Lesson LXXVI

The Codling Moth

Leading thought—The codling moth is a tiny brown moth with bronze markings which lays its egg on the apple. The larva hatching from the egg enters the blossom end and feeds upon the pulp of the apple, injuring it greatly. After attaining its growth it leaves the apple and hides beneath the bark of the tree or in other protected places, and in the spring makes the cocoon from which the moth issues in time to lay eggs upon the young apples.

Method—The lesson should begin with a study of wormy apples, preferably in the fall when the worms are still within their burrows. After the pupils become familiar with the appearance of the insect and its methods of work, a prize of some sort might be offered for the one who will bring to school the greatest number of hibernating larvæ found in their winter quarters. Place these larvæ in a box with cheese-cloth tacked over its open side; place this box out of doors in a protected position. Examine the cocoons to find the pupæ about the last of April; after the pupæ appear, look for the moths in about five days.

It would be a very good idea for the pupils to prepare a Riker mount showing specimens of the moths, of the cocoons showing the cast pupa skin, and of the caterpillar in a homeopathic vial of alcohol; pictures illustrating the work of the insect may be added. The pictures should be drawn by the pupils, showing the wormy apple, both the outside and in section. The pupils can also sketch, from the pictures here given, the young apple when just in the right condition to spray, with a note explaining why.

Observations—1. Find an apple with a codling moth larva in it. How large is the worm? How does it act when disturbed?

2. What is the color of the caterpillar’s body? Its head?

3. How many segments are there in the body? How many of these bear legs? What is the difference in form between the three front pairs of legs and the others?

4. Look at a wormy apple. How can you tell it is wormy from the outside? Can you see where the worm entered the apple? Was the burrow large or small at first? Can you find an apple with a worm in it which has the door for exit made, but closed with waste matter? How is this matter fastened together? If the apple has no worm in it, can you see where it left the apple? Make a sketch or describe the evidence of the caterpillar’s progress through the apple. Do you find a web of silk in the wormy part? Why is this? Does the worm eat the seeds as well as the pulp of the apple?

5. Take a dozen rotting apples, how many of them are wormy? Do the parts of the apple injured by the worm begin to rot first? In how many ways does the codling moth injure the apple? Does it injure other fruits than apples?

6. How late in the fall do you find the codling larvæ in the apple? Where do these larvæ go when they leave the apple?

Work to be done in March or early April—Visit an orchard and look under the loose bark on old trees, or along protected sections of fences or brush piles and bring in all the cocoons you can find. Do not injure the cocoons by tearing them from the places where they are woven, but bring them in on bits of the bark or other material to which they are attached.

1. How does the cocoon look outside and inside? What is in the cocoon? Why was the cocoon made? When was it made?

2. Place the cocoons in a box covered with cheese-cloth and place the box out of doors where the contents can be frequently observed and make the following notes:

3. When does the larva change to the pupa? Describe the pupa. How does the cocoon look after the moth issues from it?

4. Describe the moth, noting color of head, thorax, body, front and hind wings?

5. If these moths were free to fly around the orchard, when and where would they lay their eggs?

6. When should the trees be sprayed to kill the young codling moth? With what should they be sprayed? Why should they not be sprayed during the blossoming period? Why not after the calyx closes?

7. How do the nuthatches, downy woodpeckers and chickadees help us in getting rid of the codling moth?

8. Write an essay on the life history of the codling moth, the damage done by it, and the best methods of keeping it in check.

References—The following bulletins from the U. S. Dept, of Agriculture: Farmers’ Bulletin 247, “The Control of the Codling Moth and Apple Scab;” Bulletin 35, New Series, Bureau of Entomology, “Report on the Codling Moth Investigations,” price 10 cents; Bulletin 41, “The Codling Moth,” 105 pages, 15 cents, by Special Field Agent, C. B. Simpson; Bulletin 68, Part VII, “Demonstration Spraying for the Codling Moth,” price 5 cents. The Spraying of Plants, Lodeman, Macmillan Company; Economic Entomology, Smith.