Tree Fruit Research & Extension Center

Cullage Assessment & Education

Guide to Codling Moth Damage Identification

 
Laminated reprints of this guide in both English and Spanish are available upon request.

 

Figure 1

Introduction

Codling moth is one of the most serious pests of apples. The larva cause two types of damage: stings and deep entries (tunnels = wormholes). A sting is a place where a larva chews into the flesh only a short distance before either dying or turning back to re-enter at another spot (Figure 2). A sting is defined as being <1/8th inch deep. Anything deeper is considered a "wormhole". A deep entry is a site where a larva penetrates the skin and chews down to the core to feed on the seeds (Figure 3). As the larva feeds frass is pushed out and may accumulate around the entry hole (Figure 4).

 

Figure 2 Figure 3 Figure 4

 

Identifying Codling Moth Entries

Figures 1-4 show larval side entry points. However, larvae may also enter through the calyx or stem ends of the fruit. Entry or exit holes in these locations may be harder to detect. Figures 5-7 show cases where an entry hole is located at the stem end. It is easy to miss seeing these entry holes if the view is obstructed by the stem or they are covered with debris. Holes at the stem end could easily be confused with stem rubbing and splitting, so it is important to examine any suspicious fruit.

 

 

Figure 8 Figure 9

Figures 8-10 show entry holes at the calyx end of the fruit. Here CM damage could be camouflaged by residual flower parts or debris (Figures 10a & 10b).

Once the CM larva is ready to pupate, it exits the fruit either through the same hole it made upon entry, or it chews a new tunnel to the surface.

Figure 10a Figure 10b

Figures 11a & 11 b show where a larva entered this Gala in one spot and exited out a separate hole. It is important to note that the presence of two holes does not necessarily indicate that the larva has left the fruit. The fruit may have been infested by more than one larva. Or the larva may have created more than one entry hole (see the "sting" definition above).
Figure 11a Figure 11b

 

Figure 12a Figure 12b Figure 12c

Figure 12a shows where there are multiple attempts to enter this Golden Delicious apple at the stem end. The holes may have been made by different CM larvae or by a single larva. Upon cutting the fruit it appeared that only one entry was successful (Figure 12b). The larva then exited the fruit through the calyx end (Figure 12c). Figure 12b shows the secondary problem with CM larval infestation: the introduction of fungi and/or bacteria causing the fruit to rot.

 

Figure 13

 Figure 14a

 

Codling Moth Larvae

Codling moth larvae tunnel into the fruit to feed on the seed core. In the process they undergo four molts before exiting the fruit to pupate. Figure 13 shows a larva that has fed in the flesh but not made it to the core. Figure 14a shows a late stage (instar) larva feeding on seeds at the apple core. Figure 14b shows an earlier instar larva (younger) that died just under the skin surface inside a small tunnel. Figure 15 shows a close-up of an artificially raised CM larva to show body detail. The "head capsule" of the larva can vary in color from light brown (recently molted) to black. The body color can vary from off-white to pink.

Figure 14b

Figure 15

 

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