Mirid Bug Update

I’ve been seeing a few mirid bugs in the strawberry variety trial in Lincoln.  There have also been some “catfaced” fruit, which could well have been caused by mirid feeding.

Recently I gave my overgrown alyssum plants a good shake—I’m aiming to seed the cracks in the ground cloth for next season—and I was aghast to see oodles of little green things crawling amongst the seeds.  Upon closer inspection, they were all mirid bugs at various stages of development, from young nymph to adult.

‍“Ye gads!  What disastrous mistake have I made, dislodging all these pests that will now infest my strawberries!”

There is no mirid work being carried out this year on an industry level.  My biggest learnings have been visiting a local canterbury grower last autumn.  https://www.berryworld.co.nz/blog-posts/mirid-damage-to-strawberry-flowers

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It is the nymphs that are doing the feeding damage in the flowers, rather than the adults.  The flowers are where the damage is happening, earlier than the green fruit stage.

My main take-away from that farm’s experience was that mirids seem to be happy enough to stay on alternate hosts (in his case lucerne, and potatoes) until that alternate host is mowed or dies down.  If a high population is forced to move by their preferred host being destroyed, they can cause catastrophic damage to neighbouring strawberries.

In my own tunnel, those mirids had built up to incredible levels in the alyssum which is right next to the strawberries, without causing very damage to the strawberries.  Also, despite close inspection, I can’t see those mirids on the alyssum.  Crop beating (I use a cricket bat over a plastic-lined tray) is required to monitor their status in either the trap crop or the alyssum.

That’s why I think there’s a place for a managed trap crop in mirid control.

Managing a trap crop

The next logical question would be how best to manage a trap crop, particularly one like alyssum which I had intended to be healthy food for predators and parasitoids that should keep my late season aphids in check.

Clearly, if I use insecticides on my alyssum, I have to be prepared to accept some trade-offs.  There has been some work done out of California that used Beauvaria bassiana + azadiractin (Neem) against young nymphs, with reasonable success, better than either product achieved alone.  More recently there has been work done with indoxacarb (Steward Evo), and I’m awaiting more comprehensive trial results from the Californians on that option.  Of course, an option like fipronil is clearly effective, but not at all compatible with supporting the beneficials.  For any insecticide approach, nymphs are much easier to kill than the adults, which are quite hardy.

I’m interested in your experience with Mirids—are these problematic at your site?  Reply with a note or two!