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Southern Farming Systems Field Day.
Title: IPM in Action - Integrating control of slugs and all other pests Authors: Paul Horne and Jessica Page, IPM Technologies Pty Ltd PO Box 560 Hurstbridge Victoria 3099
Damage caused by slugs has become a more serious problem with the wider use of stubble retention and direct drilling. A new project funded by GRDC has commenced to investigate better control of slugs in broad-acre crops in south-east Australia. The aim of this project is to integrate control of slugs with all other pest management actions to ensure that control measures for some pests are not destroying control of other pests. There are several different species of slugs in Australia that damage crops, and all are introduced. An identification guide to slugs has been prepared and by us, and knowing which species is present in any district will help in control. So far, the dominant slug species in our samples from South Australia is Milax gagates. In Victoria the most abundant species at most sites is Deroceras reticulatum. Milax gagates is probably more of a burrowing species than Deroceras reticulatum, but we do not yet know if the distribution of slugs is typical or affected by drought. In our study, Arion intermedius has so far only been recorded from Tasmania. Other species of slugs (Deroceras panormitanum and Lehmannia nyctelia) were locally abundant at some sites. The relative numbers of each species will be different in different districts, and so the timing of stages in the life-cycle will also vary. This means that control measures targeting a certain stage would vary between districts, and probably between paddocks if they contained different species of slugs. Eg. Targeting the adults before they begin reproducing would result in more efficient use of baits. We have recorded potential biocontrol agents of slugs at each site where slugs were found. In South Australia the most abundant predators were ground beetles (Carabidae) in the genus Sarticus and the common brown earwig Labidura truncata. Feeding trials in our laboratory have proved that the carabids will kill small slugs. The increase in pest activity as a result of using stubble retention and minimum tillage are readily seen. However, there is also a much lesser known effect on increasing numbers of beneficial species that prey on pests. However, when insecticide applications result in elimination of beneficial species the the net result is a perception of minimal tillage and stubble retention as increasing pest problems. In fact, a slow increase in beneficial species does happen, and can be managed when growers know what to look for and how not to kill them. It is easy to understand that broad-spectrum insecticides such as endosulfan, talstar and lorsban kill beneficial species as well as pests. However, it is less readily understood that the effect of insecticides on beneficial species is relatively much greater, as many beneficial species have one or two year life-cycles, rather than generation times measured in weeks or months. It is highly likely that insecticide and miticide applications applied to control pests such as redlegged earth mite are destroying the biocontrol agents that may otherwise have controlled pests such as wireworms, slugs and snails. Although the timing of such applications may be perfect for control of mites, the overall impact of the application is likely to have been to destroy control of many pests. That is, there is no integration of control measures at present. We aim to improve the integration of control measures. In the same way, there are predators and parasites of pests such as Plutella, armyworm and aphids that can be used to give most of the control required. They can be supported by the use of certain management methods and chemical options but are usually destroyed by the use of non-selective pesticides. We hope that this project will provide information to growers about control of slugs and will also provide broader information on an IPM approach to controlling pests.
Dr Paul A. Horne & Jessica Page ph: 03 9710 1554
GRDC Project No. IPM00001 (Development of integrated control strategies for slugs)
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