Cereal Aphids Are Late

Aphids are beginning to appear across the state and also locally. Now there are many species of this very large family. Aphids in general are host specific meaning each species thrives on specific plants.

According to the July 5th issue of the NDSU Crop and Pest Report, pockets of increasing populations of cereal aphids are starting to show up in North Dakota. Fortunately most of the wheat and barley are passed the susceptible stage for yield loss from cereal aphids. The greatest risk of yield loss from aphids feeding on grains is when the crop is in the vegetative to boot stages. Significant yield reduction after the onset of flowering could not be demonstrated in 1997 South Dakota Research. The Journal of Economic Entomology which reported on the S.D. research project cited several reasons for this conclusion. First, after heading, the only major yield component aphids can affect the seed weight. At this stage and beyond, aphids are unable to sustain the very large populations necessary to achieve significant impact on yield. The journal also cited that other components of yield are determined earlier. For example, the number of spikelets is determined at jointing and the number of seeds is determined at flowering.

Aphids make their living feeding on the fluids of plant parts. As they feed, they pass fluid known as honeydew which is usually sweet and attractive to other insects such as ants.

Trees affected with aphids will exude this honeydew causing a sticky substance to fall upon anything below the branches. Sometimes the honeydew will turn black as a result of a sooty mold which develops. Aphids do not cause long tree damage to well established trees.

Tree of the Week

When it comes to trees, patience of us humans is severely tested. When given a choice we often select the trees which will produce the fastest growth even though we are warned the tree has problems surviving our environment and may not live very long. The two trees which quickly come to mind that fit this situation are the hybrid Poplar and Siberian elm. The latter is a hardy, fast growing tree but it is extremely susceptible to insect, disease, and herbicide damage which makes it an undesirable tree.

When we moved to our present home 25 years ago, I decided to plant some Northwest Poplars around the west and north sides of the house believing the trees would quickly give us some good protection from wind and shade for the yard and house. For the first 10-15 years the trees met my expectations but by the time they reached 20 feet or so extreme disappointment began to set in. I could not provide them with enough water to support all the leaf density. By mid-August the leaves began to turn yellow and most had already fallen to the ground well before a killing frost. A couple years like this quickly weakened the trees as evidenced by poor leaf density and dead limbs. Of the 15 trees planted in the spring of ’87, I am confident one will survive another year. It has grown to be 30-40 feet tall with a good crown. I can only speculate it found an underground water source which was not available to any of the others planted at the same time in the same general area.

Hybrid poplars have their place where good soil moisture is readily available during the growing season. However, they will not do well at sites frequently flooded. Some folks have used hybrid poplars to establish quick growth while adjacent, slower growing and more drought tolerant trees are also being established. As the health of the poplars begin to decline they are moved.

There are many cultivated varieties of hybrid Poplar. Some are more winter hardy and disease resistant than others. The Northwest Poplar I planted is known to be winter hardy but like other hybrid poplars it needed more moisture than what upland sites can provide.