Better Berries project - phase 3 (BS05003)

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Please note that as these reports may date back as far as the 1990s, the content and recommendations within them may be superseded by more recent research.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?

Australia at the time produced about 40,000 tonnes of strawberries worth $200 million each year. The main production centres were located in Queensland, Victoria and Western Australia, with winter production worth $120 million in South-East Queensland. Research conducted mostly in southern Queensland addressed major issues identified by the National Strawberry Industry in its strategic plan to improve agronomic management of the crop. The main areas of interest included runner quality, irrigation and nutrition management and the control of key pests and diseases.

Agronomy: 

Plug plants in 75 cm³ containers yielded 15 to 40 per cent less than bare-rooted plants, suggesting that plugs grown in small containers offer no economic advantage to commercial growers. Plugs in 125 cm³ containers yielded 24 per cent more than small runners and 17 per cent more than large runners, while runners from Stanthorpe yielded 15 per cent more than the runners from Toolangi. Further research needed to be conducted to determine the relative performance of plugs and runners, especially a comparison of the two plant types at different planting times in southern Queensland.

Micro-sprinklers can save up to 80 per cent of the water used during establishment compared with knockers, when they are used with correct water pressure. Reducing plant establishment water use by 80 per cent would save 30 per cent of the total crop water use or 1.8 ML per ha. It was recommended that micro-sprinklers be installed in new plantings.

Pests:

Bifenazate provided excellent control of spider mites and was compatible with the predatory mite, so that it can be used to correct an imbalance between pest and predator if necessary. Registration of this miticide was recommended to assist growers to manage miticide resistance in their crops. Indoxacarb, emamectin and spinosad controlled all species of caterpillar in test plots with no adverse effect on predatory mites. These chemicals were also less toxic to humans and the environment than the chemicals currently registered for this purpose. Spinosad has been registered for use in strawberries. The other two chemicals should also be registered. Although laboratory studies indicated that strawberries were an excellent host for Queensland fruit fly, the pest represented a minor issue in ground-grown strawberries on the Sunshine Coast. It was the reccomendation that bait sprays be registered as acceptable treatments for Queensland fruit shipped to southern states after 20 September.

Depending on the season, 1 to 4 per cent of runners supplied by Stanthorpe nurseries were infected with strawberry lethal yellows (SLY). The disease was associated with the phytoplasmas, Candidatus Phytoplasma australiense and tomato big bud, and a rickettsia-like-organism (RLO). SLY was probably transmitted by a planthopper, most likely Orosius argentatus, which was distributed throughout south-east Australia. Further research into the etiology of this disease was required in order to develop an effective management strategy.

Diseases: 

There was generally a very low level of infection with crown rot caused by Colletotrichum gloeosporioides (Cg) in the strawberry nurseries, with an average of only 0.06% of symptomless petioles testing positive for the presence of Cg over five years. Visual symptoms of crown rot, including lesions on the petioles and stolons and wilting plants, were relatively rare in the nurseries, with plant losses ranging from 0 to 0.5 per cent. Losses on fruit farms were highly variable (up to 20 per cent), but generally low and less than 0.1 per cent. There was no evidence of resistance to prochloraz. A fungicide based on cyprodininil plus fludioxinil offers promise for inclusion in a resistance management program with prochloraz.

A strategy based on applications of tolylfluanid with trifloxystrobin gave the best control of the fruit diseases powdery mildew and grey mould, and the best yields. This work contributed to a national registration for trifloxystrobin for the control of powdery mildew in strawberries.

There was a range in the level of resistance in strawberry cultivars to wilt diseases caused by Fusarium oxysporum, with severe losses suffered by some cultivars in non-fumigated soils. Cultivars with high levels of resistance to Fusarium wilt still needed to be developed for the strawberry industry.

Strawberry fields in southern Queensland were affected by a range of soil-borne diseases and weeds that have been traditionally controlled by fumigation with methyl bromide. Telone C35, chloropicrin and methyl iodide could replace methyl bromide. In contrast, metham potassium and metham sodium were less effective and would not be suitable replacements. At the time it was considered that Telone C35 would be quite safe for fruit production in coastal southern Queensland (no toxicity after planting two weeks after fumigation), particularly when the directions for its use on the label were followed (planting six weeks after fumigation).

Soil solarisation had the potential to improve strawberry production in the absence of methyl bromide. Soil solarisation with silver plastic reduced weed growth and the incidence of plant diseases, and increased plant growth and yield compared with untreated plots, with the best response recorded after three consecutive years of solarisation. In contrast, soil solarisation with clear or black plastic was less effective. Because the effect was cumulative, solarisation using plastic films had to be repeated over several successive years if it was to match the performance of commercial fumigants.