Community Ag Alliance: The good and bad of spring moisture
By now you might have started wondering if you’ve moved to the Pacific Northwest and did not know it. May was the wettest month on record in Steamboat Springs, with more than six inches of rain, triple the average amount. These rains have been a mixed blessing. While some people are getting tired of the dark and gloomy days and want the sun back, most of our trees and vegetation are growing strong and lush with this temporary abundance of moisture.
On the positive side, the spring moisture is making up for the below-average winter snow pack and will hopefully result in a very productive spring and summer with plenty of forage for cattle and game alike. This is also a good time to plant new trees. This abundant moisture should aid in the establishment of new seedlings. These conditions also make it easier to control weeds by hand, so make sure you take advantage of the saturated soils to pull some of the undesired weeds around your yard.
On the other hand, this level of consistent moisture can also result in challenging growing conditions for some of our favorite plants and trees in the valley, some of which are briefly discussed below, together with some of the symptoms you’ll need to watch for.
• Over-watering: Trees do not show symptoms of water-logged soils until a time after the overwatering occurs. The most common symptom on broad leaves is the loss of leaves in mid-summer. You might also notice some discoloration of the leaves, usually from the bottom up and inside-out of the tree (opposite to drought stress, which is from the top down, and the outside –in). Ash, aspen and honey locust are the most susceptible to drowning or wet soil conditions.
• Poplar leaf diseases: The marssonina fungus that causes marssonina blight is the most common disease on aspen and cottonwood foliage. This foliage disease develops readily in wet and cool weather, which are the exact conditions of late. Heavy infestations will cause early leaf drops. To reduce future disease problems, rake up and dispose of leaves. Ink spot disease is also the result of a fungus commonly found on denser aspen stands and also causes early leaf drop.
• Fire blight: This is a bacterial disease that can be spread by insects, but also by rain splash. It is especially detrimental on crabapples, one of our favorite spring trees due to their “spring snow,” and other species in the rose family. The bacteria spends the winter in blighted branches and, with the spring rain, multiply and move through cracks and bark pores. It is also aided by insects that like the fire blight’s sweet bacterial ooze. All flowers, leaves and fruit above the point of entry die. Infected blossoms appear water soaked and wilt rapidly before turning dark-brown. Pruning and removing newly infected twigs and branches as soon as symptoms are identified is a good way to control it.
• Aphids: Over the next weeks, aphid populations should be above average in numbers. This weather pattern almost always results in big spikes of aphids in late spring on a wide variety of plants due to the increased succulent growth that is both favorable to aphids and greatly suppresses natural enemies.
• Poplar Twiggall fly: This is another insect that thrives in these current conditions. Most of the galling occurs on younger trees that produce a lot of succulent new growth. Although these injuries continue to expand for years and produce permanent disfigurement, they do not seem to threaten tree health and there are no effective chemical controls, just natural ones, like chickadees and other birds that eat the pupae in the spring.
If you see any of these symptoms on your trees or have any questions, please give us a call.
Carolina Manriquez if a forester with the Colorado State Forest Service. The Colorado State Forest Service is committed to helping homeowners and landowners promote healthy and sustainable forest conditions. A forester can be reached at 970-879-0475.
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