In 2014 I was one of the first to report my suspicion that Willow Aphids cause honey to crystalize in the comb, making it difficult, if not impossible to extract and also spoiling the taste. I see now that my war against the Willow Aphid has been taken up by others. The Ministry of Primary industry is funding research on the pest.
To my dismay however, the Northland Regional Council is funding a Willow planting program to combat soid erosion. (2016). Taranaki Farmers are likewise advised to plant Willows. Clearly, the Willow Aphid has not yet their presence felt sufficiently in these areas. I believe that the damage of these pests is underestimated.
While, as an urban beekeeper, I may not have all the facts, I invite anyone that advocates the planting of Willows to drop in during an autumn honey harvest. My guess is that before too long the Northland and Taranaki Beekeepers will have cause to shut down any Willow planting program, hopefully before it's too late. To me it seems like we are dealing with a pest that will hang around and will potentially have far-reaching consequences to the NZ honey industry. (Perhaps someone in the know please comment on why these planiting programs are going ahead and correct my concern if I'm wrong.)
In our little urban valley we have Willows along a small creek. They grow fast, too fast to support themselves before long, and so they frequently break branches or topple over. Every single branch then sprouts new shoots and so I believe that once they are planted, they are difficult to contain.
In mid summer the aphids appear in their trillions. On every branch, every few centimeters there is a cluster of them and the sap they release can be seen and felt like rain. In late summer any area under the Willows is black with what I guess is mould and anything (other than willows) is struggling to grow there.
I recently removed a willow branch that had fallen into my property. Here are some photographs. Later this season I'll add images of my willow aphid honey "extraction".
Part of my rather unpleasent task was to run the branches through a chipper to get rid of any chance that there will be new sprouts. What you see in the image is my hand full of "aphid juice". No, it's not very pleasant.