Phosphine resistance in China Australia's future?

ENTOMOLOGISTS WITH Queensland's Department of Primary Industries (QDPI) have been working with Zhengzhou Institute of Technology researchers to sneak a glance into the future for phosphine use in Australia.

The Chinese, according to QDPI entoentomologist Manoj Nayak, have been using phosphine intensively for much longer than we have in Australia, and they have grain storage insect pests that show greater levels of phosphine resistance than any Australian grain storage pest.

This work specifically compared resistance levels detected in the rice weevil, Sitophilus oryzae, and two psocid pests, Liposcelis entomophila and L. decolor, from Australia with respective resistant strains from China.

The rice weevil is already a major pest of stored grain in Australia, particularly in the north-east grainbelt. The two psocid species are a serious problem for the central storage system in many areas of Australia, particularly at export terminals.

The work showed that the time to population extinction of the Chinese strain of S. oryzae was four days and two days longer, respectively, at phosphine concentrations of 200 and 700 ppm, compared with the resistant Australian strain (see table). Moreover, the Chinese strain had higher resistance than most resistant strains of lesser grain borer (Rhyzopertha dominica) reported in Australia.

This work forms the basis for developing fumigation protocols that can control these phosphine-resistant grain storage pests if and when the need arises. Clearly longer treatments will be needed while ever the current reliance on phosphine continues.

Time to population extinction (in days) of resistant strains of the rice weevil (Sitophilus oryzae) from Australia and China at fixed concentrations of phosphine. 25°C and 55% humidity
phosphine mg/l (ppm) Australian strain Chinese strain
0.3(200) 7 days 11 days
1.0(700) 5 days 7 days

Contact: Dr Manoj Nayak 07 3896 9431 email manoj.nayak@dpi.qld.gov.au

Region North, South, West