Options for managing chrysomelid leaf beetles in Australian eucalypt plantations: reducing the chemical footprint

Abstract

1 In Australia, eucalypt plantations require management to prevent economic damage by native chrysomelid leaf beetles, generally by aerially spraying a broad-spectrum insecticide. These beetles also pose a serious threat to plantations in other countries. 2 Various alternatives, both 'landscape' and 'control' options, for managing leaf beetles were reviewed and evaluated by a panel of experts. Options were scored on effectiveness, feasibility for use, impact on the environment, perceived social acceptability (including by certification bodies) and perceived cost. 3 None of the options were scored as well as broad-spectrum insecticide for effectiveness, feasibility and perceived cost, although virtually all of the other options scored better for environmental and social outcomes. 4 The highest ranked options were the 'landscape' option of tree improvement to reduce susceptibility to insect attack, and the 'control' option of attract-and-kill traps. The next three ranks were two 'landscape' options aimed at enhancing the effectiveness of natural enemy populations by conserving their overwintering sites and their alternative food and hosts, and then silvicultural management. 5 The best strategy for an Integrated Pest Management programme would be a combination of 'landscape' options to reduce the frequency of pest outbreaks and, if outbreaks occur, spraying with biological insecticides until attract-and-kill traps become available, possibly in combination with repellent sprays in a push-pull strategy. If control measures fail to prevent damaging defoliation, plantations could be fertilized to encourage recovery. 6 Because most of the alternative options are not yet available, many research directions were identified, with the highest priorities being to develop plantation stock that is less susceptible to defoliation and to develop attractants for leaf beetles.

Impact of defoliation in temperate eucalypt plantations: Physiological perspectives and management implications

“…Continuous defoliation at low to moderate levels in E. globulus had little effect in the long-term (Loch and Matsuki, 2010), while 100% defoliation continuing beyond three annual events caused short-term cessation of growth in E. marginata (Wills et al, 2004). Defoliation by a biotic pest is likely to have a greater impact if it coincides with silvicultural practices such as pruning (Elek and Wardlaw, 2010), as it is essentially the same as a scenario of repeated defoliation.…”

“…Natural enemies are important natural controls for defoliating insects in eucalypt plantations (Elek and Wardlaw, 2010) and it is possible that the colonisation of natural enemies in these plantations may well be as a result of an active rather than a passive process. If this is true, the adoption of management strategies that conserve the populations of natural enemies such as the more judicious use of broad-spectrum insecticides as well as the maintenance of overwintering sites for natural enemies (Elek and Wardlaw, 2010;Grimbacher et al, 2011) should clearly be promoted as a way to harness the tree's inbuilt defence mechanisms.…”

“…Outbreaks of herbivorous insects or foliar pathogens are common in eucalypt plantations (Loch and Matsuki, 2010) and a recent review has described the main damaging pests of eucalypts including both native and introduced insect herbivores and pathogens (Paine et al, 2011). Current methods of pest management in plantations vary greatly depending on the pest type and resources available (Elek and Wardlaw, 2010). Management options may rely on host resistance (deployment of resistant genotypes), chemical control (application of broad-spectrum or targeted pesticides, pheromones, or poisons for browsing mammals), biological control (e.g.…”

“…egg parasitoids for insect pests), cultural control (e.g. avoidance of sites with high pest risk, nutrient management, thinning of stands) or a combination of these strategies as part of an integrated pest management system (Stone, 1991;Elek and Wardlaw, 2010). In reality few of these practices are implemented because of economic and environmental constraints, and damage from defoliating pests is therefore a regular occurrence.…”

Biology of theEucalyptusleaf beetleParopsisterna selmani(Chrysomelidae: Paropsini): a new pest ofEucalyptusspecies (Myrtaceae) in Ireland

“…Insecticides are likely to disrupt the efficacy of established biocontrol programmes (Paine & Millar, 2002) and the management of the beetle and two new exotic psyllids on Eucalyptus in Ireland (Hodkinson, 2007;Helden, 2009) will necessitate the use of an integrated approach to pest control. The use of broad spectrum insecticides can provide a good option of control, although numerous alternative methods can be considered, as outlined by Elek and Wardlaw (2013). In Ireland, the use of insecticides in forest plantations is uneconomical and alternatives including biological control will have to be considered, especially because this method has proven to be successful against similar beetles (Kay, 1990;Tribe, 2000;Paine & Millar, 2002) and other pests in Eucalyptus growing regions of the world outside of Australia, including Europe (Cordero Rivera et al, 1999;Protasov et al, 2007).…”