This week's Weedy Wednesday is kindly brought to you by Kiwifruit Vine Health
Moth Plant is one of the most problematic weeds of North Island kiwifruit orchards and the pods are going to start forming over the coming weeks – they are currently flowering in most locations.
Now is the time to start the first round of control work to avoid the need to pull masses of vines and pods out of shelter belts and other trees Seedlings will be establishing beneath shelter belts, ready to climb into trees before flowering and forming their distinctive seed pods. A skillfully used sharp hoe will kill emergent seedlings and is an effective organic control method. Alternatively, glyphosate at one part to 100 parts water is effective on emergent seedlings. Apply under low pressure ensuring no spray drift. Moth Plant is poisonous – the milky white sap can cause dermatitis so wear gloves and protective clothing when handling it. Moth plant (Araujia hortorum), is a native of Argentina and Brazil and has been in New Zealand since 1888. It’s well-established in the upper North Island and coastal Bay of Plenty, but may be expanding southward, into Te Puke and elsewhere. Like pampas, moth plant is a problem weed especially to the kiwifruit industry, it has rapid growth to the canopy, forming large, heavy, long-lived masses which smother and kill other plants.
Pods split open when dry, typically in June and July, releasing the seed with pappus attached and can travel for kilometers. Landcare Research has recently had approval from the Environmental Protection Authority (EPA) to release two biological control agents onto moth plant – a beetle and a rust fungus. They may be very helpful in the medium-long term.
Control can be quite difficult – moth plant snaps off just below ground level if you pull it. It is then likely to regrow. Locating vines and digging them out works well – spring or early summer is the best time to control Moth Plant; in late summer or autumn the pods will be forming; drag any formed pods out of shelter trees. The sap can cause quite severe dermatitis, so people need to wear gloves, protective clothing and eye protection. Cutting vines off within 20 cm of ground level and applying a strong glyphosate stump treatment mixture (1 part glyphosate to 5 parts water, plus a spreader such as Pulse) is the safest herbicide option for a shelter belt situation.