Guide to Codling Moth Damage Identification
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Introduction
Codling moth is one of the most serious pests of apples. The larva cause two types of damage: stings and deep entries. 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 anther spot (figure 2). A deep entry is a site where the 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).
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 holes in these locations may be much 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.
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 & b). Once the CM larva is ready to pupate it exits the the fruit either through the same hole it made upon entry or it chews a new tunnel to the surface. Figure 11a & b shows where a larva entered this Gala fruit in one spot and exited out a separate hole. It is important to note that the presence of two holes does not indicate necessarily 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 “sting” on the front page.) Figure 12a shows where there are multiple attempts to enter this Golden fruit at the stem end. The holes may have been made by different CM larva 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 a CM larval infestation: the introduction of fungi and/or bacteria causing the fruit to rot.
Codlin Moth Larvae
Codling moth larvae tunnel to the seed core, undergo four molts, then exit the fruit to pupate. Figure 13 shows a larva that has fed in flesh but not made it to the core. Figure 14a shows a late stage larva feeding on seeds. Figure 14b shows an early stage larva that died just below the surface. Figure 15 shows a live larva reared on artificial diet.
