The heavy disease pressure of 2013 left an abundance of pecan scab inoculum in the orchards just waiting for the conditions we have observed this spring. The frequent rainfall has allowed scab to explode on susceptible varieties, generating more leaf scab than has been seen in a long time throughout the state. Reports from the Albany area suggest the ‘Desirable’ crop is already in danger of being lost in many orchards. I have seen scab particularly bad on Desirable but also on Stuart and other susceptible cultivars in well managed, sprayed orchards. Again, as we saw last year, scab appears to lessen as you go north from Albany.
If you are seeing leaf scab, all you can do at this point is continue on a good spray schedule. Click here for one potential spray schedule option. Tighten up to 10 days if weekly rainfall is occurring. Is the leaf scab confined to the bottom leaves or does it go all the way to the top? If you have trees over 40 ft, is scab worse in the top than in the bottom? If confined mostly to the bottom or top of the tree, you could have a coverage issue. When the nut sizing period arrives in June, Elast + Tin would probably be a good fungicide choice. But, while the appearance of scab may be disheartening, don’t give up on the crop just yet. We are used to seeing completely clean leaves. In a wet year like we are having, some scab is inevitable. Bear in mind, the trees can tolerate some scab and still make a crop.
Most orchards have good crop potential at this point. If June and July happen to turn off dry, the leaf scab we are now seeing will not lead to major problems for the crop as long as the trees remain on a good schedule. But, if the rains continue, it will be particularly difficult to keep scab off the nuts where leaf scab is heavy.