Biological and Chemical Control of Mosquito Population by Optimal Control Approach

This paper focuses on the design and analysis of short-term control intervention measures seeking to suppress local populations of Aedes aegypti mosquitoes, the major transmitters of dengue and other vector-borne infections. Besides traditional measures involving the spraying of larvicides and/or insecticides, we include biological control based on the deliberate introduction of predacious species feeding on the aquatic stages of mosquitoes. From the methodological standpoint, our study relies on application of the optimal control modeling framework in combination with the cost-effectiveness analysis. This approach not only enables the design of optimal strategies for external control intervention but also allows for assessment of their performance in terms of the cost-benefit relationship. By examining numerous scenarios derived from combinations of chemical and biological control measures, we try to find out whether the presence of predacious species at the mosquito breeding sites may (partially) replace the common practices of larvicide/insecticide spraying and thus reduce their negative impact on non-target organisms. As a result, we identify two strategies exhibiting the best metrics of cost-effectiveness and provide some useful insights for their possible implementation in practical settings.

Population dynamics of the main phytophagous and predatory mites associated with rubber tree plantations in the State of Bahia, Brazil

Rubber trees, Hevea brasiliensis, are the main source of latex in the world, being cultivated in several states in Brazil. Calacarus heveae Feres and Tenuipalpus heveae Baker are considered the main pest mites of this crop. In this study, we evaluated the population dynamics of these two phytophagous species and of the most common predatory species during a one-year period on crops of rubber tree clones FDR 5788, CDC 312 and PMB 01, located in Igrapiúna, State of Bahia, northeastern Brazil. The results indicate that outbreaks of C. heveae and T. heveae occur from January to May. Population densities vary among clones, being lower on FDR 5788. Amblyseius perditus Chant and Baker (Phytoseiidae), Parapronematus sp. (Iolinidae) and Agistemus pallinii Matioli, Tavares and Pallini (Stigmaeidae) were the most abundant and frequently encountered predacious species. The population dynamics of these predatory species were related to the abundance of the phytophagous mites. However, the efficacy of these predators to mitigate infestations of phytophagous mites under natural conditions is unresolved due to the high reproductive rate of the phytophagous species.

Identification and characterization of ace1-type acetylcholinesterase in insecticide-resistant and -susceptible Propylaea japonica (Thunberg)

Characterization and gene cloning of acetylecholinesterase (AChE) in the insecticide-resistant (R) and -susceptible (S) insects have been reported in the past. However, the studies focused mostly on herbivorous pests, rather than predacious species, such as ladybird beetles. Using R and S Propylaea japonica (thunberg), a full-length cDNA sequence (2928 bp) of the ace1-type AChE gene was determined for the first time. The ace1 encoding a protein of 645 amino acids contained typical conserved motifs, such as FGESAG domains, catalytic triad, acyl pocket, oxyanino hole, choline binding site, peripheral anionic site, omega loop and conserved aromatic residues. R P. japonica displayed 50-times greater resistance to chlorpyrifos or mathamidophos with a significantly lower AChE sensitivity to paraoxon, malaoxon, chlorpyrifos or methamidophos than its S counterpart. Five amino acids in the ace1 of R P. japonica differed from those found in S P. japonica. One of them, F358S, located in the acyl-binding pocket, might play a crucial role in the resistance of the insect to organophosphates (OPs). Whereas, K493E and I538V, which were close to some of the conserved aromatic amino acids (i.e., H509, Y511, and W499) in the gorge, and G571R and T576A near C593 that formed the disulfide bonds with C471, might also involve in the change of insecticide resistance in P. japonica. AChE insensitivity and amino acid replacements, particularly F358S, might be the determining factors in the alteration of OPs-resistance in P. japonica.

A new Oncylocotis Stål (Hemiptera: Heteroptera: Enicocephalidae) from Sabah: a predacious species associated with the yellow crazy ant, Anoplolepis gracilipes (Smith) (Hymenoptera: Formicidae)

We describe Oncylocotis (Oncylocotis) inexpectatus n. sp. (Hemiptera: Heteroptera: Enicocephalomorpha: Enicocephalidae) from Malaysia (Sabah). It is the first species of this widely distributed Old World genus from Borneo. Some plesiomorphic anatomical features of the species are discussed and illustrated; e.g., the clypeus subdivided into well delimited anteclypeus and postclypeus; prescapite present; male abdominal segment 8 not modified for genital purposes, and abdominal segments 1–8 bearing spiracles in both males and females. New data on subdivision of the abdomen and venation of the clavus in enicocephalids are provided. The predacious O. inexpectatus n. sp. was found in association with the invasive 'yellow crazy ant', Anoplolepis gracilipes (Smith) (Hymenoptera: Formicidae) which is ranked among the 100 most devastating invaders worldwide. We bring together the information on this association and review the known cases of myrmecophily in the infraorder Enicocephalomorpha. A list of insect species found as inquilines of A. gracilipes in Sabah is included.

EVALUASI LAPANG TERHADAP DAMPAK APLIKASI INSEKTISIDA ISOPROCARB PADA SERANGGA PREDATOR DAN HAMA KUTU PERISAI AULACASPIS TEGALENSIS Zhnt. (HOMOPTERA: DIASPIDIDAE) DI PERTANAMAN TEBU

Field evaluation of isoprocarb insecticide-application-effects on predacious insects and scale pest Aulacaspis tegalensis Zhnt. (Homoptera: Diaspididae) in sugarcane plantations. The sugarcane scale, Aulacaspis tegalensis Zehntner, is a new serious pest of sugarcane in Lampung Province. Over the years, most control practices against A. tegalensis rely on the use of chemical insecticide. A field study was conducted to assess the impact of isoprocarb (carbamate-insecticide) on sugarcane scale pests and their natural predators in sugarcane plantation. The results indicated that the application of isoprocarb (at recommended concentration = 1.25 mg/L) in sugarcane field failed to cause a significant reduction on scale pest populations. In contrast, the numbers of predacious insects was significantly reduced in isoprocarb-treated-field plots. The predacious insects in association with scale pests in sugarcane fields were predominantly coccinellids. Four species of primary predacious coccinellids attacking scale pests were: Chilocorus melanophthalmus, Chilocorus sp., Scymnus sp, and Telsimia sp. This field study indicated that the predacious species were more susceptible to isoprocarb than their prey.

Ladybeetles as Predators of Pest and Predacious Mites in Citrus

The acceptability of Panonychus citri (McGregor) (Tetranychidae) as prey for adults and larvae of four coccinellid species, Cycloneda sanguinea L., Exochomus childreni Mulsant, Harmonia axyridis Pallas, and Olla v-nigrum (Mulsant), was evaluated. Also, three beneficial predacious species, Euseius mesembrinus (Dean), Iphiseiodes quadripilis (Banks) and an Amblyseius sp. (Phytoseiidae), were evaluated for their acceptability as prey for H. axyridis adults. Adult females and early larval stages of C. sanguinea, E. childreni, H. axyridis, and O. v-nigrum readily consumed adult P. citri females when these were presented on leaf disk arenas in Petri dishes. The most voracious mite predator was H. axyridis. Adult female H. axyridis consumed an average of 15.14 ± 1.9 female P. citri in 24 h, and first-instar larvae consumed 6.1 ± 0.7 in 60 min. Only H. axyridis was tested with predaceous mites as prey. First-instar H. axyridis larvae consumed one or two adult Amblyseius sp. in three out of eight trials, and a single E. mesembrinus female. No I. quadripilis females were eaten by H. axyridis larvae. Adult female H. axyridis did not consume adult female phytoseiids of any species under similar conditions. If predacious phytoseiids are generally unacceptable as prey for coccinellids while P. citri is selectively consumed, then coccinellid predation would likely have a net beneficial effect in contributing to suppression of tetranychid mite populations in citrus.

Biodiversity and ecology of Australasian yeasts (fungi)

The biodiversity and ecology of yeasts associated with natural habitats have attracted little systematic research in Australasia. Most isolations concern yeasts associated with foods and beverages such as wine, fruit juices, soft drinks, dairy products, high-sugar products and processed meats. Although these yeasts have interesting physiological and biochemical properties (e.g. xerotolerance, preservative resistance, protease and lipase activity), they are similar to species found in products in other countries. Ecological studies of yeasts associated with cactus, hibiscus, morning glory plants and associated insects of New South Wales and Queensland have revealed new species including Pichia opuntiae, Clavispora opuntiae, and Wickerhamiella australiensis, Kodamaea anthophila, Kodamaea kakaduensis, Metschnikowia hibisciand a unique predacious species of Candida. New species of Cryptococcus and Rhodotorula were isolated from soils and pasture grasses in New Zealand. Clinical isolates in the genera Candida and Cryptococcus are similar to those found overseas but Cryptococcus neoformans var. gattii is uniquely associated with the red gum tree, Eucalyptus camaldulensis.

Nutrition and phylogeny of predacious yeasts

Yeast predation was studied with respect to the range of its distribution among ascomycetous yeasts, the range of yeast species that can be affected, and nutritional aspects of the phenomenon. The yeasts identified as predators belong to the Saccharomycopsis clade as defined on the basis of rDNA sequence relatedness. The 11 recognized species in the clade, plus three undescribed but related Candida species, were shown to be incapable of utilizing sulfate as sole source of sulfur, and all but two (Saccharomycopsis capsularis andSaccharomycopsis vini) were observed to penetrate and kill other yeasts under some conditions. Other unrelated sulfate transport-deficient yeasts (strains in the genera Pichia and Candida and the two known species of Starmera) are not predacious. The predacious species vary considerably as to the optimal environmental conditions that favour predation. Some are inhibited by the presence of rich nitrogenous nutrients, organic sulfur compounds, or higher concentrations of ammonium nitrogen, whereas other species may be stimulated under the same conditions. An attempt was made to correlate prey susceptibility to the excretion of substances that stimulate the growth of predators, but no correlation was detected between the two phenomena. The range of susceptible prey covers both ascomycetes and basidiomycetes, and includes Schizosaccharomyces pombe, which was previously thought to be immune. The achlorophyllous alga Prototheca zopfii is not killed by predacious yeasts, but the initial steps of penetration have been observed in some cases. Predacious species attack other predacious species, and in some cases, young cultures may penetrate older cultures of the same strain.Key words: predacious yeasts, sulfate transport deficiency, Saccharomycopsis.