–by Dr. Jeff Whitworth and Dr. Holly Schwarting
Green cloverworm adults are quite numerous and are laying eggs in alfalfa and soybeans. So, there are, or will soon be, small larvae present. Feeding by green cloverworms will probably not impact alfalfa or most soybean fields unless there are significant larval populations in really late planted fields.
Stink bug populations seem to be increasing in north central Kansas but most beans should be far enough along in their development that stink bugs should be of little concern.
For management decisions for all soybean pests, please refer to the 2017 Soybean Insect Management Guide: https://www.bookstore.ksre.ksu.edu/pubs/MF743.pdf
–by Dr. Jeff Whitworth and Dr. Holly Schwarting
Thistle caterpillars have mostly vacated their webbed cells and are or have pupated. That is why there are huge numbers of painted lady butterflies flying around on most rural roads throughout north central Kansas. Hopefully, these butterflies will head south for overwintering and will not start laying eggs in soybean or sunflower fields. However, fields need to continue to be monitored for small thistle caterpillars, especially double-cropped soybeans. Additionally, monitor for the continued presence of green cloverworms, although these populations seem to be declining quite rapidly around north central Kansas.
Phytophagous stink bugs, both brown and green, are increasing in many soybean fields. Either may insert their mouthparts into the seed within the pods and suck out juice from the developing seed. However, there are also brown stink bugs that are predatory on pests like the yellowstriped armyworm (shown below) which has been killed and is being utilized as a food source by this beneficial stink bug.
Soybean aphid populations are still present in all fields examined this week in north central Kansas, but are not increasing in density or coverage.
For management decisions for all soybean pests please see the 2017 Soybean Insect Management Guide: https://www.bookstore.ksre.ksu.edu/pubs/MF743.pdf
— by Dr. Jeff Whitworth and Dr. Holly Schwarting
Alfalfa in north central Kansas doesn’t seem to be in the overwintering mode yet. It is still growing, albeit slowly. But, the unusual situation this warmer-than-average fall weather has caused is with alfalfa weevils. On 16 November, several alfalfa fields were sampled in north central KS and many adult alfalfa weevils were captured. However, the unique situation was the sampling of many alfalfa weevil larvae. Some leaf feeding by these larvae was also evident. These insects are normally univoltine (one generation of alfalfa weevils/year). The adults are moving, or have moved, back into the alfalfa fields by now and started laying eggs. Eggs laid in the fall are not normally developed enough to hatch this time of year. Late February is usually the earliest that alfalfa weevil eggs hatch. After the coming cold front moves through and temperatures warm back up we will re-sample to determine how the cold temperatures impacted these larvae.
Also, there are many pea aphids present which is not as unusual for this time of year. Numerous lady beetles are also present but they do not seem to be feeding on either pea aphids or alfalfa weevil larvae.
–by Dr. Raymond Cloyd
Now is the time to be on the lookout for the elm leaf beetle, Pyrrhalta luteola, which may feed on all elms; however, elm leaf beetle prefers Siberian and American elm, with Chinese elm being less susceptible. Adults are about 1/4-inch long, slender, and yellow-green in color, with black stripes extending down the entire length of the abdomen. Furthermore, there are distinct black spots on the head and thorax. Adults appear in spring and eat small holes in leaves. Females lay yellow-orange eggs in clusters on leaf undersides. A single female can lay between 600 to 800 eggs during her lifetime. Eggs hatch in 5 to 6 days into green larvae that look-like grubs. Larvae are approximately 3/8 to 1/2 inches in length. Initially, they are black, and then turn yellow in color with two black lateral stripes along the sides of the body. Larval feeding causes leaves to appear skeletonized because they scrape the leaf tissue from the upper surface with their chewing mouthparts; leaving the veins intact. The tissue between the veins eventually turns brown. Larvae, which are the major source of damage to plants, feed for about 3 weeks.
The last larval instar crawls down tree trunks, where they pupate at the base of trees in and on the ground. They may also pupate in the cracks and crevices of the trunk or in large branches. In about two-weeks, adults emerge and start feeding on plant leaves. They normally feed on the same trees that larvae fed upon. Adults may be a nuisance pest in late summer and early fall when they migrate from trees and enter homes to overwinter. They will also overwinter in protected places outdoors. It is interesting to note that both adults and larvae may be present simultaneously. There are two generations per year in Kansas with the second generation causing the most damage.
Insecticides should be applied at the first appearance of both adults and larvae, and routinely throughout the summer and early fall in order to protect elm trees. This is especially the case if extensive feeding by elm leaf beetles will impact the aesthetic appearance of elm trees. When using contact insecticides, it is important to obtain thorough coverage of both the underside and upper side of plant leaves. However, avoid applying acephate (Orthene) on American elms as this may cause plant injury. If elm leaf beetle populations are minimal, then insecticide applications may not be warranted. Always read the insecticide label prior to making any applications.