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Extension Entomology

Category: Sorghum

Sorghum Update – ‘Headworms’, Beneficials, and Aphids

–By Dr. Jeff Whitworth and Dr. Holly Schwarting

Sorghum continues to get the attention of many pests and beneficials.  Chinch bug populations are not diminishing even though they are not as noticeable because most are feeding around the base of the plants and behind leaf sheaths on the stalks.  Much late planted, or at least slower developing, sorghum is still vulnerable to these chinch bugs.  Bugs may also move up to the heads as they emerge from the whorl to feed on the forming kernels that provide a succulent source of nutrients.

‘Sorghum headworms’, mostly corn earworms but also a few fall armyworms, are infesting all sorghum fields (not yet in the soft dough stage) that we monitored throughout north central Kansas.  Most fields have close to, or are exceeding, 100% infestation levels (1 or more larvae/head).  These larvae are present in all different sizes, or developmental stages, from 1st to 4th instars.  Thus, they will be feeding on these kernels for at least another 7 – 10 days.

Remember, between flowering and soft dough, these larvae will cause 5% yield loss/ worm/ head.  Very few beneficials are available to help control headworm populations.  However, there are huge populations of beneficials currently present to help control any aphid pests that are, or might be present in the near future.

 

 

Corn leaf aphid populations were common on earlier planted sorghum, and still are on later planted sorghum that is just reaching the whorl stage.  These corn leaf aphids have really helped fuel the beneficial populations.  Fields that have headed out are swarming with lady beetle adults and larvae, syrphid or hover flies, green lacewings, and parasitic wasps.

 

 

 

Sugarcane aphid (SCA) populations are becoming scattered around north central KS, slowly so far, and are really attracting the attention of all these beneficials, which will hopefully help control colony growth.

For management considerations and recommendations for these, and other sorghum pests, please refer to the 2018 Sorghum Insect Management Guide:   https://www.bookstore.ksre.ksu.edu/pubs/mf742.pdf

 

 

Sorghum Update – ‘Ragworms’, ‘Headworms’, and Aphids

–by Dr. Jeff Whitworth and Dr. Holly Davis

Late planted sorghum is still causing considerable concern throughout north central Kansas as the leaves grow out of the whorl and are significantly ‘chewed up’ looking.  These ‘ragworms’, primarily corn earworms and fall armyworms but also a few cattail caterpillars, are still active in younger plants.

 

As these plants reach reproductive stages, i.e. flowering, there will be a high probability of having ‘headworms’ (corn earworms and fall armyworms) infesting the kernels.  Sorghum heads are the most vulnerable between flowering and soft dough.  There are currently significant infestations of these headworms throughout north central Kansas with worms in various stages of development.  Headworms cause approximately 5% loss per worm, per head.

 

There are large numbers of corn leaf aphids, greenbugs, and even a few yellow sugarcane aphids around north central Kansas.  The first report of a sugarcane aphid colony from Saline Co. was made on 16 August. These aphids are attracting, and providing food for, large numbers of beneficials which seem to be keeping aphids relatively well controlled.  Insecticide applications have not been needed for aphids. More information on sugarcane aphids in Kansas can be found at My Fields: https://www.myfields.info/pests/sugarcane-aphid

 

For more information regarding sorghum insect pest management please refer to the KSU 2018 Sorghum Insect Management Guide: https://www.bookstore.ksre.ksu.edu/pubs/mf742.pdf

Sorghum Update – Chinch bugs, Headworms, and Corn Leaf Aphids

–by Dr. Jeff Whitworth and Dr. Holly Davis

 

Chinch bug populations continue to increase dramatically throughout north central Kansas.  Adults are still active, mating and ovipositing in both the developing heads and around the base of plants.  There are also large numbers of nymphs, mainly feeding in and around the base of plants, but some are on the developing kernels.  The significant populations of chinch bugs, along with continued hot and dry conditions, are causing some plants to lodge as the stalks dry down prematurely.

 

‘Headworms’, both fall armyworms and corn earworms, are also very common in all the fields we sampled that were in the flowering stages.  On 6 August, there were all different sizes of larvae detected in heads.  Many fields throughout north central Kansas are just starting to reach the reproductive stages, so these ‘headworms’ will continue to be problematic in any field that is in the flowering to soft dough stage.  Past research has indicted that ‘headworms’ may cause approximately 5% loss/worm/head.  It is important to sample in a timely manner to detect these pests while they are still small, before most of the feeding damage has been done.

 

Corn leaf aphids (CLA) continue to cause considerable concern throughout north central Kansas as these populations are still very widespread and become more apparent as the heads start to extend out of the whorl.  However, there are many beneficials present as well.  CLA should have little to no negative impact on plant development or yield other than potentially a few individual plants.

 

For more information relative to sorghum insect management, please see the 2018 Sorghum Insect Management Guide: https://www.bookstore.ksre.ksu.edu/pubs/mf742.pdf

 

 

 

 

Sorghum – Worms and Aphids

–by Dr. Jeff Whitworth and Dr. Holly Davis

 

‘Ragworms’, mostly fall armyworms but a few corn earworms (sorghum headworms) as well, continue to cause considerable concern due to the very ragged looking leaves their feeding produces.  These worms are present every year, to a greater or lesser extent, but this year does seem to be a good year for them.  However, this whorl-stage feeding activity really has little to very little negative impact upon the plants, nor does it reduce yield.  Most of the plants we examined in north central Kansas had feeding damage only – no worms, or a mature larva which had completed most of its feeding.  Therefore, insecticide application will be a waste of time, money, and will kill any beneficials which may be present.

 

 

As sorghum starts to reach reproductive stages, the developing kernels will be vulnerable to attack by the next generation of fall armyworms and corn earworms (sorghum headworms).  Between flowering and soft dough these larvae can cause about 5% loss/worm/head.  Sampling needs to be conducted carefully and in a timely manner during this window.

 

Corn leaf aphids continue to be common in sorghum whorls and are often tended by ants for their honeydew.  Beneficials are still plentiful and corn leaf aphid populations do not seem to be increasing.

For more information relative to sorghum insect management, please see the 2018 Sorghum Insect Management Guide: https://www.bookstore.ksre.ksu.edu/pubs/mf742.pdf

 

Sorghum Update

–by Jeff Whitworth, Holly Davis and J.R.Ewing

 

Chinch bugs continue to feed and develop all around north central Kansas.  However, growing conditions have improved significantly and thus the plants are much better able to tolerate this feeding.

 

As sorghum reaches the whorl stage corn leaf aphids are becoming more common.  These aphids may cause some concern as their honeydew production will occasionally be so thick and sticky as to retard the heads extending up from the whorl.  This is not typically a field-wide problem, just a few places or plants in a field and these aphids are a good source of nutrition for beneficials.

Photo by JR Ewing

In addition, as sorghum leaves grow out of the whorl stage, they are showing signs of feeding.  Fall armyworms have been feeding as small larvae within the whorl and as plants grow out and the leaves unfurl, these leaves have a very ragged appearance.  Many of these ‘ragworms’ have finished feeding and are now pupating in the soil.  Thus, spraying is not necessary as the damage is done.  Even if the worms are still in the whorl, they will not be contacted by the spray.  This whorl-stage leaf feeding doesn’t negatively impact the plant, or yield.  There will probably be a least one more generation of fall armyworms and these may be more problematic if they start feeding in the head between flowering and soft dough stages.  Feeding on these developing kernels is generally considered to cost 5% loss/worm/head.

 

 

 

 

For more information regarding sorghum insect pest management please refer to the KSU 2018 Sorghum Insect Management Guide: https://www.bookstore.ksre.ksu.edu/pubs/mf742.pdf

 

Chinch Bugs and Ragworms in Sorghum

–by Dr. Jeff Whitworth and Dr. Holly Davis

Chinch bugs continue to develop and increase in numbers throughout north central Kansas.  However, recent rains have significantly improved growing conditions.  Thus, sorghum seems to be tolerating these chinch bug populations well.  However, some fields and field borders have been treated for chinch bugs.

Fall armyworm larvae have been feeding in sorghum whorls and this leaf feeding is starting to unfurl from the whorl and thus become highly visible.  That is where the name “ragworms” comes from as they do cause ragged looking leaves, although this foliar feeding does not impact yield.

 

For more information, please see the 2018 Sorghum Insect Management Guide: https://www.bookstore.ksre.ksu.edu/pubs/mf742.pdf

 

Chinch Bugs in Sorghum

–by Dr. Jeff Whitworth and Dr. Holly Davis

Chinch bug adults continue to mate and deposit eggs, especially around the base of young sorghum plants.  As these eggs hatch, nymphs are increasing in both numbers and size and thus are removing more and more of the moisture from the plant.

 

 

This trend will probably continue from now until September and thus cause serious stress to plants, especially if environmental moisture is limited.   If treatment is warranted, it is important to use directed sprays and adequate carrier to reach the base of plants where chinch bugs are actively feeding.  This will also avoid non-target organisms as much as possible. For more information on chinch bugs, management decisions, and/or insecticide recommendations, please see:

Chinch Bugs MF3107:  https://www.bookstore.ksre.ksu.edu/pubs/mf3107.pdf

2018 Sorghum Insect Management Guide: https://www.bookstore.ksre.ksu.edu/pubs/mf742.pdf

Corn and Sorghum Update

— by Dr. Jeff Whitworth and Dr. Holly Davis

Chinch bug populations continue to increase at a very disconcerting rate.  Most corn throughout north central Kansas is far enough along in its development to tolerate large numbers of chinch bugs.  Smaller sorghum can still be seriously stressed by growing populations of chinch bugs, especially as the hot and dry conditions return.  For more information of chinch bug management in sorghum, please see the KSU 2018 Sorghum Insect Management Guide: https://www.bookstore.ksre.ksu.edu/pubs/mf742.pdf

 

One relatively mature fall armyworm larva was also detected.  Thus, in approximately 2-3 weeks there will be a new generation of fall armyworm larva ready to start feeding, most likely, on sorghum.

 

Chinch Bugs

— by Dr. Jeff Whitworth and Dr. Holly Davis

 

All life stages of chinch bugs seem to be extremely active at the present time in both corn and sorghum.  Nymphs and adults started migrating out of wheat fields at least two weeks ago, moving into any adjacent corn or sorghum fields.  Those smaller reddish nymphs have grown considerably since then, and are now either late instar nymphs or adults.

 

Many of these recently matured adults are now mating and have even started egg deposition.  These eggs are, and will continue to be, hatching which means more bugs and thus more feeding on these plants.  Fortunately, most corn is large enough to withstand considerable feeding by chinch bugs. Plus, the recent rains greatly enhanced growing conditions, which increases the plant’s tolerance for chinch bug feeding.  However, most sorghum is much less developed and won’t be able to tolerate as many chinch bugs as the larger corn plants.  Treating plants much after the V-6/V-7 growth stages is not as effective as treating smaller plants.  Like corn, good growing conditions significantly help plants withstand chinch bug feeding.  However, if dry, droughty conditions return, chinch bug feeding can significantly weaken stalks and cause lodging later in the season.  For more information on chinch bugs, management decisions, and/ or insecticide recommendations, please see:

Chinch Bugs MF3107:  https://www.bookstore.ksre.ksu.edu/pubs/mf3107.pdf

2018 Sorghum Insect Management Guide: https://www.bookstore.ksre.ksu.edu/pubs/mf742.pdf

 

Chinch Bugs in Corn and Sorghum

–by Dr. Jeff Whitworth and Dr. Holly Davis

As the wheat senesces, it continues to be less and less succulent.  Thus, chinch bugs have been, and will continue to, migrate to find a suitable food source.  They will utilize any actively growing grasses in the vicinity.  The small nymphs cannot fly and thus must crawl to the nearest food source.  They are pretty fragile and therefore can’t go very far without finding a food source before they perish.

 

Most corn planted adjacent to wheat is already large enough to withstand chinch bug feeding.  However, seedling sorghum, especially if it is already stressed by the heat and dry conditions, may be overwhelmed and thus killed by this additional stressor.  Sampling wheat for chinch bugs now, as it is still senescing, should give an idea about potential chinch bug numbers migrating from wheat.  If several samples of different 1 ft2 areas detect an average of 1 chinch bug, some chinch bug management technique should be utilized.  For more information on chinch bug biology and management recommendations please see MF3107, Chinch Bugs: https://www.bookstore.ksre.ksu.edu/pubs/mf3107.pdf and/or the 2018 Sorghum Insect Management Guide: https://www.bookstore.ksre.ksu.edu/pubs/mf742.pdf

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