Maicon Toldi

Biological performance of the predatory mite Neoseiulus idaeus (Phytoseiidae): a candidate for the control of tetranychid mites in Brazilian soybean crops

The soybean (Glycine max (L.): Fabaceae) is considered the most important agricultural crop in Brazil. Phytophagous tetranychid mites as Mononychellus planki McGregor, Tetranychus ludeni Zacher and T. urticae Koch have been considered pest in soybean crops. Neoseiulus idaeus Denmark & Muma (Phytoseiidae) is a predatory mite of T. ludeni and T. urticae. The aim of the present study was to evaluate the biological performance of N. idaeus when fed on T. urticae, T. ludeni and M. planki, coming from the Northwest region of Rio Grande do Sul state, Brazil. The study was conducted in the laboratory with individual predators supplied with different preys. The mean duration (days) of N. idaeus egg-adult development was similar independently of supplied prey (T. ludeni - 5.29±0.03; M. planki - 5.34±0.05 and T. urticae - 5.23±0.03 days). Female viability was 90% when fed on M. planki and 100% when fed on T. ludeni and T. urticae. Mean fecundity of N. idaeus was lower when fed on M. planki (4.6±1.58 eggs/female) and higher when fed on T. ludeni (21.8±3.22) and T. urticae (26.2±2.41). The mean generation time (T) was lower when N. idaeus fed on M. planki than when fed on T. ludeni and T. urticae. The net reproductive rate (Ro) was 4.42±0.49 on M. planki, 17.77±0.55 on T. ludeni and 20.59±0.48 on T. urticae. The innate capacity for increase (rm) was lower when N. idaeus was fed on M. planki (0.09) and higher when such predator was fed on T. ludeni (0.20) and T. urticae (0.22 females/females/day). These results demonstrated that N. idaeus is able to reach the complete development feeding on all the three tetranychid species. Mononychellus planki demonstrated to provide a sub-optimal diet if compared to T. ludeni and T. urticae.

The ectoparasites Dermanyssus gallinae and Megninia ginglymura: bioecology and natural enemies in commercial egg-laying hens

Abstract Egg-laying hens and free and wild birds may introduce pathogenic organisms and ectoparasites to farms linked to commercial poultry farm systems. Two mite species are reported as an economic problem for the poultry industry worldwide: Dermanyssus gallinae (Dermanyssidae) and Megninia ginglymura (Analgidae). The present study aimed to evaluate the bioecology of mite fauna especially D. gallinae and M. ginglymuraassociated with commercial egg-laying hens, and recognize which are infestation periods, favorable environments and efficient predators of these ectoparasites. Megninia ginglymura was the most abundant in feathers and more frequent in the battery cage than in free-range chickens, representing 98% of the species. Both of these husbandry systems showed high infestations at different times. On the other hand, D. gallinae was the most abundant species in traps (98.9%), being found mostly in the winter from free-range chickens, with more than twice the mites when compared with battery cage chickens. This work revealed a possible new tool for biological control of ectoparasites: Cheyletus malaccensis could be considered the main natural enemy with the best potential for controlling these ectoparasites associated with laying hens and should be taken into consideration for future biological control studies, becoming an additional strategy for controlling D. gallinae principally.

Life cycle of the predatory mite Cheyletus malaccensis (Acari: Cheyletidae) fed on Poultry Red Mite Dermanyssus gallinae (Acari: Dermanyssidae)

Abstract This study evaluated the biological characteristics of predatory mite Cheyletus malaccensis fed on Dermanyssus gallinae at different temperatures. The study started with thirty individual eggs of C. malaccensis each isolated in an experimental unit, which developed throughout their life stages while feeding on D. gallinae at each temperature tested (20ºC, 25ºC and 30±1ºC and 80±5% relative humidity). Emerged adult females were not mated, thus producing only male offspring (arrhenotoky). Fecundity was the highest at 25°C (415.62±24.78 eggs/female) and lowest at 20°C followed at 30ºC. The mean length of a generation did not displayed difference among the three temperatures, but the net reproductive rate (Ro), innate capacity for increase (rm) finite increase rate (λ) were significantly higher at 30°C and lower at 20°C. Cheyletus malaccensis was able to develop and reproduce successfully when fed D. gallinae, and the optimum temperature for development, fertility and survival was 25°C. Our findings proved that C. malaccensis might be a natural enemy of D. gallinae, because it was able to develop and reproduce while feeding exclusively on this ectoparasite.

Feeding preference and predation rate of Neoseiulus idaeus (Acari: Phytotseiidae) feeding on different preys

Abstract Soybean (Glycine max (L.): Fabaceae) is considered the most important agricultural crop in Brazil. Phytophagous tetranychid mites such as Mononychellus planki McGregor, Tetranychus ludeni Zacher, and T. urticae Koch are considered pests of soybean crops. Neoseiulus idaeus Denmark & Muma (Phytoseiidae) is a predatory mite of T. ludeni and T. urticae. This study aimed at analyzing the feeding preference of N. idaeus among three types of prey (M. planki, T. ludeni, and T. urticae), its prey-stage preference, and its predation rate under controlled conditions. During immature stages of N. idaeus, we carried out observations to monitor predator survival and to ensure food availability (eggs and different prey stages) throughout the study period. Neoseiulus idaeus preferred T. urticae compared to T. ludeni and M. planki, and it preferred T. ludeni compared to M. planki. This predator preferred T. urticae and T. ludeni when compared to leaves without prey; however, when analyzed with M. planki and leaves without prey, it showed no preference. Regarding oviposition site, T. urticae was preferred over T. ludeni or M. planki. However, between T. ludeni and M. planki, N. idaeus preferred T. ludeni. This predator preferred to oviposit where T. urticae and T. ludeni were located instead of leaves without prey. However, when it was assessed with M. planki and on dry leaves without prey, there was no preferred oviposition site. These results show a strong preference for T. urticae as food; however, in the absence of this prey, N. idaeus feeds on T. ludeni and M. planki. In all immature stages and as adults, N. idaeus preferred T. urticae eggs. In protonymphal, deutonymphal, and adult stages it also consumed prey larvae and nymphs. Only adult N. idaeus consumed adult prey. The total predation rate for eggs, larvae, nymphs, and adults of T. urticae was 55.9%, 14.34%, 22.11%, and 7.65%, respectively. The average lifespan of females of this predator was 16.07 days, when they consumed 3.05 prey/female/day. These results suggest that N. idaeus has potential to be used in an applied biological control program for T. urticae.

Influence of various preys in soybean and the biological performance of the predatory mite Neoseiulus californicus (Phytoseiidae)

Abstract Mites and insects cause damage to soybean crops (Glycine max (L.): Fabaceae). Mononychellus planki McGregor, Tetranychus ludeni Zacher (Acari: Tetranychidae) and Caliothrips phaseoli Hood (Insecta: Thripidae) have been mentioned as pests of soybean crops in Brazil, while Neoseiulus californicus McGregor (Acari: Phytoseiidae) is considered a generalist predatory mite. This work aimed to determine the biological parameters of N. californicus feeding on T. ludeni, M. planki and C. phaseoli on transgenic soybean leaves. Thirty N. californicus eggs were individually placed in arenas with T. ludeni, M. planki and C. phaseoli. Egg-to-adult duration (in days) was longest when fed T. ludeni (5.52±0.06) and shortest when fed C. phaseoli (4.89±0.06). Mean fertility was approximately 32 eggs/female and did not differ significantly when N. californicus fed on T. ludeni or M. planki. During the adult stage, N. californicus did not lay eggs when feeding on C. phaseoli and survived for only a few days. The net reproductive rate (R0) of N. californicus was larger when fed T. ludeni (20.30±0.68) than M. planki (14.66±0.29). Both M. planki and T. ludeni were suitable prey for N. californicus, while C. phaseoli was not.

Development of Cheyletus malaccensis (Acari: Cheyletidae) feeding on mite species found in commercial poultry systems: Megninia ginglymura (Acari: Analgidae) and Tyrophagus putrescentiae (Acari: Acaridae)

Abstract Intensive egg production affects the welfare of confined laying hens, which increases the risk of epidemics. Ectoparasitic hematophagous mites and saprophagous feather mites cause low productivity and decreased egg quality. This study aimed to compare the biology of Cheyletus malaccensis (Oudemans) (Prostigmata: Cheyletidae) feeding on the prey Megninia ginglymura (Mégnin) (Astigmata: Analgidae) and Tyrophagus putrescentiae (Schrank) (Astigmata: Acaridae) in order to support the potential use of this predator in biological control strategies in the poultry industry. The study started with 30 eggs of C. malaccensis, isolated in experimental units, which developed into their different stages while feeding on the feather mite M. ginglymura and the stored product mite T. putrescentiae at 25±1°C, 80±5% relative humidity and 12-hour photoperiod. Immature stages were evaluated three times a day and the adult stage once a day. Adult females were unmated. Cheyletus malaccensis feeding on M. ginglymura resulted in a higher fertility rate, with 310.7±45.8 eggs/female, than with T. putrescentiae as prey, with 32.7±4.5 eggs/female. Furthermore, the oviposition period was higher feeding on M. ginglymura, 53.0±6.3 days, than on T. putrescentiae, 12.6±1.9 days. The net reproductive rate (Ro), the innate capacity for increase (rm), the mean generation time (T) and the finite rate of increase (λ) were higher for the generation fed on M. ginglymura. Cheyletus malaccensis is a likely natural enemy of M. ginglymura, and it is able to develop and reproduce while feeding exclusively on it.

Análise da Qualidade da Água de Poços Artesianos do Município de Imigrante, Vale do Taquari/RS

Um dos maiores desafios enfrentados pelas presentes e futuras geracoes e encontrar formas de preservacao das fontes de agua, livres de contaminacoes e adequadas ao consumo da populacao. Essa dificuldade esta relacionada a contaminacao dos lencois freaticos devido a ocupacao e uso do solo pela sociedade, alterando os processos fisicos, quimicos e biologicos dos sistemas naturais, causando inumeras doencas e muitas vezes levando a morte. O presente trabalho objetivou avaliar a qualidade da agua das principais fontes naturais do municipio de Imigrante, localizado no Vale do Taquari-RS a fim de averiguar a potabilidade das aguas consumidas pelas comunidades do municipio. Na presente pesquisa foram selecionados dez pocos para a verificacao das caracteristicas fisico-quimicas e biologicas, tais como: pH, condutividade, solidos suspensos, turbidez, oxigenio dissolvido, carbono orgânico, carbono total, carbono inorgânico, nitrogenio, dureza media, temperatura, condutividade e analise microbiologica, comparando os resultados com os padroes preestabelecidos pela legislacao vigente. Dos dez pocos analisados, seis apresentaram-se fora dos parâmetros estabelecidos pela legislacao.