Walnut catkins are appearing, lengthening, opening and releasing pollen. Research indicates that this is the time when bacteria which cause walnut blight; and have overwintered embedded in the plant tissue, may emerge and disseminate. Copper is the remedy. Copper is delivered in a powerful jet of air and moisture by a sprayer, towed behind the tractor and driven via the PTO shaft. I spent over six hours today protecting the orchard, vulnerable at this time, driving the tractor listening to Tracey Chapman and Willie Nelson.
Studies indicate that copper is most effective if leaf burst has progressed to 30% of branches being in ‘prayer phase’ ie where the new growth has the appearance of hands praying. Travelling down the aisles at 4.6 km/hour I can attest that at least 30% were praying.
Three hours after I finished spraying, it rained, quite hard. Rain has always posed a dilemma. Copper is sprayed to reduce bacterial colonies that thrive with moisture. Rain may wash off the copper before it can achieve its outcome. Should copper be sprayed after rain? I don’t have the opportunity as I work in town for the next three days. And… copper is very sticky. Rain will not easily wash it off.
After filling the 3,000 L tank of the sprayer I turned on the PTO to mix the solution. I had left the switch to the fans on. I sprayed my ute with copper, briefly. Later, the copper would not hose off the windscreen easily.
I will check the trees during the week for any blight. We now have daylight saving. I have an extra hour of sunlight after work. I will spray again weekly for the next two weeks. That’s what the research says. It has worked for the last two years – fingers crossed.