This is a final research report from Hort Innovation’s historical archives. Please note that as these reports may date back as far as the 1990s, the content and recommendations within them may be superseded by more recent research.

What was it all about?

Effective integrated pest management (IPM) programs for pome fruit crops required sufficient numbers of the natural enemies of pest species to be present in the orchard at the appropriate time.

Even when selective insecticides that were relatively harmless to these beneficial insects were used, commercial apple and pear orchards could be inhospitable places for them because of a lack of food (nectar, pollen or alternative prey) and shelter.

To address this problem, a range of flowering plants were grown as cover crops in commercial orchards to assess their effects on the colonisation and performance of beneficial insects, which included lacewings, ladybirds, hover flies and wasp parasitoids.

Initially, potential cover crops were identified through a desktop study of world scientific literature on conservation biological control and habitat manipulation.

Twenty-two plant species were then tested in the glasshouse to determine their susceptibility to light brown apple moth (LBAM), a major pest of pome fruit crops. The most promising candidates were buckwheat, white mustard, chicory, yarrow, fennel, Queen Anne’s lace, Phacelia, borage, perennial ryegrass and fescue.

Finally, replicated field trials in commercial orchards were established in 2001/02 on apples (at Mooroopna North and Silvan) and on pears (Templestowe) and in 2002/03 on apples
(Harcourt and Red Hill). Insect numbers were monitored during the season using yellow sticky traps, while fruit yield and quality were assessed at the end of the trials.

Overall, the buckwheat and chicory/yarrow treatments were marginally the best performers based on the yield and damage data.

The most common form of fruit damage was russeting. This may have been induced by the relatively tall canopies of the cover crops, which maintained higher relative humidity in those plots.

Problems were encountered in establishing effective ground cover crops on orchard sites grown using biodynamic principles, where many plots became overrun with weeds. In addition, the drought in 2002/03 meant that two sites were abandoned because water for the plots was not available.

Much more field testing was required before the value of cover crops for pest management was established. It was vital that cover crops could be easily grown under the existing agronomic practices in the orchard. The researcher also needed to learn much more about the movement patterns of beneficial and pest insects between cover crops and orchard trees.