disease pressure.

Are you saying this spring was dry or your springs in general? I've never seen PLC here in west Texas. We are much drier in spring than the bay area.

Yes, especially missing that last spraying, letskki. If you're going to miss any spraying don't let it be the last one for us in Calif, especially this year, since again, we've had plenty of rain. The winter rain and temps between 45 and 68 degrees is what will favor growth of the spores, and this occurs in the winter. Which is why we get hit so hard with PLC - we have opportunity and preparedness coming together with optimal temps occurring as the same time as peak moisture. And, on top of that, when spring rolls around, temps are perfect, and we get a lot of humidity in the form of fog, and general overcast weather, which is just as bad as rain.

As far as I am aware of, there has not been any resistance to copper. The effectiveness of an copper product is directly related to two main things: percentage of copper (and MicroCop is 90% copper, you're lucky you still have some, you cannot purchase it in the state of California any longer), and the length of time the spray stays wet. The copper is active only when it is wet, when the copper ions are in solution. So, that last spray is the crucial one for us, especially when rains are late. Due to our decent winter rains these last 3 years, the fungal and spore counts are probably at record highs for us. So, if you can squeeze in 5 sprayings, timed right after rains, you'll have better success.

It is our bane in California, but, compared to other areas of the country that have a myriad of issues to deal with, with stone fruits, we're pretty fortunate. I, too, have about 5% to maybe 20% affected trees, too, even though I thought I got in enough sprayings, and with MicroCop (I stocked up before I couldn't get it here.)

Patty S.

fruitnut, for us, the spores actually bloom during our warm winters. Which is usually when we get our rains here in California - from December through Feb/March. Usually. But, it has been later for us here in Calif. We had some rains in Nov, then it was very dry for a bit, and then in March and April we got the rains we usually see in Jan & Feb. I was not able to get another spraying in before we got another deluge, and it was right after our mini-heat wave that caused everything to break super early. It was a weird year. And our disease pressure is at maximum right now due to 3 years in a row of wet winters. Not that we're complaining out here, trust me! We are coming out of a 7 year drought, so I say, bring on the rain, and I'll just try to keep up with the PLC.

Also, you need to look in your yard for ornamentals that will also harbor the fungus. I have several large ornamental shrubs in the prunus family (for the life of me I can't remember the name of this extremely common shrub used to make hedges here in Calif. It has "cherry" in it's common name) that have PLC, and I can't spray it with copper spray since it is evergreen. I may have to resort to Daconil to knock down my spore count in my yard.

Patty S.

Here is a link that might be useful: UC IPM: Peach Leaf Curl

Thanks for the response. Next year i'll hit all my dates and make sure I catch the last one at bud swell.