Action of growth regulators on soybean cultivar Davis

The effects of growth regularots on soybean plant (Glycine max) under greenhouse conditions were studied. Before flower ing, Agrostemmin (1 g/10 ml/3 1), gibberellic acid (GA) 100 ppm, and (2-chloroethyl) trimethylammonium chloride (CCC) 2,000 ppm were applied. At the flower anthesis, 2,3,5 - triio dobenzoic acid (TIBA) 20 ppm was applied. Other two applications with TIBA, with intervals of four days, were realized. Treatment with GA increased plant height while CCC presented a tendency to reduce it. Numbers of leaves, internods, and stems were not affected by the growth regulators.

Effects of growth regulators on productivity of soybean (Glycine max cv. Davis) under competition

The effects of growth substances on productivity of 'Davis' soybean maintained under competition was investigated. Before the flowering, Agrostemmin (1 g/10 ml/3 1), gibberellic acid (GA) 100 ppm, and (2-chloroethyl) trimethylammonium chloride (CCC) 2,000 ppm were applied. At the flower anthesis, 2,3,5-triiodobenzoic acid (TIBA) 20 ppm was applied. Other two applications with TIBA, with intervals of four days, were realized. The growth regulators did not affect the productivity of 'Davis' soybean maintened under competition. The competition among plants did not affect the stem dry weight and number of pods, and seeds. The competition reduced weight of pods without seeds, seed weight, and weight of 100 seeds.

A comparative study on production of five soybean (Glycine max (L.) Merrill) cultivars

Under greenhouse conditions cultivars Davis, IAC 73-228, PI 227.687, PI 171.451, and PI 229.358 of soybean were compared. PI 171.451 showed lower dry weight of stem in relation to Davis. Higher pod numbers produced by PI 227-687, IAC 73-228, and PI 229. 358 as compared to Davis were observed. Cultivars PI 227.687 and IAC 73-228 produced larger seed numbers. A larger weight of 100 seeds in Davis, PI 229.358, and PI 171. 45I cultivars was observed. The last two cultivars are sources of resistance against pests of soybean.

An evaluation of natural infestation by leaf pests on soybean (Glycine max (L.) Merrill) cultivars

Damage caused by leaf pests of soybean on five cultivars was evaluated. Afield experiment was carried out at the Piracicaba region, cultivars Davis, IAC 73-228, PI 227.687,PI 171.451, and PI 229.358 having been compared. Leaf damage was produced by natural infestation of Anticarsia gemmatalis and Plusia sp. Cultivar PI 171.451 showed lower comsumption of leaves in relation to control ('Davis') and other cultivars. Damage was more serious on IAC 73-228 than on PI 227.687 and PI 229.358.

Stink bugs (Heteroptera, Pentatomidae) and an unique host plant in the Brazilian subtropics

Stink bugs are seed/fruit sucking insects feeding on an array of host plants. Among them, an exotic tree called privet, Ligustrum lucidum Ait. (Oleaceae), is very common in the urban areas of the Brazilian subtropics, where it is utilized as food source and shelter for over a decem species of bugs, year round. The species composition, their performance and abundance on this host, and possible causes for this association are discussed and illustrated.

Studies on Trypanosoma rangeli Tejera 1920. VII - Its effect on the survival of infected triatomine bugs

The pathological effects of Trypanosoma rangeli on Rhodnius prolixus and R. robustus, and the relation of mortality to infection, were studied under laboratory conditions. Frequent observations revealed that when the first instar nymphs of R. prolixus and R. robustus were infected with T. rangeli, survival of the bugs during the stages of development to the adult stage decreased. This decrease was statistically significant when compared with uninfected control-bugs, indicating that T. rangeli is pathogenic for both species of triatomine. In R. prolixus the most affected nymphal stages were the first, second and fifth instars, where a higher mortality was also observed. In R. robustus a progressive increase of the mortality from the first to fifth instars, was observed. The pathogenicity of T. rangeli as measured by overall mortality was the same in R. prolixus and R. robustus. The possible pathogenic mechanism of T. rangeli in triatomine-bugs and its epidemiological implications, are discussed.

The cave-like sense organ in the antennae of Triatominae bugs

In the second segment of the antennae of haematophagous reduviids an unusual cave-like organ is found the function os which was investigated in Triatoma infestans. the morphology of the organ makes it difficult to ascribe it to a mechno- or chemoreceptive function, but shows some characteristics shared with thermoreceptors of other animals. The electrical activity of sense cells was recorded in the presence of stimuli that evoke behavioural responses in this species, i.e. warm, CO2, lactic and butyric acids at different concentrations. The three compounds tested failed to evoke a response at all concentrations assayed. Only thermal stimulation evinced a clear modification in the electrical activity of the sense cells.Both the morphological and electrophysiological findings support a thermoreceptive finding, habitat selection and circadian synchronization.

The ecotopes and evolution of triatomine bugs (triatominae) and their associated trypanosomes

Triatomine bug species such as Microtriatoma trinidadensis, Eratyrus mucronatus, Belminus herreri, Panstrongylus lignarius, and Triatoma tibiamaculata are exquisitely adapted to specialist niches. This suggests a long evolutionary history, as well as the recent dramatic spread a few eclectic, domiciliated triatomine species. Virtually all species of the genus Rhodnius are primarily associated with palms. The genus Panstrongylus is predominantly associated with burrows and tree cavities and the genus Triatoma with terrestrial rocky habitats or rodent burrows. Two major sub-divisions have been defined within the species Trypanosoma cruzi, as T. cruzi 1 (Z1) and T. cruzi 2 (Z2). The affinities of a third group (Z3) are uncertain. Host and habitat associations lead us to propose that T. cruzi 1 (Z1) has evolved in an arboreal, palm tree habitat with the triatomine tribe Rhodniini, in association with the opossum Didelphis. Similarly we propose that T. cruzi (Z2) and Z3 evolved in a terrestrial habitat in burrows and in rocky locations with the triatomine tribe Triatomini, in association with edentates, and/or possibly ground dwelling marsupials. Both sub-divisions of T. cruzi may have been contemporary in South America up to 65 million years ago. Alternatively, T. cruzi 2 (Z2) may have evolved more recently from T. cruzi 1 (Z1) by host transfers into rodents, edentates, and primates. We have constructed a molecular phylogeny of haematophagous vectors, including triatomine bugs, which suggests that faecal transmission of trypanosomes may be the ancestral route. A molecular clock phylogeny suggests that Rhodnius and Triatoma diverged before the arrival, about 40 million years ago, of bats and rodents into South America.

alpha-glycerophosphate dehydrogenase activity in flight muscles of triatomine bugs Panstrongylus megistus and Triatoma sordida

The alpha-glycerophosphate dehydrogenase (alpha-GPDH) activity in flight muscles of Panstrongylus megistus and Triatoma sordida, vectors of Chagas disease in Brazil, was studied. Both species showed higher enzymatic activities in fliers than in non-fliers insects. T. sordida exhibited a higher proportion of flier insects than P. megistus. A possible role of alpha-GPDH on triatomines flight is discussed.

Predation Potential of the Water Bugs Sphaerodema rusticum on the Sewage Snails Physa acuta

The sewage snail Physa acuta is a serious threat to certain economic plants and to the purification plant of sewage works by rendering the biofilters ineffective. Various attempts are being made to control it. The efficacy of the predacious water bugs Sphaerodema rusticum was judged experimentally, in the laboratory in the potential control of P. acuta. It is revealed that, when supplied separately, the first, second and third instar and the adult S. rusticum did not attack P. acuta belonging to 3.1-8 mm, 5.1-8 mm, 7.1-8 mm and <= 3 mm size classes respectively. In the remaining trials predation rate varied from zero to eight (average 2.3) individuals per predator per day. In experiments with P. acuta belonging to all the size classes supplied together, none, except the first instar S. rusticum, attacked the prey individuals belonging to the lowest (<= 3 mm) size class. The first and second instar S. rusticum, in both trials did not attack P. acuta larger than 4 mm and 5 mm in shell length respectively. The water bugs belonging to the third, fourth, fifth instar and adult stages though preyed upon P. acuta with 3.1-8 mm shell length. The average rate of predation by a single S. rusticum varied from 0.14-3.08 individuals per day depending upon the size of P. acuta and the stage of S. rusticum. A single S. rusticum, irrespective of instar and adult stages, destroyed on average 4.16 P. acuta daily irrespective of sizes. It is estimated that one S. rusticum could destroy 1,360 P. acuta in its life time. The results clearly indicate that the water bug S. rusticum may be used to control the snails P. acuta.

Experimental transmission of the parasitic flagellates Trypanosoma cruzi and Trypanosoma rangeli between triatomine bugs or mice and captive neotropical bats

Trypanosoma cruzi and Trypanosoma rangeli-like trypanosomes have been found in a variety of neotropical bat species. In this study, bats (Artibeus lituratus, Carollia perspicillata, Desmodus rotundus, Glossophaga soricina, Molossus molossus, Phyllostomus hastatus) were maintained under controlled conditions, and experiments were conducted to determine how they might become infected naturally with trypanosomes. All bats were first screened for existing infections by hemoculture and the examination of blood smears, and only apparently uninfected animals were then used in the experiments. Proof was obtained that the triatomine bug Rhodnius prolixus would readily feed upon some of the bats, and two species became infected after being bitten by bugs infected with T. rangeli. Some bats also became infected by ingesting R. prolixus carrying T. cruzi, or following subcutaneous or intragastic inoculation with fecal suspensions of R. prolixus containing T. cruzi. P. hastatus became infected after ingesting mice carrying T. cruzi. All of the bats studied inhabit roosts that may be occupied by triatomine bugs and, with the exception of D. rotundus, all also feed to at least some extent upon insects. These findings provide further evidence of how bats may play significant roles in the epidemiology of T. cruzi and T. rangeli in the New World tropics.

Ecological patterns of blood-feeding by kissing-bugs (Hemiptera: Reduviidae: Triatominae)

Host use by vectors is important in understanding the transmission of zoonotic diseases, which can affect humans, wildlife and domestic animals. Here, a synthesis of host exploitation patterns by kissing-bugs, vectors of Chagas disease, is presented. For this synthesis, an extensive literature review restricted to feeding sources analysed by precipitin tests was conducted. Modern tools from community ecology and multivariate statistics were used to determine patterns of segregation in host use. Rather than innate preferences for host species, host use by kissing-bugs is influenced by the habitats they colonise. One of the major limitations of studies on kissing-bug foraging has been the exclusive focus on the dominant vector species. We propose that expanding foraging studies to consider the community of vectors will substantially increase the understanding of Chagas disease transmission ecology. Our results indicate that host accessibility is a major factor that shapes the blood-foraging patterns of kissing-bugs. Therefore, from an applied perspective, measures that are directed at disrupting the contact between humans and kissing-bugs, such as housing improvement, are among the most desirable strategies for Chagas disease control.