Com­pla­cency lets pests get a head­start

In­sects which may at first not give grow­ers much con­cern can turn out to be a ma­jor men­ace.

NZ Grower - - Contents -

Learn­ing from other coun­tries’ ex­pe­ri­ences when it comes to biose­cu­rity can bet­ter pre­pare this coun­try’s grow­ers, Nuffield Scholar, Si­mon Cook, be­lieves. He’s re­cently been trav­el­ling in the United States look­ing at a range of in­sect pest in­cur­sions and how they’ve been han­dled.

He’s a third gen­er­a­tion ki­wifruit grower from Te Puke and first vis­ited a large ki­wifruit or­chard near Auburn in Alabama where one of the ma­jor chal­lenges is deal­ing with Brown Mar­morated Stink Bug (BMSB). A num­ber of the tech­niques dis­cussed lo­cally as pos­si­ble man­age­ment plans if there is an in­cur­sion have been used with one was the use of bait plants to lure BMSB out of the ki­wifruit so more toxic sprays could be used. But that would cause residue prob­lems and in this case it’s not suc­cess­ful as the bugs pre­fer to stay in the ki­wifruit. The next strat­egy to be tried is the use of chem­i­cal im­preg­nated cloth with bright lights shin­ing on it at night to try and at­tract BMSB. It was be­ing tri­alled with lim­ited suc­cess else­where, but there is sig­nif­i­cant risk of off-tar­get deaths. So far the most suc­cess­ful method has been the use of baited traps that are reg­u­larly cap­tur­ing hun­dreds of bugs. Tris­sol­cus japon­i­cas, the Sa­mu­rai Wasp is not present.

“A large fac­tor in the re­duc­tion of the pop­u­la­tion was be­ing cred­ited to the pres­ence of the Sa­mu­rai Wasp.

“When I got to Penn­syl­va­nia later in my trip I found the pop­u­la­tions of BMSB that ini­tially had ex­ploded in that area were now heav­ily re­duced and BMSB was not con­sid­ered as sig­nif­i­cant as it had been,” he said.

“A large fac­tor in the re­duc­tion of the pop­u­la­tion was be­ing cred­ited to the pres­ence of the Sa­mu­rai Wasp.

▶ Clint Wall, who worked for Seeka in New Zealand as a ki­wifruit tech­ni­cal rep be­fore mov­ing home to Auburn Alabama where he has setup a 100 hectare trial ki­wifruit or­chard in part­ner­ship with Cal­i­for­nian com­pany Sun Pa­cific.

▶ Huan­g­long­bing (HLB) which lit­er­ally trans­lates to yel­low dragon dis­ease in China “In China BMSB is not a ma­jor prob­lem be­cause the Sa­mu­rai wasp has de­vel­oped as a nat­u­ral con­trol to keep its num­bers in check. When BMSB is moved to a new en­vi­ron­ment with no nat­u­ral preda­tor or nat­u­ral con­trol, then there is noth­ing to stop its num­bers ex­pand­ing to plague pro­por­tions. This is the real risk with biose­cu­rity in­cur­sions where you can get the pest with­out its cor­re­spond­ing bio­con­trol and a pest which at home can seem rather be­nign sud­denly can ex­plode in num­bers and cause ma­jor prob­lems to in­dus­try.

“This can also cause prob­lems iden­ti­fy­ing what our real threats are in terms of in­va­sive species as in their home coun­tries that quite of­ten are not an is­sue. In China Yel­low Spot­ted Stink Bug (YSSB) has more of an im­pact on agri­cul­ture than BMSB.”

Next he vis­ited Flor­ida where Cit­rus Green­ing dis­ease, or Huan­g­long­bing (HLB) which lit­er­ally trans­lates to yel­low dragon dis­ease in China, ap­peared.

“The first sign of a com­ing prob­lem with HLB was the ar­rival of the Asian cit­rus psyl­lid, a well known vec­tor for the trans­mis­sion of the dis­ease. For four years they bat­tled the psyl­lid in­cur­sion with­out suc­cess keep­ing a close eye out for the first sign of HLB. The psyl­lid it­self does very lit­tle dam­age, and grow­ers started to be­come com­pla­cent to­wards the man­age­ment of the psyl­lid, which is very dif­fi­cult to con­trol.

“This all changed with the first pos­i­tive iden­ti­fi­ca­tion of HLB in an or­chard in Flor­ida. In­ter­est­ingly talk­ing with a grape­fruit grower, this still did not con­cern them as they mis­tak­enly be­lieved it would not af­fect them.

“Since the in­cur­sion around US$250m has been in­vested in re­search to try and over­come the in­cur­sion with lit­tle suc­cess. Whilst wait­ing for some so­lu­tion grow­ers find them­selves very much in sur­vival mode un­sure of their fu­ture. Many grow­ers have been forced to aban­don or­chards or cut them out and look at try­ing to grow some other crop in­stead of cit­rus. I saw a num­ber of or­chards that once pro­duced cit­rus now grow­ing blue­ber­ries, wa­ter­melon, onions, ba­si­cally try­ing any­thing they can think of to sur­vive. >

“The most likely so­lu­tion to al­low the in­dus­try to sur­vive will be the breed­ing of new tol­er­ant va­ri­eties, most likely cre­ated us­ing some kind of ge­netic mod­i­fi­ca­tion.”

“The most likely so­lu­tion to al­low the in­dus­try to sur­vive will be the breed­ing of new tol­er­ant va­ri­eties, most likely cre­ated us­ing some kind of ge­netic mod­i­fi­ca­tion. With­out the use of ge­netic mod­i­fi­ca­tion it’s un­likely a new tol­er­ant va­ri­ety will be bred any­time soon. Nat­u­ral se­lec­tion breed­ing typ­i­cally takes around 20 years to de­liver new so­lu­tions – I’m not sure the in­dus­try can wait that long.

“Whilst I un­der­stand why New Zealand farm­ers and grow­ers have been fight­ing to be GM-free with all the pres­sure be­ing ex­erted in our ma­jor Eu­ro­pean mar­kets, I can’t help think­ing this de­ci­sion may be short sighted and po­ten­tially ex­pose them to greater risk at some time in the fu­ture. If biose­cu­rity is the num­ber one risk fac­ing the agri­cul­tural in­dus­try in NZ is ge­netic mod­i­fi­ca­tion in all its forms, po­ten­tially our num­ber one so­lu­tion?

“This also brings me to Kauri dieback. If we are un­able to con­trol the spread of the Phy­toph­thora caus­ing this dis­ease then will we be left with the op­tions of los­ing Kauri all to­gether, or us­ing GM tech­nol­ogy to mod­ify the ex­ist­ing genes within Kauri’s DNA to en­able it to de­velop re­sis­tance. Are we bet­ter to have a GM Kauri than no Kauri at all?”

He then made his way north to West Vir­ginia to meet Dr Tracy Leskey of the United States Depart­ment of Agri­cul­ture (USDA), to catch up on their lat­est re­search into the con­trol of BMSB, and in par­tic­u­lar the work they were do­ing with the Sa­mu­rai Wasp. > “BMSB is thought to have first been seen in the US in 1995-96 how­ever it was not for­mally iden­ti­fied un­til 2001 in Allentown Penn­syl­va­nia,” he said. “When it ar­rived there were 25 other Pen­tato­mi­dae or shield/stink bugs species al­ready na­tive to the US. One more was not con­sid­ered to be a prob­lem and it was as­sumed the nat­u­ral con­trols al­ready reg­u­lat­ing the other Pen­tato­mi­dae species would also pred­i­tate BMSB and keep its num­bers un­der con­trol.

“The first in­di­ca­tions all was not well came in 2008-2009 from ap­ple grow­ers who started to no­tice caulk­ing in their fruit. The only re­sponse at their dis­posal was to in­crease the num­ber of hard chem­i­cal sprays they were ap­ply­ing. The aver­age grower went from us­ing in­sec­ti­cides four to five times a year in 2010 to 10-15 in 2011. This had the un­in­tended con­se­quence of knock­ing out sev­eral ben­e­fi­cial in­sects that in turn cre­ated fur­ther prob­lems.

“Once re­searchers in the US were aware of the threat that BMSB posed, they be­gan look­ing at po­ten­tial con­trol mea­sures with the most ob­vi­ous one be­ing the Sa­mu­rai Wasp. The US had be­gun the process of in­ves­ti­gat­ing the im­port and re­lease of the wasp when it was dis­cov­ered al­ready in the coun­try in small num­bers. Since then the fo­cus has been on breed­ing and re­leas­ing greater num­bers of Sa­mu­rai Wasp to bring the BMSB pop­u­la­tion un­der con­trol, which it does now seem to be.

“It was in­ter­est­ing that when I vis­ited grow­ers in this area, BMSB was no longer con­sid­ered a ma­jor threat. Dam­age in or­chards whilst still present, has dropped from up to 90 per­cent fruit-loss to less than five per­cent. This was fan­tas­tic news as it cer­tainly in­di­cated that some level of con­trol was be­ing achieved that we could learn from.

“No one would guar­an­tee the Sa­mu­rai Wasp is the cause for the de­crease in BMSB num­bers, how­ever it is strongly sus­pected but there may also be other fac­tors not fully un­der­stood yet.

“In its home, China, BMSB is not a ma­jor pest to agri­cul­ture, in fact the yel­low spot­ted stink bug is con­sid­ered a greater pest. A nat­u­ral preda­tor keeps BMSB num­bers in check as na­ture seeks to main­tain a bal­ance. When you take BMSB out of China with­out its nat­u­ral preda­tor to keep it un­der con­trol, then its num­bers can ex­plode to plague pro­por­tion caus­ing sig­nif­i­cant dam­age as we saw in the US in 2010-2015.”

On his fi­nal day in this area he was looked af­ter by Mark Sut­phin, an ex­ten­sion agent with Vir­ginia Tech who took him to the town of Winch­ester to have a look at the Spot­ted Lan­tern­fly

This is the real risk with biose­cu­rity in­cur­sions where you can get the pest with­out its cor­re­spond­ing bio­con­trol and a pest which at home can seem rather be­nign sud­denly can ex­plode in num­bers and cause ma­jor prob­lems to in­dus­try.

(SLF), Ly­corma del­i­cat­ula in­cur­sion there.

“It was first no­ticed in Penn­syl­va­nia in around 2015,”he said.

“The ini­tial in­cur­sion is thought to be from egg masses that had been laid on paving stones in China and then im­ported to the US. From the ini­tial site they for­ward traced any move­ments of stone to a paving stone de­pot in Winch­ester Vir­ginia. For two years they con­tin­ued to mon­i­tor the site with no sign un­til the first SLF were ob­served two years later. There is no known pheromone or ag­gre­ga­tion traps for SLF so the only method of find­ing them is vis­ual ob­ser­va­tion and sticky tape at­tached to trees.

“One of the keys to find­ing SLF is the pres­ence of Ailan­thus al­tissima or the Tree of Heaven as it is com­monly known. Ailan­thus was im­ported from China as a dec­o­ra­tive tree but has now spread widely through­out the US and is con­sid­ered a pest plant. SLF seem to fo­cus heav­ily on pop­u­lat­ing Ailan­thus as ma­ture adults around the time they breed. It is not known if the plant plays an im­por­tant role in this process or is just a pref­er­ence at this stage. Dur­ing pre­vi­ous life­cy­cle stages as a crawler SLF has been ob­served feed­ing on over 70 dif­fer­ent plant species, the only plant it has so far not shown an in­ter­est in feed­ing on is conifers. This is where part of the danger in this pest lies, its abil­ity to hap­pily feed on a wide range of host plants. “To be hon­est I wasn’t over­whelmed by what I was look­ing at, rather I viewed this in­cur­sion that for two years had not moved more than a mile, as be­ing rel­a­tively easy to erad­i­cate. It wasn’t un­til I spent time in Penn­syl­va­nia where the in­cur­sion is far greater that I re­ally got a feel

It prefers to lay its eggs on trees when num­bers in­crease it will lay its eggs any­where. Egg masses have been seen on stone, tim­ber pal­ings, rusty me­tal – ba­si­cally any­where, and this is where the real risk of SLF be­ing spread comes. “I came away with the feel­ing that if you could iden­tify an in­cur­sion early enough, and were pre­pared to go hard at it, then there was ev­ery chance you could suc­cess­fully erad­i­cate a SLF in­cur­sion in NZ.”

for the threat this in­sect could pose. Lan­tern­fly is not dif­fi­cult to kill and if you had sec­tioned of all the af­fected prop­er­ties and rail­road area in Winch­ester, sprayed it with some­thing rea­son­ably toxic, then I be­lieve it would be rel­a­tively easy to erad­i­cate.

“This high­lights one of the cru­cial ad­van­tages we have in deal­ing with an in­cur­sion, the pow­ers the Min­istry for Pri­mary In­dus­tries (MPI) are given un­der the Biose­cu­rity Act 1993. I didn’t re­ally ap­pre­ci­ate the im­por­tance of this leg­is­la­tion and how vi­tal it is to our suc­cess in deal­ing with in­cur­sions un­til I spent time in the US. “In the US the Fed­eral Au­thor­i­ties have al­most no pow­ers and the State only has a lit­tle more. The Fed­eral and State Au­thor­i­ties can ask the home­own­ers per­mis­sion to carry out ac­tiv­i­ties on their prop­erty but have no way of forc­ing the home­owner to com­ply. So in the mid­dle of an in­cur­sion you can have a home­owner refuse to co­op­er­ate and thereby cre­at­ing a reser­voir to re-in­fect treated neigh­bours, mak­ing erad­i­ca­tion all but im­pos­si­ble.

“SLF on its own can­not travel far. Dur­ing its in­star or crawler phases of which there are four, it looks to climb the near­est tree or ob­ject. It will tend to fall of a struc­ture and then look to climb back up. In its adult form it can fly but is more of a hop­per and will only fly very short dis­tances and on its own won’t travel far. The real risk is that whilst it prefers to lay its eggs on trees when num­bers in­crease it will lay its eggs any­where. Egg masses have been seen on stone, tim­ber pal­ings, rusty me­tal – ba­si­cally any­where, and this is where the real risk of SLF be­ing spread comes.

“I came away with the feel­ing that if you could iden­tify an in­cur­sion early enough, and were pre­pared to go hard at it, then there was ev­ery chance you could suc­cess­fully erad­i­cate a SLF in­cur­sion in NZ. The real risk is not find­ing it in time be­cause once es­tab­lished, the wide host range could mean SLF is un­stop­pable. At this stage there is still no known nat­u­ral preda­tor and the pri­mary con­trol be­ing used is in­ject­ing a sys­temic neon­i­coti­noid Dinote­furon into Ailan­thus trees killing SLF af­ter they feed.

“When SLF feed as an in­star or adult they suck phloem sap from trunks stems and leaf peti­oles. SLF feed­ing in large num­bers can be se­vere enough to cause shoot dieback and, in some cases, plant death. One grape grower had re­ported the plants that had seen heavy feed­ing in spring had not been able to sur­vive win­ter dor­mancy. Heavy feed­ing on hops has also been seen with buds be­ing tainted by the feed­ing leav­ing them un­able to be used for pro­duc­tion of beer.

“Whilst it is feed­ing the SLF also pro­duces large vol­umes of honey dew that can re­sult in sig­nif­i­cant lev­els of sooty mould.

“It wasn’t un­til I headed back up to Penn­syl­va­nia and the city of Read­ing which is at the cen­tre of the SLF in­cur­sion there that I re­ally started to get an un­der­stand­ing of the threat this in­sect poses. It has now spread across 60 coun­ties in Penn­syl­va­nia and cov­ers an area of 6,000 square miles. While I was in the US the first sight­ings in New Jersey were an­nounced mean­ing it had now spread to three states. In South Ko­rea within three years of first be­ing iden­ti­fied it had spread through­out the coun­try.

It has now spread across 60 coun­ties in Penn­syl­va­nia and cov­ers an area of 6,000 square miles.

“I vis­ited The Pagoda in Read­ing which sits on top of a hill and has one of the worst in­fec­tions in the

sur­round­ing park. All around and over the Pagoda were sig­nif­i­cant num­bers of SLF. As I was walk­ing back down a hill I no­ticed from a dis­tance the grass around one of the trees was shiny from honey dew. As I got closer I could also see the base of the tree was black from sooty mould. Stand­ing un­der the tree it felt like there was a soft driz­zle and look­ing up you could ac­tu­ally see the honey dew be­ing se­creted, such was the vol­ume.

“Not only will this pose ma­jor prob­lems in terms of sooty mould, but the large vol­ume will po­ten­tially pro­vide a sig­nif­i­cant food source for wasps. “I left that area and headed

10km away. I had to stop for gas and as I was stand­ing there fill­ing up the car I no­ticed sev­eral SLF just hang­ing out on the petrol pump. It was then I started to un­der­stand the dif­fi­culty faced con­trol­ling this pest once it started to spread.

“A few days later I at­tended a meet­ing on SLF run by Penn­syl­va­nia Sec­re­tary of Agri­cul­tural Rus­sell Red­ding and Penn State Uni­ver­si­ties Dean Rick Roush. Both orig­i­nally trained and worked as en­to­mol­o­gists and in Penn­syl­va­nia both have dealt with the in­cur­sions of BMSB, Fruit Fly, Spot­ted Wing Drosophila and now SLF. Roush made the com­ment dur­ing most dam­ag­ing and great­est threat to agri­cul­ture of all the in­va­sive pests he’s seen. This was a pretty sober­ing com­ment and re­in­forced the threat this in­sect poses.”

I no­ticed sev­eral SLF just hang­ing out on the petrol pump. It was then I started to un­der­stand the dif­fi­culty faced con­trol­ling this pest once it started to spread.

Next Si­mon will look at Ba­nana Panama dis­ease in Queens­land, Fruit Fly in the South of Aus­tralia and the BMSB in­cur­sion in San­ti­ago, Chile.

“It’s thought that the most likely spot for an in­cur­sion to oc­cur in NZ is in an ur­ban area, so what is hap­pen­ing in Chile is of par­tic­u­lar in­ter­est.”

▶ Mul­ti­ple fourth in­star spot­ted lan­tern­fly con­gre­gat­ing in num­bers on a shoot. ▴ Two stages of lan­tern­fly with the sin­gle one an adult fe­male spot­ted lan­tern­fly.

◀ The black­ness cre­ated by sooty mould and shin­ing on the grass leaf is honey dew se­cre­tion from lan­tern­fly. A wasp can be seen feed­ing on the honey dew which is a food source and could re­sult in in­creased num­bers.

▶ Ben Hayes of Hayes Farms, Cul­man County, Alabama.

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