Spray­ing put on hold in gypsy moth fight against in­va­sive pest

More mon­i­tor­ing and sticky bands may be bet­ter egg op­tions

The Hamilton Spectator - - LOCAL - RICHARD LEITNER

The Hamil­ton Con­ser­va­tion Au­thor­ity will ex­pand its mon­i­tor­ing of gypsy moth eggs in An­caster and at Iro­quoia Heights this win­ter be­fore as­sess­ing the need for an ae­rial spray­ing of a bi­o­log­i­cal pes­ti­cide to com­bat the in­va­sive pest.

Ter­res­trial ecol­o­gist Les­ley McDonell said this spring’s in­fes­ta­tion in the Dun­das Val­ley went mostly as ex­pected in ar­eas sur­veyed last win­ter with mod­er­ate de­fo­li­a­tion of trees by the Her­mitage in An­caster.

But she said a more se­vere de­fo­li­a­tion that was ex­pected in a stand of wal­nut trees south of Lit­tle John Road by Uni­ver­sity Plaza in Dun­das turned out to be mod­er­ate.

McDonell said as­sess­ing the dam­age from the gypsy moth cater­pil­lars was com­pli­cated by an out­break of fall canker­worms, which also de­voured tree leaves this spring.

She said this win­ter’s mon­i­tor­ing will be ex­panded to lo­ca­tions by Jerseyville Road and ad­di­tional ar­eas by the Her­mitage where gypsy moths were the con­firmed cul­prit, as well as at Iro­quoia Heights.

“It’s usu­ally about an eight-to-10year cy­cle, so it seems be on the rise now, and un­for­tu­nately it kind of co­in­cided right with the fall canker­worm,” McDonell said.

“The fall canker­worm we’re not as wor­ried about be­cause it is a na­tive pest and our birds and chip­munks and squir­rels, they like to eat those cater­pil­lars, same as gypsy moths.

“But they tend to bring down that pop­u­la­tion quickly.”

McDonell said the au­thor­ity is dis­cussing the pos­si­bil­ity of an ae­rial spray­ing next spring with the city and other mu­nic­i­pal part­ners but will mon­i­tor egg pop­u­la­tions in the mean­time.

She rec­om­mended against spray­ing this year be­cause, apart from be­ing ex­pen­sive, the favoured Btk bi­o­log­i­cal pes­ti­cide kills other moths and but­ter­flies at the same de­vel­op­ment stage.

McDonell said some less costly mea­sures proved ef­fec­tive, in­clud­ing plac­ing sticky bands around the trunks of heav­ily in­fested trees by Lit­tle John Road to catch the moths in their cater­pil­lar stage.

“We have trees, side by side — one that was sticky banded and one that wasn’t — and the one that wasn’t is com­pletely de­fo­li­ated at the top and the one that had the sticky band still has about 50 per cent of its canopy,” she said.

McDonell said this year’s wet spring and sum­mer may also be help­ing com­bat the in­fes­ta­tion in two ways.

Trees are bet­ter able to re-grow leaves af­ter de­fo­li­a­tion, and the wet con­di­tions are good for a fun­gal virus that kills the cater­pil­lars nat­u­rally, she said.

“We’ll only see that when we ac­tu­ally do our sur­veys again. If we find dead cater­pil­lars or if we see less egg-mass pro­duc­tion, then that means some of cater­pil­lars were killed by this virus.”

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