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OSC Activity F.7

Control of Rosy Apple Aphid (RAA) in organic apple orchards

Activity Researchers

Name Affiliation
Linda Edwards, Lead Researcher
ledwards@nethop.net

University of British Columbia
757 Riorden Rd
Cawston, BC V0X 1C2

Objectives

In this study, we are proposing to test one chemical and two mechanical control strategies to reduce the spring populations of rosy apple aphids.  The chemical strategies include autumn and spring oil applications at various application dates.  The mechanical strategies include the removal of plantain, the alternate host, from the orchard system through flail mowing, and rotavating and reseeding with an orchard grass mix. The timing of applications is crucial for both autumn and spring applications. As such, we will be using pheromone traps to verify the timing of the autumn migration of rosy apple aphids in southern BC.  We will also be using a degree day model developed by Graf et al. (2006) to time the spring oil applications. 

Activity Summary

The rosy apple aphid, Dysaphis plantaginea, is considered one of the most serious apple pests worldwide. It was introduced to Canada over a century ago from Europe along with its winter and summer hosts, apple, and plantain. In organic orchards it has proven to be especially problematic. In the future it may become more of a problem in conventional orchards because there are reports of increasing resistance to insecticides.

In a given year, rosy apple aphids may remain at low levels in some organic orchards, while in others high densities can cause significant fruit damage. In an orchard with up to 100% of trees infested, as was the case in many orchards in 2007, 76% of the harvest can be lost.

Conservation biological control for rosy apple aphids can be effective at low pest populations, but cannot prevent extensive damage in bad years. Organically acceptable horticultural oils are available, but spring applications are not always effective once aphid feeding starts, as aphids are then protected from sprays by the curled leaves.  As a result, much of the research focus in the past 10 years has been on autumn control of this insect using a range of both organic and conventional products.  Properly timed conventional products gave between 90 and 100% control.

The goals of this research are three-fold.  The first is to investigate the potential of an organically acceptable product, Superior dormant oil, to control the rosy apple aphid when applied both in the autumn and in the spring. Superior oil will be tested at multiple autumn and spring application dates and with varying numbers of repeat applications. A degree day model will be tested to ensure that spring oil applied just after egg hatch and before feeding begins can be effective.  

The second is to determine the timing of autumn migration using pheromone traps in order to time the autumn applications effectively. 

The third is to evaluate the mechanical control method of removing the alternate host plant from the orchard environment by rotavating and reseeding with an orchard grass mix in the autumn.  Without its alternate host, the rosy apple aphid cannot complete its lifecycle and return to the apple trees in the fall to lay eggs. This method will be assessed for its ability to reduce the percent cover of plantain in an orchard and to reduce the spring rosy apple aphid population. 

In the Similkameen Valley of British Columbia (BC), organic apple production is a large

and growing industry and this pest remains one of the last without an organically acceptable solution.  This research will provide growers with multiple tools that can be used against this pest. 

Background and Supporting Documents

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