The Japanese maple is an attractive landscape tree that sports reddish leaves during its spring-to-fall growing season. Two types of black insect pests can attack this tree, so it's wise to watch for them and treat them promptly.
Aphids and Their Control
A black-coloured species of aphid can attack your Japanese maple tree. Aphids are small, soft-bodied pests that suck fluids from plants, causing leaves to curl or become distorted. If you control ants, you'll have fewer aphids because ants carry this insect to plants and feed on its excretion. Non-toxic insecticidal soap is a spray gardeners rely on to kill aphids.
Scale Insects and Their Control
Scale insects can be black or dark brown in colour and suck fluids from Japanese maples. They are small, from 1/8 to 1/4 inch long and look like bumps on leaf veins and branches. They remain in one location when they mature. Because of their armoured shell, you must mix horticultural oil or simple cooking oil with insecticidal soap and spray your tree several times for effective control.
Other Possible Insect Pests
Although the Japanese beetle is typically a large, green insect and not black, it is a common pest of the Japanese maple tree. Collect sleepy beetles in the early morning and drop them into a bucket of soapy water. Natural insecticides such as neem are said to be helpful as are traps you set at the edges of your property.