Winnipeg Free Press - Section G - - HOMES -

The lily’s saviour could come in the form of a bio­con­trol agent. Naomi Cap­puc­cino, an as­so­ciate pro­fes­sor in the Depart­ment of Bi­ol­ogy at Car­leton Univer­sity, has been con­duct­ing re­search into the bi­o­log­i­cal con­trol of the lily leaf bee­tle. Bi­o­log­i­cal con­trol uses nat­u­ral en­e­mies to com­bat pest species and re­duce their pop­u­la­tions. With the lily leaf bee­tle threat­en­ing to dam­age or de­stroy not only some of the most com­mon lily cul­ti­vars but also her­itage va­ri­eties and, in some ar­eas, na­tive species, the bat­tle has taken on a new ur­gency. In a re­cent phone in­ter­view, Cap­puc­cino said there have been re­ports of the lily leaf bee­tle on the Canada lily, a na­tive of east­ern North Amer­ica as well as Michi­gan lily and Clapleaf Twist­ed­stalk, a north­ern species that grows in the un­der­story of the for­est. It can be found grow­ing in Gatineau Park near Ot­tawa, and is a rare species in cer­tain ar­eas of the U.S.. Cap­puc­cino ex­plained bio­con­trol some­times works fab­u­lously well and some­times doesn’t. For­tu­nately, the in­tro­duc­tion of a par­a­sitic wasp, Te­trastichus setifer, by Cap­puc­cino and her sum­mer re­search stu­dents into test gar­dens in Ot­tawa, Mon­treal Botanic Gar­den, and na­tive lily pop­u­la­tions in Que­bec is show­ing promis­ing re­sults. Cap­puc­cino said the par­a­sitism rate has been close to 90 per cent. This is ex­cit­ing news for gar­den­ers and, in­deed, the en­tire lily in­dus­try. Cap­puc­cino gives credit to the work done by Lisa Tewks­bury, a re­search as­so­ciate at the Univer­sity of Rhode Is­land who to­gether with Richard Casagrande, have been in­volved in a lily leaf bee­tle bio­con­trol project for many years. In a phone in­ter­view, Tewks­bury said that in the U.S., be­fore a clas­si­cal bio­con­trol project can re­ceive ap­proval from the U.S.D.A., re­search must first show the in­sect planned for in­tro­duc­tion is safe as well as host spe­cific. While the work of her bio­con­trol lab be­gan in 1996, re­leases did not take place un­til 2001. “The area where we started,” said Tewks­bury, “is Welles­ley, Mas­sachusetts.” Her col­league, Casagrande, teaches a Master Gar­dener class in that area and many of the stu­dents have re­ported they no longer have a prob­lem with the pests rav­aging their lilies. Casagrande said the wasp or par­a­sitoid has been suc­cess­ful in main­tain­ing a very low pop­u­la­tion of lily leaf bee­tles. How does T. Setifer con­trol the lily leaf bee­tle? First, al­though it is a wasp, it does not sting peo­ple and is tiny in size, al­most like a gnat. The fe­male wasp lays its eggs in­side the lar­vae of the lily leaf bee­tle. Ac­cord­ing to Tewks­bury it con­tin­ues to look like a lar­vae and once it is done eat­ing it drops to the ground and forms a soil co­coon around it­self. Par­a­sitic lar­vae take over the lar­vae of the lily leaf bee­tle. Nor­mally, a lily leaf bee­tle would emerge, feed for awhile and then go back in and over­win­ter. In­stead, the par­a­sitoids re­main in the co­coon and must over­win­ter. Tewks­bury’s re­search in­volves three dif­fer­ent types of par­a­sitic wasps, all of which are cur­rently in dif­fer­ent parts of Switzer­land. The wasps have been re­leased in one or two test ar­eas in each state in New Eng­land. Cap­puc­cino is plan­ning a con­trolled re­lease of T. Setifer in Man­i­toba in 2016. Work­ing to­gether with the Man­i­toba Re­gional Lily So­ci­ety, a test gar­den has been iden­ti­fied north of Win­nipeg. This sum­mer hun­dreds of lily bee­tles are be­ing col­lected for the test site. Ed Czar­necki, Pres­i­dent of the MRLS, and Ian Wise, an en­to­mol­o­gist, will visit the gar­den about three times weekly. One of their tasks will be to count bee­tles and eggs. While there is no doubt that the lily leaf bee­tle is able to sur­vive our harsh win­ter, it re­mains to be seen if the par­a­sitoid wasp can over­win­ter. Tewks­bury says that in some ar­eas there are high num­bers of the wasps but there is also a high mor­tal­ity of the par­a­sitoid each year. In or­der to as­sist in the spread and es­tab­lish­ment of the wasp, Tewks­bury rec­om­mends hand pick­ing of adult lily bee­tles and egg masses and avoid­ing pes­ti­cide use. She also rec­om­mends not dig­ging up bulbs which can dis­turb the site where a par­a­sitoid is over­win­ter­ing and min­i­miz­ing mulching. Mulch might af­fect mois­ture lev­els not con­ducive to the wasp or that at­tract preda­tors. In ad­di­tion, Wise says a deep layer of mulch could hin­der the wasp’s abil­ity to emerge in spring. Both Tewks­bury and Cap­puc­cino say it will take about three to five years af­ter re­leases of the par­a­sitic wasp be­fore we can ex­pect to see a sig­nif­i­cant de­crease in the lily bee­tle pop­u­la­tion. Tewks­bury stresses the use of bi­o­log­i­cal con­trols will not re­sult in the erad­i­ca­tion of the lily leaf bee­tle. In a bi­o­log­i­cal con­trol sit­u­a­tion, par­a­sitoids still need their host so gar­den­ers will have to ac­cept that the lily, just like most other plants in the gar­den, will still show oc­ca­sional signs of pest dam­age. Pro­vid­ing T. Setifer chooses to es­tab­lish it­self in our lily gar­dens here in Man­i­toba, what should we do in the mean­time? Nigel Strohman, owner of The Lily Nook, in Neep­awa rec­om­mends us­ing an all-pur­pose fer­til­izer (14-14-14) to aid healthy growth. He also sug­gests adding bone meal around the base of lilies and scratch­ing it into the sur­face. There are many beau­ti­ful her­itage lilies that have been bred in Man­i­toba and Saskatchewan, says Strohman. “To pull these up and de­stroy them is dis­heart­en­ing.” Is a reg­i­men of pick­ing and squish­ing bee­tles re­ally ef­fec­tive? Fol­low­ing a suc­cess­ful pick and squish pro­gram ev­ery morn­ing last sum­mer at Assini­boine Park, Craig Gille­spie, head gar­dener of the English Gar­den and Leo Mol Gar­den, says pop­u­la­tions of the lily leaf bee­tle are down by al­most 75 per cent. “We made a con­certed ef­fort to main­tain good san­i­ta­tion by clean­ing up af­fected de­bris and re­mov­ing and de­stroy­ing all lily plant ma­te­rial that was cut down last fall,” said Gille­spie. Last fall, an ad­di­tional 500 lily bulbs were planted. Mon­i­tor­ing bee­tle pop­u­la­tions re­mains nec­es­sary but only ev­ery two or three days. Sa­man­tha Tom­chuk has been the groundskeeper at the Univer­sity of Man­i­toba since 1983. A cer­ti­fied prairie hor­ti­cul­tur­ist and ar­borist, Tom­chuk grows nu­mer­ous lilies in her St. Vi­tal gar­den. As part of her daily mon­i­tor­ing rou­tine, Tom­chuk looks for any lily leaves miss­ing their tips or those with a trans­par­ent or lacy ap­pear­ance. Ex­pe­ri­ence has told her those are most likely the leaves with eggs on the un­der­sides. Some­times it is too dis­gust­ing to re­move the lar­vae so Tom­chuk snips off the leaf with a pair of scis­sors and drops the leaf, to­gether with the scis­sors, into a pail of soapy wa­ter.


Te­trastichus setifer, a par­a­sitic wasp

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