Black Cutworm and Armyworm Caterpillars Should be Evident

Doug Johnson, Extension Entomologist, University of Kentucky

Our insect development estimator, using the insect trap captures as our Biofix and current temperatures from the Princeton weather station indicate that egg hatch has begun and small

Armyworm and Black cutworm Flights Continue

Doug Johnson, Extension Entomologist, University of Kentucky

Capture of armyworm (AW) and black cutworm (BCW) moths continue at a considerable, if slightly lower capture, compared to last week. The AW trap captured 449 moths while the BCW trap

Black Cutworm & Armyworm Moth Captures Show a Big Increase

Doug Johnson, Extension Entomologist, University of Kentucky

Fig. 1 Black cutworm moth.

Black cutworm (BCW) and armyworm (AW) moths captured in the IPM traps at the UK-REC in Princeton, KY show a substantial increase for the trap week ending Friday, April 10th. In the case of BCW, 37 moths were captured when about 8 would be expected. For armyworm, 541 moths were captured when 119 would be average at this time. Captures for both of these pests are significantly greater than their rolling five- year averages. In addition, if the armyworm counts continue to increase at this rate, the population will approach the outbreak levels seen in 2006 & 2008. These are years when known pest problems either caused loss or required extra insecticidal control. See the Insect Trap Graphs on the UK-IPM webpages.

Cool and Wet Can Only Help Cutworms

Doug Johnson, Extension Entomologist



Fig. 1. Black cutworm moth.
 

Capture of black cutworm moths in the IPM traps has been above the rolling five year average for the last several weeks. The activity of this insect has been notoriously difficult to predict over the years, even with years of data on its’ flight activity. Nevertheless given that the moth capture is above “normal” and we are experiencing unusually cool and damp weather, it may be that we should keep a closer check on our young corn plants.

Armyworm & Cutworm Moth Flights Rather Ordinary

Doug Johnson, Extension Entomologist, University of Kentucky

Black cutworm moth

Capture of both armyworm and cutworm moths have decreased during the previous trap week. At present the data indicate that neither pest is set for a big outbreak. Of course this can change especially if we get a sustained week of good weather. This does not mean that there are no pests around, there certainly are. Nevertheless, flight patterns compared to the rolling five year average do not show any sign of an elevated risk of outbreak.


 

Armyworm moth

Even though we have a good outlook for the short term we still need to remember that “only about 15 percent of corn has been planted which is well behind last year’s 73 percent and the five year average of 32 percent” (KY Weekly Crop & Weather Report Apr. 22, 2013). Remember, both black cutworm and armyworm are migrating to KY from more southern states, and the timing of their migrations are dependent upon temperature just as are planting and corn development. So it is still very possible that larger populations of either or both of these pests could show up in the early vegetative stages of corn development.So, for the moment things look good, but one best pay attention to future developments.

Tracking moth flights isn’t your only preparation option. With both insects but black cutworm in particular providing a weed free seed bed for at least two weeks prior to planting can make a big difference. Early preplant herbicide programs have shown a positive impact in the prevention of cutworm and common stalk borer infestations. Removing weeds especially grass weeds by whatever mechanism, ahead of planning is a good strategy for these early arriving insects.

Refuge Requirements for Transgenic Insect Control Traits in Field Corn.

Doug Johnson, Extension Entomologist

2013 is one of those transitional years for changes in refuge requirements for transgenic control traits in field corn. Several changes have been made over the last several years and one can expect for changes to continue as we (likely) move away from large structural refuges and toward refuge in a bag. Generally the % of refuge seed (those seed without transgenic insect control traits) has dropped from 20% to 10% or even 5% depending upon the traits included and the company. In addition those products that  require separate structural refuges (usually as blocks or a series of rows) is giving way to the inclusion of not traited seed within the bag of traited seed; the so called refuge in a bag (RIB). The result is a somewhat confusing situation where products are available that contain different refuge requirements. Obtaining the desired corn genetics which contains the correct transgenic traits to control the likely pests and planting this with the correct refuge in the proper location can be very confusing.

If you follow the link:    http://pest.ca.uky.edu/EXT/Recs/ENT16-Field%20corn.pdf ,    it will take you to ENT-16, the 2013 Insecticide Recommendations for Corn. On pages 6 and 7 of this publication you will find a Bt Trait Table that list the various packages of transgenic insect control traits by trade name, insect toxins, and the event used to include the toxins in the corn plant. This table also includes relative ratings for how well these toxin packages works against the most common and important insect pests of field corn in Kentucky. Additionally, the type (block vs RIB) of refuge and the percent of non-traited seed required to be in the refuge.

In Kentucky producers can expect their greatest and most consistent return on investment from protection against European corn borer (ECB) and southwestern corn borer (SWCB). Traits for control of western corn rootworm (WCRW) are not needed nor recommended in corn fields that are rotated with non-corn crops. Corn that is not rotated (continuous corn) should be planted with products that contain more than one or “stacked” western corn rootworm (WCRW) traits. In any case products containing only the Cry3Bb1 corn rootworm toxin should not be planted in non-rotated corn. Though not yet noted in Kentucky, this is the trait for which resistance has been show in several states to our north. So far this has only occurred in corn planted in the same field for three successive years and using only the Cry3Bb1 trait for protection against western corn rootworm. Black cutworm (BCW), corn earworm (CEW) and fall armyworm (FAW) infestations are very much dependent on the growing year. Very early planting may benefit from BCW traits while very late plantings will likely benefit from control of corn earworm and fall armyworm.

Relative Efficacy of Single and Stacked Corn Traits Against Insect Pests in Kentucky

Ric Bessin, Extension Entomology, University of Kentucky
Latest update: May 2011

Corn Types	Insect toxins		Dual modes of Action	ECB	SWCB	BCW	CEW	FAW	WCRW	Min. Refuge Requirement
YieldGard CB	Cry1Ab			++++	++++		++	++		20% block
Herculex 1	Cry1F			++++	++++	++	+	+++		20% block
Agrisure CB	Cry1Ab			++++	++++		++	++		20% block
YieldGard RW	Cry3Bb1								++	20% block
Herculex RW	Cry34Ab1, Cry35Ab1								++	20% block
Agrisure RW	mCry3A								++	20% block
YieldGard Plus	Cry1Ab, Cry3Bb1			++++	++++		++	++	++	20% block
Herculex Xtra	Cry1F, Cry34Ab1, Cry35Ab1			++++	++++	++	+	+++	++	20% block
Agrisure 3000GT	Cry1Ab, mCry3A			++++	++++		++	++	++	20% block
YieldGard VT3	Cry1Ab, Cry3Bb1			++++	++++		++	++	+++	20% block
YieldGard VT2 Pro	Cry1A.105, Cry2Ab2		yes	++++	++++	++	+++	++++		5% block
YieldGard VT3 Pro	Cry1A.105, Cry2Ab2, Cry3Bb1			++++	++++	++	+++	++++	+++	20% block
SmartStax	Cry1A.105, Cry2Ab2, Cry3Bb1, Cry1F, Cry34Ab1, Cry35Ab1		yes	++++	++++	+++	+++	++++	+++	5% block
Optimum Intrasect	Cry1Ab, Cry1F		yes	++++	++++	++				5% block
Agrisure Viptera 3110	Vip3Aa, Cry1Ab			++++	++++	+++	++++	++++		20% block
Agrisure Viptera 3111	Vip3Aa, Cry1Ab, mCry3A			++++	++++	+++	++++	++++	++	20% block
AcreMax 1	90% Cry1F, Cry34Ab1, Cry35Ab1 + 10% Cry1F			++++	++++	++	+	+++	++	RIB + 20% block
AcreMax RW	90% Cry34Ab1, Cry35Ab1								++	RIB
SmartStax Refuge Advanced/Complete	Cry1A.105, Cry2Ab2, Cry3Bb1, Cry1F, Cry34Ab1, Cry35Ab1 + 5% refuge seed		yes	++++	++++	+++	+++	++++	+++	RIB

ECB = European corn borer
SWCB = Southwestern corn borer
BCW = Black cutworm
CEW = Corn earworm
FAW = Fall armyworm
WCRW = Western corn rootworm


‘ + ‘ = Poor to fair control
‘++’ = Good control
‘+++’ = Very good control
‘++++’ = Excellent control
May 2011