Four-striped plant bug: Spots and lines

Bob Dluzen
Special to The Detroit News
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A couple of days ago, I glanced at some potato plants in my garden and in the corner of my eye noticed a yellow and black-striped bug crawling over the leaves. It was a four-striped plant bug. On closer inspection, I saw quite a few more.

These insects are very elusive making them difficult to find sometimes. They quickly scurry to the underside of a leaf if they see you coming. If you try to catch them they will drop to the ground, making it hard to kill them by hand.

While four-lined plant bugs are native to our state, their populations seem to differ from one location to another. In one spot they are the annual scourge of the garden while in another they are nowhere to be found.

The bugs feed by poking their beaks into the leaf surfaces of plants. In order to extract their food, they inject large amounts of saliva that contains enzymes that liquify surrounding plant cells allowing them to suck out the juices.

What’s left behind after feeding are areas of dead plant cells that dry up and form spots. These spots look a lot like spots caused by certain plant diseases. Often the material from these dried spots will fall out leaving behind holes.

A four-lined plant bug with typical feeding damage.

The nymph stage of the insect feeds the same way as the adults resulting in identical damage.

During some years the population builds up to very high numbers and quite a bit of damage can occur. Fortunately the bugs don’t stay around the whole season. They have only one generation per year. After mating, the females lay eggs in plant stems. Both male and female adults die. The eggs are left behind waiting to hatch for next year’s brood.

Four-lined plant bugs are not fussy eaters, they seem to be happy on a wide range of herbaceous and woody plants. One reference mentions the bugs have been found on at least 250 different kinds of plants.

In many cases the best policy is to simply live with the damage and let nature take its course. Perennial flowers may be pruned below the damage and left to regrow new, fresh foliage replacing the unsightly damaged parts.

If you happen to have a special, rare plant that suffers from a lot of damage each year or are growing plants for show in a public place, then an application of insecticide would be warranted. 

To reduce next year’s infestation, clear out and destroy any plant residue in the fall. That will remove many of the eggs that were laid in plant stems by this year’s adults.

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