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Extension Entomology

Tag: lady beetles

Sorghum Update – (chinch bugs, corn leaf aphids, corn earworms)

–by Dr. Jeff Whitworth and Dr. Holly Schwarting

 

Chinch bugs continue to be very active in both corn and sorghum throughout north central Kansas.  Both nymphs and adults are present.

 

Many adults are still mating, which indicates that there are more eggs, nymphs, and adults yet to come.  One consolation relative to the numerous chinch bugs in sorghum fields is that the four spotted egg eater, Collops quadrimaculatas, seems to be plentiful as well.  They have been collected in samples while sweep sampling alfalfa and are also present in sorghum fields.  These little beetles are predacious on insect eggs, and it has even been reported that they feed on chinch bug eggs.  Not sure they will be able to provide a great deal of control on chinch bug populations but it sure can’t hurt!

 

Corn leaf aphids are also very plentiful throughout north central Kansas.  These aphids usually feed on developing corn tassels and silks, but probably are more commonly associated with, or at least noticed in, whorl stage sorghum.  These aphid colonies sometimes produce enough honeydew, and it is so sticky, that often the sorghum head gets bound up in the whorl and therefore doesn’t extend up properly.  These colonies are not usually dense enough on a field-wide basis to justify and insecticide application.  These plentiful aphids are also serving as a food source for many predators, i.e. lady beetles, green lacewings, etc.

 

 

Corn earworms are still plentiful in corn but as they mature, pupate, and become adults they most likely will migrate to sorghum to feed on developing kernels (between flowering and soft dough), and soybeans where they will feed on developing beans within the pods.

For more information on sorghum and soybean pest management, please consult the KSU Sorghum Insect Management guide: https://www.bookstore.ksre.ksu.edu/pubs/mf742.pdf

And the KSU Soybean Insect Management Guide: https://www.bookstore.ksre.ksu.edu/pubs/MF743.pdf

 

 

Wheat Update – Aphids

–by Dr. Jeff Whitworth and Dr. Holly Schwarting

Wheat aphids have really started showing up in wheat fields throughout north central Kansas.  English grain and bird cherry-oat aphids are the two most commonly observed so far.

These aphids usually do not build up in sufficient populations to stress wheat or impact yield, especially when growing conditions are good, which they have been for the last couple of weeks.  These aphids can vector barley yellow dwarf virus, however at this time of year this should not impact yield.  These aphids are providing a plentiful food source for lady beetles, and all wheat fields sampled in the last seven days contained significant numbers of lady beetles.

Therefore, it is prudent not to spray for these wheat aphids unless there are 20+/tiller on a field-wide basis.  Especially do not include an insecticide in a mixture with a fungicide “just in case”.

Alfalfa Update

–by Dr. Jeff Whitworth, Dr. Holly Schwarting & JR Ewing

Alfalfa weevil larvae have been hatching throughout north central and south central Kansas for the last couple of weeks.  However, as of 9 March, there doesn’t seem to be much feeding or development yet (Photo1).  There are also a few of these tiny larvae that are dead (Photo2).  Because these larvae are so small and vulnerable it is difficult to determine the cause of death.  At least some of the mortality could be related to weather fluctuations that have reached mid 70’s for several days but also dropping into the mid to low 20’s some nights.

 

 

 

Most of these larvae are so small that they are well enclosed within the plant terminals to the point that they cannot be dislodged by shaking the stems into a bucket, as the most accurate sampling method specifies.  This can definitely cause you to underestimate larval populations.  Probably the easiest solution is to hold off sampling until the middle of next week, if the weather turns cooler as predicted.  There are a few more mature larvae present, along with adult weevils (Photos 3, 4). Adults will probably continue depositing eggs for a few more weeks, thus extending the period of larval hatching.

 

 

There are also a few pea aphids present.  Populations do not seem to be increasing now, and there are lady beetles and parasitoid wasps actively attacking these aphids.  Also, reports of cowpea aphids in south central Kansas bear watching.  These aphids are usually more numerous in warmer summer months.  They can add stress to plants by feeding, but they also produce copious quantities of honeydew which can become covered with sooty mold.  This may further stress alfalfa by interfering with photosynthesis, especially with small plants coming out of winter dormancy and experiencing dry conditions and fluctuating temperatures.

 

 

 

 

Corn Update

–by Dr. Jeff Whitworth and Dr. Holly Schwarting

Lady beetles are unusually common in corn fields right now.  Most corn plants in north central Kanas are from V2-V6.  Checking corn rootworm plots revealed western corn rootworm larvae of various sizes and thus they are starting to feed enough to cause a little root damage.

CRW larvae

CRW larvae_sizes

CRW larva on root

CRW root damage

Seems like, despite the recent cooler, wetter conditions, the rootworm development is about where it usually is at this time.  Most western corn rootworms have completed the larval stage by the 1st of July, thus root damage will be completed later this month as the larvae begin to pupate in south central and north central Kansas.

 

Alfalfa Update

–by Dr. Jeff Whitworth and Dr. Holly Schwarting

Potato leafhoppers continue to inhabit every alfalfa field sampled in north central Kansas.  Populations are still mostly composed of adults but a few nymphs are emerging.  These potato leafhoppers have few natural enemies and thus populations will just continue to increase.  There are still relatively plentiful numbers of lady beetles and green lacewings in most alfalfa fields, and while they probably won’t help with potato leafhoppers, they should continue to help control any developing aphid populations.

Alfalfa Update

–Dr. Jeff Whitworth and Dr. Holly Schwarting

Much of the alfalfa in northcentral Kansas that could be swathed has been in the last week.  The cool damp weather has kept the adult alfalfa weevils in the fields.  They are congregated under windrows in the cut fields where they do a little feeding on the stems, resulting in characteristic spots of epidermis removal, called ‘barking’.  As these windrows are picked up there will be the characteristic striping across the fields where the windrows held back the regrowth underneath, plus provided the weevils with a protected site to continue feeding.  Fields not yet swathed also have significant populations of adults but this should not impact the foliage prior to cutting.

AW adult and barking

Windrows

Pea aphids are also present in both cut and uncut fields, but lady beetles and green lacewings are also, so would not expect pea aphid populations to have a negative impact on alfalfa.

Pea aphids adult and nymph

greenlacewing

pinkspotted lady beetle

Sevenspotted lady beetle

Potato leafhopper adults are already present in all alfalfa fields we checked over the past week.  This is earlier than usual for these pests as they typically don’t migrate into the state for another month, between the 2nd and 3rd cutting.  Some of these populations already exceed the treatment threshold with just adults, so hatching nymphs will just increase the populations further.  These potato leafhopper populations need to be monitored throughout the rest of the growing season.

PLH adult and nymph

Wheat Update

By — Dr. Jeff Whitworth, Dr. Holly Schwarting

Wheat fields sampled in NC Kansas over the last week have diminishing populations of aphids.  Many fields had to be sampled relatively vigorously to find any aphids.  However, lady beetles are still quite plentiful which should bode well for not allowing the aphid populations to rebound.

Scattered white heads are starting to be easily distinguished in the green wheat.  If the stem pulls out easily, with some apparent feeding in the stem, this is from the wheat stem maggot.

wheat stem maggot

The number of infested stems in always negligible relative to yield loss but often causes concern because of the easily noticed white heads.

Wheat Update

–Dr. Jeff Whitworth and Dr. Holly Schwarting

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.

Lady beetle larva 2

lady beetle adult

Last week these English grain aphids were inadvertently identified as greenbugs.

English grain aphids

Wheat Update

–by Dr. Jeff Whitworth and Dr. Holly Schwarting

Received a report from north central Kansas about a small wheat field infested with ca. 20 aphids/tiller, but the aphids weren’t identified.  All wheat fields we visited in the last week had aphids, including bird cherry-oat, English grain, and/or greenbugs.  However, we were only finding about 1/10 plants or less and beneficials (lady beetles, lacewings, and parasitic wasp activity) were present in all of these fields.  Most wheat averaged Feekes 6-8 and no other pests really have been noted.

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