Eggs
Pheromone-baited traps are the primary method for detecting and delimiting new isolated gypsy moth populations in previously uninfested areas. Pheromone-baited traps are a very sensitive tool that can be used to detect very low density populations that could not be detected using any other method. Every year, over 300,000 traps are deployed in the USA for detection/delimitation alone (Tobin et al., 2012). When a new population is detected using pheromone traps, it is a common practice to make a search for gypsy moth life stages in order to confirm the presence of a reproducing population. However, given the difficulty of detecting low-density populations in this way, life stages cannot always be found in all populations.
Larvae on foliage are easily distinguishable from other defoliators. Late in the year, host pupae and egg masses on tree trunks indicate gypsy moth infestation. Egg mass counting is a common practice for monitoring infested areas to estimate population density and predict future outbreaks. In North America, the detection of gypsy moth outbreaks is also based on aerial defoliation surveys.
Related invasive species
- Lymantria dispar
Related Farm Practice
- Defoliation
- Feeding
The gypsy moth is likely to ultimately occupy virtually all portions of the temperate world where oaks and other suitable host plants occur. Consequently, the northern hemisphere is more at risk for establishment than the southern hemisphere though some suitable hosts do occur in these areas. The gypsy moth is apparently not able to persist in very cold (e.g. Finland) or warm (subtropical to tropical) regions.
The gypsy moth is a 'proven' invader. The broad range of host plants that it utilizes (Liebhold et al. 1995), along with its high reproductive rate combine to make this insect a very successful invader of many types of forest and urban landscapes. Another characteristic that contributes to the gypsy moth's invasiveness is its propensity to be transported on human-made objects (e.g., egg masses can be laid on vehicles, logs, etc.). Perhaps the greatest limitation this species has as an invader is that females (of the European strain) are incapable of flight and this limits its rate of unassisted range expansion. However, as females of the Asian strain are capable of flight and all strains can lay their eggs on human-made objects, established populations are nevertheless able to spread.
Hatching larvae usually start feeding on flushing buds and later on newly-expanded leaves. High populations often result in total tree defoliation, often across a large spatial area.
Main hosts are defined as those that can be consumed by all gypsy moth instars without loss in developmental rate, developmental success, and adult fitness;other hosts are defined as those that can be consumed by some gypsy moth instars (often later instars) but with negative impacts, such as reduced developmental rate or reduced fecundity as adults. For a full list of main hosts, other hosts, and plants that have been shown to be non-suitable hosts, see Liebhold et al. (1995).