Develop a plan for aphids

In all the years I’ve been helping growers, I’ve never seen such a severe year for aphids. Is there a reason? I don’t know with certainty, but I can guess it has something to do with a few key factors.

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1. In areas of the country with mild winters, many aphids survived outdoors on weeds that never went dormant. These are often called “winter weeds.” The numbers of aphids present and moving were very small, but it doesn’t take many early to cause you real eventual problems.

2. Obviously, any weeds you leave in greenhouses over winter provide a home for early aphid populations. Kill all weeds in early winter.

3. More growers are buying plugs or liners to start crops these days. This saves a great amount of energy money that is not spent to heat greenhouses early in the season. However, it has one great danger. Insect pests, most commonly aphids, come in with this plant material. Again, they may arrive in tiny numbers.

4. In tiny numbers, aphids are hard to detect. Once they build up, they are just that much harder to control. Do not shortcut your time spent on detection early in the season. Aphids rarely come to sticky cards unless it is late in the population and numbers have already built up.

System management

With a good system, aphids are not that hard to control. Here are the parts I like to stress.

1. Upon first detection, do not rely too much on spot spraying. Remember, you probably do not see the edges of the infestation, where the small numbers of the pests reside.

2. At first, use wet-down sprayers and do not skimp on spray volume. Later you can use low-volume sprayers.

3. Spray weekly at first. Before you back off to biweekly sprays, scout carefully to see that all the pests are dead.

4. I’ve found that traditional products work best. If most growers were not generally on rescue (detect then treat) programs, I would probably recommend more biological controls. Here is a list of products you can select from.

Products for aphid control

5. I don’t have a set pesticide rotation policy for aphid control. Resistance exists but it’s quite variable around the country. Rotate away from a product if you see that it doesn’t seem to be working. Rule out all other technical factors before deciding to rotate. You probably will not be able to go back to that product for that season. Never use a pyrethroid by itself. I do recommend using them in tank mixes because they’re very good agitators.

6. I have not given specific labeling directions in this article. You must do that before use on any particular crop or site. For instance, make sure vegetables or herbs (spices) are on labels if you intend to spray them.

Newer Web search pages are becoming very good for this. The search pages are not good for determining whether or not a chemical is legal indoors, outdoors or in both sites. I use the label search engine: www.cdms.net/LabelsMsds/LMDefault.aspx?t=.

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It is a mouthful, but it works.

- Charles C. Powell