Aphids and Their Control
Aphids, members of the order Homoptera, are probably the most notorious pests in the world. Aphids
seem to cause us problems both early and late in the growing season. Those first aphids you
discover in the spring were probably hatched from over-wintered eggs. That’s why garden
cleanliness — keeping places where the eggs might survive the frozen months — is important to
aphid control. On the other hand, once hatched, the young nymphs can be carried over great
distances by the wind.
Though there are many types of aphids — some 4,000 species have been counted — most of those
born from over-wintered eggs arrive already pregnant. This is one of the major divisions between
aphid types. Many kinds of aphids give birth, amazingly, to live young. In warmer climates, aphids
may go through as many as 12 generations before laying eggs to over winter. This explains why you
might see a few aphids one day and a full-blown infestation the next.
In spring an egg hatches, producing a wingless female aphid who soon begins
parthenogenetically (reproduction in which an egg develops into a new
individual without being fertilized) producing new wingless females. Generation after generation of
wingless females survive one another until hot weather comes or maybe the plant on which they are
living dies and then suddenly some of the females grow wings and fly off.
Though aphids look so plump and dumpy that they could never fly far, in fact they can travel hundreds
of miles with the assistance of low-level jet winds.
This new generation of female winged aphid very well may at this time find a plant host of a
completely different species from that on which their spring generations developed. For instance,
Green Peach Aphids overwinter as eggs on peach and related trees but in spring they move to
various weeds and agricultural crops, and then still later they move onto potato crops, only in the fall
returning to peach and related trees.
A newly born aphid becomes a reproducing adult within about a week and then can produce up to 5
offspring per day for up to 30 days!
If aphids aren’t controlled or defeated early in the game before damaged plant parts can be
auto-corrected and outgrown, they can cause considerable economic damage to an otherwise
beautiful garden.
An aphid feeds by inserting its proboscis, stylet or straw-like mouthpart into the phloem or inner cells
of a plant. Upon insertion the aphid draws the plant’s juices or sap. This feeding activity will normally
cause leaf and stem deformities and it can aid the transmission of various plant diseases, both
bacterial and viral, all of which can affect the plant’s appearance and value.
If the infestation becomes large enough, is the formation of black-sooty mold growing on the sugary,
ant-attracting excrement of these pests. This excrement (a.k.a. poop) is known to attract sugar-feeding
ants which may, in an effort to manage their food source, herd or physically move aphids and protect
them from bio-controls, natural and introduced. This last condition, if the aphid population grows large
enough to support ants, can make organic aphid control even more challenging.
Green Lacewings feed on a large number of soft bodied pests, mites and insect eggs. A voracious
predator, they can consume as many as 60 aphids an hour. Shipped as eggs packed in a carrier
(rice hulls), larvae soon hatch out and will feed for 2-3 weeks before becoming adults.
For more infomation see: Beneficial Insects, Green Lacewings.
Make a homemade aphid spray by mixing a few tablespoons of a pure liquid soap (such as castile) in
a small bucket of water. Avoid using detergents or products with degreasers or moisturizers. Apply
with a spray bottle directly on aphids and the affected parts of the plant, making sure to soak the
undersides of leaves where eggs and larvae like to hide. The soap dissolves the protective outer
layer of aphids and other soft-bodied insects, eventually killing them. It doesn’t harm birds or
hard-bodied beneficial insects like lacewings, ladybugs or pollinating bees. You can also purchase
ready-to-use insecticidal soaps online or at a local nursery.
The organic compounds in neem oil act as a repellent for aphids and other insects, including mealy
bugs, cabbage worms, beetles, leafminers, ants and various types of caterpillars. However, it may
repel beneficial insects, so use caution when and where they are present. Follow package
instructions for diluting the oil in water or use a ready-to-use neem oil spray, and spray the affected
areas. Neem oil is also good for controlling different types of fungus.
Adult Ladybugs (ladybeetles) don't eat nearly as many aphids as they do in their larval stage, which
is why many people are disappointed with the lack of control they see after releasing purchased live
ladybugs into their garden. There needs to be a large enough aphid population to keep the ladybugs
fed long enough to mate and lay eggs — because it’s the larvae that eat the most aphids.
For more information see: Beneficial Insects, Lady Bugs.
Discouraging early season aphids is helped by controlling the nitrogen your plants are getting. Using
soluble nitrogen fertilizer early in the growing stages (often just when you want to use it). Aphids are
attracted by high levels of nitrogen in plants. That’s why you might find plants you’ve just pruned
attacked. The aphids will seek out the high-nitrogen new growth that comes of pruning. Instead of
highly soluble nitrogen fertilizers, including manures and fish emulsions, use something that’s
slow-released. When fertilizing roses, peonies or other flowers, use a formula that’s higher in
phosphorus than nitrogen. Keep pruning to a minimum if you’re having aphid trouble.
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Voles — The Good and the Bad