Summer pasture pest numbers on the rise

AgResearch scientists are predicting larger than normal numbers of the pasture pests porina and black beetle this summer.

“The mild winter and warmer than normal spring are perfect conditions for adult black beetle and porina survival,” says Dr Alison Popay, AgResearch Science Team Leader – Biocontrol & Biosecurity.

“We are giving farmers the heads-up – they need to be aware of the potential for increased pasture damage from these pests.”

Porina are grazers that will eat all herbage that is on surface of the ground. The amount of damage depends on the number of insects; at low densities they are direct competitors with stock for food and reduce the amount of foliage available. At higher densities plants are destroyed allowing inferior plant species to establish reducing long term pasture quality and production.

“This time of year, particularly in porina prone areas, the adult insects start to fly; they will be banging into farmers’ windows as they are attracted to light,” says Dr Popay.

“Paddocks that are two to three years out of cultivation are particularly prone to porina infestation.

“Farmers that are constantly battling against this pest can continue paddock monitoring and plan to spray four months after the sighting flying moths with the insect growth regulator Diflubenzuron.”

Black beetle numbers are also on the rise.

“Black beetle adults usually go into a rest period over winter, becoming more active again when it warms up in spring,” says Dr Popay.

“Their ability to feed dictates their egg-laying cycle, so this year we are likely to have an earlier and more successful hatching.

“If these warm conditions continue and high soil moistures don’t reduce survival of the very young larvae, black beetle will be on the increase. Awareness will help farmers plan for combat strategies to make up for the feed consumed by this pest. These may include putting in a maize silage block or buying in additional feed if appropriate.

“Farmers can find out more about the control of both porina and black beetle at the AgPest website.”

Built for farmers and agricultural professionals, the recently updated AgPest (formally Pestweb) is a free online tool to assist with pest and weed management decision making.

“Visitors can find 50 pests and weeds that affect New Zealand pasture in the pest directory. Each pest profile includes the biology of the pest, its impact on pastures and the latest information on control measures,” says AgResearch weed scientist Dr Katherine Tozer.

“One of the site’s key features is the ability to help farmers identify a particular weed or insect pest they find on the farm through a simple query and response system.

“We also took the opportunity to update the pest search function, improve the viewability of the images on the site and expanded our PestAlerts service.

“PestAlerts is a free subscription email service providing timely alerts to farmers about pest outbreaks in their region. They are delivered via email, text, Twitter or Facebook and link to the AgPest site for further information. Farmers can sign-up for the service on the AgPest site.”

The website is managed by AgResearch with support by numerous industry partners such as MPI, DairyNZ, Beef + Lamb New Zealand, AbacusBio Ltd and The New Zealand Plant Protection Society.