Equilibrium control of nonlinear verticum-type systems, applied to integrated pest control

Linear verticum-type control and observation systems have been introduced for modelling certain industrial systems, consisting of subsystems, vertically connected by certain state variables. Recently the concept of verticum-type observation systems and the corresponding observability condition have been extended by the authors to the nonlinear case. In the present paper the general concept of a nonlinear verticum-type control system is introduced, and a sufficient condition for local controllability to equilibrium is obtained. In addition to a usual linearization, the basic idea is a decomposition of the control of the whole system into the control of the subsystems. Starting from the integrated pest control model of Rafikov and Limeira (2012) and Rafikov et al. (2012), a nonlinear verticum-type model has been set up an equilibrium control is obtained. Furthermore, a corresponding bioeconomical problem is solved minimizing the total cost of integrated pest control (combining chemical control with a biological one)

Impulsive Biological Pest Control Strategies of the Sugarcane Borer

We propose an impulsive biological pest control of the sugarcane borer (Diatraea saccharalis) by its egg parasitoid Trichogramma galloi based on a mathematical model in which the sugarcane borer is represented by the egg and larval stages, and the parasitoid is considered in terms of the parasitized eggs. By using the Floquet theory and the small amplitude perturbation method, we show that there exists a globally asymptotically stable pest-eradication periodic solution when some conditions hold. The numerical simulations show that the impulsive release of parasitoids provides reliable strategies of the biological pest control of the sugarcane borer

A two-agent model applied to the biological control of the sugarcane borer (Diatraea saccharalis) by the egg parasitoid Trichogramma galloi and the larvae parasitoid Cotesia flavipes

The paper is aimed at a methodological development in biological pest control. The considered one pest two-agent system is modelled as a verticum-type system. Originally, linear verticum-type systems were introduced by one of the authors for modelling certain industrial systems. These systems are hierarchically composed of linear subsystems such that a part of the state variables of each subsystem affect the dynamics ofthe next subsystem. Recently, verticum-type system models have been applied to population ecology as well, which required the extension of the concept a verticum-type system to the nonlinear case. In the present paper the general concepts and technics of nonlinear verticum-type control systems are used to obtain biological control strategies in a two-agent system. For the illustration of this verticumtype control, these tools of mathematical systems theory are applied to a dynamic model of interactions between the egg and larvae populations of the sugarcane borer (Diatraea saccharalis) and its parasitoids: the egg parasitoid Trichogramma galloi and the larvae parasitoid Cotesia flavipes. In this application a key role is played by the concept of controllability, which means that it is possible to steer the system to an equilibrium in given time. In addition to a usual linearization, the basic idea is a decomposition of the control of the whole system into the control of the subsystems, making use of the verticum structure of the population system. The main aim of this study is to show several advantages of the verticum (or decomposition) approach over the classical control theoretical model (without decomposition). For example, in the case of verticum control the pest larval density decreases below the critical threshold value much quicker than without decomposition. Furthermore, it is also shown that the verticum approach may be better even in terms of cost effectiveness. The presented optimal control methodology also turned out to be an efficient tool for the “in silico” analysis of the cost-effectiveness of different biocontrol strategies, e.g. by answering the question how far it is cost-effective to speed up the reduction of the pest larvae density, or along which trajectory this reduction should be carried out

Estudo de Estabilidade de Equações Diferenciais Ordinárias Autônomas e Aplicação

http://dx.doi.org/10.5902/2179460X14644The aim of this work is to introduce some important results on stability of solutions of autonomous ordinary differential equations and use them in the stability study of a mathematical model of the biological pest control of the sugarcane borer.Pretende-se com este trabalho introduzir alguns resultados importantes sobre estabilidade de soluções de equações diferenciaisordinárias autônomas e utilizá-los no estudo de estabilidade de um modelo matemático do controle biológico de pragas da broca dacan

A simulation modeling approach to aid research into the control of a stalk-borer in the South African Sugar Industry.

Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermartzburg, 2008.The control of the African stalk borer Eldana saccharina Walker (Lepidoptera: Pyralidae) in sugarcane fields of KwaZulu-Natal, South Africa has proved problematical. Researchers at the South African Sugarcane Research Institute (SASRI) have since 1974 been intensively investigating various means of controlling the pest. Among the methods of control currently being investigated are biological control, chemical control, production of more resistant varieties and crop management. These investigations, however, require many years of experimentation before any conclusions can be made. In order to aid the research currently being carried out in the Entomology Department at SASRI (to investigate biological control strategies, insecticide application strategies and the carry-over decision), a simulation model of E. saccharina growth in sugarcane has been formulated. The model is cohort-based and includes the effect of temperature on the physiological development of individuals in each life-stage of the insect. It also takes into account the effect of the condition of sugarcane on the rate of E. saccharina infestation, by making use of output from the sugarcane growth model CANEGRO. Further, a crop damage index is defined that gives an indication of the history of E. saccharina infestation levels during the sugarcane’s growth period. It is linked to the physiological activity of the borer during the period spent feeding on the stalk tissue. The damage index can further be translated into length of stalks bored and hence the percentage of the stalk length bored can be calculated at each point in the simulation using the total length of stalks calculated in the CANEGRO model. Using an industry accepted relationship between percent stalks damaged and reduction in sucrose content of the crop, reductions in losses in the relative value of the crop when the various control measures are implemented can be compared. Relationships between the reduction in percent stalk length bored (and hence gains in the relative value of the crop) and the various control strategies are obtained

Statistical methods and models for analyzing sugarcane (Saccharum species hybrids) plant breeding data

Early generation selection of sugarcane families using means is inadequate while visual seedling selection is subjective and inefficient. Data from advanced variety trials (yield, quality and agronomic traits) are collected over several crop-years to determine yield potential and ratooning ability of genotypes follow a multivariate repeated measures structure. In Louisiana, the sugarcane borer and recently the Mexican rice borer are major insect pests of sugarcane. Both borers have similar feeding habits, providing an opportunity for investigating if genotypes resistant to one species would provide resistance to the other (cross-resistance). The objectives of the study were to identify statistical methods to evaluate family yield potential and repeatability, enhance seedling selection for yield, analyze advanced variety trials data and prove cross resistance between the sugarcane borer and the Mexican rice borer. Random coefficient models (RCM) identified elite families with higher cane yield potential and higher repeatability between seedlings and clones. These elite families comprised a larger proportion of higher yield seedlings that produced high yielding clones. Logistic regression models (LRM) provided an objective statistical decision support tool for selecting high yielding seedlings and were more flexible at adjusting the number of seedlings to advance than visual selection. The LRM can be used to identify important traits in breeding populations as well as directionally shifting population trait values during selection. Neural network models can be used to automate the LRM. The multivariate repeated measures analysis (MRM) reduced Type I errors associated with univariate analysis by including covariance to compute experimental errors. The MRM showed greater statistical differences among genotypes for yield traits than univariate analysis. Cross resistance between the sugarcane and Mexican rice borer was proved using log linear models, and using a population with known sugarcane borer resistance status. Using RCM will significantly increase the efficiency of early generation selection by identifying families with high yield potential and repeatability while LRM will increase efficiency of identifying high yielding seedlings from these elite families. MRM will increase the accuracy of evaluating genotypes for yield and ratooning ability. Cross-resistance will allow breeders to take advantage of parents from the sugarcane borer recurrent selection program

Sustainable control of infestations using image processing and modelling

A sustainable pest control system integrates automated pest detection and recognition to evaluate the pest density using image samples taken from habitats. Novel predator/prey modelling algorithms assess control requirements for the UAV system, which is designed to deliver measured quantities of naturally beneficial predators to combat pest infestations within economically acceptable timeframes. The integrated system will reduce the damaging effect of pests in an infested habitat to an economically acceptable level without the use of chemical pesticides. Plant pest recognition and detection is vital for food security, quality of life and a stable agricultural economy. The research utilises a combination of the k-means clustering algorithm and the correspondence filter to achieve pest detection and recognition. The detection is achieved by partitioning the data space into Voronoi cells, which tends to find clusters of comparable spatial extents, thereby separating the objects (pests) from the background (pest habitat). The detection is established by extracting the variant and distinctive attributes between the pest and its habitat (leaf, stem) and using the correspondence filter to identify the plant pests to obtain correlation peak values for the different datasets. The correspondence filter can achieve rotationally invariant recognition of pests for a full 360 degrees, which proves the effectiveness of the algorithm and provides a count of the number of pests in the image. A series of models has been produced that will permit an assessment of common pest infestation problems and estimate the number of predators that are required to control the problem within a time schedule. A UAV predator deployment system has been designed. The system is offered as a replacement for chemical pesticides to improve peoples’ health opportunities and the quality of food products

Development of handling and transport protocols for Eldana saccharina (Lepidoptera: Pyralidae) sterile insect technique (SIT) programme

Thesis (MScConsEcol)--Stellenbosch University, 2021.ENGLISH ABSTRACT: Eldana saccharina Walker (Lepidoptera: Pyralidae), is indigenous to sub-Saharan Africa and is a serious economical pest of sugarcane in South Africa. Recent area-wide integrated pest management (AW-IPM) efforts have proven to be effective in lowering infestations and better predicting population growth and spread into new areas. The sterile insect technique (SIT) promises to provide great benefit as a component of the AW-IPM strategy. This study aimed to establish parameters for collection, packaging, and transport of recently emerged E. saccharina adult males, within a maintained cold chain conjointly with methodologies for the routine assessment of the performance and competitiveness of sterilized insects. These treatments should not impact the fitness nor mating ability of the adults exposed to them. Several major outcomes were realized, summarized as follows: Parental male and female pairs exposed to 100 Gy irradiation prior to mating provided an 83.3 % male biased first filial generation. Thus, a male biased, semi sterile generation could be reared for collection and release using this technique; difference between average male (0.0700 g) and female (0.133 g) pupal weights (as an indication of adult weight) were identified as a morphological trait that could be exploited to obtain a high degree of sex separation; and the plenum collection box was effective in collecting male and female adult E. saccharina (a mean of 80.67 % ± 4.56 % adults were collected when placing 200 adult moths (male : female = 1:1) into the prototype collection system overnight for 12 hours replicated three times). Furthermore, the effect of exposure of virgin E. saccharina males to 5 °C for 24, 48 and 72 hours on male mating frequency and longevity was measured to determine the impact of prolonged periods of cold exposure to male fitness. The 72 hour treatment showed a significant decrease in male mating frequency (average of 4.4 females mated at 48 h versus 2.7 females mated at 72 hours). It is therefore possible to hold E. saccharina at 5 °C for 48-hours without impacting on moth fitness in terms of mating frequency. Bran was identified as a good temperature insulating material to use as a packaging substrate for adult males, as it buffered temperature fluctuations over time inside a transportable freezer set at 5 °C (1.5 °C to 5.5 °C) when fully stocked with bran, versus being empty (0 °C to 6 °C). Bran’s effect as a packaging substrate on male fitness during high density packaging and exposure to 5 °C for 24, 48 and 72 hours showed no significant decrease in male mating frequency (mean mating frequency of 2.8889 females mated). Males did have a decreased mating frequency (1.4667 females mated) after 72 hours for the no bran packaged adults. A visual rating system was tested to measure the difference in loose scale cover - on the eyes, dorsal surface, ventral surface, as well as scale loss from the pronotum - between bran and no bran packaged moths. There was a clear improved visual quality with bran packaged adults compared to no bran packaged adults with less scale loss from the pronotum and less loose scales covering the eyes and ventral and dorsal surfaces, indicating that this visual rating system could be valuable as a quality control check at the point of elease.AFRIKAANSE OPSOMMING: Eldana saccharina Walker (Lepidoptera: Pyralidae), is inheems aan Suider Afrika en is 'n ernstige ekonomiese plaag op suikerriet in Suid-Afrika. Onlangse pogings tot area wye geïntegreerde plaag bestuur was effektief. Die steriele insek tegniek (SIT) beloof om 'n groot voordeel te lewer as komponent van die area wye strategie tot beheer. Die produksie van E. saccharina kan voortdurende produksie volumes van mededingende motte verseker. 'n Stralingsdosis van 200 Gy het geen invloed op die paringsgedrag of die algemene fiksheid van volwasse motte nie en laat mannetjies gedeeltelik steriel vir gebruik in ‘n SIT program. Hierdie studie poog om parameters vas te stel vir versameling, verpakking en vervoer binne 'n onderhoude koue ketting, tesame met metodieke vir die roetine-assessering van die mededingendheid van gesteriliseerde insekte. Die blootstelling van mannetjie en wyfie ouer-pare aan bestraling van 100Gy voor paring het 'n 83,3% mannetjie opeenvolhende generasie gegee. Die meerderheid mannetjie, semi-steriele generasie kan dus groot gemaak word vir versameling en vrylating. Verskil tussen mannetjie en vroulike mot gewigte is geïdentifiseer as 'n morfologiese eienskap wat gebruik kan word om 'n sterk mate van skeiding te verkry. Die plenum-versamelingskis is effektief vir die versameling van mannetjie en wyfie E. saccharina. Deur motte bloot te stel aan koue temperature vir hoë digtheid verpakking vir bestraling, vervoer tot met vrylating verhoed dit dat liggaamlike aktiwiteit mot fiksheid sal beskadig. 'n Immobiliseer- en houtemperatuur van 5 °C is gebruik wat bo die motte se kritieke minimum temperatuur van 4,4 °C is. Die effek van blootstelling van maagdelike E. saccharina mannetjies aan 5 °C vir 24, 48 en 72 uur op mannetjie parings frekwensie en langlewendheid is gemeet om die impak van langdurige periodes van koue blootstelling aan mannetjie fiksheid te ondersoek. Die 72 uur behandeling het 'n beduidende afname in die parings frekwensie vir mannetjies getoon in vergelyking met alle ander behandelings. Dit is dus moontlik om E. saccharina by 5 °C te hou vir tot 48 uur sonder om die motfiksheid in terme van parings frekwensie te beïnvloed. Semels is geïdentifiseer as 'n goeie temperatuur isolerende buffer om as verpakkingssubstraat te gebruik, en het dus ook getoon dat temperatuurswisseling verminder as die temperatuur met verloop van tyd binne die vervoerbare vrieskas gemeet word wanneer dit vol met semels is teenoor om leeg te wees. Semels se effek as verpakkingssubstraat op mannetjie fiksheid tydens hoë digtheid verpakking en blootstelling aan 5 °C gedurende 24, 48 en 72 uur het geen beduidende afname in mannetjieparings frekwensie getoon nie. Mannetjies het wel na 72 uur 'n verlaagde parings frekwensie gehad vir die nie-semels verpakte motte. 'n Visuele waarderingstelsel is getoets om die verskil in losskaal bedekking aan die oë, rugkant, ventrale kant sowel as skaal verlies te meet aan die pronotum tussen semels en geen semels verpakte motte. Daar was 'n duidelike verbeterde visuele kwaliteit met semels verpakte motte in vergelyking met geen semels verpakte motte , wat daarop dui dat hierdie visuele waarderingstelsel waardevol kan wees as 'n gehaltebeheer op die punt van vrylating.Master

Status, Impact and Management of Invasive Alien Species in Tanzania

Invasive alien species (IAS) are among the significant drivers of environmental change worldwide and important causes of biodiversity losses. They contribute to economic hardship and social instability, placing constraints on sustainable development, economic growth, and ecological problems in various parts of the world, including Tanzania. This study was undertaken to provide information on the status of invasive species and their management needs in Tanzania. The study used three methodological approaches including documentary search, interviews with relevant stakeholders and limited field visits. Findings from the study have indicated that the awareness, trends, distribution and impacts of the invasive alien species in Tanzania are variable, and similarly are the management and control requirements and practices for these species. Among the major impacts associated with the IAS in the country include loss of biodiversity, where in some cases has caused disappearance of certain species of fauna and flora, social and economic distress to human being due to the disappearance of plants and animal species that are regarded as important sources of livelihoods. The study shows that currently there is limited demonstrated capacity in terms of human and financial resources to address the issue of IAS, except for a few cases such as the water hyacinth (Eichhornia crassipes) in Lake Victoria. In addition, there are no clearly defined long term strategies to address the issue of invasive species in many institutions. Experience shows that many of the legislations and policies dealing with biodiversity and/or resource management in the country do not directly address invasive alien species. This shortfall may be responsible for the inadequate attention being accorded to the management of invasive species. Thus for effective management of invasive alien species, policies and legislations should be encouraged to directly deal with invasive species. Such situation calls for integrated efforts including various institutional frameworks and collaborations.Key words: Invasive alien species, biodiversity loss, management of IAS,sustainable development, Tanzania