A couple of weeks ago, I saw a bad infestation of aphids on Betty Boop, my favorite rose. I also saw some soldier beetles already on the job, eating them. I checked them a few days later, and both aphids and soldier beetles were gone.
But I know that those soldier beetles
laid eggs under the leaf mulch in my beds, and their larvae will be patrolling
under that mulch for the next 10-11 months, eating any insects they can catch
and kill. They pupate and become adults
in April and May and emerge, ravenous for aphids to make their eggs.
I learned this the spring after I
bought my house, in 2000. All the roses
that came with the property were heavily infested with aphids, and I waited for
weeks for lady beetles to show up and clean them up and make their young, who
likewise eat aphids. But the infestation
just got worse, until I got nervous and decided to spray them with soap. I was heading out there with the spray bottle
in hand, when I saw about 50 soldier beetles flying around the most infested
bush and mating—so I didn’t spray but I did look up these red and black beetles
and learned their habits. Within a few
days, both aphids and soldier beetles were gone.
I had been waiting for lady beetles
because, in Arizona, I had a single broccoli plant that was infested with
aphids. I had learned that aphids are
specific for particular types of plants.
This being the only brassica in my garden, I knew there was nothing else
that they would eat, so I didn’t pull the plant, wanting its seeds. After a while, it became a lady beetle
factory, feeding at least 100 of a several different sizes and colors of lady
beetles, including young and pupae.
But here in Southern Oregon, lady
beetles have to compete with soldier beetles, which, with their short adult
life span, are more ravenous when they emerge from the mulch.
Later in the summer, I tend to have aphids on corn, which attract lady beetles in large numbers and don’t really hurt the corn. They also do the same thing on sun flowers, though birds are more likely to eat them there. A couple of years, I had large, grey aphids on my fringe pussy willows, which were eaten by hummingbirds, chickadees and woodpeckers.
Later in the summer, I tend to have aphids on corn, which attract lady beetles in large numbers and don’t really hurt the corn. They also do the same thing on sun flowers, though birds are more likely to eat them there. A couple of years, I had large, grey aphids on my fringe pussy willows, which were eaten by hummingbirds, chickadees and woodpeckers.
Aphids are manna for predators that
eat them, crowding together in large numbers for easy picking, full of sugar as
well as protein. Those that grow on
poisonous plants, like hellebores, often are not eaten by anything. I have seen soldier beetles eating aphids on
hellebores, but only once, so I am more likely to spray them there. But most of the time, they are useful to
bring in predators that might stick around and eat other insects as well.
But soldier beetles won’t lay eggs
where there isn’t any mulch cover for their young. Don’t use finely-ground bark, which leaches
its natural preservatives into soil and kills everything in the soil but plants. Coarse bark, like walk-on fir or nugget bark,
can provide shelter and help keep soil moist, but the best garden mulch is
leaves, which feed fungi and soil life and become rich soil.
Rycke Brown, Natural Gardener 541-955-9040 rycke@gardener.com
