Worms de­stroy grass

Matamata Chronicle - - Rural Delivery -

An army of worms is on the march across pad­docks in the top half of the North Is­land and DairyNZ is ad­vis­ing farm­ers to check their new pas­tures for army­worm.

DairyNZ con­sult­ing of­fi­cers have been re­ceiv­ing re­ports of dam­age to new pas­tures by army­worm in North­land, Waikato and the Bay of Plenty.

These pests can dev­as­tate pas­tures in a very short time.

‘‘ Pas­tures most at risk are those planted af­ter a crop, es­pe­cially maize, or in re­cently flooded ar­eas,’’ said DairyNZ Farm Sys­tems Spe­cial­ist Phillipa Hed­ley.

‘‘All new pas­tures have some risk as there is al­ways a res­i­dent pop­u­la­tion of army­worm. Given the right con­di­tions there can be a pop­u­la­tion ex­plo­sion. These con­di­tions usu­ally oc­cur in sea­sons with the cy­clone-like events we have had re­cently. Pas­tures that have been flooded are high risk as the eggs get washed to the flooded ar­eas, con­cen­trated and cater­pil­lars hatch just in time to at­tack the re-sown new grass.

‘‘Dur­ing the ex­tended dry pe­riod preChrist­mas it was of­ten too dry for the pre-emer­gence her­bi­cides to be to­tally ef­fec­tive when the maize was es­tab­lished. Weed con­trol was there­fore poor in maize crops. This com­bined with an ex­tra gen­er­a­tion of army­worm due to warm tem­per­a­tures has re­sulted in the cur­rent pop­u­la­tion ex­plo­sion.’’

If they have an in­fes­ta­tion DairyNZ is ad­vis­ing farm­ers to con­tact their mer­chant or spray con­trac­tor for ad­vice on what to spray.

‘‘Check your new pas­ture now and if you have an in­fes­ta­tion hit it fast and hit it hard,’’ said Ms Hed­ley.

Paul Ad­di­son from Nu­farm said that sprays with the ac­tive in­gre­di­ent chlor­pyri­fos or di­azi­non were reg­is­tered for use in pas­ture.

‘‘There are also other sprays that are ef­fec­tive that are not reg­is­tered for use in pas­tures,’’ he said.

The name army­worm comes from the way the cater­pil­lars ‘‘march’’ across a field in for­ma­tion, eat­ing all suit­able plant ma­te­rial in their path. Colours vary. Cater­pil­lars grow up to 50mm long. Pop­u­la­tions de­cline as win­ter starts.

In sum­mer the eggs hatch within a week and the cater­pil­lars take about 3 to 4 weeks to fully de­velop. The pu­pal stage lasts about two weeks and the fe­male moth be­gins lay­ing eggs about four days af­ter it emerges from the pupa.

Sev­eral gen­er­a­tions oc­cur dur­ing spring to au­tumn de­pend­ing on the av­er­age tem­per­a­ture; the ex­act num­ber is not known.

Over-win­ter­ing is known to take place at the lar­val stage, al­though pu­pae may also over win­ter.

Newspapers in English

Newspapers from New Zealand

© PressReader. All rights reserved.