Integrated Pest Management in Arboriculture: From Theory to Practice

Article Figures & Data

Table 1. Action thresholds for selected insect pests (^a).

Type of insect	Number of insects/unit area
Type of insect	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.