This time of year, many of the messages coming into our local Master Gardener Help Desks are commonly asked questions that track with our seasonal weather. Here are a few:
A: Once the weather pattern changes from hot and dry with limited humidity to either hot with lots of humidity or cooler with humidity, lawn fungal diseases can develop. Also, those nights with dew, which makes walking in the lawn in the mornings a wet affair, are really going to promote disease. There are fungicides available, but to be successful will mean getting out there before there are signs the disease is present to prevent the disease. Applications now may prevent the lawn from looking worse but cannot bring back those spots or patches. Make a note on your 2021 planner or in your smartphone to start sprays at least two weeks before you noticed the signs this year.
Q: I am seeing a lot of leaves with spots and bumps on my shade trees. Can I treat it?
A: One is a foliar disease concern, the other an insect concern. Foliar leaf disease is rarely ever fatal and always seems to show up on the lower more visible tree limbs. (For example, tar spot on maple trees.) These kinds of foliar diseases got started way back this spring during the wetter, cooler weather and are just now strongly showing up. Those lumps, bumps, and galls also got their start at bud break and while the leaves were young and tender. Insect eggs are laid as the buds begin to open. At first, the leaves remain green, but as the insect develops within the leaf structure, the galls will grow. As the insect matures, the galls also will likely change color. In these cases, there is normally never enough damage to warrant any kind of treatment.
A: Vine crops need to be protected from what is commonly called the squash vine borer. The adult squash vine borer (which we never seem to see), lays eggs at the base of the vine crop. Those eggs hatch into larval worm stage that bores into the stem and begins to feed, chewing the inside of the stem and leaving behind that sawdust looking frass. Similarly, the cucumber beetle feeds on the stem and also can spread cucumber wilt. The goal is prevention, by protecting either an emerging seedling or a transplant by using a covering to protect the plants from the egg laying stage of the squash vine borer (or the feeding of the cucumber beetle) until the vine crops begin to flower and “vine.” This is done by using one of the spun polypropylene or polyester coverings available. It is very light, floating on the young plants, and it lets light and water in, but keeps our pests out. A bonus is you get to use it again in the fall to protect against frosts, extending your harvest.
About the author: Richard Hentschel’s expertise extends across several subject areas with specialties in lawn care, fruit tree production, woody ornamentals, and home and community gardening. During his 45-year career in horticulture and agriculture, Hentschel became a well-known and respected expert for commercial and homeowner audiences, industry organizations, and media. He retired from University of Illinois Extension in April 2022 with nearly 30 years of service as a Horticulture Specialist and Educator in northern Illinois.