2011 IPM forum highlights

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.