Secondary Plant Compounds for Field Control of the Potato Moth  (Phthorimaea operculella)

A project undertaken by The Faculty of Rural Management, The University of Sydney and supervised by G Gurr

The overall aim of this project is to develop a new, ecologically sustainable option for the management of potato moth.  This is a key pest of potatoes in Australia and other warm production regions around the world.  Pesticides are widely used in attempts to control potato moth in the field but tend to work poorly and can have undesirable environmental and health effects. 

A clue to a new approach for field control of this pest comes from traditional practice in  “developing” countries.  Here, farmers prevent damage to stored potatoes by mixing them with various types of aromatic plant material.

Substituting conventional pesticides with plant extracts is an attractive prospect.  The plant materials being used in this project are already widely used in foods, perfumes or ‘herbal’ medicines so will be environmentally benign, as well as safe for farmers and consumers.   An additional advantage is that the plant extracts tend to work by altering pest behaviour rather than as an outright toxin.  This means that resistance to extracts is less likely to develop.

This three-year study has involved screening extracts from 164 plant materials of Australian, South Asian and European origin. Laboratory bioassays measured adult oviposition or larval movement and survival.  Sixteen extracts had statistically significant inhibitory/repellent affects and these could be applied to potato crops to disrupt recognition by immigrating pests and repel any adults that developed from pre-treatment infestation.  A further eight plant extracts exhibited stimulatory/ attractant effects.  These have potential utility as treatments to non-crop vegetation where ovipositing adults could be 'tricked' into laying their eggs for subsequent destruction by, for example, mulching or mowing.  Attractant and repellent compounds could be used in combination in a 'push-pull' strategy to minimise crop damage.

Field experiments indicated that further work is necessary to achieve reliable control though the plant materials could readily be adopted for post harvest protection of potatoes.  Follow-up experiments have indicated that the efficacy of plant extracts is strongly affected by the extraction method used and that specific compounds found in plant extracts can have markedly different levels of insecticidal activity.  An industry partner is now being sought to undertake this further work.