This garden infestation is becoming increasingly common, and it can devastate an entire season's crop
Gardening columnist Don Kinzler offers advice on a squash vine infestation, as well as how to kill creeping Charlie in lawns and ways to prevent green areas on potatoes.
Q: Attached is a picture of my squash vines this year. Every day the leaves droop like the plants need water, so I’ve been watering every day, even after rain. The squash vines perk up overnight but during the day the leaves wilt again, just like the photo. Do you have any idea what might be going on? I’ve always grown squash and never had this problem before. — Connie K.
A: Your squash vines are reacting with classic symptoms of a squash vine borer infestation. This problem has become increasingly common, and I’ve experienced it myself in recent years. It can totally devastate an entire season’s squash crop.
The adult moth is dark gray with an orange abdomen and makes a noticeable buzzing sound as it flies. The moths lay eggs along lower squash stems in late June. As the eggs hatch, the inch-long, cream-colored larvae enter stems, tunneling throughout and causing vine collapse. Leaves often temporarily recover at night, but eventually wilt permanently.
Prevention must begin earlier in the season, because once the wilting happens, the borers are safely inside the squash stems. Apply insecticide spray or dust such as Sevin, Eight or spinosad to the base of plants around June 20 and repeat in seven days.
The insecticide must thoroughly coat the stems below the leafy canopy, especially the 12 inches above soil level. The insecticide kills the newly hatched borers as they attempt to chew their way into the stem. Spraying the leaves isn’t effective.
Besides insect sprays, aluminum foil can be wrapped around the basal 12 inches of stems to prevent borer entry. As vines grow, you can also cover stems sections with soil in several places. These covered stems will produce roots, lessening the chance that borers will affect the entire planting because the plants will be rooted in multiple spots.
Remove and dispose of all vines in the fall, or earlier if they collapse and die.
Q: Can you remind us of the product that was recommended to kill creeping Charlie in lawns? — Victor M.
A: Creeping Charlie is among a group of weeds considered hard to kill, because it proliferates so readily from its winter-hardy perennial root system and its ability to vigorously spread. It doesn’t creep — it sprints.
Some lawn weed herbicides aren’t tough enough to control these persistent weeds. Look for a herbicide with the active ingredient triclopyr, which will be indicated on the label, often in fine print listed under “active ingredient.”
Apply the product following all label directions. For best control, apply triclopyr in early September and again next May. Because these weeds are tenacious, spring and fall applications should be made religiously this year and next. Eventually, you can out-persist these persistent weeds.
Q: Every year the potatoes that are closest to the surface develop green areas, even though the tubers aren’t exposed. I know if they’re exposed to sunlight they turn green. Our potato plants are doing well, and I want to prevent the green areas that we end up cutting off when we’re cooking them. Is there a way to prevent green potatoes? — Ben C.
A: Even if the potato tubers aren’t peeking out of the ground, if the soil cover is too shallow, light can still penetrate and cause green chlorophyll and toxic alkaloids to develop.
To prevent greening, the base of the potato plants should be covered with a generous amount of soil. That’s why, as the potato plants grow, it’s customary to “hill up” soil around the developing plants so the tubers form at a depth well below light penetration.
Even if hilling wasn’t accomplished earlier in the season, greening can usually be eliminated or reduced now by adding soil around the plant. If there isn’t enough accessible soil between rows to pull up around the plants, extra soil can often be found at the garden’s perimeter. Straw, grass clippings free of herbicide, and other mulches can also be added to exclude light.
If you have a gardening or lawn care question, email Don Kinzler, NDSU Extension-Cass County, at firstname.lastname@example.org. Questions with broad appeal may be published, so please include your name, city and state for appropriate advice.