By Jeff Whitworth
Alfalfa
Alfalfa weevils are still active throughout north central Kansas. Even fields that had insecticide treatments which were well timed and effective have been having more larval feeding. These fields need to be treated again as soon as possible as these larvae are still capable of considerable defoliation for the next week or so, especially as we continue to see the fluctuating temperatures.
Remember, the insecticides for alfalfa weevil control are contact insecticides so coverage is very important. Also, please pay attention to the pre-harvest interval (PHI) for whatever product you use as many fields are getting close to the first cutting.
Figure 1. Alfalfa weevil.
Wheat aphids
Last week wheat aphid populations were active and had increased considerably from the previous couple of weeks in north central Kansas. Populations of bird cherry-oat aphids, English grain aphids, and greenbugs were all reproducing and still migrating in. This week however, in fields we sampled in north central Kansas, the aphid populations had decreased drastically and the beneficials, especially lady beetles, had increased greatly.
Figure 2. Lady beetle larva (left) and adult stages.
New pest in wheat
Sipha maydis is a new invasive aphid that was recently found in Colorado and could potentially be found in Kansas.
"Wheat and barley are this aphid’s preferred hosts, although it can feed on many weedy grasses, corn and sorghum. It is a particular concern in wheat and barley since it can kill leaves and transmit barley yellow dwarf virus."
Read more about this potential threat here:
http://wci.colostate.edu/shtml/Sipha.maydis.shtml
https://smallgrains.ces.ncsu.edu/2016/04/new-invasive-aphid-of-wheat-now-in-south-carolina/
Figure 3. Sipha maydis aphid.