Friday, March 29, 2024

Velvetleaf risk is elevated in maize

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More than two years since it was discovered in Waikato velvetleaf has spread further and maize contractors are being targeted to try to slow the spread of the insidious weed.
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The number of sites with the weed detected has leapt from 36 to 50 in the past year with the latest discovery only days ago in a maize crop near Cambridge, Waikato Regional Council biosecurity pest plants team leader Darion Embling said.

The weed was detected in Canterbury three years ago, its incursion linked to imported fodder beet seed.

With its hardy seed and capacity for high seed production the plant is recognised as a major threat to arable crops and seeds can endure in the soil for longer than 50 years.

“This latest discovery was outside the current distribution area and was linked to a dirty machine coming out of Pukekohe,” Embling said.

“As soon as we found this out we knew who the contractor was and this was linked to another incursion last year.”

With maize crops bolting ahead under perfect growing conditions and velvetleaf starting to flower, Embling urges contractors to ensure equipment is well cleaned between harvests of maize silage crops in coming weeks.

“Plants will be starting to pod and the recent rain will encourage this. 

“The seed count in this weed is high at about 15,000-16,000 a plant in a mature maize field so even one plant can have a significant impact with seed that lasts a very long time.”

Spray control for velvetleaf is virtually impossible once the plant is established.

Farmer awareness of the weed varies but merchants and their field staff have a good handle on recognising and reporting the weed’s presence and Embling was encouraged by the latest incursion being recognised and reported by a farmer.

“But we won’t really know until the end of the autumn just how well they have recognised the weed.”

The council has made significant efforts to educate farmers about the weed’s appearance and significance and there are several research projects under way to better understand it and how to control it.

“MPI has established a control plan with co-ordinators for the North and South Islands. It has stepped up for this and extended monitoring into the Auckland region too. The Sustainable Farming Fund and AgResearch have also built a big research programme around velvetleaf.”

In the South Island it appears climate conditions might help in some areas to limit the weed’s spread, with coastal areas exhibiting slower spread than inland.

Cropping consultant Mike Parker said key places to identify the weed are around headlands and gates where row widths are wider, encouraging more light and therefore weed growth.

“It is too late now but it’s important to spray those areas post emergence early on. From here on in if its detected it has to be hand pulled and carefully bagged to avoid losing the seeds.”

Embling said prevention of velvetleaf establishment is far better than treatment and keeping mechanical gear clean between crops is vital.

“Once you have it, you have a lifetime sentence with it.”

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