Simon Cook’s Nuffield Thoughts: Part 7
BMSB and Spotted Lanternfly
After leaving Florida I flew North to Philadelphia in Pennsylvania, my final stop before heading home. I hired a car, and yes, I did drive around listening to Bruce Springsteen’s Streets of Philadelphia. One of the simple joys of driving around the US is the number of songs you grow up listening to that relate to places in the US, Sweet Home Alabama got plenty of airtime when I was there, and I enjoyed listening to Tennessee Whiskey as we were leaving the Jack Daniels factory in Tennessee. They are no longer just great songs but are now fantastic memories as well.
I made my way south to the neighbouring state of West Virginia where I was due to meet Dr Tracy Leskey of the United States Department of Agriculture (USDA). Dr Leskey leads the Appalachian Fruit Research Station in Kearneysville West Virginia. Dr Leskey will be familiar to local growers who attended presentations and workshops she ran while visiting New Zealand with the support of KVH in August last year. The main purpose of my visit was to catch up on their latest research into the control of Brown Marmorated Stink Bug (BMSB), and in particular the work they were doing with Trissolcus Japonicus or as its commonly known, the Samurai Wasp. I was also interested to learn a little more about the initial incursion of BMSB into the US and how it became such a significant problem.
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. When BMSB arrived in the US, 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. At first it was thought to be calcium deficiency, however in 2010, they realised it was caused by BMSB feeding. By then the impact was so severe growers were saying they would be out of business in 2-3 years. 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 4-5 times a year in 2010 to 10-15 in 2011. The increased use of hard chemicals also 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. The most obvious control was its natural predator back in China, 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% fruit-loss to less than 5%. This was fantastic news as it certainly indicated that some level of control was being achieved that we could learn from. It was really pleasing to see that this natural predator did seem to be having an impact in drastically reducing BMSB numbers, especially when the EPA have now given approval for the import and release of Samurai Wasp in the event of an incursion in New Zealand. No one would guarantee the Samurai Wasp is the cause for the decrease in BMSB numbers, however it is strongly suspected to be due to its presence. Proving the decrease in numbers is solely due to the Samurai Wasp is difficult as there may also be other factors not fully understood yet.
In its natural home of China BMSB is not a major pest to agriculture, in fact the yellow spotted stink bug is considered a greater pest. The reason BMSB is not a major threat is that its natural predator keeps its 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. Its not hard to think of examples that have already heavily impacted New Zealand – possums, rabbits and gorse to name a few. This does highlight the difficulty of assessing potential threats to New Zealand agriculture as a pest that at home hardly raises an eyebrow could be devastating if it arrived here with no form of natural control.
The main reason we are aware of the pests we are currently working to keep out like BMSB, Fruit Fly and now Spotted Lanternfly is due to the biosecurity failings of other countries, giving us an opportunity to witness these pests without control. As a grower travelling overseas I was continually reminded how lucky we are to have an organisation like MPI working hard on our behalf to try to prevent incursions into New Zealand in the first place. The old adage prevention is better than cure could also be updated for biosecurity, prevention is a hell of a lot cheaper than cure.
After spending a couple of days meeting Dr Leskey and some of her team, my final day in this area saw me drive just across the border into the state of Virginia where I was looked after by Mark Sutphin, an extension agent with Virginia Tech. In America there are approximately 70 plus universities/technical institutes that were created under the Land Grant provisions of the Morrill Acts of 1862 and 1890. The Morrill Acts allowed for the gifting of Federal land to individual States, for the purpose of being sold to create Land Grants to fund the establishment of institutes of higher learning focusing on agriculture, science and engineering. A key component of these grants was that research and technology had to be made available to the local community. To achieve this transfer, attached to each Land Grant institute are extension agents who act as a middleman between researchers and farmers. The extension agents also act as a conduit to take problems farmers are facing and help organise researchers to try and come up with solutions. This system of researchers and farmers working together was one of the most impressive things I noticed in my time in the US.
The reason I met with Mark was to get him to take me to the town of Winchester to have a look at the Spotted Lanternfly (Lycorma delicatula) incursion there. Just a little history first to set the scene, Spotted Lanternfly (SLF) was first noticed in Pennsylvania in around 2015. 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. One of the sites the stone was moved to is a paving depot in Winchester, Virginia. For two years they continued to monitor the site with no sign until the first Spotted Lanternfly was observed two years later in 2017. Just a point to note, at this stage 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.
The paving stone depot in Winchester backs onto the local railroad which provides a contiguous stretch of trees and bush area around the tracks. From the initial site the SLF have only been observed to have traveled less than a mile either direction, primarily North up the rail line. 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 life-cycle 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 Conifer. 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 for the threat this insect could pose. Lanternfly is not difficult to kill and if you had sectioned off all the affected properties and railroad area in Winchester, sprayed it with something reasonably toxic, then I believe it would be easy to eradicate. This highlights one of the crucial advantages we have in dealing with an incursion, the powers 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. Basically, in the land governed for the people by the people, the individual homeowner has all the rights. 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. Therefore 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. This same absolute right of the individual is also part of the underlying problem around gun control, where the right of the individual is viewed as more important than the good of the community.
SLF on its own cannot travel far. During its instar or crawler phases of which there are 4, it looks to climb the nearest tree or object. It will tend to fall off 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. The real risk is that whilst it prefers to lay its eggs on trees as is the case still in Virginia, 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 New Zealand. 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 Dinotefuran 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 die-back 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. Obviously, this has the potential to be catastrophic for the wine industry. 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. Once the public realise the threat this poses to beer and wine I’m sure we won’t have a problem getting their support.
Whilst it is feeding the SLF also produces large volumes of honey dew that can result in significant levels of sooty mould. To give you an idea, think of a severe passion vine hopper infection and what that leads to in terms of sooty mould – then imagine the PVH are the size of cicadas. I have seen orchards suffer 20-30% fruit loss because of PVH, I can see this resulting in fruit loss of 80-90% with SLF.
It wasn’t until I headed back up to Pennsylvania and headed to 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 3 states. In South Korea within 3 years of first being identified it had spread throughout the country.
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 the Pagoda and all 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 towards my hotel, 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 “Town Hall” presentation on SLF as part of the Pennsylvania State Ag field-days. A “Town Hall” meeting is an opportunity for politicians or elected officials to meet with constituents to discuss topics of interest. The meeting was run by Pennsylvania Secretary of Agricultural, Russell Redding and Penn State Universities Dean Rick Roush. Both originally trained and worked as entomologists so have a wealth of knowledge on invasive pests. In Pennsylvania both have dealt with the incursions of BMSB, Fruit Fly, Spotted Wing Drosophila and now Spotted Lanternfly. These four are all in KVH’s most unwanted list and all feature prominently. Dean Roush made the comment during the meeting that he felt SLF was the 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.
There was still plenty more to learn but after 10 weeks overseas travelling it was time to head home for a few weeks to catch up with family, work and other commitments before heading off again. At this stage the next trip will include Banana Panama disease in Queensland and Fruit Fly in the South of Australia. I will also look to spend time in Santiago, Chile looking at the BMSB incursion in the city to see how they are handling the urban battlefield. It is thought that the most likely spot for an incursion to occur in New Zealand is in an urban area, so what is happening in Chile is of particular interest.