Apples have become one of the most recognizable fruits of our diet, but it's a long way from the mountains of Eurasia to kitchen tables around the world. Apples belong to the rose (Rosaceae) family, which also includes pears, peaches and quinces. For over a thousand years, growers built and traded fruit along the Silk Road. The growing popularity of apples also unwittingly spread a small but destructive label: the codling moth moth (Cydia pomonella).
The codling moth begins its life as a worm and almost anyone can relate to finding a worm in their fruit. As children, we often see pictures of the friendly green worm in a big red apple. In France there is a common phrase: "le vers et dans le obst" or "the worm is in the fruit", which means that the damage has already been done. Today codling moth is a major pest in most places where apples are grown and can cause significant fruit damage. They are also a serious threat to walnut growers, who are reportedly devoting 10% of their agricultural budget to controlling this pest.
Fruit production can often be seen as advanced gardening because of the investment of time and space. Many apple and pear trees do not produce fruit until a few years after they have been planted. It can be daunting to battle pests after you've patiently waited to taste the literal fruits of your labor. This blog introduces various methods that you can use to control the moths and ultimately enjoy an abundant harvest.
Good products for getting rid of codling moth:
Codling Moth overview
The cod moth is a common apple pest. Source: Gailhampshire
It's not uncommon for codling moths to have more than two generations per year, depending on the local temperature and climate. Under favorable conditions, moths can live up to four generations between spring and autumn. Mature male and female moths are 1/2 to 3/4 inches long and gray or brown in color. Male codling moths also have some bronze streaks and spots on their wings.
Life cycle of codling moths
From early spring, when the first fruit blooms begin to form, adult female moths emerge from their winter pupae to lay oval eggs, which hatch in six to 14 days. A single female moth can lay up to 100 eggs, which are almost transparent and very difficult to see! The first generation of eggs are mainly found on leaves. During the growing season, female moths continue to emerge and lay eggs on various parts of the tree, including the bark and fruit.
As with many insects, this insatiable larva is the most destructive of its life cycle. A newly hatched moth larva begins at about 1/10 of an inch in length with a black head and a cream colored body. The larva of the codling moth turns slightly pink with age and can grow up to 1 to 2 cm in size. In walnuts, moth larvae feed directly on the kernel. In pome fruits such as apples and pears, the larvae burrow through the pulp to feed on the seeds.
After 3-5 weeks, fully grown moth larvae pupate the fruit and leave behind a pile of feces called brown frass. Nobody wants to bite into a worm, so watch out for this tell-tale sign that the fruit may be contaminated!
As soon as mature larvae leave the fruit, they look for protected pupation sites to spin cocoons. Leaf litter around the tree and its bark are some of the most common places. In two to three weeks, most of the mature larvae pupate and emerge as second generation adult moths to start the destructive process again. Some first generation larvae will instead dormant and reappear the following spring.
The peak moth season in North America is July. Second and third generation moths are particularly troublesome when their eggs are laid directly on growing fruit and their larvae can easily access their food source.
The last generation of larvae overwinter in cocoons directly under the bark or in the leaf litter surrounding the host tree. Many of these larvae are eaten by birds, but enough remains in winter and even freezing temperatures to wreak havoc the following spring.
Common habitats for codling moths
Cod moths are found in temperate regions where apples are grown. Some countries like Japan have very strict import and quarantine treatment for agricultural products and are able to limit the populations of codling moths. Adult moths are not active during the day and prefer to hide under loose bark, leaves, or some other protected area. They become more active at dusk and are most active on warm summer nights.
What do Codling Moths eat?
The cod larvae eat channels through the fruit and leave behind them. Source: Crux
The codling moth got its name from an English cooked apple called codling moth because it was such a common problem among apple growers. As the name suggests, this moth is particularly suitable for feeding apples. However, other fruits like peaches, plums, and quinces are also susceptible.
Walnuts are another of her favorite food sources. The fruit can be damaged by surface-nourishing wounds or tunnels as the codling moth larvae move through the fruit to feed on the seeds. Untreated moth larvae can damage 80-90% of the fruit. Walnuts infected with moths are completely inedible.
How to Get Rid of Codling Moth
Much research and literature have been conducted on the control of codling moths because of their economic impact on commercial orchards. As a business, commercial producers have relied on chemical pesticides, which have negative environmental and health effects. The codling moth populations also developed resistance to these chemical controls. Since then, more funding has been allocated to integrated pest control research, and we can adapt some of these techniques for use in the home orchard.
Organic control
Cod moth with wings outstretched. Source: Davidshort
In recent years, home gardeners have been able to purchase a new organic insecticide, CYD-X, or the moth granulosic virus, as a target method to control the moth. A moth larva needs to ingest CYD-X in order for the virus to attack its digestive tract. The virus kills the larva three to seven days later. Carefully plan your insecticide applications. Spray the fruit thoroughly after seeing signs that the first generation of eggs have hatched. Continue spraying weekly throughout the growing season until harvest. CYD-X is currently approved for organic farming in commercial and private orchards.
Spinosad is another biological control substance and is made from Saccharopolyspora spinosa, a naturally occurring soil bacterium. Spinosad is more toxic to beneficial insects than CYD-X and should be sprayed a maximum of six times per season. Do not use seven days before harvest. Spinosad and CYD-X can be mixed with 1% horticultural oil to increase their overall effectiveness against codling moths. Similar to CYD-X, Spinosad disrupts the life cycle of the eggs and prevents new generations of moths from maturing.
Environmental control
Hygiene is an extremely important method of pest control. Since most apples require multiple trees for cross-pollination to bear fruit, a tree that is heavily infested with codling moth will inevitably spread to surrounding trees. While your fruit is forming, it is important to inspect the fruit weekly for any signs of codling moth and remove any affected fruit immediately. Pick up any fallen fruit and tidy the area around the base of the tree to limit the potential habitat for codling moths. Pay special attention to the moth high season from May to June.
Thin large clusters of fruit on just one or two. Thinning not only helps with general hygiene, it also encourages the remaining fruit to grow larger. After the fruit is 1/2 to 1 inch in diameter, you can wrap the fruit in paper bags (# 2 brown lunch boxes) or cotton bags to create a physical barrier against the moths. Make sure the bag is sealed tightly around the fruit so that adult moths cannot reach it. Be aware that strong winds can be a problem for your bags! If you live in a windy area, you can use kaolin clay as a physical control against these moths.
A traditional method of controlling moth populations is to wrap the trunk of a tree with a 1 1/2 to 2 inch band of corrugated cardboard or burlap to encourage adult females to lay eggs on them instead of the host plant. This method works well on trees that have smooth bark and that have few natural crevices. However, you need to be vigilant when removing these ligaments, otherwise this method can backfire. Many commercial growers use stem tapes or pheromone traps to monitor the codling moth population and better plan their insecticide use.
Cod moths themselves can become part of the food chain for other insects. Since the early 20th century, there has been a search for the right parasitoid, parasitic insects that kill their host before the hosts can mature. Commercial breeders have seen some success in releasing parasitic wasps in combination with other control techniques. Trichogramma platneri is a parasitic wasp native to the western US that lays eggs in the eggs of the moth eggs and prevents the moths from completing their life cycle. This parasitoid has been shown to be most effective west of the Rocky Mountains, where it is naturally adapted. These wasps can be bought online and released at home. However, you need to plan the release correctly to ensure there are enough moth eggs for them to parasitize.
Prevention of moths
Damaged apples that are likely to have cod larvae in them. Source: Patrick Clement
Preventing codling moths, as with many other crops, can begin with careful plant selection. Early ripening apples like Galas and Red Delicious as well as late-leaved walnuts are less prone to moth damage because their fruit production time is not synchronized with the maximum moth activity. Apple trees naturally grow very tall, which makes it difficult for the home gardener to examine and control pests in the canopy. However, you can buy apples grafted onto a dwarf root that limits the height of the mature tree.
You can use different types of traps to monitor moth numbers and improve moth control. Moths are attracted to sugary liquids and you can easily make a liquid trap with a dilute mixture of water mixed with molasses, juice or beer and place it near or in the tree.
Alternatively, you can use coding moth pheromone traps, which mimic female sex pheromones, to lure male moths onto a sticky surface. You may need to place two to four pheromone traps per tree and replace them monthly. Use caution when removing male moths from pheromone traps to avoid transferring the sex attractant to other surfaces. Put sugar or pheromone traps off as the days warm up. If you've caught some early moths, you can expect eggs to be laid a few days later. Many commercial apple growers use pheromone traps to determine the degree days for spraying apple trees for worms.
Breaking mating is another form of pheromone control. According to researchers at Colorado State University, this method is not recommended for home gardeners or commercial growers with fewer than 10 acres of trees. The mating interruption technique uses a large amount of female pheromones that attract male moths to confuse male moths and prevent mating. However, it does not affect female moths that have already mated or moths that may fly outside of the mating disorder area to mate.
As always, it is good practice to encourage beneficial insects, birds, and bats in your garden or orchard. You can help limit the emergence of the first generation of moths by feeding on the pupae before spring, and manage future generations at various stages in the moth's life history from eggs to adults.
frequently asked Questions
Cydia pomonella also affects pears, walnuts and other fruits. Source: Gailhampshire
Q: Can you eat apples with codling moth?
A: Yes, you can still eat apples with some moth damage by cutting away contaminated pulp and brown food.
Q: Where do moths come from?
A: Cod moths originated in Central Asia, probably near what is now Kazakhstan, along with their main food sources such as apples and walnuts.
Q: How do you make a moth trap?
A: Homemade bait can be used to catch adult moths. Like many other garden pests, these insects are attracted to the scent of fermenting sugars. Mix one part molasses, juice or beer with a few drops of soap to seven parts water and pour the mixture into an open container. Hang the trap in the treetops.
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