Over 20 years ago, a project was undertaken in Tasmania to investigate the most effective control measures for black nightshade in potato crops. Trial sites were established across four states, and it resulted in a new product registered for grower use. In early 2018, project leaders Ian Macleod and Phil Frost spoke to Potatoes Australia about this project, and how it has impacted today’s weed management practices.

Along with fat hen and radish, black nightshade is among the most problematic weeds for potato growers, particularly in Victoria and Tasmania.

All weeds have an impact on potato crops, however black nightshade is more problematic as it is the same genus as potatoes (meaning it’s closely related, but not quite family). It is therefore more difficult to selectively control with herbicides.

Black nightshade is a vigorously growing weed – it will compete with the crop to be managed. This competition leads to a reduction in yield, and black nightshade also acts as a host for potato disease-causing organisms.

In 1996, funding for research was obtained from the Horticultural Research and Development Corporation (now Hort Innovation) through the fresh potato and potato processing research and development levies, to evaluate and develop weed management strategies for control of black nightshade.

This project was led by Ian Macleod and Phil Frost, who were working for Serve-Ag’s Research Division in Tasmania, which subsequently evolved into the independent research company, Peracto, where the pair still worked at the time this article was published. They spoke to Potatoes Australia about the three-year project, which concluded in 2000.

Control of Black Nightshade (Solanum nigrum) and Other Weeds in Potatoes (PT96047) was a strategic levy investment under the Hort Innovation Fresh Potato and Potato Processing Funds.

A major problem

Casting his mind back 22 years ago, Mr Macleod said that black nightshade had become an issue in Tasmania and researchers had to look further afield in managing this widespread weed.

“At the time, we were working fairly broadly across a number of crops: potatoes was one that was a concern for growers and they were keen to invest some money in trying to find better ways to manage the weeds in the crop,” he said.

“The existing strategies they used were damaging the crop – whether that was some of the herbicides causing damage or through mechanical weed control causing damage. There was a push to find better ways of doing things.”

Mr Macleod and Mr Frost looked at a number of potato growing areas around Australia and, after liaising with agronomists in those areas, set up trial sites in four states including Western Australia, South Australia, Queensland and Tasmania.

“We looked at setting up some crops with typical weed problems, particularly nightshade, and tried different trial strategies to see how they worked on different soil types in different climatic zones, and in different potato varieties,” Mr Macleod said.

Project results

Based on these trials, Mr Macleod said the research team discovered a range of strategies to control black nightshade in certain circumstances and conditions.

“We did find some new herbicides that provided good results and we were able to generate data to get one of those products registered for use,” Mr Macleod said.

National registration of products with the active ingredient clomazone, such as Command, occurred in August 1999. The results from the project also translated into long-term benefits for the industry.

While black nightshade is still an issue for potato growers today, Mr Frost said that there was a better understanding of the weed itself as well as the crop protection products available, how they worked and how best to use them in a management strategy for the fast-growing weed.

“Certainly, the management of black nightshade in potatoes now is not as much of an issue as it was back then (in 1997- 2000),” he said.

“Like any pest or disease, a lot of these management strategies involve a number of different approaches to tackle the problem or a pest. It’s really about managing nightshade in your cropping system and management in fallow and other crops, not just potatoes.

“I think growers’ understanding of how to manage those weeds in their cropping systems is better; there are more tools now to manage some of these weeds which helps, so there’s a lot of different ways they can do that.”

Find out more

The final report for this project is available on the InfoVeg database.

This project was funded by Hort Innovation using the fresh potato and potato processing research and development levies, voluntary contributions from industry and contributions from the Australian Government.

Project Number: PT96047