Common Stalk Borer Back »

Written collaboratively by Adam Varenhorst, Laura Edwards, Patrick Wagner, and Amanda Bachmann.


Corn throughout South Dakota has either emerged or is beginning to emerge. During this time, it is important to scout border rows for the common stalk borer. The common stalk borer is considered a minor and occasional pest in South Dakota; however, it is capable or reducing plant stands near the edges of fields or wherever grass or weeds are adjacent to the field. The common stalk borer is an early season pest that initially feeds on corn leaves, but eventually tunnels into the stalks during the early vegetative growth stages. This tunneling can cause “dead heart” and subsequent plant death.

Profile & Appearance

The adults of the common stalk borer are small, brown moths. The front wings span approximately 1 to 1.4 inches and are typically gray-brown in color with a few clusters of small white spots. Common stalk borer caterpillars are distinctive and easier to identify than the moths. The common stalk borer caterpillars have solid orange head capsules that have a single black stripe along each side (Figure 1). Younger caterpillars have a distinctive purple-brown band, sometimes referred to as a “saddle”, behind their true legs that extends to the second pair of abdominal prolegs. The purple-brown band is distinctive during the early stages of caterpillar development, but this band fades as caterpillars age. The latter part of the abdomen is cream in color. Fully developed caterpillars are 1.5 to 2 inches in length.


Figure 1.
Common stalk borer caterpillar. Credit: A. Varenhorst.
 

Lifecycle & Behavior

Common stalk borers have one generation per year in South Dakota. Adult moths emerge between August and October and are short lived. Females lay eggs predominately on dead vegetation, and prefer narrow-leaved perennial grasses (e.g., giant foxtail, chardgrass, winter wheat) over broad-leaved plants or annual grasses. Eggs are laid either within curled leaves or between the plant stem and the leaf sheath. The eggs overwinter and hatch in late spring. Common stalk borer caterpillars feed on a wide range of plant species, and newly hatched caterpillars tunnel into the first suitable host plant available. The caterpillars eventually outgrow their smaller host plants, and begin searching for larger hosts such as corn and occasionally soybean. Usually only one caterpillar is found within smaller host plants as common stalk borer caterpillars are cannibalistic. However, larger host plants can contain multiple caterpillars as long as they are not in close proximity to one another.

Predicting common stalk borer migration to corn fields.

The hatching and movement of common stalk borers to corn can be calculated by using degree days (41°F base temperature). Common stalk borer eggs typically begin to hatch at ~575 degree days, and the majority of eggs will finish hatching by ~750 degree days. The caterpillars begin moving from smaller grass host plants to corn at ~1,400 degree days, with 50% of common stalk borer caterpillars moving into corn around ~1,700 degree days (Table 1).

In South Dakota, we have exceeded the 575 degree days mark and much of the state has exceeded 750 degree days. This indicates that common stalk borer hatch is well underway, but movement to corn fields has yet to begin (Table 2). Scouting should begin within a week.

Table 1. Color coded key based on accumulated degree days and caterpillar activity.

Accumulated Degree Days Since January 1, 2017 Caterpillar Activity
0-574 Conditions approaching egg hatch
575-750 Egg hatch
750-1300 Development on weeds and grasses
1300-1400 10% of caterpillars moving to corn
(begin scouting corn)
1400-1700 50% of caterpillars moving to corn
 

Table 2. Accumulated degree days for locations within South Dakota in 2017.

Location Accumulated Degree Days
Since January 1, 2017
Britton 748
Brookings 732
Clear Lake 654
Custer 714
Eureka 717
Mahto 733
Mt. Rushmore 722
Pactola Dam 697
Roscoe 735
Summit 699
Watertown 712
Waubay 742
Webster 686
Aberdeen 835
Academy 952
Alexandria 929
Andover 817
Baltic 793
Belle Fourche 1060
Beresford 903
Bison 899
Bridgewater 891
Buffalo 885
Camp Crook 987
Canton 849
Cedar Butte 1143
Centerville 912
Colton 790
Cottonwood 1045
De Smet 809
Dupree 1063
Edgemont 1170
Elm Springs 987
Faith 853
Faulkton 846
Flandreau 750
Ft. Meade 985
Gettysburg 822
Groton 779
Hamill 999
Harrold 899
Hereford 962
Hill City 821
Hot Springs 1207
Howard 796
Huron 912
Interior 1174
Ipswich 776
Kennebec 1131
Lead 861
Lemmon 912
Madison 802
Maurine 929
McIntosh 861
Menno 1049
Milesville 986
Mission 938
Mitchell 997
Mobridge 904
Murdo 956
Newell 971
Nisland 904
Oelrichs 953
Oral 1026
Parkston 929
Philip 1061
Pierre 989
Pine Ridge 1037
Pollock 838
Rapid City 994
Red Owl 860
Redfield 858
Salem 853
Selby 779
Sioux Falls 912
Sisseton 822
Spearfish 969
Timber Lake 883
Turton 812
Tyndall 946
Vermillion 1070
Victor 767
Volga 758
Wasta 1144
Wessington Springs 822
White Lake 851
Wilmot 765
Wind Cave 992
Winner 1154
Wood 998
Yankton 998
blog comments powered by Disqus

Sign Up For Email!