Organic Production of a New Australian-bred Scab Resistant Apple in Queensland, Australia

Middleton, S., Zeppa, A.G., Horlock, C.M. and Nimmo, P.R.
Department of Primary Industries and Fisheries, Queensland, Australia

The first crop of organically-grown Australian-bred scab resistant apples (Malus domestica Borkh.) has been produced at an experimental site in Queensland, Australia, characterised by sandy soils and a warm, summer rainfall climate. The planting is in its fourth leaf and consists of one hectare of trees of a selection resistant to apple scab (caused by Venturia inaequalis) from the Department of Primary Industries and Fisheries, Queensland (DPI&F) apple breeding program. All trees are planted on MM.106 rootstock at 5.0m x 1.8m spacing (1111 trees/hectare).

With minimal lime sulphur and wettable sulphur sprays, no apple scab has occurred on leaves or fruit of the resistant apple. Apple scab infected 3-5% of ‘Galaxy’ (comparator cultivar) fruit in the first cropping season. To date the most significant causes of insect damage to fruit have been native budworms and Light Brown Apple Moth (LBAM). This season spinosad applications and LBAM pheromone disruption are providing effective management of these pests.

White clover (Trifolium repens) planted in the alleyways is growing prolifically and appears to be attracting damaging insects, including western flower thrip, away from the trees. Kangaroos have been a problem, attracted to the lush groundcover in dry autumn months and occasionally damaging growing points and foliage. Fruit set at the site is excellent and has necessitated some hand thinning.

In a factorial experiment to compare the effectiveness of weed mat and sugar cane mulch in weed control, and the effect of supplementary organic compost on tree growth and productivity, larger apples were produced from trees treated with organic compost and sugar cane mulch.

Nutrient status at the site continues to be monitored via soil and leaf nutrient analysis. Insect biodiversity and soil health are being compared with an adjacent block of conventionally-grown apple trees.

 

Presentation given at the Symposium