WAA and Lorsban/Butt Drenching

Ask an ExpertCategory: QuestionsWAA and Lorsban/Butt Drenching
Matt McMahon asked 5 years ago

Heya folks,
Just a quick question about the timing and efficacy of spraying Lorsban through the weedspray to target WAA before/as they start moving from the roots up in to the tree? I know it isn’t ideal, but better than spraying the canopy, right??
Also seeking your thoughts and experience on ‘fertigating’ Confidor/Samurai. It is my understanding that both these products are systemic, so applying them close to the root system achieves the best results. So in blocks that have inline drippers 0.5m apart the trees are getting a good dose using this method. However, would this theory not also work for older style trees where the drippers are ‘set’, be that within 1m from the base of the trunk, or in some cases between 2 trees – if they have been there for some time, wouldn’t the feeder roots all be where the drippers are applying water? and would this not be more effective than drenching the butts? Just questioning a directive to butt drench in favour of ‘fertigating’ in these situations.
Thanks in advance.

1 Answers
emilycrawford answered 5 years ago

Kevin Dodds (NSW DPI) and Stephen Quarrell (UTAS) responded:
Hi Matt,
Thanks for your questions.
Our IPM recommendation for WAA is to  encourage all the beneficials that we know can control WAA, like Aphelinus mali, lacewings, earwigs etc. There are examples where growers are finding WAA can be biologically controlled (over multiple seasons) just by adopting the soft approach and protecting the biological control agents. First step is to review your current spray programs and look for anything that might be causing your WAA problem and speak with your chemical supplier about soft alternatives. These might include avoiding certain chemicals used for crop thinning (ie Carbaryl) and early insecticides like Chlorpyrifos.
Responding to your question about ground application of certain WAA insecticides……   
Of the products you mention in your message, Samurai® (Clothianidin) is the only one that has a label recommendation for application through the micro-irrigation system. Therefore it can be used legally by this method (the others you mentioned cannot). We suggest speaking with your chemical supplier or the product manufacturer for advice on the likely efficacy of Samurai® applied through the irrigation system. As always, follow all the label directions.