The appearance of aphids in October on fresh new spring growth is invariably accompanied by a demand in the nursery for “a spray to get rid of those (insert expletive of your choice) aphids”.
Very understandable – as aphids are highly visible infuriating sap sucking plant terrorists who spread disease, distort new growth, excrete large quantities of honeydew attracting ants and leading to sooty mould which in turn reduces photosynthesis and reduces plant vigour and production.
So while we have near universal condemnation of aphids, what we don’t have is universal agreement on how to get rid of them. Eight years ago at BAAG we embarked on an Integrated Pest Management (IPM) strategy. We introduced a range of predator insects and mites into the nursery and stopped using insecticides. Now we have about one week when aphid numbers build up in the roses and we resist the urge to go for the spray bottle, then the aphids just seem to go away and the problem is over. If you look closely you can see mummified aphids where parasitic wasps have been busy, and lots of ladybirds around. This pattern repeats around the nursery as numbers build up in an area, and then natural predators move in, and a healthy balance is achieved, with little to no damage to the plants.
Because this is a nursery and plants come in, and go out, we need to occasionally replenish our predator numbers, but at home, I seem to have achieved a good number now, and no longer add in new ones. I haven’t sprayed for years. My neighbours have a bee hive, so I am reluctant to use insecticides anyway, and we have achieved a harmonious balance, my predators have moved across the fence and their bees pollinate my blueberries, a win win.
It is easy to order predator bugs these days, even for non-commercial applications. Bugs for Bugs in Queensland will post them to you. They have an excellent web site.
If you struggle as aphid numbers build up, you can spray them off with a jet of water. Resist the call of the spray bottle, and go with the easier balanced option.