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Category: Corn

Corn Leafhopper: New Publication

Posted on by Department of Entomology
Corn leaf hopper

The K-State Extension Bookstore releases a new publication on corn leafhopper authored by J.P. Michaud, Extension Entomologist. Identifying corn leafhoppers and understanding their life cycle can help prevent corn stunt disease and protect crop yields. Learn more about this pest in this new publication.

The corn leafhopper, Dalbulus maidis (Hemiptera: Cicadellidae), is native to tropical and subtropical Central and South America. Although it damages corn directly by removal of plant sap, most economic losses are caused by transmission of various plant diseases, including maize bushy stunt phytoplasma, fine streak virus (maize rayado fino virus, or MRFV), and the causal agent of corn stunt, Spiroplasma kunkelii, which may be the most important factor limiting corn production in Central and South America. Recent outbreaks of corn leafhopper in Argentina have resulted in up to 12% of the corn crop being lost to corn stunt, with yield losses estimated at 500 pounds of grain per acre.

To read the full publication, visit the K-State Extension Bookstore.

Fall Armyworm Active Across Kansas

Posted on by kansasbugs

Fall Armyworm, Spodoptera frugiperda, can damage several important Kansas crops as well as pasture, turf and home landscaping and is currently being reported across the state in various crops and pasture scenarios.  The first fall armyworm flight into Kansas occurred during the first week of July in south central parts of the state and trap counts of adult moths continued to increase in those areas through July while moths also started showing up in the central and northeast part of the state in notable numbers.  There were scattered and treatable infestations of caterpillars in these areas during that timeframe. During this first two weeks of August, fall armyworm moths are noticeable statewide. Trap counts of moths are increasing dramatically in south central areas and reports of significant infestations in the central and eastern parts of the state have been reported.

Given these recent trap observations and reports of caterpillar outbreaks, scouting should continue until the first frost of the season for at risk crops and pasture.  It is critical to scout often and treat, if needed, when the caterpillars are less than a half inch long.  Larger caterpillars are harder to control and do the most damage.  Recommended thresholds and products labeled for control of fall armyworm caterpillars (Table 1) can be found below.

 

Fall Armyworm Thresholds

Alfalfa:  1-2 caterpillars per square foot can destroy seedling alfalfa.  10-15 per square foot can destroy 12” tall plants.

Corn:  damage to whorl stage in early summer is typically not a concern and will not impact yield.  Bt corn may prevent ear damage.

Sorghum:  damage to whorl stage in early summer is typically not a concern. 1-2 larvae/head during flowering to soft dough reduces yield 5-10%.

Wheat:  Larval “window-paning” in early planted wheat can be a concern. Very late second generation fall armyworm will be the biggest concern for wheat.  If 25-30% of plants show damage, examine field frequently.  Treat at 2-3 active larvae/ft.

Pasture/Brome: If damage is notable or there is window-paning, treatment may be warranted with 4 to 5 caterpillars per square foot.

You can read more about fall armyworm in turfgrass here.

Chemical Name Trade Name Mode of Action Class Alfalfa Corn Sorghum Wheat Grass Forage/Hay
alpha-cypermethrin Fastac CS 3A yes yes yes yes yes
beta-cyfluthrin Baythroid XL 3A yes yes yes yes yes
bifenthrin numerous products 3A yes yes
biological insecticide Fawligen – yes
carbaryl Sevin 1A yes yes
chlorantraniliprole Vantacore 28 yes yes yes yes
cyfluthrin Tombstone 3A yes yes yes
deltamethrin Delta Gold 3A yes yes
gamma-cyhalothrin Proaxis 3A yes yes yes yes
indoxacarb Steward EC 22A yes
lambda-cyhalothrin+chlorantraniliprole Besiege 3A+28 yes yes yes
lambda-cyhalothrin numerous products 3A yes yes yes yes yes
methomyl Lannate 1A yes yes yes yes*
methoxyfenozide Intrepid 2F 18 yes
permethrin numerous products 3A yes
spinosad Blackhawk 5 yes yes yes yes
zeta-cypermethrin Mustang MAXX 3A yes yes yes yes
zeta-cypermethrin+bifenthrin Hero 3A yes

Table 1. Registered products for the control of fall armyworm in Kansas crops.  For more specific information relative to any insecticide, always refer to the actual label on the product. *for use only in bermudagrass pasture

 

By Anthony Zukoff

 

 

It’s time to scout for insects in cotton and corn fields

Posted on by Department of Entomology

MANHATTAN, Kan. — Kansas cotton fields are entering the critical squaring phase, so Kansas State University agronomist Logan Simon and entomologist Anthony Zukoff say timely scouting will be essential to protect yield potential.

“Overall, Kansas cotton acres are down this year like most of the US cotton belt and the cotton we have is generally behind in development compared to normal,” Simon said. “Although south-central Kansas had severe storm damage that hurt the cotton down there, many were able to hold on pretty good.”

As cotton enters this key reproductive stage, as evidenced by early formation of flower buds, K-State Extension entomologist Anthony Zukoff shared the importance of monitoring for cotton fleahoppers and tarnished plant bugs, also known as lygus bugs.

“These two insects can be very detrimental to overall yield so it’s important to keep an eye out for them now,” Zukoff said.

“They are very excitable, so they can be tricky to scout for. We recommend using a drop cloth or sweep net method to determine if these insects are in the field,” Zukoff said. “Depending on the method, the threshold will be different, so we recommend using our cotton insect management guide to determine if the insect count is over that threshold.”

The cotton flea hopper is about 1/8 of an inch and lime green color, while the lygus bug is about twice the size and a tan color. Zukoff noted that control options are available if populations reach economic thresholds.

“If they do reach that threshold, all is not lost,” he said. “Producers can save their fields if they take action quickly. The important thing is to be proactive rather than reactive; get out there right now and scout.”

“The early and first position squares are the most important fruiting positions on a cotton plant as they will contribute the most to the final yield,” Simon said. “Once the plant matures, those insects will not be as much of a problem for later squares.”

Zukoff and Simon also advised corn growers to be scouting for western bean cutworm.

“The western bean cutworm is a pest of corn, specifically corn ears as they tassel,” Zukoff said.

“Western bean cutworm overwinters in the soil as pupa, and this time of year adult moths will be emerging from those pupae and laying eggs. Those eggs hatch and caterpillars make their way to the tasseling corn fields,” Zukoff said. “Once the pest gets to the field, it will eat developing kernels and cut the silks on its way up, which makes it detrimental to final yields and developing crops.”

For more information, read the K-State agronomy newsletter at www.eupdate.agronomy.ksu.edu.

By Madeline Drake, K-State Research and Extension News Service

Western Bean Cutworms Active in Western Kansas

Posted on by Department of Entomology

Western bean cutworms (Figure 1) are primarily a pest of corn in Kansas and activity is generally isolated to the western part of the state.  This pest overwinters as prepupa in the soil in earthen cells about 3 to 9 inches deep.

Figure 1. Adult western bean cutworm moth (Adam Sisson, Iowa State Univ., Bugwood.org).

The moths begin emerging in southwestern Kansas in mid-June and in early July for northwestern Kansas, usually around the time that corn is close to tasseling.  White eggs are laid in masses on the upper surface of leaves and gradually turn purple as they get closer to hatching (Figure 2).  After about a week, the eggs hatch and caterpillars (Figure 3) enter corn ears to feed on the developing kernels.  Mature caterpillars exit the corn ears and enter the soil to overwinter.  There is a single generation of this pest each year.  Pheromone trap counts of western bean cutworm moths are not a metric for determining losses in corn, but can be utilized to help detect when moths start to emerge from the soil in order to properly time scouting efforts.  Early detection of egg masses is important, as any chemical control, if warranted, needs to happen before larvae enter corn ears.  When the field is almost fully tasseled, an average of 6-8 % of plants with eggs or small caterpillars justifies control measures. Control will be reduced if applications are delayed until all silks have emerged or if larvae have already entered the ear tips.

Figure 2. Maturing western bean cutworm eggs. Photo credit- Marlin Rice.
Figure 2. Maturing western bean cutworm eggs (Marlin Rice).
Figure 3. Western bean cutworm caterpillar. Photo credit- KSU Entomology
Figure 3. Western bean cutworm caterpillar (KSU Entomology).

Currently, trap counts indicate that the western bean cutworm flight is light in southwest Kansas and began slightly later than in 2024. In northwest Kansas, trap counts of adult moths have been increasing over the last several weeks. The moth flight should conclude in early August. Until then, any at risk fields should continue to be scouted.

Control options and additional information on western bean cutworm can be found in the 2025 Corn Insect Pest Management Guide.

Fall Armyworm Season Approaches

Posted on by Department of Entomology

Fall Armyworm, Spodoptera frugiperda, can damage several important Kansas crops as well as pasture, turf and home landscaping.  This insect does not overwinter in Kansas.  Rather, it is native to the tropical regions of the western hemisphere and is active year-round along the gulf coast and southern Florida, migrating in from these locations each year.  Two full generations are possible in Kansas with defoliation and grain damage being the biggest concerns.  Each generation’s abundance and distribution across the landscape are usually different; the first generation does not necessarily impact the abundance of the second generation.  Feeding damage from fall armyworm during the vegetative stage in corn and sorghum causes chewed up and ragged looking leaves.  In fact, one of the common names used for fall armyworm during this stage is “ragworm”.  Sorghum is particularly at-risk during grain fill as fall armyworm will completely consume berries as they develop.  This caterpillar has been causing increased concern in eastern Kansas brome fields the last couple of seasons.  Brome fields can rapidly decline from fall armyworm feeding (Figure 1) as large numbers of caterpillars can be present consuming leaf material; often larger caterpillars are found along with younger ones.

Figure 1. Brome field damaged by caterpillars (Tina Sullivan).

Fall armyworm tends to begin arriving in Kansas towards the end of June, so scouting should start for this pest in at risk crops and on a weekly basis for the remainder of the growing season.  Caterpillars increase in size at an exponential rate and most of the feeding occurs during the later stage of development.  It is critical to scout early and treat, if needed, when the caterpillars are less than an inch long.  Larger caterpillars are harder to control and do the most damage.  Often, infestations are discovered after it is too late to treat. Recommended thresholds can be found below.

Fall Armyworm Thresholds

  • Alfalfa:  1-2 caterpillars per square foot can destroy seedling alfalfa.  10-15 per square foot can destroy 12” tall plants.
  • Corn:  damage to whorl stage in early summer is typically not a concern and will not impact yield.  Bt corn may prevent ear damage.
  • Sorghum:  damage to whorl stage in early summer is typically not a concern. 1-2 larvae/head during flowering to soft dough reduces yield 5-10%.
  • Wheat:  Larval “window-paning” in early planted wheat can be a concern. Very late second generation fall armyworm will be the biggest concern for wheat.  If 25-30% of plants show damage, examine field frequently.  Treat at 2-3 active larvae/ft.

Pasture/Brome: If damage is notable or there is window-paning, treatment may be warranted with 4 to 5 caterpillars per square foot.

Figure 2.  Caterpillars found damaging a brome field. Infestations can often include multiple species and multiple life stages (Tina Sullivan).

Since fall armyworm is present for several months of the growing season, it is possible that sometimes mixed infestations of different caterpillar species can occur (Figure 2).  As with any pest, proper identification is important to ensure that the right control recommendations are followed.  A species often confused with fall armyworm is true armyworm, Pseudaletia unipuncta.  The two species can be told apart with a couple of easily seen characteristics.  Fall armyworm has a noticeable inverted “Y” on its head (Figure 3), while true armyworm does not.  Additionally, the thickest stripe on the side of the fall armyworm caterpillar will be dark, while on true armyworm the thickest stripe is tan to orange (Figure 4).

The fall armyworm is depicted in a c-shape, with one thick black strip on its lateral sides.
Figure 3. Fall armyworm. Notice the thickest stripe is black (K-State Entomology).
Figure 4. True armyworm. Notice the thickest stripe is a light color (K-State Entomology).

For more information regarding fall armyworm management, take a look at the following Insect Pest Management Guides:

Anthony Zukoff – Extension Entomology, Western Kansas Research and Extension
Tina Sullivan – Northeast Region Extension Agronomist