Newsletter Renewal Time

It's that time of the year again!  Time to gear up for the new crop production season and time to re-subscribe to the Northeast Nebraska IPM-Crop Production Newsletter.

The subscription rate for 2002 is once again only $20.00.  For this reasonable sum you can expect objective information on pest management, fertility, irrigation scheduling, crop development, and other crop management information on a weekly basis during the growing season.  This newsletter is designed specifically for Northeast Nebraska.  The subscription fee basically covers our costs for supplies and stamps.    If you would like to receive the newsletter in hard copy format, give Pat a call at (402) 584-2837 or e-mail pbathke1@unl.edu.

If you have access to the internet, the newsletter can be read free of charge at this site.  If you do access the newsletter regularly on the internet, we do ask that you call Linda Renner at 402-370-4000 or email her at lrenner2@unl.edu so we can get a handle on how many people are using the information. Also, if you want an e-mail reminder of when the newsletter is on the web you can subscribe to a listserve that will automatically contact you when the letter is ready.  To subscribe to the listserv, send an e-mail message to: LISTSERV@UNL.EDU and in the Message Field (Not subject) type SUBSCRIBE IPM.  Do not include a signature, as Listserv will try to interpret each line as a command.  If you have any problems, contact Linda. Thanks.   If you have received notification in the past, you will continue to receive it unless you unsubscribe.

For another option for subscribing to the IPM newsletter reminder or other agricultural listservs, go to http://nerec.unl.edu/aglistserv.htm.  Just click the listservs you would like to receive and fill in the form.  You’ll receive any newsletters, ag notices, etc., that are sent.

The second newsletter will come out during the week of April 15.

Army Cutworms in Alfalfa

Army cutworms are the first pests usually reported in crops.  While not a common a pest in northeast Nebraska, we have had occurrences in the past (1999 in Boyd Co.) where they have held back the initial green up of alfalfa in the spring.  The warm fall could have enabled moths to flay back from the Rocky Mountains where they spend the summer and lay eggs in alfalfa.  This winter was very mild which could have helped overwintering larvae survive.  Lack of green up could very well mean an insect problem instead of weather- related winterkill or drought.  What few wheat fields we have should also be scouted.

Army cutworms can be serious pests of wheat and alfalfa.  The eggs are laid in the fall.  The eggs hatch, the larvae feed for a short time and then overwinter in the soil. They begin feeding as soon as their host crop comes out of dormancy and starts to grow.   Army cutworms are brownish-black without any distinguishing markings and will be found in the soil around the crowns of the plants during the daytime.  They feed on the foliage above the surface of the ground at night.  After completing development the adult moths fly to the Rocky Mountains before returning to complete the cycle.

In established alfalfa fields, stand loss is rarely observed, but the delay in green up may reduce yields of the first cutting if cutworms are numerous. Consider treatment in established fields when four or more cutworms per square foot are found.  In fields less than a year old, food reserves in the roots are limited and feeding may be enough to kill individual plants and produce stand loss.  Treatment should be considered if 2 or more cutworms are found per square foot in newly seeded alfalfa.

Wheat recommendations are similar, with stressed wheat at the lower level of 2 per square foot.

Ambush, Pounce, Warrior, Baythroid, Mustang and Lorsban (chlorpyrifos) are compounds that should control army cutworms in alfalfa. Warrior and Mustang are registered for use on wheat.  If surface moisture is adequate use the lowest labeled rates, they should work fine.

Plan to Scout for Alfalfa Weevils

Alfalfa weevil damage in the northern half of the state is usually noticeable when 375 Growing Degree Days (base 48) have occurred.  While we are yet short of this accumulation, it wouldn’t be a bad idea to begin to plan to scout for this important pest.  On average, northeast Nebraska will hit 300 growing degree days sometime around April 20-25.  It appears the week of the 23rd would be a good time to start looking for small larvae feeding in the tips of alfalfa.  More on alfalfa weevils in the next issue. 

Controlling winter annuals in no-till corn 

Many producers in southeast Nebraska and other parts of the state are starting to notice scattered purple blankets in their no-till fields. Henbit has become more prevalent and by the time you notice this purple flowering weed, it is too late to do anything. In addition to henbit, other winter annual weeds such as horseweed (marestail), pennycress, shepherdspurse, and tansy mustard are showing up more regularly in no-till cornfields.

Why have these weeds become a problem and what do we do about them? First, we need to talk a little about biology. Since these weeds are annuals they have one year to germinate, grow vegetatively and set seed. Basically it is the annual's job to produce seed so that the species will continue the next year; everything else is secondary. The life cycle of these winter annual weeds differs from summer annuals like foxtail and velvetleaf, which typically germinate and produce seed within the growing season. These winter annual weeds actually germinate in the fall and begin growing before winter. In the spring, they usually bolt and produce seed before corn or beans are planted. 

Why should you worry about controlling winter annuals? Many southeast Nebraska producers have found that no-till fields are excellent at conserving moisture in dry-land situations. Unfortunately winter annuals will use valuable moisture that could be available to the crop.
 
Many people wonder why have these winter annual weeds have become such a problem lately. One speculation is that winter annual weeds are popping up in no-till cornfields where the increased use of Roundup-Ready soybeans means there is little or no herbicide residual to control these weeds. When conventional soybean were the norm, traditional herbicides provided residual control to keep many of the winter annuals from germinating or growing in the fall.

What are the best herbicides for control of winter annuals?  The biggest issue is timing. Most of the herbicides work best before the weeds have bolted. This typically requires monitoring fields early and spraying as soon as temperatures warm up enough for plant growth. Below are several products that will provide control of henbit and will provide similar or better control of horseweed (marestail), pennycress, and other winter annuals.

Treatment	Rate
2,4-D ester	1 pt
2,4-D ester + Banvel	1 pt + 1/2 pt
Atrazine + COC	2 qt
Gramoxone	1.5 pt
Roundup Ultra	1 pt
Roundup Ultra	1.5 pt
Roundup Ultra +2, 4-D	1pt + 1pt

Brady Kappler
Weed Science Educator

Where to Get Scouting Supplies 

With the potato leafhopper problems the past few year, there has been more of interest in obtaining scouting equipment, particularly sweep nets.  There are several national outlets that sell field collection and monitoring equipment.  A couple are Great Lakes IPM, 10220 Church Road NE, Vestaburg, MI 48891 (Telephone 517- 268-5693) and Gemplers, 100 Countryside Drive, PO Box 270, Belleville, WI 53508 (1-800-874-4755).  Bioquip Products, 17803 LaSalle Avenue, Gardena, CA 90248-3602 (310-324-0620) is a good source of many kinds of biological equipment.  Contact them and they will send you a catalog of their products.  Nets, hand lenses, and pheromone traps are a few of the things available.   Sweep nets generally run about $25.00-30.00 with replacement nets about one-third the cost.