Beneficial of the Week: THe Dull Roar Effect

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  The importance of beneficial insects and mites is often missed.  Until they are missed. We learned this years ago when “cover sprays” that included multiple pesticides in a “cocktail” were used repeatedly in hopes of controlling a range of pests, but had the unintended consequence of reducing or eliminating beneficial insect, mite, and spider species. 

Without these beneficials, we created monsters such as spider mite infestations on burningbush euonymus, that were much worse when cover sprays reduced beneficials.  We lost the “dull roar” effect of these beneficials that, while not eliminating pests, kept them at more manageable levels, even though we did not know how much they helped at the time.


beneficials on corneliancherry


  This “dull roar” is an aspect of beneficial insects and biological control that is often forgotten or lumped in with the sometimes ineffectiveness of “augmentative” biological control.  Adding beneficial insects, especially in landscapes (compared to more manageable and less complex greenhouse environments) often is ineffective in changing the overall equation of pests and beneficials. But that “dull roar” - very important. How important?


syrphid fly beneficial



  Check out: “Ecology of herbivorous arthropods in urban landscapes.” Annual Review of Entomology 55:19-38 by Michael Raupp, Paula Shrewsbury and OSU’s Dan Herms. One such study looks at azalea lace bug and its much lower numbers and much lesser damage in complex ecosystems with a diversity of woody and herbaceous plant species vs. simple landscapes with a few woody plants and some lawn. The diverse species mix leads to the sustenance of multiple niches for predatory beneficials.


hover flys as beneficials


  So: enjoy the pictures of beneficial insects (from blue-winged wasps and grubworm control to syrphid flies and aphid predation) in this post, and another recent bygl-alert post on Robber Flies; Robber Flies on the Wing - all by OSU’S Joe Boggs, and look for a Beneficial Insect of the Week post from here to eternity.  

Finally, from Jonathan Swift, a mere three centuries ago:

 “So, naturalists observe, a flea
Hath smaller fleas that on him prey;
And these have smaller still to bite ‘em;
And so proceed ad infinitum
Thus every poet, in his kind
Is bit by him that comes behind.”