Blight Control

This is good topic for a blogletter, raised by Andy Philpott. We can all learn if you share your blight control experiences.

Dear Nick & Pauline
Enjoyed your comments on Copper Spraying and Walnut Blight – about 3 years ago I was overseas and left careful instructions for copper spraying with a guy who worked for me. I didn’t discover until about February that he had ignored my instructions because he decided that I was asking him to apply dangerous “non natural“ chemicals.

I must confess that the blight levels that year were no different from previous years’ of spraying and I have not sprayed for the past 3 years.
Valda & Otto Muller tell me that they do not use copper sprays either, so it may be that our drier Central Otago climate controls bad blight. I do recognize that my position is weakened because I have not got off my chuff and done a Blight Count so I shall try and do one this year and perhaps spray the next year

Does anyone have any advice on using Fertigation techniques because I have picked up a 1,000 litre ? plastic container in a cage and wondered about putting this in my Irrigation Circuit , any advice on various “ brews” that one can use ?. If one is using Fertigation in summer would the nutrients be available that summer to the trees or would this require a season for the nutrients to take effect?
I am also wondering about applying Boron in my orchard since I only have soil levels at the moment – my reading suggests that Boron can be rather toxic and there is a relatively small window between too much and too little
With regard to frost damage and Air Frosts which hit my trees in a random fashion, the effects seem to be scattered throughout my lower orchard and I would probably have to remove some walnut trees to change any drainage patterns. I am hoping that this will be an infrequent event!
Keep up the good work
Jeffrey A Feint

Thanks for your comments.

I wrestle with the decision to spray every year. Of the 3 years I have sprayed just copper, it was effective only once. This year I am trying Mankocide to see if it makes any difference. But it is an expensive operation, and needs to make a significant contribution to the crop both in quantity and quality to be worthwhile. On the plus side, I have people beating on my door wanting more nuts. But then again I have quite a few customers asking, “Do you spray?” before deciding to buy when I sell at the local Farmers Market.

I would encourage you to be brave, and seriously consider applying Boron. For years I held back because Boron is toxic in excess, and there is that small window between too much and too little that you talk about. But the window between MUCH too little and enough is much larger. Franquette seems to be more sensitive to a lack of Boron than other varieties. For years my Franquette trees did not crop AT ALL. But then one branch on one tree started to crop. It was over part of the nursery that had pots we were fertilizing with Triabon. (An all inclusive slow release formulation that had Boron.) So I cautiously applied Boron to other trees. The Franquette all started cropping.

Then I thought, “How do I tell when I am overdoing it?” I had an almond that was doing nothing, and would not matter if it died from Boron poisoning. So I gave it a lethal dose. I gave it a whole cup full of Boron, instead of the usual half teaspoon. I thought, “That will set an upper limit to what I can put on.” The almond tree loved it! It came out in a mass of flower, and set a crop of nuts for the first time in 20 years. So now I no longer fret about putting on too much Boron – on this place anyway! Have you got a tree that you could happily kill with Boron poisoning?

As for the time for mineral nutrients to get into the tree; I remember an experiment where they applied radioactively labelled Urea to plants, timing how long before it showed up in the leaves. It took 20 minutes! Fertigation has an instant effect, and even minerals applied to the soil work pretty quickly. They always reckon that lime takes 6 months to work. But I had a break from applying lime to my walnut stand one summer. When I resumed work after a fortnight I am certain the leaves were greener up to the line where I stopped. Of course minerals in the leaf veins do take time to initiate extra flower buds, but it could translate to bigger nuts if applied in early summer and therefore increase crop that way.

All the best