Sap is a fluid that circulates through a plant's vascular system, in a similar way to blood moving through our veins. Phloem sap carries the sugars produced in the leaves by photosynthesis down to roots and other storage organs, as well as carrying minerals and hormones. Xylem sap is watery and transports nutrients absorbed by the roots upwards to the rest of the plant. Some plants leak sap from wounds or pruning cuts, and this is known as bleeding.

sap

Elaeagnus

Suckers are growths that appear from the root systems of many trees and shrubs such as lilac, cherries, Robinia. On grafted plants such as roses, suckers can grow from below the graft union, on the rootstock material. Suckers are usually removed by gently pulling off when young.

Eleagnus sucker can affect the appearance of Eleagnus but does not usually reduce the vigour of Eleagnus plants and so control is not necessary. Plant suckers can be a part the biodiversity a heathy garden supports. 

• Often suckers do not affect the growth or vigour of plants and so can be tolerated
• Encourage predators and other natural enemies of suckers, in the garden, such as birds, ladybirds, wasps and ground beetles
• If necessary distorted leaves can be removed from the plant however, this may cause more damage than the insect

Adult elaeagnus sucker are 2-4mm long and have two pairs of have transparent wings with black shading which are held roof-like over their abdomen when at rest. The orange-yellow nymphs are wingless and flattened so the width of their bodies is much greater than the depth. Older nymphs have large pads on the margins of the upper thorax where the wings will develop.

It has several generations during the summer with the largest populations occurring on the new growth in the spring. It probably overwinters as eggs which hatch in mid-February.