Aphids in a greenhouse can quickly become a serious problem. They may start as a localized infestation, but if there are no natural predators in your greenhouse, these highly reproductive insects will quickly spread. To control aphids in your greenhouse, you must catch them early if at all possible. But even if the infestation is significant, pesticides are rarely necessary. By applying a variety of control measures you'll find it easy to banish aphids from your greenhouse.
Watch for crawling aphids on your greenhouse plants. First, check the tops of leaves for trails of sticky, clear honeydew or black streaks of sooty mold that often grows on top of it. Then, check the underside of the leaves (especially curled ones) for aphid colonies.
Physically remove the aphids from your plants. Aphids may be small, but they make themselves easy to remove by gathering in colonies. Prune away any leaves that are housing aphid colonies and place them in a sealable plastic bag. Then spray the affected plants with the hose to dislodge any stray aphids. Once knocked to the ground, the aphids won't likely be able to find their way back to the plant and will starve to death.
Release predatory insects. Insects like parasitic wasps, parasitic midges, ladybeetles or lacewings will feed on aphids. The type of predatory insect that is right for your greenhouse will largely depend on the type of aphids that you have and the conditions in your greenhouse. But, like aphids, these insects will also multiply so you will have to periodically release them. Once outside, they should help control the outdoor population of aphids and keep them from coming into your greenhouse in the first place.
Trap and monitor flying aphids by placing yellow sticky traps around your greenhouse. Yellow sticky traps attract aphids by mimicking healthy, delicious leaves. Place the sticky traps around infested plants to trap flying aphids looking to lay eggs. Place them near the doors and perimeter of your greenhouse to track the point of entry of the aphid infestation.