Published: August 20, 2009 11:10 pm      

Bugs from 10 feet away

This one is for all of the country music fans out there, Keith Whitley fans in particular. He sang a song called “Ten feet away” that told the story of two people falling in love from across the room. I’m not sure that has ever actually happened, but I experienced something similar last week. Well, similar in a different sort of way.

I was standing on my back porch petting the dogs before I headed into the garden. As I looked across the yard to the garden, which is about 30 feet away, I noticed something strange about the okra. This day was particularly windy, so the large okra leaves were really flapping, showing their undersides each time a gust came. The backs of the leaves were black. At first I thought it must be just the shadow, but it wasn’t. It looked like soot had been smeared all over them.

Then I realized what it was. I could see the bugs from across the garden. When you can see aphids from 30 feet away, it is safe to say that there’s a problem. This is where the song jumped into my head, but it wasn’t exactly love that I was feeling across the yard that day.

Aphids are what one might call a pest of all trades. They can be found on thousands of species of plants, and there are several types of aphids. Nearly all species of plants have one or more aphid species that feed on them. The aphids on my okra were packed on the leaves side by side. They were climbing on top of one another just to move around on the leaves.

Aphids feed by sucking plant juices. They have a piercing mouth part that resembles a needle. It is inserted into the plant and they are able to extract liquids from the plant. All of this food they eat has to go somewhere. It comes out the other end of the aphid as a substance called honeydew. It is sugary and sticky. Because of the sugars in the honeydew it can spoil or mold, turning black in color; which explains why my okra leaves were black. The black honeydew is referred to as sooty mold.

These pests are not only phenomenal at feeding. They excel in rearing young as well. The “typical” aphid species may produce several wingless generations in the spring, followed by a generation of winged forms. The winged forms can fly to other plants, where many more wingless summer generations may be produced.

As days become shorter and cooler, a generation of winged aphids may be produced, which fly back to the winter host. Some aphids have distinct winter and summer hosts (the winter host may be an evergreen and the summer host an annual weed or deciduous plant).

Aphids can increase rapidly in an extremely short time. During warm weather some species can complete a generation in less than two weeks. In many species, most or all of the summer generations consist of females that give birth to live female young, and are produced without sexual reproduction (parthenogenesis).

That’s right. The aphids have succeeded in finding a way to live without men! Males may be produced near the end of the season. The overwintering stage may be eggs, or the adults may be active through the winter.

My first reaction to this wild aphid infestation in my okra was to light the plants on fire and kill them, but then I began to look a little closer. I noticed two things that gave me some hope. The first thing I saw were swollen aphids that were tan in color as opposed to all of the rest, which were black and green. These tan-colored ones had been parasitized; meaning that another insect, most likely a parasitic wasp, had deposited an egg inside the aphid. This kills the aphid and the wasp will hatch out of the aphid carcass and go on to kill more aphids.

The second glimmer of hope I found was what I thought was a lady beetle larva. Lady beetle larvae are maggot-like and feed on aphids voraciously. But when I sent pictures of my discovery to OSU’s entomologist, he informed that it was not a lady beetle larva, but rather a syrphid fly larva. Both are beneficial insects that have similar body shapes, but their colorings are slightly different.

Between the parasitized aphids and the syrphid fly larvae, I thought it was best to leave the plant alone and let nature run its course. Many times nature’s cycle will solve the problem much better than we could.

If I would have sprayed the okra plant with an insecticide, I most likely would have killed the beneficial insects as well as the aphids. This sounds like a good thing, but the catch is that some of the aphids would have survived the spray. Then the plant would be quickly repopulated, but this time with no beneficials.

Ideally, my aphid pests should not have ever gotten so far ahead of me. Regular scouting should have allowed me to find the pests earlier. When found early in their populating process, a strong stream of water from the garden hose will knock them down sufficiently.

So do as I say, not as I do, and hopefully you won’t be spotting bugs from 10 feet away.



SAMANTHA SNYDER is a horticulture educator for the Oklahoma County OSU Cooperative Extension Service.