It seems appropriate in a discussion about battling aphids to paraphrase a quote by Sun Tzu from his book The Art of War: “If you know the enemy and know yourself, you need not fear the result of a hundred battles. If you know yourself but not the enemy, for every victory gained, you will also suffer a defeat.”
Though he was referring to military strategy, in reality, there’s not much difference when the enemy is six-legged and threatening the health of a crop. This is especially true with aphids, which can have an exponential growth rate and cause significant harm to plants.
The first thing a grower needs to do to treat an aphid issue is to identify what kind of aphid has infested the crop. Aphids, though they can vary widely in color and relative size, are fairly easy to distinguish from other plant pests.
A unique feature of these sap-stealing foes are the “tailpipe” structures on their rear abdomen, called cornicles, which are used to excrete a warning chemical when attacked. You may also notice shiny honeydew on leaves or sooty mold growing on the honeydew — a sign that aphids have been feeding. An increase in the number of ants crawling up pots and benches can also clue you into aphid populations since ants are known to farm and protect aphids for the sugary, sticky waste aphids produce as a byproduct of feeding on plant phloem. But, with 5,000 different possible aphid species worldwide, the task of differentiating them becomes a bit trickier.
Why Proper ID Is Critical
Many people assume that because they have identified their pest as an aphid that the work is done. Not so! Identifying the genus (at a minimum) can save you a lot of time and money. Here is a list of reasons why it could be important to properly identify the genus or species of the aphid on your plant: