Biosecurity threats posed by Silverleaf Whitefly (SLW) transmitted viruses

Cherie Gambley, Senior Plant Pathologist with DEEDI, outlined the threat of virus transmission by Silver Leaf Whitefly  Bemisia tabaci, Biotype B.

SLW is capable of transmitting viruses from several different taxonomic virus groups. Out of all virus groups the Begomovirus genus pose the greatest threat to Australian cotton, grain, vegetable and nursery industries.

Silverleaf Whitefly

 Begomoviruses have become a significant constraint to horticulture and field crop production worldwide and are considered one of the major emerging viral threats to crop production. Losses in the order of billions of dollars – attributed to these viruses – have occurred in cassava in Africa, cotton in Pakistan, grain legumes in India and tomatoes in Florida. These losses and the inability to effectively control the diseases caused by begomoviruses has contributed to major socio-economic problems including food shortages and grower suicides in Pakistan and SE Asia.

One of these SLW-transmitted diseases, Cotton leaf curl disease (CLCuD), is a major biosecurity threat for the cotton industry. This disease is also capable of infecting and causing production losses to vegetable crops such as cucurbits, tomato, capsicum and chilli as well as ornamental horticulture species such as hibiscus. There are also at least five begomovirus species capable of infecting grain legumes, particularly soybean, mungbean and cowpea.

Begomoviruses

To address the risk of begomoviruses, a cross-industry project has commenced with the aim of reviewing regional control of SLW as a virus vector, investigating the feasibility of using SLW indexing as an early warning surveillance tool for detection of exotic viruses and reviewing potential entry pathways for exotic viruses.

Pest Suppressive Landscapes and Habitat Function  

Nancy Schellhorn and Jamie Hopkinson gave an outline of the Pest Suppressive Landscape project. This project seeks to explore the link between surrounding habitats, pest and beneficial insect dynamics and pest suppression.     

Landscape complexity has been shown to increase the ecosystem service of pest suppression, although the mechanisms responsible remain elusive.  Ecological theory predicts that early predation by a few predators can result in higher pest suppression than late predation by many predators.   

In the Lockyer Valley, we tested the effects of earliness of predator impacts on the suppression of Aphis gossypii (cotton aphid) in 19 horticultural landscapes that differed in landscape complexity. Predator impacts were manipulated using exclusion cages on sentinel aphid populations. The following treatments were used: 1) early predation (only during week 1), 2) late predation (only during week 2), 3) continuous predation (during both weeks), and 4) predator exclusion control.  We found that predators can have a significant impact on aphids, but only some landscapes contributed predators early.     

On the Darling Downs we are identifying the source habitats of pests and natural enemies, assessing their movement between habitats and determining their time of crop colonization. To date we have determined that native vegetation has higher densities of beneficials, and infrequently harbour pests. Crops near this native vegetation have more beneficials than crops that are located further away. In both landscapes, pest densities are higher for crop further away from native vegetation than for crops that are nearby native vegetation.  These results will contribute to guidelines for IPM at the field, farm and landscape scale.  

Solenopsis mealybugs: farm hygiene and IPM  

Melina Miles and Susan Maas provided an update of solenopis mealybug. Outbreaks of this pest have occurred in cotton crops in the Burdekin, central Queensland and most recently in Byee. Impacts have been locally damaging and resulted in plant death and reduced yield.  

Mealybug specimens from cotton and other hosts have been submitted to the DEEDI taxonomists over the past 3 years. The current situation in cotton is that the distribution is still restricted to Queensland with no positive identifications from NSW cotton-growing regions.  Preliminary work by DEEDI has focused on addressing the immediate needs of the industry in terms of indentifying key sources of infestation, and controlling damaging infestations in-crop.  

Winter surveys of on-farm vegetation in the Emerald Irrigation Area found solenopsis mealybug on a number of weed hosts. Cotton volunteers and ratoons would appear to be key hosts; raising the perennial issue of crop and farm hygiene in minimising sources of insect pest infestations from one season to the next.  

Solenopsis mealybug on bladder ketmia host

 Whilst a permit has been available for methidathion to control solenopsis mealybug in cotton, the use of a broadspectrum option is unlikely to be the mainstay of mealybug control. Investigation into the population dynamics, impact of early infestations on crop growth and subsequent yield, and the potential of soft options to control infestations are warranted. CRDC has recently funded a 3 year project (2010-2014) which will include research that addresses key issues integral to developing a management strategy for solenopsis mealybug in the cotton-grains farming system.

The forums are being held at two locations on Thursday the 28th of July:

The  Dalby RSL:  9am – 11.30am

and

The Brookstead Hall:  1.30pm – 4.00pm

 Topics and presenters

 Cotton Bunchy top     

(Murray Sharman – DEEDI Virologist,  Lewis Wilson – CSIRO Entomologist, Jeff Werth – DEEDI weed scientist)

After the prevalence of cotton aphids and cotton bunchytop in some parts of the Downs, now is the time to start thinking about how to reduce aphid populations and remove sources of bunchytop that may otherwise invade your cotton crops next season. 

Seedling pests of cereals 

 (Hugh Brier – DEEDI Entomologist)

 Winter and spring crops are susceptible to a host of establishment pests, and cool and wet conditions can exacerbate the damage they cause. Learn what might be a problem this season, and how to identify the pest and its damage, and what you can do to control or manage the problem. Hugh will run through the common, and not-so-common, establishment pests.

Pest suppressive landscapes

  (Nancy Schellhorn - CSIRO Entomologist  and Jamie Hopkinson – DEEDI Entomologist)

Ever wondered whether the trees and shrubs along the creek, or in that nearby reserve were harbouring beneficial insects that might be benefitting your crops? Well, this is the focus of research being undertaken on the Downs, in NSW and WA. Nancy Schellhorn is leading a project that is examining the relationship between remnant vegetation and pest and beneficial abundance to answer questions about the role of this vegetation in the agricultural landscape.

Minimising the risk of a Solenopsis Mealybug outbreak 

 (Melina Miles,  DEEDI Entomologist)

You may have heard about the mealybug outbreak in Emerald cotton two seasons ago. You may be wondering if this new pest is coming your way. Melina has been involved in preliminary work on this pest, and will discuss some key management and monitoring strategies to minimise the likelihood of an outbreak in your crops.

For more information contact Melina Miles at the Toowoomba DEEDI office on 4688 1369, or 0407113306.  

Morning and afternoon tea will be provided. For catering purposes please RSVP to melina.miles@deedi.qld.gov.au

Participants in the forum were from industry, research, extension and stakeholders. The aims of the IPM Forum were to exchange the latest information about research and projects and to maintain linkages between IPM projects and people across industries.

The Forum mostly focused on R,D & E being conducted in NSW and Qld, in the broadacre farming system. The broad range of topics covered in presentations included some key pests – green mirids, stink bugs, helicoverpa and silverleaf whitefly.

Of particular interest were presentations by a number of postgraduates from The University of Queensland.

• James Hereward – Dispersal and host plant interactions of green mirids (or ‘Where do mirids come from – are we dealing with locals or immigrants from far inland?’)
• Corinna Lange – The population genetic structure of native budworm, Helicoverpa punctigera, in the Australian landscape (or ‘My trip to pick grubs off wildlowers in the middle of Australia’)
• Jamie Hopkinson – Host acceptance behaviour of an aphid parasitoid (or ‘How I learnt to dissect tiny aphids and find even tinier wasp eggs inside them’).

It was interesting that many IPM Forum participants were noticeably envious of Corinna’s work – but less so of Jamie’s!

Other welcome participants included the Grains Research and Development Corporation Crop Protection Program Team who seized the opportunity to meet with project leaders and discuss research results.

If you have any questions about the 2007 IPM Forum, leave a post below.

Until next time, Big Bug.

Photo: The GRDC Crop Protection Program Team includes (L to R) John Sandow, GRDC Crop Protection Manager, Ralph Burnett, Western Panel member, Allan Mayfield, Southern Panel member, Rohan Rainbow, GRDC Project Manager, and Bill Yates, Northern Panel member. Photo provided by GRDC.

Until now, The Beat Sheet has simply been a newsletter circulated via email and snail mail (going back further, its orginal name was the Heliothis Hotline). While the newsletter format will continue for the time being, we are excited about the potential for this move into the world of blogs and blogging.

So who are we? The team looking after this blog is made up of the the following Queensland Department of Primary Industries and Fisheries entomology staff.

• Big Eyed Bug (a.k.a. Austin McLennan, Development Extension Officer – IPM)
• Big Bug (a.k.a. Dr Dave Murray, Principal Entomologist)
• Lady Bug (a.k.a. Dr Melina Miles)

To all our longstanding readers of the newsletter format, we’re confident you’ll find The Beat Sheet blog is a much more convenient and timely way to receive updates on insect pest management issues relevant to the grain cropping regions of Queensland and northern NSW.

To both new and old readers, if you have any ideas about how to improve The Beat Sheet, please let us know by posting your comments to this blog.

Welcome and Enjoy!