The Natural Gardener: Aphids on Roses are Good

          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.

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