Garden Update
Week of May 23, 2022
Kathleen Cue, Nebraska Extension Horticulture Educator in Dodge County
Regional Gardening Issues
In addition to cold injury and problems associated with winter dryness, plants are afflicted with leaf tattering, rose slugs, and leaf rust, to name a few.
Leaf Tattering
Strong winds and/or hail are responsible for shredded leaves on many plants. Once leaves are tattered, the aerodynamics have changed, making them even more prone to the ravages of wind. Native plants will be the best at weathering leaf tatters and most plants will send out new growth where leaf tattering is severe. Keep plants well hydrated with about 1 inch of water per week (rain and irrigation water combined). Fertilization of trees, shrubs, and native perennials can deepen stress, so refrain from fertilizing.
Photo: Carrie C Heitman - Wind Damage on Echinacea
Rose Slugs
Rose slugs are not slugs at all but the immature stage of a sawfly. In the spring, the adult female sawfly lays her eggs on the underside of rose leaves. The rose slugs themselves are translucent, yellow-green in color, and grow to less than 1 inch in length. When slugs first hatch out, their feeding on rose leaves resembles tiny windows in the leaf tissue. As rose slugs grow, their larger appetites mean defoliation is more apparent. There are many rose slug species, giving rise from one to six generations per year. Because the rose slug is a soft-bodied insect, there are a variety of management techniques that are highly effective. Hand picking, a strong stream of water from the garden hose, allowing birds to eat them, and application of a purchased product (Neem oil, insecticidal soap, bifenthrin) will be effective.
Photo: Carrie C Heitman - Rose Slug Damage
Penstemon Rust
The beloved ‘Husker Red’ Penstemon, as well as other Penstemons, can get a foliar fungal disease known as rust. There are four species of fungus that cause leaf rust in Penstemon. Round yellow blister-like spots on leaves are the first indication of leaf rust. Rarely does this disease warrant application of a fungicide. Instead, pick off the worst leaves and re-direct irrigation heads away from plants to decrease humidity that favors these fungal pathogens.
Photo: Carrie C Heitman - Penstemon Rust