Monarchs and Aphids Munch on Milkweed
Les Harrison is the Wakulla County Extension Director
The cool evening and noticeably shorter days remind Wakulla County residents of the impending season change. The autumn equinox is a week away.
One of the much anticipated events in fall is the annual migration of Monarch butterflies. The area is lucky to be in the flyway for this centuries old passage of the vibrant insects as they make their way to winter habitat in Mexico.
To aid the delicate voyagers, many local landowners, gardeners,and people with a special interest in nature’s colorful balance have planted milkweed.
Monarchs are dependent upon this plant, both the native and non-native varieties, as a food source for future generations of the polychromatic flyers.
While milkweed is now assiduously cultivated as an annual plant worthy of exceptional attention with the relatively recent understanding of the Monarch’s needs, the unaltered genetic makeup is that of a hardy wild plant or weed.
As such, it has become a regular source of food for a number of the creatures which have resided in the area since long before recorded history began.
Aphids are one of several bugs which have a taste for the tender tissues of milkweed. This tiny, soft body insect has the ability to pierce the leaves and stems with its mouth parts and suck out the juices.
Aphids are found worldwide, but are most common in the temperate zones.
The aphid family has about 4,400 different species, all with the same habit of attacking tender plants.
The piercing practice has several negative effects on the leaves of any plant which falls under the gaze of the ever hungry aphids.
Removal of the necessary sap from the plant will at best damage the cosmetic appearance resulting in curled leaves and noticeable scars or spots on the affected feeding site.
Just as bad, if not worse, aphids can spread diseases between plants as part of the colony will move between feeding sites.
These diseases and viruses can cause decay, loss of leaves and branches, and plant death.
For the concerned gardener who has put time and effort, and borne expenses to cultivate milkweed for the purpose of feeding the Monarch larva, a voracious horde of aphid can be quite disconcerting.
Given the nature of the project, the use of insecticides to discourage the aphids will also suppress the Monarchs.
Luckily, there are a few options which will help insure the continuation of the colorful butterflies. Nature provides one response which has the coldblooded efficiency of every lethal predator.
Aphids are a link in the food chain for some of the native carnivorous insects. Top among those are ladybugs.
A concentration of aphids will almost guarantee the appearance of one or more ladybugs. While they have the colorful image and shape of a small
child’s toy, they are in reality an aphid’s worst nightmare.
With a hard shell, the ability to fly, and mandibles designed to chop up and consume prey, aphids never stand a chance. Individual aphid’s only hope is the ladybug gets tired of eating before reaching it.
Even ladybug larva seek out and consume the tender and hapless aphids.
If the female Monarchs reach the milkweeds in the coming weeks, the ladybugs will likely have thinned the aphid substantially.