MSU Extension Service
Home Grown is an educational,
entertaining, question-answer column seen weekly in "News from
the Genesee MSUE Office," a weekly newsletter for Genesee
County Master Gardeners. Special thanks to the Genesee, Oakland and
Livingston county MSU Extension offices for providing this service.
01-13-05 Fungus gnats; deer protection
01-19-05 After cutting down trees: to
chip or not to chip? Also: starting seeds indoors for spring
01-27-05 Excessive plant growth in ponds;
problem trees and/or problem sites
02-11-05 Diplodia Tip Blight on Pine
trees; caring for African violets
02-14-05 Caring for Ficus in winter;
indoor pests: larder beetles
02-14-05 bonus! Fertilizer for gardens -
designer vs "regular"; why gardenias don't like our
02-21-05 vole damage in lawns & woody
plants; how to root cacti and succulents
03-04-05 tree-climbing vines; hibernating
03-08-05 deer pests in the landscape;
grain moths in kitchens
03-15-05 ants in the kitchen;
mythological apple trees
04-07-05 spring care of ornamental
grasses; little beetle in basements
04-13-05 Preventing crabgrass; flies on
04-18-05 Buying perennials in boxes; care
of perennials in early spring
05-20-05 Dogs and lawns; winter injury on
05-27-05 Sawfly larvae on Scotch Pine
trees; rabbit-eaten Burning Bushes
06-07-05A Dead spots in the lawn; grow your own maple field?
This week's HomeGrown
HOME GROWN 303
I grow several kinds of mint in my garden for use in the kitchen. I went out to harvest some and something terrible is happening to the tops of the plants. They have little brown round spots that have a black ring around the outside. The brown spot is translucent. I thought I saw something red, like a bug, but it was really little. What’s going on?
What’s going on is a Four-Lined Plant Bug fiesta. These insects suck the chlorophyll out of leaves. This creates the brown circle that is basically just the top and bottom of the leaf with all the good stuff vacuumed out. If there are enough of these pests, the spots can touch each other or new leaves can look black. Four-Lined Bugs will dine on the new leaves at the top of the stems on a number of plants. Besides all kinds of mints, they also damage chrysanthemums, feverfew, veronica and a bunch of others. Right now, when they are immature, these pests are red with a bit of black on their backs. When you see them feeding, they run down the stem is a spiral fashion. As these guys mature, they eventually become a lime “tennis ball” green with four black stripes, running from front to back. Kill them while they are babies, like today. There will soon be enough plant damage that your culinary plant volunteers will look so disgusting you won’t use them. Four-Lined plant Bugs rarely kill plants. They just make them look tragic. To terminate your little red devils, spray them with insecticidal soap. Purchase insecticidal soap rather than mix your own. You get something that is designed for plants and the product is consistent in quality and strength. Sneak up and spray the very tops of the plants. Do this with enough spray so it runs down the stem and leaves faster than this insect. Check every day to see if there were any survivors. Mints can be trimmed to remove the bad ends. They will produce lateral growth and continue to grow. If you have continued problems with these bugs, an ancient gardening book offered up a good, pesticide free solution. These guys lay next years eggs on the woody stems of perennials that stand all winter, like chrysanthemums and mint. In March, prune off the dead stems to the ground and toss them in the burning barrel. Toast the eggs and stems to golden perfection. This can help that future generation. Leave your stems over the winter to help hold snow in the garden for plant protection. Toast on.
Four years ago I put in a rose garden. The first year, the plants looked tremendous. The next year, they didn’t look as good. Every year since, they have declined. I water them, I have tried rose fertilizers and I mulch them. Every spring, I take my little tiller and till the cocoa bean mulch in for nutrients. I just got a soil test and all I needed was nitrogen. They grow in full sun. Why are they looking this bad?
I was wondering too, until you got to that mulch part. Mulch is great for roses but tilling it in every year is cutting lots of roots off plants. You are giving them an extreme root pruning at the beginning of each growing season. By the end of the season, they have begun to recover
but…dang…they get chopped again. Roots do more than just hold the plant up. They take in moisture and nutrients, to just name two. It’s tough to grow or bloom when your parts keep getting amputated. Keep dong everything except tilling. And promise never to till them again. Nutrients can be added to the soil surface and water will take the nutrients into the soil. Keep two or three inches of mulch for insulation and protection from evaporation but let their little roots run free.
Gretchen Voyle, MSU Extension-Livingston County Horticulture