| Type of insect | Number of insects/unit area | ||
|---|---|---|---|
| Spring | Summer | Fall | |
| Aphids on hardwood leaves | 2/leaf | 4/leaf | SIN |
| Soft scales | 5 mature females/m branch length | ||
| Pine needle scale (pine) | 2/needle+ | 4/needle+ | SIN |
| Spider mites | 1 /beat | 3/beat | SIN |
| Spruce gall adelgids | 15/2 m tree | ||
| Pine shoot moths | 5 laterals/2 m tree | ||
| Defoliators; hardwoods | 20% defol. | 40% defol. | SIN |
| conifers | 30% uniform defoliation | ||
| Bronze birch borer | 1 emergence hole | ||
| Lilac borer: in ash | 4 pupal skins/2 m of trunk | ||
| in lilac | 1 pupal skin plant | ||
↵(a) Action threshold is the pest population density that signals the need for or justifies intervention activities. Values are for vital plants and are estimates based solely on the experience of the author.
SIN: Spray inappropriate now; census population again in spring.
↵+ Density higher than in previous generation.