The last couple of months have been dominated by cool fronts moving in from the north and northwest.  This is NOT favorable for black cutworm establishment.  Light trap counts have been extremely low up to this time.  From here on out, corn planted after the rain delay into heavy residue, or fields with winter annuals, or fields planted into spring killed alfalfa (that may attract egg laying moths) have a slightly higher potential for cutworms. When weeds are destroyed mechanically or by herbicides, they will feed on the newly emerging corn.  Because most damage from cutworms occurs roughly in the first two weeks after emergence, growers should be on the lookout.

utworms that overwinter as larvae generally prefer to lay eggs in the fall in green vegetation such as small grain stubble, legumes, rye, and pasture.  The eggs hatch and the larvae feed on the vegetation present before overwintering.  In the spring, after the previous crop is removed and the corn emerges, the cutworms will transfer their feeding activity to the corn.  Recent experience has been that corn planted into alfalfa that has been killed in the spring has a greater potential for cutworm problems.

Tillage has minimal effect on cutworm populations.  If fields are tilled before black cutworm migration, it may limit egg laying in those fields.  Cutworms already in the field may suffer some mortality by mechanical action, but there is no guarantee that tillage by itself will eliminate cutworm problems.  Many cutworm problems have occurred in fields that have been tilled.

It is extremely rare to experience cutworm problems in continuous corn.  Corn stubble is not a preferred egg-laying site.  Potential problems in continuous corn may be the result of a previous year's late season flush of weeds, an interseeding of a fall cover crop such as rye, or a flush of winter annuals this spring, which possibly attract egg laying moths. (KJ)

This is the second part of the article published on April 25, Issue Number 3.

Risks associated with the widespread use of HTC: Potential risks (ecological and economic)  associated with the widespread use of HTC includes: (1) single selection pressure, (2) shifts in weed species, (3) gene escape, (4) gene flow and contamination of organic crops, (5)  HTC as weeds,  (6) promotion of chemical weed control mentality, (7) drift and mis-application, (8) attitudes of world market and food labeling and (9) ethics.

One of the major ecological concerns with wide spread use of the same HTC and  repeated use of same herbicide creates a single selection pressure on weed population. This has been reported as the main reason for herbicide resistance. Examples include atrazine and ALS resistance in the US and Canada. The risk is that repeated use of glyphosate can result in weed resistance. There are already several weed species that are resistant to glyphosate. Examples include: rigid ryegrass (Lolium rigidum)  in Australia, goosegrass (Eleusine indica) in Malaysia, ryegrass in California, and horseweed (Conyza canadensis) in Delaware and Tennessee. Resistance in the above cases resulted from repeated use of glyphosate.

Furthermore, despite the fact that glyphosate and glufosinate control many weed species, they do not control all plant species.  It is well known that glyphosate controls many grasses. However, certain broadleaf species in field crops of US and Canada have shown tolerance to the label rates of glyphosate.  Therefore repeated use of glyphosate can result in the shift of weed species. Examples of such species include:  wild buckwheat (Polygonum convolvulus), Pennsylvania smartweed (P. pensilvanicum), lady’s thumb (P. lapathifolium), ivyleaf morning glory (Ipomea hederacea), venice mallow (Hibiscus trionum),  horseweed (Conyza canadensis), Yellow sweetclover (Melilotus officinalis), and field bindweed (Convolvulus arvensis).

Another risk with HTC is the potential for escape of resistant gene via  pollen from HTC to other plant species, especially to closely related wild relatives. Gene escapes from HTC is not a new phenomenon, it has occurred before. It was  reported that resistance gene was naturally transferred via pollen from herbicide tolerant IMI-wheat to jointed goatgrass  (Aegilops cylindrica).  Another report said that pollen flow as the main reason for naturally occurring multiple resistance of canola (Brassica napus) to glyphosate, glufosinate and imazethapyr. Recently, the Nature magazine recently reported that the Bacillus thuringiensis (Bt) and glyphosate resistant genes are contaminating wild corn in Mexico, which has > 60 of indigenous (wild) corn used as the “gene library”.  More than 80 scientists from 12 countries urged the Mexican government to stop genetic contamination of natural library of corn genes which reduces natural diversity. The chance of gene flow increases further if the plant species are closely related (i.e. same genus) due to the possibility of cross pollination. The list of so called “high risk crops” and their weedy relatives includes: (1) sorghum and its weedy relatives shattercane and johnsongrass; (2) canola and mustards; (3) wheat and jointed goat-grass and quackgrass; (4) rice and  red rice; (5) sunflower and wild sunflower.

Another concern related to gene flow is the contamination of non-GMO crops, especially organically grown crops. For example, organic soybean is a common crop in Nebraska and a good source of income to organic producers. However, the wide spread use of glyphosate tolerant soybean created major problems for the production of organic soybeans due to contamination by glyphosate resistant genes via pollination. Another risk is the control of HTC as volunteer crops. For example, glyphosate does not control volunteer glyphosate tolerant corn in glyphosate tolerant soybean, which requires additional herbicides and is an economic burden.

Eventhough the HTCs present a new weed control technology, in reality it is just another way of chemical weed control. Therefore the wide spread  use of HTC represents a risk of  promoting and continuing the same “chemical mentality” that has been around for the last 40 years, and made weed management rely exclusively on herbicides. Drift and non-target movement of non-selective herbicides such as glyphosate is also a risk, as well as misapplication and misidentification of fields planted with HTC compared to non-HTC.

Another risk to US producers is potential for losing part of the world’s food market, due to current anti-biotech sentiment in Europe and Japan. There is already an estimated 30% reduction in US exports of various products related to glyphosate tolerant soybeans, mostly due to worlds market opposition towards biologically engineered crops.

Biotechnology and biologically engineered crops also raised the issues of ethics in science. In essence, there is a strong opposition around the world about the potential for gene transfer from one species to another. Some are asking if it is unnatural to genetically engineer the plants while others are concerned about using gene transfer for even animal and human research.  Currently there are no international regulations on those issues.

Producers in the US have also experienced a risk with marketing strategies of some companies. For example, during 1999 and 2000 in order to favor their technology and penetrate the market, certain chemical companies were not selling their better yielding conventional soybean varieties in order to sell their HTC.  This is not surprising  because the seed industry is now controlled by the chemical industry. However, such behavior is a serious breach of trust and ethics.

Conclusion:            To maintain a positive attitude, excellent weed control tools are available regardless whether cropping systems are based on HTC or conventional crops. HTC is a valuable technology,  but it will not solve weed control problems. The key is the management of this technology. HTC should be used as just another tool for weed control and only when it is needed. Their use should be only within the principles of integrated weed management in order to remain a valuable tool to producers. Despite the concerns and risks with this technology,  many producers use HTC as the main weed control tactic. Understanding philosophies and attitudes of producers towards weed control can be challenging at times. Many times weed control decisions are based on the perceptions of weed populations rather than the actual economic losses from weeds. For example, despite the fact that many studies indicated that control of late emerging weeds may not be necessary they are perceived by producers as important because: (1) they are commonly used as
indicators of their agronomic skills, (2) controlling all weed escapes is essential in order to renew the land leasing contracts and (3) marketing strategies of the herbicide industry have made season-long weed control as the industry standard.  Currently, many herbicide companies market their weed control programs as guaranteed to provide weed-free fields regardless of environmental or agronomic conditions, and many fields are regularly resprayed free of charge.   As a result, producers in the United States are less likely to use alternative control measures, which has become major obstacle for reducing herbicide use in agriculture. (SK)