May 26, 1995
Since ancient times, scholars have suspected that walnuts have harmful effects on nearby plants. In the 1880s, scientists isolated a compound called juglone from the fruit of walnuts. They demonstrated that injury and sometimes death result when this phytotoxic material interacts with susceptible plants.
Carpenter ant nests are very common inside trees, especially older trees that are hollow or have a significant amount of dead limbs and branches. The nests are usually in rotted, decayed wood, although some nests may extend into sound heartwood in the center of the tree.
European pine sawfly larvae have already been reported in several parts of Iowa, and NOW will be your last chance to discover any defoliation in time to treat effectively. Defoliation of pine trees and shrubs by clusters of European pine sawfly larvae is a common problem during the month of May. Full grown larvae that are usually present by Memorial Day weekend, may be a little later this year. Look for 1-inch long grayish-green larvae with 2 light stripes and 1 dark stripe on each side of the body and shiny black legs and head.
It's the time of year when noses and eyes are directed to the beauty and fragrance of certain plants. A genus of plants well known for both is Syringa, known commonly as lilac. Lilacs offer gardeners a large variety of plant shapes, sizes, and flower colors. The parade of lilac flowers begins in late April and early May and continues through mid-June. Hybridizers have worked extensively with the common lilac resulting in over 1000 different varieties. Some lilac species to look for include: