May 25, 1994
Defoliation of pine trees and shrubs by clusters of European pine sawfly larvae should be apparent by now. Larvae of this common pest species are grayish- green with 2 light stripes and 1 dark stripe on each side of the body. The legs and head are shiny black. Full grown larvae will be about 1 inch long.
Rainfall amounts this spring have been below normal in most areas of Iowa. If the dry conditions persist, the yields of strawberries and raspberries could be reduced.
Strawberries and raspberries require adequate moisture throughout the growing season for good fruit production. However, the most critical time is from bloom to the end of the harvest. Insufficient moisture during fruit development may cause the fruit to fail to develop full size or to dry up. If rainfall is inadequate, apply 1 to 1 1/2 inches of water per week.
A bacterial disease called watermelon fruit blotch has appeared occasionally in Iowa. Symptoms often appear at midseason as water-soaked or coffee- colored stains on fruit. The stains develop cracks, and secondary microorganisms can then invade and rot the fruit. In some cases, infected fruit actually split open. Economic losses in an infected field can be very high; even fruit that show only the staining are unsaleable. The seedborne nature of the disease means that can it can be brought into a field on infected seed or transplants.
Now is the time when homeowners will notice medium-sized cockroaches wandering about the house in the middle of the day. These are usually wood cockroaches, also known as wood roaches.
Wood roaches are similar in appearance to the household cockroaches, but they live exclusively outdoors. They live in rotted logs, tree stumps, hollow trees and under the loose bark of dead trees and firewood. They are especially noticed at this time when the males are active and attracted to lights.
Anthracnose is a common springtime disease of ash, especially when we have wet weather. Diseased leaves show brown to black spots, usually developing from the margin inward. Leaf tissue often appears distorted as it sometimes curls or bends towards these leaf spots. People become aware of anthracnose on ash when infected leaves begin to fall in the spring. Although significant defoliation may occur, trees usually recover by producing new leaves. Fungicide sprays are generally not warranted.
Last week, Richard Jauron wrote about unusually high mortality of sour cherry trees this spring. Our calls and personal observations indicate that tree death is very common and widespread this year, and not just in cherries. In most cases, these trees were not actually flooded above ground level during last year's wet spell. Many species are affected, including ash, maple, hackberry, white pine, Douglas fir, Scots pine, black cherry, and others. Some of these trees failed to leaf out at all and their twigs are dry and crispy.
If you would like to transplant spring-flowering bulbs, wait until the foliage has turned yellow and begins to die. (Most tulip and daffodil varieties die back in early to mid-June.) The bulbs may be replanted immediately. If they can't be planted, the bulbs should be stored until fall. Once dug, thoroughly dry the bulbs for 2 to 3 weeks. Then place the bulbs in mesh bags and store in a cool (50 to 65 F), dry place until fall planting. Inspect the bulbs several times during the summer and discard any which show signs of decay.
Landscaping with light is a popular way of enhancing landscape plantings, turf, and gardens. This is done through the use of low voltage lighting systems. Besides the added dimension night lighting provides in the landscape, landscaping with light gives additional safety and security around the home.
Bacterial blight of lilac is caused by the bacterium Pseudomonas syringae. The organism causes brown spots on leaves. These spots may enlarge and coalesce, causing leaves to become misshapen. Eventually leaves may be killed.
When the infection spreads around a twig, the twig becomes girdled and dies. Shoots turn a black color, droop over, and die. This phase of the disease is evident as young shoots develop in the spring. (The symptoms are similar to fire blight on apple.)