Understanding Codling Moth and Its Generations in a Single Growing Season

Codling moths, scientifically known as Cydia pomonella, are one of the most significant pests affecting apple and pear trees. These moths can cause extensive damage to fruit crops, leading to significant economic losses for growers. Understanding the life cycle, appearance, behavior, and management of codling moths is crucial for effective pest control and ensuring a healthy harvest. This comprehensive blog will delve into the details of codling moths, their generations within a single growing season, and strategies for monitoring and managing their populations.

What is Codling Moth?

The codling moth is a small, yet highly destructive pest that primarily targets apple and pear trees, though it can also infest other fruit trees such as walnuts, plums, and quinces. Adult codling moths are small, grayish-brown moths with a wingspan of about 15 to 20 millimeters. They have distinctive gray and white banding on their wings, which helps in their identification. The larvae, commonly known as "worms," are the most damaging stage of the insect. They are creamy-white caterpillars with a brown head, growing up to 20 millimeters long.

Damage Caused by Codling Moths

The primary damage caused by codling moths occurs when the larvae tunnel into the fruit to feed on the seeds. This tunneling not only makes the fruit unsightly and unmarketable but also causes premature fruit drop and increases the risk of secondary infections by pathogens entering the fruit through the feeding holes. The damage typically manifests as small holes in the fruit, often accompanied by frass (larval excrement) around the entry points.

Mating and Growth Cycles of Codling Moths

The lifecycle of the codling moth is closely tied to the growing season of apple and pear trees. Understanding this lifecycle is key to effective pest management.

1. Overwintering and Emergence:

   • Codling moths overwinter as mature larvae in cocoons beneath tree bark, in soil, or in other protected areas. As temperatures warm in the spring, these larvae pupate and emerge as adult moths.

2. Mating:

   • Adult codling moths typically emerge in the spring, around the time of apple and pear tree bloom. Mating occurs shortly after emergence. Female moths release pheromones to attract males, and after mating, the females lay eggs on developing fruit or nearby leaves.

3. Egg Laying and Hatching:

   • Females lay tiny, flat, oval eggs on the fruit or leaves. These eggs hatch in about 6 to 14 days, depending on temperature. The newly hatched larvae then seek out fruit to bore into.

4. Larval Stage:

   • The larvae tunnel into the fruit, where they feed on the seeds and surrounding flesh. This feeding stage lasts about 3 to 5 weeks, after which the larvae exit the fruit to find a suitable place to pupate.

5. Pupation:

   • The larvae spin cocoons in protected areas and enter the pupal stage, emerging as adult moths after a few weeks to begin the cycle anew.

Generations of Codling Moth During a Growing Season

Codling moths typically have multiple generations within a single growing season, especially in warmer climates. The number of generations can vary from one to three, depending on environmental conditions.

First Generation

• Timing: Spring, shortly after apple or pear trees bloom.
• Lifecycle: Adult moths from the overwintering generation emerge and begin mating. Females lay eggs on the developing fruit or nearby leaves. The larvae hatch, bore into the fruit, and cause the first wave of damage.
• Damage: The larvae tunnel into the fruit, leading to "wormy" apples or pears. This generation often causes the initial significant damage of the season.

Second Generation

• Timing: Early to mid-summer.
• Lifecycle: The first generation larvae mature, pupate, and the next generation of adult moths emerges. These adults mate and lay eggs on the fruit, leading to another round of larval infestation.
• Damage: The larvae from the second generation also tunnel into the fruit, compounding the damage from the first generation. This generation can be particularly damaging as fruit size increases, providing more resources for the larvae.

Third Generation (in warmer climates)

• Timing: Late summer to early fall.
• Lifecycle: In warmer regions, a third generation can occur. The cycle repeats with adults emerging, mating, and laying eggs. The larvae from this generation often infest late-season fruit.
• Damage: This generation can cause late-season fruit damage, affecting the final harvest and storage quality.

Monitoring and Managing Codling Moth Populations

Effective management of codling moth populations requires diligent monitoring and timely intervention. Two key tools in monitoring are sticky traps and pheromone lures.

Sticky Traps

Sticky traps are simple yet effective devices that capture adult moths. These traps are typically coated with a sticky substance that immobilizes the moths upon contact. By counting the number of moths caught in the traps, growers can estimate the population size and activity levels.

Pheromone Lures

Pheromone lures are used in conjunction with sticky traps to increase their effectiveness. These lures emit synthetic versions of the female moth's sex pheromone, attracting male moths to the traps. This method not only helps in monitoring population levels but can also disrupt mating by reducing the number of successful matings, a strategy known as mating disruption.

Trap kits combine both sticky traps and lures.

Implementing a Monitoring Program

1. Placement of Traps: Place sticky traps with pheromone lures in the orchard before the first expected flight of adult moths, typically in early spring. Position the traps at head height in the upper third of the tree canopy.

2. Regular Monitoring: Check the traps regularly, at least once a week, and record the number of moths caught. This data will help in determining peak flight periods and the timing of control measures.

3. Degree-Day Models: Utilize degree-day models to predict the emergence and development stages of codling moths based on accumulated temperature data. This information can help in timing interventions more precisely.

4. Biological Control: Encourage natural predators and parasitoids of codling moths, such as Trichogramma wasps and other beneficial insects, to help manage populations.

5. Cultural Practices: Implement cultural practices such as removing infested fruit, maintaining orchard hygiene, and using barriers like fruit bagging to reduce moth access to the fruit.

6. Chemical Control: If necessary, apply insecticides based on monitoring data and degree-day predictions. Target applications to coincide with vulnerable stages of the moth lifecycle, such as the egg-hatching period. Please be mindful of the impact for pesticides in the environment, and always follow safety instructions on the product labels.

In Summary

Codling moths are a persistent and damaging pest for apple and pear trees, requiring vigilant monitoring and management throughout the growing season. By understanding their lifecycle, recognizing the timing and impact of each generation, and implementing effective monitoring tools like sticky traps and pheromone lures, growers can significantly reduce the damage caused by these pests. Combining these strategies with cultural practices and biological control methods can lead to a more integrated and sustainable approach to managing codling moth populations, ensuring a healthy and productive fruit harvest. Staying proactive and informed is key to protecting your fruit trees from this challenging pest.

Read More

1. Codling Moths in Home Orchards - University of Minnesota Extension This article provides a comprehensive overview of codling moths, focusing on their identification, lifecycle, and the damage they cause to apples and pears. It outlines two generations of codling moths in Minnesota, detailing the stages from overwintering larvae to adult moths and the subsequent egg-laying and larval feeding periods. The article also offers practical advice on managing codling moths through cultural practices, trapping, and the use of pesticides. Read more at UMN Extension​ (Extension at the University of Minnesota)​

2. Life Cycle of the Codling Moth - Oregon State University Extension Service This article discusses the codling moth's lifecycle, emphasizing the importance of understanding the pest's developmental stages for effective management. It explains how larvae overwinter and transform into pupae, and how adults emerge in spring to lay eggs on fruit and leaves. The article highlights the need for targeted pest management strategies during the vulnerable stages of the codling moth's life, particularly focusing on the timing of control measures. Read more at OSU Extension​ (OSU Extension Service)​

3. Managing Codling Moth in the Home Orchard - Montana State University Western Agricultural Research Center This detailed guide provides strategies for managing codling moths in home orchards, including cultural controls like orchard sanitation and fruit thinning, as well as fruit bagging and trunk banding. The article also covers the use of beneficial insects and natural predators, and provides information on chemical control options. It emphasizes the importance of taking early action and using an integrated approach to manage codling moth populations effectively. Read more at Montana State University Extension​ (MSU Ag Research)