Pheromone traps have been established at several locations in eastern Nebraska to monitor for several spring migrants to Nebraska; black cutworm, variegated cutworm and true armyworm moths. Nebraska Extension faculty Wayne Ohnesorg, Ron Seymour, Gary Lesoing, Laura Thompson and Justin McMechan are monitoring pheromone traps in their areas.

Pheromone trapping is useful for determining the presence of different species in our area, but cannot be used to make treatment recommendations. Rather it is an early warning that we should be monitoring for the larvae of these moths which may be found in our crop fields.

See NebGuide G1153, Corn Cutworms, for more information.

May 20, 2020 Trapping Update

The following are updated cutworm moth trapping results through May 20^th.

Table 1.3

		Total Cutworm Moth Capture Per Week
		April 5-11			April 12-18			April 19-25			April 26 - May 2			May 3-9			May 10-16			May 17-20
County	Location	Black	Variegated	Armyworm	Black	Variegated	Armyworm	Black	Variegated	Armyworm	Black	Variegated	Armyworm	Black	Variegated	Armyworm	Black	Variegated	Armyworm	Black	Variegated	Armyworm
Adams	Hastings	-	-	-	-	-	-	-	-	-	1	41	0	0	11	0	1	0	0	-	-	-
Lancaster	Hickman	0	9	1	0	1	2	1	0	0	1	0	0	0	0	0	0	8	0	0	0	0
Madison	Norfolk	-	-	-	-	-	-	-	-	-	-	-	-	5	7	0	3	3	4	-	-	-
Nemaha	Auburn	0	2	2	0	0	1	10	0	1	1	2	1	0	5	0	0	1	0	0	1	0
Nemaha	Johnson	0	7	2	1	1	0	1	0	2	6	0	1	0	9	0	0	3	3	1	0	1
Otoe	Palmyra	0	9	4	0	5	5	0	0	1	0	9	0	0	5	0	1	0	0	0	0	0
Richardson	Falls City	1	3	2	0	2	2	0	0	0	4	0	0	0	2	0	0	2	0	-	-	-
Saunders	ENREC	4	2	0	1	3	1	-	-	-	-	-	-	-	-	-	-	-	-	-	-	-

April 29, 2020 Trapping Update

We continue to capture moths in our pheromone trapping network. We received a significant capture of black cutworm moths at Auburn on April 23 (Table 1.2). A significant capture is defined as 8 or more moths over 2 nights. A significant capture is used to initiate the degree day model described below (Table 2).

Based on average temperatures at Auburn, we expect that 300 degree days will be reached by May 18. This is the point that black cutworm larvae emerging from eggs laid by these moths will be big enough to begin cutting corn stems.

If you are not routinely monitoring fields for cutworm feeding, this is a good time to target initiation of scouting in the Auburn area. Remember that we have several other cutworm species in Nebraska that overwinter as larvae, so it is always a good idea to scout corn beginning at emergence for cutworm injury and other early season pests, regardless of pheromone trap captures. 

Table 1.2

		Total Cutworm Moth Capture Per Week
		April 5-11			April 12-18			April 19-25			April 26-29
County	Location	Black	Variegated	Armyworm	Black	Variegated	Armyworm	Black	Variegated	Armyworm	Black	Variegated	Armyworm
Adams	Hastings	-	-	-	-	-	-	-	-	-	1	19	0
Lancaster	Hickman	0	9	1	0	1	2	1	0	0	1	0	0
Madison	Norfolk	-	-	-	-	-	-	-	-	-	-	-	-
Nemaha	Auburn	0	2	2	0	0	1	10	0	1	1	2	1
Nemaha	Johnson	0	7	2	1	1	0	1	0	2	6	0	2
Otoe	Palmyra	0	9	4	0	5	5	0	0	1	0	0	0
Richardson	Falls City	1	3	2	0	2	2	0	0	0	4	0	0
Saunders	ENREC	4	2	0	1	3	1	-	-	-	-	-	-

April 23, 2020 Trapping Update

We are starting to see low levels of these moths at several locations in Nebraska (Table 1.1).

Table 1.1

		Total Cutworm Moth Capture Per Week
		April 5-11			April 12-18			April 19-22
County	Location	Black	Variegated	Armyworm	Black	Variegated	Armyworm	Black	Variegated	Armyworm
Adams	Hastings	-	-	-	-	-	-	-	-	-
Lancaster	Hickman	0	9	1	0	1	2	0	0	0
Madison	Norfolk	-	-	-	-	-	-	-	-	-
Nemaha	Auburn	0	2	2	0	0	1	1	0	1
Nemaha	Johnson	0	7	2	1	1	0	1	0	1
Otoe	Palmyra	0	9	4	0	5	5	0	0	0
Richardson	Falls City	1	3	2	0	2	2	0	0	0
Saunders	ENREC	4	2	0	1	3	1	-	-	-

GDD Model for Black Cutworm

In the case of the black cutworm, research has developed a degree-day model (Table 2) to predict when cutworms will be large enough to cut corn stems. At that time, more intense scouting is recommended. In Nebraska we have several other cutworm species that overwinter in the state, so scouting at corn emergence is recommended.

Table 2. Black Cutworm Degree-day Model

Cumulative degree days	Black cutworm stage	Black cutworm activity
0 (biofix)	Significant moth capture*	Egg Laying
90	Egg hatch
91-311	1st-3rd instar	Leaf feeding
312-364	4th instar	Cutting begins
365-430	5th instar	Cutting
431-640	6th instar	Cutting
641-989	Pupa	No feeding

*Significant moth capture is defined as 8 or more moths over two nights

Cutworm Moth Descriptions

Adults of the black cutworm have a drab gray or brownish appearance with two black wedge-shaped markings near the end of the forewing (Figure 1). The hind wings are lighter in color, generally whitish with grey to brown shading.

Variegated cutworm moths are also generally drab, with a variable tan, gray or brown coloration on the front wings (Figure 2). Often the markings are indistinct, but the outer margin of the front wing has seven black notches of which the first four and last two appear paired. The hind wing has a pearly gray appearance.

Adult armyworm moths are generally tan or light brown in color (Figure 3). The front wings are usually specked with black spots and possess a small white spot centrally. The hind wings are similarly tan to grayish-brown, and usually lighter towards the base of the wing.

Figure 1. Black cutworm moth. Photo courtesy of UNL Entomology Department.

Figure 2. Variegated cutworm moth. Photo courtesy of UNL Entomology Department.

Figure 3. True Armyworm moth. Photo courtesy of UNL Entomology Department.