Two Pukekawa trials in New Zealand are showing some early promise for potato growers when it comes to greater control of the potato tuber moth, Phthorimaea operculella (PTM). Glenys Christian describe the trials in an article first published in NZ Grower magazine and re-published by Potatoes NZ on its website. Below is a summary.
Organophosphate pesticides have been relied on at the later stages of potato growth for PTM control but due to overuse, environmental impact and resistance developing many are now being phased out, said Pukekohe company, Inta-Ag’s chief executive officer, Shane Smith.
Integrated pest management (IPM) strategies have been looked to for the future, but biological controls can be affected by ultraviolet light or rain. IPM programmes are being focused on but being slower to work.
So Inta-Ag has been running a trial on a potato grower’s land at Pukekawa using straw mulch to see what effect it can have on PTM. The one hectare trial site had 10 tonne of straw mulch applied in October last year with several traps set up to catch PTM as well as TPP.
It was too early to yet tell how effective mulching was with full results from the Pukekawa trial expected in April or May, but Shane Smith said from his weekly visits to the trial site it already appeared that nightshade, potato growers’ worst weed threat, was being kept at bay. Already there are plans for the trial to be repeated next season over a larger area.
Shane said he was aware of the mulching technique being used by organic potato growers in the United Kingdom which kept the soil moisture levels higher as well as preventing the PTM larva getting to potato tubers so easily. Mulching also brought about several other benefits which weren’t foreseen, with growers there noticing fewer weeds in their crops and better disease control, particularly when it came to sclerotinia.
Another PTM trial which is in its first year at Pukekawa is also being run by Inta-Ag. It’s looking into the effect of different cover crop mixes sown on potato headlands.