The first velvetleaf infestation occurred more than 15 years ago and was associated with maize cultivation in Auckland and Waikato and affected about 80 properties.

Following discoveries on two new properties in Waikato in April this year, farmers are being advised to consider their farm gate as a boundary.

Linton expects one of the new finds to be returned to pasture to minimize risk, resulting in a loss of 30 hectares of corn growing area for the industry.

“So far, no clear source property has been identified for these two cases and since velvetleaf is an annual weed, we must wait until spring before we can continue our investigative efforts.”

In the past, tracing has shown that machinery and contaminated maize silage are the most common reasons for the spread.

Constant vigilance on the part of farmers and growers is required, as well as strict hygiene protocols for machinery in the crop production sector.

Maize cultivation trial deals with difficult soil types

Fourth-generation farmers David and Sarah Rawnsley from Waikato are open to new farming methods.

They are one of four farms in Waikato participating in a four-year FAR maize trial using no-till and strip tillage.

The Rawnsleys’ farm and leased effluent consist of heavy marine clay, which is considered the most difficult soil type when using no-till techniques.

They have turned away from maize silage because scorch marks appeared on the pastures after feeding.

After several consecutive dry summers and poor chicory crops required the purchase of maize, the Rawnsleys resumed growing 4.8ha of maize silage on the drainage area in the 2020-21 season when the trial began.

David wants to increase profitability and meet changing environmental standards.

The experiment on his farm with its clay soil was an educational journey.

During the four-year trial period, an average maize silage yield of 22.8 t/dry matter/ha was achieved under full cultivation.

This is followed by subsoil direct sowing with an average yield of 20.9 t dry matter/ha, direct sowing with 20 t dry matter/ha and strip sowing with 19.7 t dry matter/ha.

Conditions over the four years ranged from very dry to very wet.

Dirk Wallace, senior environmental researcher at FAR, said the key is choosing the right tool for the job.

By working with David, they were able to find out which tools work on heavier soils over multiple seasons.

“There is still room for further profitability improvements in each of these startup methods as we refine best practices,” said Sam McDougall, senior field researcher at FAR.

“The results of the Rawnsley trial suggest yield and gross yield improvements in no-till crop and subsoil systems, but these must be weighed against the potential for long-term improvement in soil quality.”

Funding the Fall Armyworm

In June, research on fall armyworm received a boost from MPI’s Sustainable Food and Fibre Futures (SFFF).

A new project led by FAR and supported by Vegetables NZ is covering a range of topics including establishing economic thresholds for chemical pest control in maize silage, grain maize and sweetcorn, and investigating opportunities for integrated pest management.

Ash Mills, FAR project leader and biosecurity officer, said working on the economic threshold was important because the impact of FAW feeding damage varies across crop species.

Current control options for fall armyworm in New Zealand are limited to an insecticide (Sparta, active ingredient spinetoram) and a number of beneficial insects. Cotesia The most active are parasitoid wasps, but they can also fall victim to insecticides used elsewhere.

Genetic studies abroad already indicate that there is probably Sparta resistance in the New Zealand population.

In tackling this problem, the economic threshold and Cotesia Work overlaps.

“We want to understand how big the influence Cotesia sp on FAW and its relationship to other pest species, and we will use this information, along with an improved understanding of economic damage thresholds for different crops, to develop an integrated pest management (IPM) program for FAW,” said Mills.

In Australia, the fall armyworm has spread rapidly.

New Zealand and Australian researchers exchange their experiences and work together to combat the fall armyworm.

Mills said New Zealand’s cooler climate had previously led to a significant population decline, and while the Australian data was worrying, it did not necessarily mean the same would happen here.

“The situation in Australia simply shows us that we need to prepare for a future season where a larger, more damaging population could cause problems in maize and spread to other crops grown in the affected regions.”