I planted a quince tree this year and so far it is doing well. Unfortunately, it is also infested with aphids. Once a week or so I get out the hose and blast them off, but they return after a day or two.
These critters are probably either Green Apple Aphids or Spirea Aphids- they are very similar to each other and both are known to live on quince trees. I have found ladybugs (aphid predators) exploring this tree before, but it appears that the aphids are doing just fine regardless. According to an Ohio State University website , these aphids produce nymph (or baby) aphids all by themselves without a male. See the two different sized aphids in the photo? The small ones are the nymphs, the large ones are the adults. Because they reproduce on their own, aphid populations can explode in a hurry. Once the plant gets too crowded, new aphids will suddenly grow wings so they can fly away and find another plant to colonize.