Structural Damage Detection Using Modal Curvature and Fuzzy Logic

A fuzzy logic system (FLS) with a new sliding window defuzzifier is proposed for structural damage detection using modal curvatures. Changes in the modal curvatures due to damage are fuzzified using Gaussian fuzzy sets and mapped to damage location and size using the FLS. The first four modal vectors obtained from finite element simulations of a cantilever beam are used for identifying the location and size of damage. Parametric studies show that modal curvatures can be used to accurately locate the damage; however, quantifying the size of damage is difficult. Tests with noisy simulated data show that the method detects damage very accurately at different noise levels and when some modal data are missing.

Can feral pig harvesting and co-ordinated control reduce damage to grain crops?

Commercial and recreational harvesting of pigs is often encouraged by pest managers because it is essentially a ‘free’ reduction in pest density. However, the reduction in numbers may provide minimal damage mitigation and may be inappropriately allocated in space and time. Additionally, more effective control (e.g. baiting) may not occur because of the incorrect perception that harvesting is effective or because pigs are valued for recreational use.

Growth of koster’s curse (Clidemia hirta) from seedlings to reproductive maturity and following mechanical damage

Koster´s curse is a highly invasive, perennial shrub with potential to become a major weed in many parts of Queensland and elsewhere in Australia. Presently, there is one infestation discovered in Australia and the species is a Class 1 weed. It grows to 5 m and can produce over 500 berries annually which are dispersed by birds and water. This study quantified growth and the effects of damage on survival and time to reproduction under both field and shade house conditions in the Wet Tropics of north Queensland. Plants recovered to their original size and were capable of setting seed in as few as 86 days and 194 days after being cut back to 10 cm and 0 cm respectively.

Evaluation of weed eradication programs: containment and extirpation

Weed eradication programs often require 10 years or more to achieve their objective. It is important that progress is evaluated on a regular basis so that programs that are 'on track' can be distinguished from those that are unlikely to succeed. Earlier research has addressed conformity of eradication programs to the delimitation criterion. In this paper evaluation in relation to the containment and extirpation criteria is considered. Because strong evidence of containment failure (i.e. spread from infestations targeted for eradication) is difficult to obtain, it generally will not be practicable to evaluate how effective eradication programs are at containing the target species. However, chronic failure of containment will be reflected in sustained increases in cumulative infested area and thus a failure to delimit a weed invasion. Evaluating the degree of conformity to the delimitation and extirpation criteria is therefore sufficient to give an appraisal of progress towards the eradication objective. A significant step towards eradication occurs when a weed is no longer readily detectable at an infested site, signalling entry to the monitoring phase. This transition will occur more quickly if reproduction is prevented consistently. Where an invasion consists of multiple infestations, the monitoring profile (frequency distribution of time since detection) provides a summary of the overall effectiveness of the eradication program in meeting the extirpation criterion. Eradication is generally claimed when the target species has not been detected for a period equal to or greater than its seed longevity, although there is often considerable uncertainty in estimates of the latter. Recently developed methods, which take into consideration the cost of continued monitoring vs. the potential cost of damage should a weed escape owing to premature cessation of an eradication program, can assist managers to decide when to terminate weed eradication programs.

Will biological control of Lantana camara ever succeed? Patterns, processes & prospects

Despite biocontrol research spanning over 100 years, the hybrid weed, commonly referred to as Lantana camara, is not under adequate control. Host specificity and varietal preference of released agents, climatic suitability of a region for released agents, number of agents introduced and range or area of infestation appear to play a role in limiting biocontrol success. At least one of 41 species of mainly leaf- or flower-feeding insects has been introduced, or spread, to 41 of the 70 countries or regions where lantana occurs. Over half (26) of these species have established, achieving varying levels of herbivory and presumably some degree of control. Accurate taxonomy of the plant and adaptation of potential agents to the host plant are some of the better predictors of at least establishment success. Retrospective analysis of the hosts of introduced biocontrol agents for L. camara show that a greater proportion of agents that were collected from L. camara or Lantana urticifolia established, than agents that were collected from other species of Lantana. Of the introduced agents that had established and were oligophagous, 18 out of 22 established. The proportion of species establishing, declined with the number of species introduced. However, there was no trend when oceanic islands were treated separately from mainland areas and the result is likely an artefact of how introductions have changed over time. A calculated index of the degree of herbivory due to agents known to have caused some damage per country, was not related to land area infested with lantana for mainlands nor for oceanic islands. However, the degree of herbivory is much higher on islands than mainlands. This difference between island and mainland situations may reflect population dynamics in patchy or metapopulation landscapes. Basic systematic studies of the host remain crucial to successful biocontrol, especially of hybrid weeds like L. camara. Potential biocontrol agents should be monophages collected from the most closely related species to the target weed or be phytophages that attack several species of lantana. Suitable agents should be released in the most ideal ecoclimatic area. Since collection of biocontrol agents has been limited to a fraction of the known number of phytophagous species available, biocontrol may be improved by targeting insects that feed on stems and roots, as well as the agents that feed on leaves and flowers.

Predicting risk and benefit a priori in biological control of invasive plant species: a systems modelling approach

While the method using specialist herbivores in managing invasive plants (classical biological control) is regarded as relatively safe and cost-effective in comparison to other methods of management, the rarity of strict monophagy among insect herbivores illustrates that, like any management option, biological control is not risk-free. The challenge for classical biological control is therefore to predict risks and benefits a priori. In this study we develop a simulation model that may aid in this process. We use this model to predict the risks and benefits of introducing the chrysomelid beetle Charidotis auroguttata to manage the invasive liana Macfadyena unguis-cati in Australia. Preliminary host-specificity testing of this herbivore indicated that there was limited feeding on a non-target plant, although the non-target was only able to sustain some transitions of the life cycle of the herbivore. The model includes herbivore, target and non-target life history and incorporates spillover dynamics of populations of this herbivore from the target to the non-target under a variety of scenarios. Data from studies of this herbivore in the native range and under quarantine were used to parameterize the model and predict the relative risks and benefits of this herbivore when the target and non-target plants co-occur. Key model outputs include population dynamics on target (apparent benefit) and non-target (apparent risk) and fitness consequences to the target (actual benefit) and non-target plant (actual risk) of herbivore damage. The model predicted that risk to the non-target became unacceptable (i.e. significant negative effects on fitness) when the ratio of target to non-target in a given patch ranged from 1:1 to 3:2. By comparing the current known distribution of the non-target and the predicted distribution of the target we were able to identify regions in Australia where the agent may be pose an unacceptable risk. By considering risk and benefit simultaneously, we highlight how such a simulation modelling approach can assist scientists and regulators in making more objective decisions a priori, on the value of releasing specialist herbivores as biological control agents.

Specificity of Carvalhotingis visenda (Hemiptera: Tingidae) as a biological control agent for cat's claw creeper Macfadyena unguis-cati (Bignoniaceae) in Australia

Biological control is considered the most suitable management option for cat's claw creeper, Macfadyena unguis-cati, a major environmental weed in coastal and sub-coastal areas of Queensland and New South Wales, Australia. The potential host range of the leaf-sucking bug, Carvalhotingis visenda (Hemiptera: Tingidae) was evaluated on the basis of nymphal survival and development, adult feeding and survival, and oviposition preference using choice and no-choice tests involving 38 plant species in 10 families. In no-choice tests, although adults survived on a few of the non-target plants, no eggs were laid on any of the non-target plants. In no-choice condition, the tingid oviposits and completes nymphal development only on M. unguis-cati. There was also no visible feeding damage on any of the non-target plants. In choice tests, adults showed distinct preference for M. unguis-cati, and the preference level increased over time as the tingids moved away from the non-target plants. At the end of the trial no adults were evident on any of the non-target plants. Host specificity tests confirm that the tingid is a highly host specific biocontrol agent, and does not pose risk to any non-target plants in Australia. This agent has been approved for field release by the relevant regulatory authorities in Australia.

Temporal patterns in incidence and abundance of Aconophora compressa (Hemiptera: Membracidae), a biological control agent for Lantana camara, on target and nontarget plants

The membracid Aconophora compressa Walker, a biological control agent released in 1995 to control Lantana camara (Verbenaceae) in Australia, has since been collected on several nontarget plant species. Our survey suggests that sustained populations of A. compressa are found only on the introduced nontarget ornamental Citharexylum spinosum (Verbenaceae) and the target weed L. camara. It is found on other nontarget plant species only when populations on C. spinosum and L. camara are high, suggesting that the presence of populations on nontarget species may be a spill-over effect. Some of the incidence and abundance on nontarget plants could have been anticipated from host specificity studies done on this agent before release, whereas others could not. This raises important issues about predicting risks posed by weed biological control agents and the need for long-term postintroduction monitoring on nontarget species.

Local dispersion and damage of Corymbia citriodora subsp. variegata (Myrtaceae) regrowth by eriophyid mites (Acari: Eriophyoidea).

Eriophyid mites (Acari: Eriophyoidea: Eriophyidae: Rhombacus sp. and Acalox ptychocarpi Keifer) are recently-emerged pests of commercial eucalypt plantations in subtropical Australia. They cause severe blistering, necrosis and leaf loss to Corymbia citriodora subsp. variegata (F. Muell.) K.D. Hill & L.A.S. Johnson, one of the region's most important hardwood plantation species. In this study we examine the progression, incidence and severity of these damage symptoms. We also measure within-branch colonisation by mites to identify dispersive stages, and estimate the relative abundance of the two co-occurring species. Rhombacus sp., an undescribed species, was numerically dominant, accounting for over 90% of all adult mites. Adults were the dispersive stage, moving mostly within branches, but 12% of recruitment onto new leaves occurred on previously uninfested branches. Damage incidence and severity were correlated, while older leaves had more damage than younger leaves. "Patch-type" damage was less frequent but was associated with higher mite numbers and damage scores than "spot-type" damage, while leaf discoloration symptoms related mostly to leaf age.

A scientific approach to agent selection

The prioritisation of potential agents on the basis of likely efficacy is an important step in biological control because it can increase the probability of a successful biocontrol program, and reduce risks and costs. In this introductory paper we define success in biological control, review how agent selection has been approached historically, and outline the approach to agent selection that underpins the structure of this special issue on agent selection. Developing criteria by which to judge the success of a biocontrol agent (or program) provides the basis for agent selection decisions. Criteria will depend on the weed, on the ecological and management context in which that weed occurs, and on the negative impacts that biocontrol is seeking to redress. Predicting which potential agents are most likely to be successful poses enormous scientific challenges. 'Rules of thumb', 'scoring systems' and various conceptual and quantitative modelling approaches have been proposed to aid agent selection. However, most attempts have met with limited success due to the diversity and complexity of the systems in question. This special issue presents a series of papers that deconstruct the question of agent choice with the aim of progressively improving the success rate of biological control. Specifically they ask: (i) what potential agents are available and what should we know about them? (ii) what type, timing and degree of damage is required to achieve success? and (iii) which potential agent will reach the necessary density, at the right time, to exert the required damage in the target environment?

Pest-damage relationships for Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) on soybean (Glycine max) and dry bean (Phaseolus vulgaris) during pod-fill.

The response of soybean (Glycine max) and dry bean (Phaseolus vulgaris) to feeding by Helicoverpa armigera during the pod-fill stage was studied in irrigated field cages over three seasons to determine the relationship between larval density and yield loss, and to develop economic injury levels. H. armigera intensity was calculated in Helicoverpa injury equivalent (HIE) units, where 1 HIE was the consumption of one larva from the start of the infestation period to pupation. In the dry bean experiment, yield loss occurred at a rate 6.00 ± 1.29 g/HIE while the rates of loss in the three soybean experiments were 4.39 ± 0.96 g/HIE, 3.70 ± 1.21 g/HIE and 2.12 ± 0.71 g/HIE. These three slopes were not statistically different (P > 0.05) and the pooled estimate of the rate of yield loss was 3.21 ± 0.55 g/HIE. The first soybean experiment also showed a split-line form of damage curve with a rate of yield loss of 26.27 ± 2.92 g/HIE beyond 8.0 HIE and a rapid decline to zero yield. In dry bean, H. armigera feeding reduced total and undamaged pod numbers by 4.10 ± 1.18 pods/HIE and 12.88 ± 1.57 pods/HIE respectively, while undamaged seed numbers were reduced by 35.64 ± 7.25 seeds/HIE. In soybean, total pod numbers were not affected by H. armigera infestation (out to 8.23 HIE in Experiment 1) but seed numbers (in Experiments 1 and 2) and the number of seeds/pod (in all experiments) were adversely affected. Seed size increased with increases in H. armigera density in two of the three soybean experiments, indicating plant compensatory responses to H. armigera feeding. Analysis of canopy pod profiles indicated that loss of pods occurred from the top of the plant downwards, but with an increase in pod numbers close to the ground at higher pest densities as the plant attempted to compensate for damage. Based on these results, the economic injury levels for H. armigera on dry bean and soybean are approximately 0.74 HIE and 2.31 HIE/m2, respectively (0.67 and 2.1 HIE/row-m for 91 cm rows).

Pest-damage relationships for Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) on vegetative soybean.

The response of vegetative soybean (Glycine max) to Helicoverpa armigera feeding was studied in irrigated field cages over three years in eastern Australia to determine the relationship between larval density and yield loss, and to develop economic injury levels. Rather than using artificial defoliation techniques, plants were infested with either eggs or larvae of H. armigera, and larvae allowed to feed until death or pupation. Larvae were counted and sized regularly and infestation intensity was calculated in Helicoverpa injury equivalent (HIE) units, where 1 HIE was the consumption of one larva from the start of the infestation period to pupation. In the two experiments where yield loss occurred, the upper threshold for zero yield loss was 7.51 ± 0.21 HIEs and 6.43 ± 1.08 HIEs respectively. In the third experiment, infestation intensity was lower and no loss of seed yield was detected up to 7.0 HIEs. The rate of yield loss/HIE beyond the zero yield loss threshold varied between Experiments 1 and 2 (-9.44 ± 0.80 g and -23.17 ± 3.18 g, respectively). H. armigera infestation also affected plant height and various yield components (including pod and seed numbers and seeds/pod) but did not affect seed size in any experiment. Leaf area loss of plants averaged 841 and 1025 cm2/larva in the two experiments compared to 214 and 302 cm2/larva for cohort larvae feeding on detached leaves at the same time, making clear that artificial defoliation techniques are unsuitable for determining H. armigera economic injury levels on vegetative soybean. Analysis of canopy leaf area and pod profiles indicated that leaf and pod loss occurred from the top of the plant downwards. However, there was an increase in pod numbers closer to the ground at higher pest densities as the plant attempted to compensate for damage. Defoliation at the damage threshold was 18.6 and 28.0% in Experiments 1 and 2, indicating that yield loss from H. armigera feeding occurred at much lower levels of defoliation than previously indicated by artificial defoliation studies. Based on these results, the economic injury level for H. armigera on vegetative soybean is approximately 7.3 HIEs/row-metre in 91 cm rows or 8.0 HIEs/m2.

Skin damage to two new mango cultivars during irradiation and cold storage.

Mangoes can express several skin disorders following important postharvest treatments. Responses are often cultivar specific. This paper reports the responses of two new Australian mango cultivars to some of these treatments. 'Honey Gold' mango develops "under skin browning" early during cold storage. This is thought to be partly caused by a discolouration of the latex vessels which then spreads to the surrounding cells. The symptoms appear to be worse in fruit from hotter production areas and that have been cooled to temperatures below 18C soon after harvest. Current commercial recommendations are to cool fruit to 18C, which limits postharvest handling options. Recent trials have confirmed that delayed or slowed cooling after harvest can reduce under skin browning. The defect may also be associated with physical injury to the skin during harvesting and packing. Irradiation is potentially an important disinfestation treatment for fruit fly in Australian mangoes. The 'B74' mango cultivar develops significant skin damage following irradiation, mainly due to discolouration of the cells surrounding the lenticels. Recent results confirmed that fruit harvested directly from the tree into trays without exposure to water or postharvest chemicals are not damaged by irradiation, while commercially harvested and packed fruit are damaged. Several major harvest and postharvest steps appear to increase lenticel sensitivity to irradiation. Further work is required to develop commercially acceptable protocols to facilitate 'Honey Gold' and 'B74' mango distribution and marketing.

Genetic and Epigenetic Characterization of Colorectal and Endometrial Cancer

Colorectal cancer is one of the three most common cancers today, for both men and women. Approximately 90% of the cases are sporadic while the remaining 10% is hereditary. Among this 10% is hereditary nonpolyposis colorectal cancer (HNPCC), an autosomal dominant disease, accounting for up to 13% of these cases. HNPCC is associated with germline mutations in four mismatch repair (MMR) genes, MLH1, MSH2, MSH6, and PMS2, and is characterized by a familial accumulation of endometrial, gastric, urological, and ovarian tumors, in addition to colorectal cancer. An important etiological characteristic of HNPCC is the presence of microsatellite instability (MSI), caused by mutations of the MMR genes. Approximately 15% of sporadic cases share the MSI+ trait. Colon cancer is believed to be a consequence of an accumulation of mutations in tumor suppressor genes and oncogenes, eventually resulting in tumor development. This phenomena is accelerated in HNPCC due the presence of an inherited mutation in the MMR genes, accounting for one of the two hits proposed to be needed by Knudson (1971) in order for the manifestation of the MSI phenotype. MMR alterations alone, however, do not occur in the majority of sporadic colon cancers, prompting searches for other mechanisms. One such mechanism found to play a role in colon cancer development was DNA methylation, which is known to play a role in MLH1 inactivation. Our objective was clarification of mechanisms associated with tumor development in both HNPCC and sporadic colorectal cancer in relation to tumorigenic mechanisms. Of particular interest were underlying mechanisms of MSI in sporadic colorectal cancers, with attention to DNA methylation changes and their correlation to MSI. Of additional interest were the genetic and epigenetic events leading to the HNPCC tumor spectrum, chiefly colon and endometrial cancers, in regards to what extent the somatic changes in target tissue explained this phenomenon. We made a number of important findings pertaining to these questions. First, MSI tumor development differs epigenetically from stable tumor development, possibly underlying developmental pathway differences. Additionally, while epigenetic modification, principally DNA methylation, is a major mechanism in sporadic MSI colorectal cancer MLH1 inactivation it does not play a significant role in HNPCC tumors with germline MLH1 mutations. This is possibly an explanation for tumorigenic pathways and clinicopathological characteristic differences between sporadic and hereditary MSI colorectal cancers. Finally, despite indistinguishable genetic predisposition for endometrial and colorectal cancers, instability profiles highlighting organ-specific differences, may be important HNPCC tumor spectrum determinants.

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