Four-lined bugs assemble in rows to attack plants


June 25, 2000

Q. Many of the plants in my borders, including peppers, black-eyed Susan, oregano, mint and salvias were all attacked by some insect or virus this spring. Small, round spots would appear in rows along the leaves, and the tops of the plant would die. It seems to have slowed down recently. What could be going on?

A. Had you looked closer, you would have caught the pest -- the four-lined plant bug. The nymphs are bright red, and the adults are greenish yellow with four black stripes. Their numbers seemed to have been high this spring, so the signs of feeding were dramatic. But this pest is short-lived, and your plants will grow out of the damage with no problem.

Q. Help! Some of my tomato plants are not doing well. The bottom leaves are turning yellow and the top leaves look like they have dandruff -- lots of little white flecks. I water and fertilize regularly and can't bear to lose any of my plants. What should I do?

A. The white flecks are probably the cast-off "skins" of aphids. Look for these small, pear-shaped, sucking insects on leaf undersides. Control them by handpicking or with a spray of ultra-fine horticultural oil. Predators and parasites of the aphids are probably already at work helping to control the infestation. Bottom leaves will naturally turn yellow and die during the growing season. Keep up the watering but you may be over-fertilizing your plants, which can encourage aphid feeding and reduce fruit set.

Q. My neighbors and I have been noticing large, hard brown growths on the twigs of our oak trees. There seem to be more this year. What are they and is there anything to be concerned about?

A. Those are gouty or horned oak galls, caused by a small wasp. The wasp produces chemicals that interact with the oak tree hormones, producing the woody, protective galls under which the wasp larvae develop. Most galls, especially leaf galls, are harmless. However, twig galls on oak will cause twig and branch dieback and should be physically removed if they can be safely reached.


1. Leave snakes alone! Snakes are active because it is mating season. These are beneficial creatures. Call the number below to request a copy of our fact sheet on snakes in Maryland.

2. Remove excess peach and apple fruits so that the remaining fruits have room to expand to full size without touching a neighbor.

3. Mow 'em high and let 'em lie. Practice grasscycling by letting your clippings decompose naturally on top of your lawn. You'll reduce your labor and mowing costs. Grasscycling does not lead to thatch buildup.

Garden tips are provided by the Home and Garden Information Center of the Cooperative Extension Service of the University of Maryland. For additional information on these questions, or if you have questions of your own, call the center's hot line at 800-342-2507, or visit its Web site at

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