Some plants and pollinators have unique relationships. Take the rush milkweed.
Most years our rush milkweed plants only produce one or two seed pods each.
This year, however, the plants are covered with seed pods.
To figure out, we need to go back a few weeks. At that time the plants were covered with flowers.
We also saw a lot of tarantula hawk wasps visiting the flowers.
Although they are clumsy giants, tarantula hawks are especially good at pollinating milkweeds. Their long legs slide into the grooves in the flowers, where they collect the sticky sacs of pollen called pollinia (for more information, see BugGuide). When the wasps visit the next flower, the process is reversed, leaving the pollinia behind to pollinate the plant.
This year the tarantula hawk wasps were abundant and now the seed pods are, too, which hopefully means
soon we’ll see more milkweed seeds,
which will glide away on their silky parachutes to make more rush milkweed plants, which are
good for the monarch caterpillars that eat them, and
which turn into monarch butterflies, important pollinators for many other wildflowers.
Here is what the plants looked like on March 19, a month ago.
The stems were covered with oleander aphids.
On April 17, 2018 you can’t find a single aphid.
What did I do to get such clean plants?
Nothing. Let nature take its course.
Insects like aphids have boom and bust cycles.
Back on March 19, these aphids were under attack. They were turning into mummies, which means they were parasitized by tiny wasps.
The aphids were also being eaten by flower fly larvae, aphid flies, and a few other insects.
Inside, the plant might have been mounting a defense, too. Plants can increase their chemical fortifications in response to insects feeding on them. Milkweeds are well defended because they contain cardenolide toxins, as well as a milky latex. The aphids can overcome the plants toxins better than most insects, but eventually it is probably has a toll and the aphids are weakened.
Although they are gone right now, the oleander aphids are likely to be back again. It is a natural cycle.