Fruit IPM Fact Sheet Fruit IPM Fact Sheet
CODLING MOTH
Scientific Name-
Cydia pomonela (Linnaeus)
Family-Tortricidae
Reference: Common Tree Fruit Pests Angus Howitt, 1993, NCR 63 - Michigan State University
The Codling Moth originated in Asia Minor. It was carried into Europe by invading migrants and from this point was disseminated to all apple growing areas of the world. It was brought to America by the colonists and has been one of the principal apple pests for more than 200 years.
It became a serious problem in the Midwest shortly after the Civil War and continued to be a problem until about 1900, when use of arsenicals became widespread. From this time to the early 1930's, commercial orchardists generally controlled it effectively, though some losses began to occur about 1925. These control failures were due largely to the codling moth's development of resistance to lead arsenate.
Increasing losses were experienced until 1946, when DDT came into use. The insect was well controlled for the next 10 years. DDT then began to lose its effectiveness, but with new insecticides such as Sevin and Guthion, injury by this pest was very light from 1959 to 1961. In certain periods, it was undoubtedly a major insect pest of apples, but at other times it was relatively unimportant. Even with the new effective spray chemicals of today, the codling moth must still be considered an ever-present threat. Recently, resistance to organophosphate insecticides has become a problem in some areas of Washington and Oregon.
Life Stages
Egg: The egg is very small, flattened, almost transparent and elliptical, measuring 1 to 1.2 mm in diameter.
Larva: Just-hatched larvae are very small-about 2 mm long and 0.5mm in diameter. At this stage, the head is almost twice as wide as the body. When the larvae are young and boring into the fruit, they are pale yellow. The mature larva is white, usually tinged with pink; its head is brown, and it measures approximately 13 mm. The full-grown larva can be distinguished from Oriental fruit moth and lesser appleworm larvae found in fruit by the absence of the chitinous protuberance on the end of the abdomen called the anal comb. There are five instars.
Pupa: The brown pupae vary from 10 to 12 mm in length with a width of 3 mm. The pupae of females are usually longer and wider than the pupae of males. Immediately after the transformation of the larva into the pupa, the color of the pupa is the same as that of the larva. Later it changes, gradually becoming brown. Pupae that will develop into males can be identified by the presence of two clearly marked little circles-the future gonads-on the ventral surface of the sixth abdominal segment.
Adult: The moth averages about 19 mm across the expanded wings and 9 mm long with the wings folded. It is gray-brown, crisscrossed with fine alternating gray and white bands. Near the tips of the forewings are bronzed areas characteristic of the codling moth.
Host Range
The codling moth is a pest of apples and pears and a pest of walnuts on the West Coast. It is present in all fruit-growing areas of the United States and Canada. It was an apricot pest in the past and is found in quince, peach, plum and cherry.
Injury or Damage
The codling moth causes two types of injury to the fruit: deep entries and stings. Deep entries are caused by larvae that eat through the skin into the side or from the calyx end. Sting entries occur where the larvae died before gaining entry or where they began tunneling, stopped and then began other feeding entrances elsewhere on the fruit. Second-generation larvae cause most of the damage.
Factors Affecting Abundance
In all seasons, climatic conditions influence the activities of the codling moth. Temperature is the most important of the climatic factors, but humidity, rainfall and winds are also important. If high temperatures prevail during the season, adult codling moths will emerge earlier in the spring and deposit more eggs. These will hatch earlier in the season and in greater numbers and, in turn, more of these larvae will succeed in finding and entering fruit. In the fruit, they feed more voraciously than they would in cool weather and mature earlier. They leave the fruit to find cocooning quarters and the moths again emerge earlier.
A warm, early spring may result in accelerated development of the first and second generations, sometimes resulting in a partial third "suicide" generation. The young larvae of this partial generation will not survive overwintering.
Rainfall and moisture are needed to hasten the development of pupae and the emergence of moths. Low humidity, on the other hand, seems to help the larvae enter the fruit. Heavy winds will cause the moths to cling to protected hiding places, while light breezes will aid in their flight and distribution.
Life History
Codling moths overwinter as mature larvae in tightly constructed silken cocoons located principally under loose bark on the tree trunk and larger limbs. Cocoons may also be found in other places in the orchard, such as piles of wood, brush, posts and occasionally in coarse mulch, such as weed stalks and corncobs. In addition, larvae overwinter in stored baskets or crates that have held cull fruit and in the walls of packing sheds and other buildings adjacent to the orchard.
The overwintering larvae start to transform to pupae inside the cocoon about the time that the first blossoms show color. The bulk of pupation usually occurs during bloom, but some larvae may not transform until a month later. Prior to pupation, the larva cuts a circular opening in one end of the cocoon and the pupa thrusts its way out through this aperture just before the moth emerges.
The first moth of the season usually appears as the last petals fall from the apple blossoms. Peak emergence may occur within four or five days after the first moth emerges. Weather conditions such as low temperatures may delay it as much as 10 or 12 days. The last moths of the first brood may not appear until six or seven weeks after petal fall. Moths emerge usually during the morning hours and begin laying eggs within two or three days if the evening temperatures are favorable, i.e., above 62 F. Few eggs are laid at this low point, but when temperatures approach 70 F, egg deposition increased greatly, and above this point even more will be laid.
Eggs are laid on the fruit or on nearby leaves. A female may lay up to 100 eggs. Eggs hatch in six to 14 days, depending on the prevailing temperatures. The newly hatched larva is white with a black head and is large enough to be seen with the naked eye. Those hatching on leaves wander about seeking the fruits, which many of them fail to find. On the fruit, larvae may wander about seeking a rough area such as the calyx or a scab spot, which aids them in making an entrance. The silken threads against which the brace themselves while digging in are more securely anchored to rough areas on the apple's surface.
If successful in entering, they feed inside the apple for about three weeks, after which they leave it to seek a cocooning site on the trunk or larger branches of the tree. If the apple has fallen to the ground, the emerging larva will travel in circles until it comes to the tree trunk or another solid object where it will find cocooning quarters.
The time spent in the cocoon depends on temperature and rainfall but is usually 14 to 21 days. Many larvae do not transform to pupae during this time, however, but continue as larvae until the next spring. Those that will emerge as moths of the second brood pupate in the cocoon as already described and start emerging as early as July. Second-brood moths will lay eggs over about two months. Mature larvae of the second brood start leaving the apples in mid-August and continue until apples are removed from the orchard or until very cold weather arrives. There larvae, together with those of the first brood that did not pupate, will overwinter and start the cycle again the next spring.
Monitoring
At full bloom, use one pheromone trap per 10 acres of orchard. Set the traps in the foliage at eye level on the north side of the tree. Place the traps in the portion of the orchard most likely to be entered by moths from wild hosts or abandoned or poorly sprayed orchards. Traps should be checked once a week. If the total moth counts in the commercial orchard are 14 or more per trap per week, sprays are needed. Traps and caps should be replaced about mid-July. When problems exist, apple maggot sprays will dictate the timing of the codling moth sprays that are required in the latter part of July and mid-August.
Check for first generation damage in mid-July by searching for apples with frass. This will help determine the potential of the second generation.
Using 50 degrees F as a base, degree-days (DD) for codling moth activity* are:
| 150 DD | first adult emergence. |
| 250 DD | first eggs laid |
| 500 DD | peak adult emergence |
| 550 DD | peak egg laying |
| 1,150 | first emergence of second generation adults. |
| 1,600 | peak emergence of second generation adults |
| 1,700 DD | peak egg laying by second generation adults |
| *Data from MSU PETE model. | |
Control
Codling moth control requires careful monitoring and timing of insecticide applications to coincide with the hatching of larvae. If insecticides are applied too late, larvae will have tunneled into the fruit, where the insecticides can not affect them.
The first spray to control the first generation codling moth is applied at 500 to 550 DD accumulated after April 1, or 250 DD after the first sustained catch in the pheromone traps. A second application can be made two to three weeks later, if needed. Growers who don't want to make routine applications can use an action threshold of five moths per trap per week. If the number of moths trapped exceeds this number, an insecticide application should be made in seven to ten days. Repeat applications should be made only if the moths exceed this threshold 14 days after the insecticide application.
Sprays for the second generation are applied at 1,400 to 1,600 DD, before peak adult emergence and before the eggs start to hatch.
