Effective Armyworm Control in Wheat: Sustainable Strategies to Protect Yield and Quality

Changing climatic conditions, mild winters and intensive cultivation of cereals have contributed towards a rise in the occurrence of armyworm in wheat in many wheat-growing areas. These are aggressively attacking the wheat foliage for food and can quickly swarm into the fields in very large numbers, and concentrate their attack in a short time to produce a lot of economic armyworm damage in wheat. Larvae tend to feed at night and stay in the ground during the daytime in early infections and may remain undetected.

The amount the wheat is being damaged by armyworms becomes more apparent with population growth, resulting in defoliation, loss of photosynthetic ability and damaged grain heads. Because excessive populations can cause problems in grain yields due to reduced grain filling, it is important to monitor populations early for a successful armyworm management of armyworm in wheat.

Data on the occurrence of Armyworm in wheat fields

Armyworms are apt to establish an outbreak as soon as adult moths begin to lay their eggs in the wheat leaves or adjacent grass. Larvae after hatching go through several feeding stages, progressing through them by eating more plant material. Younger larvae feed on the surface of leaves, and older caterpillars eat leaves entirely; and may even defoliate wheat heads at close range at full crop growth when mature.

Armyworm infestations can be rapidly established in wide production areas since armyworms are able to move throughout the counter from neighboring crops and grassy weeds. Timely control of armyworms is critical to minimize the losses as these feed very rapidly once mature.

Detecting damage due to Armyworms in Wheat

The appearance of irregular holes in the wheat leaf and leaf margins appearing shredded or chewed on are the first symptoms of armyworm damage in wheat. With rising larval numbers, wheat plants can be stripped bare leaving the stems.

For particularly heavy infestations growers can expect to see:

• Feeding on young leaves through holes in the windows.
• Ragged leaf edges.
• Patches in fields that have been defoliated that are moving.
• Wheat heads are prematurely cut to some extent close to harvest.
• Less vigour and cultivar maturity.

It is important to scout often early in crop growth to keep armyworm under control in wheat before reaching the economic threshold.

Larvae can be found on both land and sea.Environmental Conditions that Favor Armyworm Infestation.

There are a few setbacks for an armyworm attack on wheat crops. The warm weather coupled with the relatively moist conditions is conducive to moth flights and larval development. The dense canopy of the crop also offers protection and helps to support humid conditions which are conducive to larval survival.

Fields are also likely to be more vulnerable if they have a grassy edge, or opportunities for the development of larvae and migration of moths from grassy borders, areas of pasture or previous cereal crops. If it is feasible to produce continuous cereal without crop rotation, repeated exposure to armyworms may further increase the pressure in armyworms in wheat pesticide for armyworms program.

Some traditional methods of treating armyworms in wheat are listed below

The conventional control methods against armyworms in wheat stress on use of synthetic insecticides for armyworms in wheat. Foliar applications are made many times to control larval populations when levels are above economic thresholds. There are several types of insecticides for armyworms in wheat which will give rapid knockdown when applied early in the larval stage.

Some chemicals used the same way over time, however, can lead to resistance building and may not last as long. In addition, many sprays can result in higher production expenses, and can have a negative impact on the beneficial insects that contribute to natural pest control.

The challenges mentioned above, coupled with other factors, have increased the interest of many wheat producers in integrated approaches of false armyworm control in wheat involving monitoring, cultural practices and biological control of armyworm infestations.

Diseases and pesticides are biological weapons that can be used to control armyworms

Bacillus thuringienesis is one of the best studied biological control agents for armyworm, and is becoming a part of biological control program.

It is a naturally occurring soil bacterium that forms proteins after it's eaten that target specific caterpillar pests. Larvae which have taken up these proteins destabilize their digestive systems, thereby inhibiting their feeding an ultimately killing them.

Unlike most broad spectrum insecticides, biological insecticides for armyworms in wheat that include Bacillus thuringiensis (Bt) are generally not harmful to pollinators, predatory insects or the environment. They are useful for sustainable farming and resistance management programs because of their low genetic diversity.Their low genetic diversity value is useful in agriculture for sustainable farming systems and resistance management of armyworm in wheat programmes.

Bacillus thuringensis technology was found very effective in reducing the oriental armyworm populations in wheat cultivation systems by Yang Yu and Zhiming Wei, which further establishes the role of B. thur. in the modern crop protection program.

The timing of armyworm control in wheat can make the difference between success and failure

Timing is crucial to manage armyworm in wheat. It is much easier to manage the young larvae than the mature caterpillars as they eat less foliage and are more susceptible to armyworm treatment insecticide. A focus on newly hatched larvae in the field rather than in search of heavy feeding should be done prior to severe feeding, therefore. Information on crop edges/grassy areas and previous crop infestation hotspots can help optimise timing of armyworm treatment in wheat and enhance control.

Applying BCF during early stages can minimize re-sprays and help to grow more sustainable approaches to controlling armyworms in wheat with insecticide.

Together, sustainable Armyworm Management with BT produces benefits for farmers

Novobac is a biotechnology company with a focus on biological crop protection and microbial solutions towards sustainable agriculture.

Biological control of armyworm and other caterpillar pests of cereal and vegetable crops using Bacillus thuringiensis – this is what Novobac's Growth Range BT Thuricide is used for when looking for environmentally responsible armyworm control in wheat.

BT Thuricide works when ingested, by impairing feeding activity of larvae, helping to limit their numbers before they can cause significant crop damage. Sprays specifically target caterpillar pests thereby enhancing beneficial insect conservation and being well suited to Integrated Pest Management programs.

With the increasing threat of armyworm in wheat production in the largest wheat-growing areas of the world such as Canada, the United States, India, Australia and parts of Europe, growers are increasingly using BT Thuricide as part of their sustainable armyworm management programs.

The challenge is to develop an Integrated Armyworm Management Strategy

Success with armyworms can't be achieved using just one product or technology – it's a long-term solution. A mix of approaches is being used on an integrated management program to reduce pest pressure and contribute to field health.

Effective strategies include:

• Regular field scouting.
• Monitoring moth activity.
• Good weed and grass control at perimeter areas.
• Crop rotation (if possible).
• Early intervention of larvae.
• Use of biological tools along with traditional tools.

These solutions can be integrated to decrease the need for additional pesticide applications for armyworms, increase sustainability and help maintain healthy beneficial insect populations.

Discovering what works and what doesn't in an effort to achieve future sustainable and effective control of the armyworm.With the concerns around resistance that are increasing, there should be a greater role for biological technologies in wheat production systems around the world. Bt products will allow growers to control pests and good stewardship while maintaining the effectiveness of the pest management program.

Integrated implementation of biological agents, target and site validation and good crop management is the future of organic control of armyworm. To ensure yields, long-term sustainability and healthy farm ecosystems, Wheat producers need to take a new approach to implementing strategies that work together hand-in-hand today.

Frequently Asked Questions

Why are armyworms infesting in wheat fields?
-Tip on armyworm above occurs typically after the migration of armyworm insects, climatic conditions which are favorable to development and nearby grassy hosts in and around wheat crops.

When/what are the first signs of the armyworm damaging wheat?

-Symptoms begin with irregular openings in leaves, leaves shredding and window pane feeding on young plants of wheat.

Timing of proper armyworm control in wheat?

-Generally best treated in early infestation when larvae are actively feeding and small.

Do biological products work good in controlling armyworms in Wheat?

-Yes. Bacillus thuringiensis products have been effective as a component of an integrated biological control program for armyworms.

Could biological control be an option to reduce the use of pesticide for armyworms?

-This biological strategy can help decrease the need for repetitive chemical treatments and provide beneficial insects and help sustain long-term beneficial effects.

References:

1. Yu, Yang, and Zhiming Wei. “Increased oriental armyworm and aphid resistance in transgenic wheat stably expressing Bacillus thuringiensis (Bt) endotoxin and Pinellia ternate agglutinin (PTA).” Plant cell, tissue and organ culture 94 (2008): 33-44.
2. Young, S. Y., and D. C. Steinkraus. “Control of armyworm on heading wheat with Bacillus thuringiensis products and baculoviruses, 1994.” Arthropod management tests 21.1 (1996): 318-319.