–by Dr. Jeff Whitworth, Dr. Holly Schwarting and J.R. Ewing
Most sorghum is at least flowering with much into milk, soft dough and even black layer. Thus, headworm susceptible stages are mostly past as flowering to soft dough is the time frame for headworm vulnerability. Once these advanced stages have been reached the head moth will start ovipositing in soybeans. Soybeans then need to be continuously monitored, as long as there are new pods, for podworm damage and/or smaller podworms.
— by Dr. Jeff Whitworth, Dr. Holly Schwarting and J.R. Ewing
Much sorghum throughout north central Kansas is at least in the soft dough stage and thus has passed through the most susceptible stages for sorghum headworm infestations. However, any sorghum yet to head out will still be susceptible to these headworms as there will still be at least one more generation.
All four aphids species, corn leaf, greenbugs, sugarcane, and yellow sugarcane, are still in every sorghum field we sampled throughout north central Kansas. All populations seem to be increasing but there are relatively healthy populations of beneficials present as well.
–by Dr. Jeff Whitworth and Dr. Holly Schwarting
Double cropped sorghum may still have some ragworm feeding during the whorl stage (see photo). In addition, there will probably be at least one more generation of headworms and thus later planted sorghum needs to be monitored for headworms between flowering and soft dough when it is vulnerable. Also, continue monitoring for aphids as there still seems to be a pretty good mixture of greenbugs, corn leaf, yellow sugarcane, and sugarcane aphids. Some of the fields treated for headworms have reduced numbers of beneficials so they may not be there in sufficient numbers to help control these aphids. However, some of the fields sampled this week that were sprayed for headworms at least 2 weeks ago had pretty good populations of beneficials already building back up.
— by Dr. Jeff Whitworth and Dr. Holly Schwarting
The situation seems about the same throughout north central Kansas with regard to insect pests. Still finding mixed populations of aphids (greenbugs, corn leaf, yellow sugarcane, and sugarcane) but beneficial insect populations (mainly green lacewings, lady beetles, parasitic wasps, and occasionally syrphid fly larvae) still remain plentiful. Headworms are also plentiful in just about every field that is not yet at soft dough. Remember, expect 5% loss/worm/head between flowering and soft dough. Chinch bugs, both adults and nymphs, are also plentiful at the base of most plants but can also be found feeding on young developing berries in the heads.
–by Dr. Jeff Whitworth and Dr. Holly Schwarting
Sorghum is in various stages of development around NC Kansas. The late planted, which seems to be just in the whorl stage- to soft dough, or even farther along. Corn earworms (often called sorghum headworms/soybean podworms etc., depending upon the crop infested) are causing significant infestations and therefore concern because of the highly visible whorl feeding and subsequent “ragged”-looking leaves as they expand from the whorl. This feeding probably will have no effect on yield, and by the time the damage is noticed the worms are mostly finished feeding anyway. Therefore, treatment is rarely justified. Feeding on the kernels however which is the marketable product is a different story. Sampling for head-feeding worms is really relatively easy. Just take a small white bucket, bend the head over into the bucket and vigorously shake it against the sides of the bucket which dislodges the larvae. Then count the worms and divide into the number of heads sampled.
Rule of thumb: kernel-feeding larvae cause 5% loss/worm/head. Sorghum heads are most vulnerable from flowering to soft dough. These larvae are relatively susceptible to insecticides so efficacy is usually pretty good. However, these insecticides will reduce beneficial insect populations which can help later if any aphid populations develop.
–by Jeff Whitworth and Holly Schwarting
Double cropped sorghum in north central KS seems to have a significant infestation of “ragworms”. The larvae are a combination of fall armyworms and corn earworms and are of various sizes.
Leaf feeding in the whorl by either species is highly visible but should not have a significant effect on the plants or yield.
Also, most fields in north central KS are infested with aphids. Corn leaf aphids can produce a great deal of honeydew but mostly in the whorls. This honeydew may retard head extension but usually does not affect many plants over a large area.
Also found greenbugs and yellow sugarcane aphids. None of the invasive sugarcane aphids were detected in north central Kansas. However, many beneficials are, and will continue to be, present in sorghum fields as evidenced by the numerous green lacewing eggs and lady beetle eggs.
–by Dr. Jeff Whitworth and Dr. Holly Schwarting
Chinch bugs are really common in sorghum fields throughout north central Kansas. Their feeding will weaken stalks if dry conditions are prevalent.
Green lacewing eggs were present, indicating the presence of future beneficials to help with control of potential future aphid populations.
—by the KSRE Field Crop Extension Entomology Team
Our team has been actively scouting sorghum fields the past few weeks for any infestations of sugarcane aphid, which is a relatively new pest affecting Kansas sorghum. We received a report from Jill Zimmerman (KSRE Extension Agent, Cowley County, KS) on July 18, 2016 of a potential infestation in a commercial field near the Sumner/Cowley County border; the report was confirmed in two fields this morning by a state specialist. Based on the size of the aphid populations observed, which included several plants that were producing winged aphids (i.e., alates), this field was first infested approximately 3-4 weeks ago. A significant number of natural enemies were observed feeding on aphids, which can help to slow aphid growth.
Sugarcane aphid populations have been slow to build in Texas and Oklahoma this growing season. This record is approximately 10 days sooner than when we found aphids in 2015. Aphid densities are well below threshold, but those with sorghum fields are encouraged to scout fields now.
Report all new infestations by contacting your county extension agent. For myFields.info users, submit reports using the Pest Sampler module (https://www.myfields.info/pest_sampler). To receive pest alerts about sugarcane aphid, create an account (https://www.myfields.info/user/register) and include your state and county information to receive notifications specific to your area.
For more information on sampling procedures, action thresholds, or effective insecticides, visit https://www.myfields.info/sca.
Scout early, scout often, and know before you spray.
–by Dr. Jeff Whitworth and Dr. Holly Schwarting
As wheat senesces, or matures, the chinch bugs are migrating to adjacent corn and/or sorghum fields. V6+ stage corn can withstand considerable chinch bug feeding but younger plants may be stressed, especially dryland corn.
Seedling sorghum adjacent to wheat will be somewhat protected by insecticide seed treatments if chinch bug populations aren’t overwhelming as they migrate from the wheat, but only for about 28 days, maximum. Waiting about 2 weeks after wheat harvest to plant sorghum will mitigate chinch bug nymph infestation problems. For more information on chinch bug biology and management, please visit: https://www.bookstore.ksre.ksu.edu/pubs/MF3107.pdf
—by the KSRE Field Crop Extension Entomology Team
This week, Kansas received a section 18 approval for the use of Transform (sulfoxaflor) against sugarcane aphid for 2016, which will give sorghum growers two effective materials to manage aphid infestations. Note, there are differences in price between these two products, which should be factored into any treatment decisions, especially when multiple applications may be necessary.
Recent reports have sorghum receiving insecticide treatments for relatively light populations of sugarcane in south Texas, but the aphid is beginning to slowly move north, so the potential exists for much earlier infestation of Kansas sorghum this year. There are also confirmed reports that the aphid overwintered on Johnsongrass rhizomes just north of Lubbock, TX. This is about about 80 miles further north than in 2015. Reports from Texas indicate some of the cultivars rated as resistant seem to be holding up well, probably with the assistance of good natural enemy populations.
The Sorghum Checkoff has a list of ‘tolerant’ (= resistant) hybrids, but it does not indicate any regional adaptations for the hybrids. We have not yet ranked Kansas-adapted hybrids for resistance to sugarcane aphid, but efforts are underway to evaluate hybrids this summer. We strongly recommend that growers and extension agents contact their local entomology specialists for advice, as management recommendations will vary regionally.
Scout early, scout often, and know before you spray!
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