I often hear things like "plant garlic by your roses to deter aphids" but does this actually work? And does it also work for milkweed aphids (Aphis nerii) or just the kind of aphids that go for rose bushes. When I google aphid+rose it seems that kind of aphid is Macrosiphum rosae?
Likewise I've also been told sage repels aphids from celery, but when I google aphid+celery it seems that kind of aphid is Myzus persicae.
Another suggestion is that aphids are repelled by the smell of marigolds. Which aphids? Which marigolds? (French Marigold, Tagetes patula; Mexican marigold, Tagetes erecta; English marigold, Calendula; Tree marigold, Tithonia diversifolia; Desert marigold, Baileya multiradiata; Corn marigold, Glebionis segetum; Marsh marigold, Caltha palustris)
Others say sticky yellow traps are the way to go.
It's all very confusing to a novice gardener such as myself.
Has anyone ever tested these aphid deterrents for effectiveness? Does anyone want to help test them?
What I suggest is we do some research!
(how did you know I was going to say that? ;->)
If you know of any other supposed aphid repellents then please post them to this thread. For instance our aphid factsheet also mentions banana peel as at deterrent.
Want to be a tester? The trick to research is to focus on the thing you are testing by eliminating as many variables as possible. So we need everything else to be the same, the only difference will be in the deterrents.
So get 2 or more large pots or planter bags. I reckon PB8 would be a good size. That is 8 pints or 4.8L. But whatever you use make sure they are all identical. Buy a bag of potting mix and put the same amount of potting mix in each bag. This will make sure any differences are not due to the soil chemistry.
Plant a couple of seeds in each container. Use the same sort of seeds for the whole set, eg all G.physocarpus, or all A.currassivca etc.
Leave one pot with just the host plant. That will be your control. Then plant your chosen deterrents in the other ones. Label the pot carefully. A good way is to label the pots A,B,C and somewhere else record A= Tagetes patula, B=control, C=banana peel or whatever you use.
Put them somewhere where they can be close to each other, but not too close. We don't want the Tagetes patula or whatever in pot X to protect all the other pots as well. They should also be in similar conditions. We don't want one in the shade and another in full sun for example. Finally whatever else you do to them, do it the same to all of them, eg the same amount of water etc.
Then wait for the aphids to come calling. When they do resist the temptation to squash them or wash them off, just wait and see what happens. Finally you could ask a friend or neighbour who doesn't know what you are testing to rate the plants in terms of aphid attack. Photos of each would be great too.
Then post your results here. If we have a lot of testers we should be able to build up a pretty good picture of tried and true Aphis nerii deterrents.
