Aphids are
small, mostly less then one tenth of an inch, soft-bodied
insects of the family Aphididae. The daylily aphid, Myzus
hemerocallis, is, not surprisingly, often found
on daylilies but there are many other kinds of aphids;
some of which may also affect daylilies from time to
time. The daylily aphid is light green in color and
feeds in colonies between the leaves of the plant,
inserting the mouth parts into plant tissue and sucking
up the juices. Whitish specks are often noticed on
the plants when aphids are present. These are the cast
skins left behind after molting.( See lower image below.)
They also excrete a sticky substance called
"honeydew". The image accompanying this text
is of the related green peach aphid (Myzus persicae).
The life cycle of aphids can be rather complex and can
vary somewhat according to species and geographical region.
In mild weather aphids can produce continuous generations
rapidly by live birth without mating, most of the population
being female. With the imminent onset of cold weather in
Fall, males may be produced, mating occurs and the females
lay overwintering eggs. In warm climates and in greenhouses,
some species may omit the egg-laying stage and continue
to reproduce by live birth through the winter, although
where it is slightly colder they may hibernate as adults.
Most aphids are wingless, but sometimes you will see winged
forms. Natural enemies may keep populations down to levels
where no treatment is necessary. Aphids are especially
partial to plants fertilized with large amounts of nitrogen.
If control is desired, insecticidal soap can be effective
if the aphids are located where they can be directly hit
by the spray. Numerous other low or non-toxic remedies
are discussed in various references including repellent
companion plants such as the allium (onion) family, coriander
and anise. |
