about another 100 trees which is not going to give you anything like the production advantage
possible from properly looking after a smaller number.

PEST AND DISEASE RESISTANCEWHEN CHOOSING ROOTSTOCKS
With the industry movement toward integrated pest management, it is vital that we stay with
woolly apple aphid resistant rootstocks.At present, most of our orchard plantings are on tolerant
rootstocks.This means that the small proportion planted on susceptible rootstocks such as M.9,
M.26 and Mark are not under heavy infection pressure, thus making woolly apple aphid control
relatively easy. If the proportion of susceptible rootstocks increased markedly, we can anticipate
substantially more difficulty with woolly apple aphid infestation of susceptible rootstocks.

New dwarfing and semi-dwarfing rootstocks with woolly apple aphid resistance are under
development.Until these rootstocks become commercially available, I believe trees propagated
using M.9 or Mark interstock on our standard rootstocks are our best option.

There are now a number of interstock blocks planted and they are beginning to look pretty
spectacular. A word of warning about fire blight infection of M.26.Over the years we have
heard stories from the USA of M.26 trees being killed by fire blight at the bud union as a result
of systemic infection travelling down the tree from a strike in the scion.This season I came
across this type of fire blight infection here.It appears as if it may become a problem where
susceptible varieties such as Gala are grown on M.26 in warmer districts which favor fire blight
activity.We, therefore, need to be very diligent about fire blight control for orchards planted on
this rootstock.

M.9 and MM.106 are both reported from the US to be susceptible to fire blight as well but, to
date, I have not come across reports of problems with tree deaths due to fire blight infection to
the union.Until we have something better, these M.9 or Mark interstocks with either MM.106 or
M.793 rootstocks look to be our best options.