Insect Snapshots from the Field

Just a quick overview of some insect issues presenting themselves recently.

True Armyworm

Lots of reports of armyworm being found in wheat and corn. With reports of wheat harvest starting/getting close, reports of armyworm in corn seem to be taking over. I’ve seen a range of larvae stages from 2nd-4th instars. Injury to the whorl and ragged leaf margins is usually noticed around field margins first.  Armyworm larvae are night feeders and will usually spend the day in soil cracks, under dirt clods, or in the whorl. Control may be justified when 25% of the plants are being damaged. Things to consider: hot spots in the field and also size of the larvae. Larvae greater than 1 ¼” will have completed most of their feeding.

IMG_5699a

Armyworm larvae (Photo courtesy of Stephanie Porter)

 

Corn Rootworm

Reports of lightning bugs in the central part of the state along with degree day accumulations suggest rootworm hatch is underway.

CRW June 9

Corn Earworm

We picked up our first corn earworm moth last week. To date, we’ve trapped a total of 10 moths in Champaign. We expect those numbers to slowly pick up over the next couple of weeks.

 

Corn earworm moth (Photo courtesy of University of Maine)

Corn earworm moth
(Photo courtesy of University of Maine)

Fall Armyworm

A few fall armyworm moths have been picked up in our traps here in Champaign. We expect those numbers to increase in the next few weeks as well.

 

European Corn Borer

We have yet to pick up any moths in our trap in Champaign. We also have been sampling action sites (dense stands of tall grasses along roadsides ditches or waterways) by making 100 sweeps with a standard insect sweep net. To date, no moths have been recovered in any of the samples statewide.

 

European corn borer  (Photo courtesy of Marlin Rice)

European corn borer
(Photo courtesy of Marlin Rice)

Stalk Borer

A few reports of stalk borer in corn. These younger larvae did not have the distinct purple “saddle” that we often use to ID these insects. Young larvae will be light brown with a narrow white stripe running down its back from head to tail. There will be a similar white stripe on each side of the body that is interrupted by a purplish-brown band that circles the front third of the body. As larvae get bigger they move from the grass hosts they are quickly outgrowing to larger hosts, such as corn.

Stalk borers will attack corn in 2 different ways:

  • Burrow into stalks at ground level and chew upwards through the center of the plant. Wilted leaves will be the first obvious symptom with this injury along with the potential for some plants to buckle at ground level.
  • Some larvae may crawl to the top and feed down through the rolled leaves into the stalks. Ragged leaves, along with frass on the leaves may allude to this type of feeding which may also cause wilting of the top half of the plant.

 

Stink Bugs

I’ve also gotten reports of stink bug injury in southeast Illinois. Stink bug can cause three different types of injury – tillering, stunted plants, and may even kill small seedlings. Signs of stink bug injury will include oval holes where they have inserted their needlelike mouthparts.  The stink bug sticks the base of the plant or their leaves with their small needle-like mouth. When they do this, they are causing these plants to die as a small seedling, produce stunted plants- such as misshapen ears instead of tassels- or suckering- the production of tillers form the base of damaged plants. Most often, you see this pest in fields that are no-tillage, near wooded areas, or conventional fields as well as along field edges.

 

Slugs

Slug injury has been reported across much of southeast Illinois as well and as far north at Livingston county in both corn and soybeans. Slugs are generally a problem in no-till fields; especially if they are late-planted. Slugs take advantage of the smaller plants and as the plants grow, they quickly outpace the slugs. Feeding generally occurs on the lower parts of the plants. Symptoms may resemble that of the corn flea beetle (narrow, irregular tracks or scarring), but the presence of a slime trail will be indicative of the presence of slugs.

 

Black Cutworm

Once again, we received sustained flights across much of Illinois. Several counties saw repeated significant flights. This map gives you a good indication of projected cutting dates, but several counties like Champaign and Lee saw 4-5 significant flights, so the bottom line is that some of this late planted corn will still be susceptible for BCW injury. Speaking of BCW injury, I have had a few reports of feeding around the state. No indication of anyone area being more severe than another. There is still a lot of small corn across the state that could be susceptible.

BCW May 26

Centipedes/Millipedes

I’ve also fielded a few call on centipedes and millipedes last week, though with the warm, dry weather, I don’t suspect to hear much more about these.

 

 

Information compiled with the assistance of Kaela Miller, University of Illinois Agriculture Communications.

 


Impressive Moth Flights across Midwest

Impressive moth flights have not only kept the Illinois insect monitoring network cooperators busy, but neighboring states are reporting lots of black cutworm and true armyworm moth activity as well. The current forecast and planting progress has raised questions about the potential for these pests in the coming weeks.

With the assistance of University of Illinois Extension educators, producers and industry volunteers, nearly 60 trap sites have been established across Illinois. Captures of both black cutworm and true armyworm have been common across the state. Several counties have reported significant flights (nine or more moths caught over a 2-day period). In fact, several counties have repeated significant flights.

BCW Apr28

Illinois black cutworm projected potential cutting dates based on degree day accumulations.

 

 

As shared in previous Bulletin articles, more complete information about the biology, life cycle, and management of black cutworms, a fact sheet is available from the Department of Crop Sciences, UIUC. Provided below is a brief overview of some key life cycle and management facts concerning black cutworms.

  • Black cutworm moths are strong migratory insects with northward flights commonly observed from Gulf States into the Midwest from March through May.
  • Moths are attracted to fields heavily infested with weeds such as chickweed, shepherd’s purse, peppergrass, and yellow rocket.
  • Late tillage and planting tends to increase the susceptibility of fields to black cutworm infestations.
  • Cutting of corn plants begins when larvae reach the 4th instar — with a single cutworm cutting an average of 3 to 4 plants during its larval development.
  • Cutting tends to occur most often during nights or on dark overcast days.
  • Fields at greatest risk to cutting and economic damage are in the 1-to-4 leaf stage of plant development.
  • An early warning sign of potential economic damage includes small pinhole feeding injury in leaves (caused by the first 3 instars).
  • Producers are encouraged to look for early signs of leaf feeding as a potential indicator of cutting, rather than waiting for cutting to take place.
  • Don’t assume that all Bt hybrids offer the same level of cutworm protection. Plants in the 1- to 4-leaf stage are most susceptible to cutting.
  • Cutting of plants earlier than these projected cutting dates is possible — localized intense flights may have occurred and were not picked up by our volunteers.
  • A nominal threshold of 3% cutting of plants has traditionally been used as a point at which growers should consider a rescue treatment.
  • Not all Bt hybrids offer adequate protection against black cutworm damage. Growers should consult the Handy Bt trait table prepared by Dr. Chris DiFonzo at Michigan State University to determine the level of protection provided by their chosen Bt hybrid.

 

Switching our focus to true armyworm, this insect has also been very active this spring. Illinois has seen steady flights across the state with numbers slowing down only within the last week. Christian Krupke, Purdue, summarized the potential threat very well in a recent article. Remember, true armyworms prefer to lay eggs in grass covered areas. Wheat as well as corn planted into cover crops will be a prime target. The Handy Bt trait table above is also a great reference for hybrids that may offer some protection, but once again, don’t assume it’s 100% full-proof. With significant infestations, some damage may be observed before the Bt-proteins will suppress the feeding.

The take-home message today? Be vigilant with your fields this spring. The mild winter and warm spring certainly got things rolling. This upcoming cool and wet period may slow things down, but both black cutworm and true armyworm moths have been abundant up until this point (and they pick back up again). Please feel free to share updates from the field by email (kcook8@illinois.edu) or twitter (https://twitter.com/ILPestSurvey).

 

 

 

 


Black Cutworm Activity Increasing Across Illinois

*Edited April 28 to include significant flights and projected cutting dates for Carroll, Effingham, and Ford counties.

Black cutworms have been observed in traps across the state for the past couple of weeks. Several counties have reported significant moth flights (9 or more moths over a 2-night span). We can use the date of the significant flight to predict potential cutting dates based on degree day predictions.

For more complete information about the biology, life cycle, and management of black cutworms, a fact sheet is available from the Department of Crop Sciences, UIUC. Provided below is a brief overview of some key life cycle and management facts concerning black cutworms.

  • Black cutworm moths are strong migratory insects with northward flights commonly observed from Gulf States into the Midwest from March through May.
  • Moths are attracted to fields heavily infested with weeds such as chickweed, shepherd’s purse, peppergrass, and yellow rocket.
  • Late tillage and planting tends to increase the susceptibility of fields to black cutworm infestations.
  • Cutting of corn plants begins when larvae reach the 4th instar — with a single cutworm cutting an average of 3 to 4 plants during its larval development.
  • Cutting tends to occur most often during nights or on dark overcast days.
  • Fields at greatest risk to cutting and economic damage are in the 1-to-4 leaf stage of plant development.
  • An early warning sign of potential economic damage includes small pinhole feeding injury in leaves (caused by the first 3 instars).
  • Producers are encouraged to look for early signs of leaf feeding as a potential indicator of cutting, rather than waiting for cutting to take place.
  • Don’t assume that all Bt hybrids offer the same level of cutworm protection. Plants in the 1- to 4-leaf stage are most susceptible to cutting.
  • Cutting of plants earlier than these projected cutting dates is possible — localized intense flights may have occurred and were not picked up by our volunteers.
  • A nominal threshold of 3% cutting of plants has traditionally been used as a point at which growers should consider a rescue treatment.
  • Not all Bt hybrids offer adequate protection against black cutworm damage. Growers should consult the Handy Bt trait table prepared by Dr. Chris DiFonzo at Michigan State University to determine the level of protection provided by their chosen Bt hybrid.

Weekly trap counts in their entirety can be found at the link below and are also shared weekly via Twitter (@ILPestSurvey) along with current pest alerts.

March 28- April 4

April 5 – April 11

April 12 – April 18

April 19 – April 25

 

The 2016 Illinois Pest Monitoring Network is part of the Area-wide Pest Monitoring Project that is supported by the National Institute of Food and Agriculture, U.S. Department of Agriculture, under award number 2014-70006-22557 and is made possible through a network of volunteer cooperators.

Kelly Estes, Illinois State Agricultural Survey Coordinator, Illinois Natural History Survey