The problem with Aphids isn’t really Aphids themselves, who rarely do significant damage to a plant, the problem is their excreta. Aphid excreta has been dubbed “Honeydew” because it attracts ants. Honeydew can also lead to sooty mold, which is also unpleasant for cannabis plants. You don’t have to worry about Aphids while planting or before the first leaves show. Aphids are attracted to soft new plant growth. It’s when this appears that you need to have a look.
NATURAL ENEMIES OF THE APHID
Aphidoletes aphidimyza is predatory midge, which will happily control your Aphids for you. You don’t need more than 1 for every 100 square feet.
If Aphids have been around before, make sure Aphidoletes aphidimyza is also around from the first leaf growth, and then apply every week during the cycle of your crop. But there is a catch. Before letting this predatory midge loose in your greenhouse, you’ll have to get rid of all the ants. The problem with ants and the Aphids’ Honeydew, is that Honeydew is a valuable substance to ants, and they will go to great lengths to ensure they protect the Aphids in order to “farm” them and get their greedy maws on the Honeydew. If ants feel their precious Aphids are under attack, they have been known to relocate their Honeydew producers to safer areas within crops.
Aphidius colemani are very small parasitic wasps. They’re about 2 to 3 mm long, dark in color and they don’t sting. They’re natural enemies of the Aphid. These little wasps use the Aphids as hosts for their larvae. When the larvae begin to pupate, the Aphids become rigid, mummified, and that’s it for the Aphids. It’s good to keep Aphidius colemani around if you have Aphids. They home-in on Aphid colonies quickly, finding all those little pests. However, just using Aphidius colemani alone won’t be enough. They’re best deployed along with Aphidoletes aphidimyza and ladybugs.