Blog & News

Predator Satiation in Black Ash

Published on Wednesday May 24, 2023
Authored by PEIISC

I’m sure you’ve all heard the old adage “keep your friends close… and your enemies closer.” This is something that certain prey species truly live by!

PREDATOR SATIATION is a survival strategy wherein a prey species will become highly abundant for a brief period of time at long intervals. The fact that times of abundance are few and far between means that predator populations will not be overfed every year, keeping predator population size down. This means that there will probably be some prey left over after predators have had their fill, allowing for remaining prey to reproduce without as much pressure from predators.. This reproductive habit is known as MAST SEEDING in trees and shrubs. This event often occurs at the same time as other tree species to concentrate the effects and provide an even higher chance of seed survival. Oaks are a well-known group that demonstrates MAST SEEDING, but a rarer example is the case of black ash, Fraxinus nigra

Black ash produces a good seed crop at irregular intervals, usually only every seven to nine years. Black ash is the only tree species on PEI registered as threatened by COSEWIC (Committee on the Status of Endangered Wildlife in Canada). Black ash is of extraordinary cultural and ecological significance, and PEI remains one of the few areas in the tree’s native range free from the emerald ash borer (EAB), Agrilus planipennis. EAB is an extremely destructive pest of true ash trees, introduced from East Asia. EAB has killed over 99% of the trees it has infested to date. EAB larvae tunnel through the tree while feeding, cutting off pathways by which nutrients and water are moved and killing the tree. PEI could become infested in the future, so during times of MAST SEEDING, it is important to collect black ash seeds when you are able to preserve the species in seed. If you can’t collect any seeds, what else can you do to help preserve black ash on PEI?

Work is currently ongoing to discover where on PEI black ash trees are growing, collect seeds, and bolster PEI’s black ash population. Healthy, mature trees with sizeable seed crops are rare on PEI. If you are aware of any black ash growing on PEI, conservationists would like to know! If you have wild black ash seeds available to be collected, contact the Canadian Forest Service National Tree Seed Centre for information on how to collect the seeds and what to do once the seeds are collected: 

Atlantic Forestry Centre, National Tree Seed Centre

  • 1350 Regent Street
  • Fredericton NB E3C 2G6
  • Tel: 506-452-4162
  • Fax: 506-452-3525

Preventing EAB from becoming established on PEI is crucial to the future of our island’s black ash populations.

  • DON’T MOVE FIREWOOD! Prevent the establishment of EAB on PEI by not moving firewood over provincial boundaries.
  • EARLY DETECTION IS KEY: Monitor ash trees on your property for signs of EAB. Together we can protect and restore this vital component of the Acadian forest! Signs include:
    • 3.5 – 4.1 mm wide, D-shaped exit holes.
    • Vertical splitting in the bark, called “bark cracking”.
    • Production of new young shoots at the base of the tree, called “epicormic shoots”.
    • S-shaped galleries from larval feeding on water-conducting tissues (this activity can create gaps that prevent the tree from moving water and nutrients through itself, called girdling).
    • Canopy dieback, beginning in the tree’s crown.
    • Evidence of woodpecker feeding activity on the bark, called “blonding”.
    • Scar tissue that appears as a lumpy or deformed mass. Called “callus formation”. 
    • Irregular notches in leaves from adult beetle feeding.
    • Sloughing off of bark.
  • SHARE: The first step toward effective invasive species management is learning. Together we can spread the word to combat invasive species and help out native species at risk!