The codling moth (Cydia pomonella) is a major pest of apples, pears and other fruit crops worldwide. Understanding the life cycle of this destructive insect is key to implementing effective control strategies.
What are the stages in the codling moth life cycle?
The codling moth goes through four distinct life stages during its development:
- Egg
- Larva (caterpillar)
- Pupa
- Adult moth
How does the codling moth life cycle begin?
The lifecycle begins when adult female moths emerge from their pupal stage in early spring. After mating, females lay tiny, flat, oval eggs on leaves, fruit or branches of host plants. Each female can lay up to 100 eggs over a 2 to 3 week period.
What happens in the egg stage?
The tiny codling moth eggs are difficult to see with the naked eye. They are only about 1 mm long and pearl white to clear in color when first laid. As they develop, the eggs turn tan, pink or red. The incubation period for the eggs is typically around 10 to 14 days.
What does the codling moth larva (caterpillar) look like?
When the eggs hatch, small codling moth larvae or caterpillars emerge. Newly hatched larvae are just 2 to 4 mm long. They burrow straight into fruit or leaves to feed. As the caterpillars grow, they reach 1 to 1 1⁄2 inches long. Codling moth caterpillars are identified by their pinkish-white bodies and brown heads.
What happens in the larval stage?
The larval stage lasts for 2 to 4 weeks. During this time the caterpillars feed on leaves at first, then burrow into fruit. They feed on pulp and seeds inside, causing major damage. When fully grown, the larvae chew their way out of the fruit and seek protected sites to spin silken cocoons and pupate.
What does the codling moth pupa look like?
The codling moth pupa is contained within a silken cocoon made by the mature larva. It is reddish-brown in color and around 1⁄2 inch long. The pupal stage typically lasts anywhere from 1 to 2 weeks in the summer.
When do adult codling moths emerge?
Adult codling moths emerge from their pupal cocoons to start the cycle again. The moths have grayish-brown wings with darker brown banding across their wingtips. Adults are around 3⁄4 inch long with a wingspan up to 1 inch. Males are slightly smaller than females.
How many codling moth generations per year?
The number of codling moth generations per year depends on the climate:
- Warmer climates: 3 or more generations per year
- Cooler climates: 1 to 2 generations per year
In most areas, there are 2 to 3 generations of codling moth annually. Overwintering in the pupal stage allows the pest to survive cold winters and re-emerge the following spring.
What environmental factors influence codling moth development?
Several key environmental factors influence the lifecycle and development of codling moths:
Temperature
Higher temperatures accelerate codling moth development. Optimal temperatures for growth range from 68°F to 86°F. Temperatures above 90°F can be detrimental. Cooler temperatures slow development down.
Day length
Increasing day length in spring triggers adult emergence and initiates mating. Shortening days late in the season can induce diapause or hibernation.
Humidity
Codling moths thrive in areas with moderate humidity. Low humidity is detrimental to larvae hatching and survival. High humidity promotes fungal diseases.
Host availability
Synchronizing moth emergence and egg laying with fruit set and growth is key. Larvae need ripening fruit to feed on.
What damage do codling moths cause?
Codling moth larvae are extremely destructive. Feeding damage includes:
- Tunneling into fruit
- Feeding on seeds and flesh
- Causing rot and decay
- Stunting fruit growth
- Premature fruit drop
They can ruin up to 90% of an untreated apple crop. Damaged, rotten fruit is unmarketable.
How can you control codling moths organically?
Some common organic and natural control methods for codling moths include:
Sanitation
Removing fallen fruit, leaves and debris eliminates overwintering sites. Sticky barrier bands around tree trunks prevent larvae from climbing up.
Mating disruption
Synthetic pheromones confuse male moths and prevent them from finding females. This reduces mating and egg laying.
Parasitic wasps
Releasing Trichogramma wasps that parasitize codling moth eggs can reduce their populations.
Bacillus thuringiensis (Bt)
Applying this natural bacterial insecticide to trees kills larvae when they feed on treated plant material.
Horticultural oils
Coating trees with lightweight horticultural oils in early spring smothers overwintering larvae.
Botanical insecticides
Natural insecticides made from neem, pyrethrins or essential oils can be sprayed on trees to control larvae and adults.
What chemical insecticides target codling moths?
Some common conventional insecticides used against codling moth include:
- Carbaryl
- Malathion
- Permethrin
- Esfenvalerate
- Spinosad
It’s important to rotate between different chemical classes to prevent resistance. Always follow label directions carefully.
How can codling moth be managed conventionally?
Conventional codling moth management relies heavily on chemical insecticides. Key strategies include:
Timing insecticide applications
Spraying is timed to coincide with peak egg hatch and larval development. Multiple applications are needed for successive generations.
Coverage and penetration
Insecticides must thoroughly coat fruits and leaves to reach internal plant tissues where larvae feed.
Mating disruption
Like in organic systems, pheromones are widely used to disrupt mating and reduce overall populations.
Chemical rotation
Rotating insecticide classes and modes of action reduces resistance development.
Residual activity
Some products like spinosad persist on plant surfaces for 7-14 days, controlling multiple life stages.
What is the best integrated pest management (IPM) for codling moth?
The most effective codling moth programs integrate multiple tactics in a strategic IPM approach:
- Monitoring with traps and degree day models to time control measures
- Mating disruption pheromones to reduce mating
- Resistant apple varieties
- Selective insecticides when thresholds are exceeded
- Cultural controls like sanitation, tree bands, removing alternate hosts
- Natural biological control with introduced parasitic wasps
IPM provides long-term, sustainable codling moth suppression with minimal insecticide use. Preventive measures are favored over reactive sprays.
How can you monitor for codling moth?
Accurate monitoring and forecasting are essential for well-timed codling moth control. Methods include:
Pheromone traps
Traps baited with female sex pheromone attract males. Trap counts detect emergence patterns, flight peaks and need for control measures.
Blacklight traps
Blacklight traps draw in moths at night. Checking for codling moths indicates their presence.
Fruit and trunk inspections
Checking developing fruit for sting entries or larvae indicates an active infestation.
Degree day models
Degree day models estimate development based on daily temperatures to predict emergence and treatment windows.
What are some key codling moth thresholds?
Some common treatment thresholds used for codling moth management include:
- 5-10 moths per pheromone trap per week
- 5% infested fruit
- 1 larva entry per 100 fruit
- 0.5 larvae per tree
- 200-400 degree days since biofix
These thresholds trigger insecticide applications or other controls before populations escalate.
What tactics should be avoided for codling moth control?
Some ineffective or counterproductive codling moth practices include:
- Broad spectrum insecticides that kill beneficial insects
- Applying insecticides on a calendar schedule with no monitoring
- Using the same mode of action insecticides repeatedly
- Not rotating between different insecticide classes
- Poor coverage when spraying
- Letting populations build up too high before treating
These practices can flare secondary pests, disrupt IPM programs and lead to insecticide resistance.
Conclusion
In summary, the codling moth undergoes four main life stages of egg, larva, pupa, and adult. Temperature and day length drive seasonal development, with larvae causing the most damage by tunneling into fruit. Integrated pest management with mating disruption, monitoring, biological control, selective sprays and cultural practices is key for sustainable, effective control. Understanding the insect’s lifecycle and biology provides insights into controlling this major pest.
