Cabbage Moth Control: Proven Strategies to Protect Brassica Crops from Caterpillar Damage

Cabbage plants are extremely susceptible to insects at all developmental stages. Cabbage moths and larvae are among the most serious pests since they can feed rapidly which results in considerable loss of leaves, decrease in head quality and decrease in crop productivity. The first sign of insect damage typically occurs when growers see white moths flying over their cabbage canopy or irregular holes in the leaves. But most often the damage occurs when the culturing is in the caterpillar stage under foliage.

Modern farmers are now raising more practical questions like:

 What can be done to prevent early infestation of cabbage moth?

 What is the reason why the cabbage crop gets re-infested again and again?

 Do biological controls work on diamondback moth on cabbage?

 What methods are there for growers to minimize the development of insecticide resistance and still maintain yield?

Cabbage moth control today is not an option solely based on insect when damage is detected. Nowadays, the emphasis is placed on early detection of pest, biological control, and optimization of time of pest attack.

Cabbage Moth: What is it?

It is also commonly known as:

 Diamondback moth

 Cabbage white butterfly

 Cabbage looper

 Imported cabbageworm

Of these, the diamondback moth on Cabbage is one of the more important pests of world-wide importance.

The cabbage moth is extremely unimportant as an adult but the very hungry larvae are a serious problem in the crops. An awareness of the life cycle is important in establishing a control program for this pest.

The moths lay their eggs securely on the underside of cabbage leaves and the process repeats. Immediately after hatching, larvae start feeding on plant tissues and are in the most harmful state. They feed usually below the leaves, thereby avoiding the weather and general contact insecticides. It is worse when brassica crops are grown continuously over the warm seasons as this can allow more moth generations in a year, due to continual food source.

Early detection is very important in the control of cabbage moths. Early symptoms consist of small feeding holes in young leaves, skeletonizing and chewed heads on cabbage. The second indicator of a good sign is white moths which can be seen in the early morning or late evening flying on the fields. High feeding pressure can cause rapid loss of vigor in the crop, secondary infection, low market value and can defoliate an entire commercial vegetable crop in one season.

Why is cabbage moth control becoming more difficult?

Traditional spray programs are no longer as effective as when they were first developed, many growers complain. One prime reason is the rising levels of insecticide resistance, especially in populations of the diamondback moth exposed to the same insecticide products within an extended number of growing seasons.

Integrated pest management strategies are emerging in which growers are focusing on beneficial insects, pest monitoring, biological control devices, and early detection of resistance as some tools to help manage pest populations. Modern programmes of sustainable pest management practice control that is both ecological and pesticide-low.

Frequently involve the following strategies:

• Regular field scouting and monitoring
• Alternation of pest control measures
• Maintain natural enemies (check populations before adding other pesticides or herbicides).
• Enhancing cropping systems.
• Incorporation of biological pesticide products and use of biological pesticides.

Bacillus thuringiensis or Bt is a naturally occurring microbe that occurs in the soil and is commonly used in the sustainable agriculture and biological pest management.

This bacterium is selective on specific pests and will not persist on foliage or be harmful to beneficial insects, pollinators and the environment.

If you are interested in learning more about this environmentally-friendly management tool, this directory includes a number of in-depth articles on Bt and how it works in biological pest management.The Bt proteins interfere with the digestive system of cabbage moth larvae causing the larvae to stop feeding after eating or to die when larvae are feeding when a treated plant is present. Since Bt is specific to caterpillar pests, it has proven to be a useful aid in controlling: Diamondback moth, Cabbage loopers, Armyworms, and Various leaf-feeding caterpillars.

Bt is a biological insecticide that is widely used in commercial vegetable production and is currently a popular addition to the IPM strategy, as well as a control tool.

This is indirectly related to Bt for the Diamondback Moth (DBM)

The use of Bacillus thuringiensis has been found to be effective in control of diamondback moth in cabbage production method, as cited by several scientific studies.

Legwaila et al (2015) tested Bt var. kurstaki on eggs and larvae of diamondback moth under greenhouse cabbage conditions. These researchers found that larval suppression was significant when Bt was applied when larval stages were young, demonstrating the critical need for correct timing of Bt in the pest's life cycle.

Ivey and Johnson (1997) undertook further research in the use of Bt in addition to cultivar resistance of cabbage. They proved that Bt products could be an effective tool in controlling larvae, and were effective in an IPM strategy for IPM in cabbage.

Bt is still a useful biological tool for cabbage-pest management for sustainable agriculture as demonstrated in these studies.

APHIS will facilitate development of Best Practices for maximizing the use of Bt

Bt product success is related in large part to application timing and coverage. Bt must be eaten for caterpillars to be controlled.

Typically, growers will find more success when they:

• Checking moth on a regular basis
• The treatment will aim at attacking newly hatched larvae.
• Early applications of treatments
• Providing adequate fill-in of leaf area.
• Applying more frequently as needed following heavy rain showers.

Generally, younger larvae are more easily controlled than older caterpillars and early action is critical for successful suppression of pests.

The Sustainability Benefits of Biological Pest Control

Biological pest control program aids in reducing reliance on continual chemical usage and maintains ecological balance over time. Biological solutions can provide a number of benefits to broad-spectrum insecticides for Lower resistance pressure, Protection of beneficial insects, Reduced pesticide residues, Brought soil and crop health up to standard, and Increased sustainable production of vegetables.

Because of this, most commercial cabbage growers are now using Bt products as integrated pest management practices.

Novobac BT Thuricide for Caterpillar Management

Novobac is a biological pest control, microbial crop protection and sustainable solutions provider, also producing biological insecticide BT Thuricide specifically for the control of caterpillars in vegetables.

Novobac BT Thuricide biological pest control solution is suited for growers of vegetable crops such as cabbage in Africa, Central Asia and other parts of the world, to control destructive caterpillar pests and support sustainable agriculture. Bacillus thuringiensis is a bacterium which disrupts the feeding activity of the larvae shortly after ingestion and contributes to reduction of the crop damage and pest pressure.

The utilization of Bt is part of an integrated pest management programme

Bt products work best as part of an integrated pest management (IPM) program. Instead of using one control, growers use biologicals in addition to cultural and agronomic control to put pest populations down for the long term.

Common parts of an IPM programme are the following: monitoring and scouting crops, field sanitation, crop rotation, conservation of the use of beneficial insects, resistant cabbage varieties, and appropriate irrigation and crop nutrition programmes.

When used in combination with Bt, these suites of practices allow for a more robust and sustainable pest management program and limit the potential for Bt resistance.

A combination of the different approaches is more effective in reducing pest outbreaks and decreasing the dependence on program control solely by chemicals.

Finally, the use of integrated programs slows development of resistance to insecticides, increasing long-term effectiveness.

How to Minimize Future Cabbage Moth Infestations for Growers?

Cabbage moth control must include prevention as well as the treatment of moth flights.

To reduce the pressure, growers can take these steps to reduce infestation:

• Agricultural residues and stubbles after harvest; why is it better to remove crop residues after harvesting?
•  Rotating brassica crops
•  Control weeds in and around fields.
•  Regular moth monitoring
•  Encouraging beneficial insects
•  Getting Bt early in larval development compared to later times

When severe damage due to cabbage moths is observed it is often then that the preventative management strategies need to be taken.

The future of cabbage pest management

Sustainable practices for pest management systems are becoming more popular and involve more than just chemicals; they also rely on monitoring and controlling pests throughout their entire lifecycle.

The emphasis is shifting to:

•  Early pest detection
•  Biological pest control
•  Ecological balance
•  Resistance management
•  Long-term crop resilience

Biological control measures are becoming an important part of the commercial cabbage production going on all over the world, as research has demonstrated that bacillus thuringiensis –bt is effective in control of cabbage pests.

Early knowledge of cabbage moths combined with targeted Bt treatments may minimize losses to the pest and allow growers to maintain good quality cabbage yields while maintaining sustainable production systems in the future.

Reference:

• Legwaila, Mitch M., et al. "Efficacy of Bacillus thuringiensis (var. kurstaki) against diamondback moth (Plutella xylostella L.) eggs and larvae on cabbage under semi-controlled greenhouse conditions." International Journal of Insect Science 7 (2015): IJIS-S23637.
• Ivey, Paul W., and Seth J. Johnson. "Efficacy of Bacillus thuringiensis and cabbage cultivar resistance to diamondback moth (Lepidoptera: Yponomeutidae)." Florida Entomologist (1997): 396-401.