No. 260, September 2015 ISSN 1175-9755

Newsletter of the Scion Forest Protection team. Edited by Nicolas Meurisse and Lindsay Bulman, Scion, Private Bag 3020, Rotorua 3046, New Zealand. Email: nicolas.meurisse@scionresearch.com. Website: http://www.scionresearch.com/biosecurity

Halyomorpha halys, commonly known as the brown marmorated stink bug (BMSB), is a severe crop and fruit pest that originated from Eastern Asia. In the mid-1990s an invasion of BMSB was detected in Pennsylvania USA. The species is highly polyphagous. Within its native range, there are reports of occasional losses of fruit crops including apple, peach, pear and persimmon. In 2010, populations in the USA hit a record high, and commercial fruit orchards incurred substantial losses. Generally, orchard plots most at risk are those bordered by a forest, as the BMSB tends to move regularly between shelter areas (in the forest) and feeding areas in orchards. Due to this behaviour, the worst BMSB damage is found at the edges of orchards bordered by forests or hedge rows. However, during population outbreaks, high levels of damage can occur orchard-wide. Another concern is that BMSB is a vector of a phytoplasma that causes witches’ broom in Paulownia trees, a favourite host tree.

BMSB is believed to have entered the USA as a ‘hitchhiker’ associated with packing crates imported from its native region. BMSB is now established in over 40 states in the USA, and there are reports of establishment in Europe including Switzerland and France. MPI has intercepted BMSB both dead and alive at the New Zealand border in particular from vehicles, sea containers, air freight and passenger luggage. Within the USA, from mid-September there is a four week period of mass dispersal of BMSB to favoured overwintering sites. This results in large aggregations of bugs in dark, dry places, such as attics, warehouses, and wheel arches of vehicles. During this period, there is obviously a higher likelihood of bugs hitchhiking (as above).

With BMSB now firmly established in the USA, researchers are striving to find ways of protecting orchards, with a focus on apple and peach stands. Currently, populations in affected locations are being controlled with the use of monitoring traps and rigorous pesticide regimes. For New Zealand, it is very important that BMSB is not allowed to become established. Projects are underway to study the behaviour and pheromone responses of BMSB in

order to develop appropriate detection methods for bugs entering through high risk pathways.

One such project is the detection of BMSB based on its biogenic volatile organic compounds. BMSB and many other stink bugs, when disturbed, produce alarm volatiles with a strong, very characteristic smell (hence the name). Laura Nixon, a Lincoln University/Better Border Biosecurity PhD student, is looking at whether these compounds can be used to chemically detect BMSB associated with imports. Sensitive analytical methods are being developed and tested in order to identify these compounds in large and complex spaces. In this work it is necessary to take into account the context in which BMSB release these alarm compounds. This has led to planned studies, in collaboration with US Department of Agriculture researchers in West Virginia and Maryland, to examine the behaviour of BMSB in response to disturbance whilst they are overwintering and to sample the volatiles emitted by BMSB while they are in this stage. Ultimately, the aim is to develop a reliable chemical detection method for BMSB for circumstances where visual inspections are not suitable or practical.

Laura Nixon (Lincoln University PhD student), Ecki Brockerhoff (Scion), Stephen Goldson (AgResearch) and Michael Rostas (Lincoln University).

Brown marmorated stink bug (BMSB, Halyomorpha halys) on an apple leaf. Note the characteristic white bands on the antennae.

KEEPING THE BROWN MARMORATED STINK BUG OUT OF NEW ZEALAND

Forest Health News 260, September 2015

Printed by Scion Digital Print Centre, Rotorua (07 343 5711)

In June 2015, we gave an update on research to control dothistroma needle blight and red needle cast using copper fungicide (FH News 257: Controlling needle diseases of pines).

Work on another type of fungicide to control red needle cast has also made good progress. Phosphite has been shown to control Phytophthora diseases associated with woody plants, e.g. sudden oak death in North America and root rot in New Zealand forest nurseries.

Phosphite fungicides are systemic and act in two ways - directly on the pathogen and also indirectly by stimulating host defence responses to suppress disease development.

after mixing. The effect was demonstrated by NMR spectroscopy and droplet spread tests. This was a surprising result given the early successes demonstrated by the Agri-Fos®600 and Du-Wett® product/adjuvant combination.

Experiments carried out by Plant Protection Chemistry NZ found that another phosphite product, Foschek™, did not break down Du-Wett®, and other adjuvants, at any concentration tested. More importantly, the uptake of Foschek™, applied at the equivalent of 12 kg/ha phosphite, was over five times better than that of Agri-Fos®600, with no difference in uptake between Foschek™ applied alone and in combination with an adjuvant.

The effect can persist for over a year after application, however, persistence is host dependent. In order to work most effectively, phosphite needs to be taken up efficiently by the host. If phosphite uptake can be maximised then the applied dose can be accordingly reduced, hopefully leading to less chemical applied with efficacy maintained. Uptake of phosphite can be improved by using adjuvants which have the potential to improve spray deposition, penetration, droplet spread and retention.

Initial tests found that phosphite applied as the fungicide Agri-Fos®600 with the adjuvant Du-Wett® gave good uptake of the active ingredient. However, subsequent experiments indicated that the adjuvant was being rapidly degraded by Agri-Fos®600, basically rendering the effect of the adjuvant null, resulting in poor uptake. This was particularly so at rates of phosphite tested above an application dose of 6 kg/ha, when not applied immediately

That result is supported by spread tests on cabbage leaves (an accepted medium for droplet spread tests*) shown above. Note the limited droplet spread on the left hand photo compared with the right.

This work has markedly advanced progress towards deployment of an operational chemical control system for red needle cast. Foschek™ did not interfere with the adjuvant and, more importantly, an adjuvant may not be required to enhance uptake of phosphite when applied as this product.

This outcome should have positive effects on the cost/benefit of spraying phosphite for control of red needle cast.

Carol Rolando and Stefan Gous

*and the best use of cabbage known to man (Editor)

Agri-Fos 12kg/ha and Du-Wett Foschek 12kg/ha and Du-Wett

Phot

os c

ourt

esy

of P

lant

Pro

tect

ion

Chem

istr

y NZ

PHOSPHITE SHOWS PROMISE FOR RED NEEDLE CAST CONTROL

Typical droplet spreading on cabbage leaves of solutions applied one hour after mixing.