Chance Of Choice Research Articles

Bioactivity of aqueous extracts of annonaceous from the amazon savannah of Roraima on the cowpea aphid

Aphis craccivora Koch (Hemiptera: Aphididae), known as the cowpea aphid, is a polyphagous pest that causes severe damage throughout the phenological cycle of several economically important crops. For the control of this hemiptera, as for most agricultural pests, the chemical method has been the most used. Considering the Integrated Pest Management - IPM, the use of plant extracts is an option that has been widely considered. Thus, this study aimed to evaluate the bioactivity of aqueous extracts of Annona glabra, A. hypoglauca, A. montana and A. squamosa leaves, obtained in the Amazonian Savanna of Roraima, Brazil, on A. craccivora under laboratory conditions. Regarding the biological aspects on the cowpea aphid, the toxicity and repellency were evaluated with and without chance of choice. It was verified that the aqueous extracts of the four species of the genus Annona cause mortality in both nymphal and adult stages of A. craccivora, besides presenting repellent effect for this aphid. Because the aqueous extracts of leaves of the studied species present promising effects against A. craccivora, additional field studies of bioactivity of these Annona species on the black aphid, as well as their activity on beneficial and non-target organisms are suggested.

Effect of Food Attractants and Insecticide Toxicity for the Control of Spodoptera frugiperda (Lepidoptera: Noctuidae) Adults

An alternative for the population suppression of Spodoptera frugiperda is the use of toxic baits. The objective of this study was to evaluate the dietary preference and toxic effect of insecticides associated with the attractiveness of S. frugiperda adults as a pest management method. The following attractions were tested: 1) 5% sucrose solution, 2) 10% sugarcane syrup, 3) 10% honey, 4) 5% hydrolyzed protein, 5) Noctovi® 43sb, 6) Noctovi® OVI PLU 1-3, 7) Noctovi® OVI PHE/PAL 50-50 in the study with choice. Attractions: 1) sugarcane syrup 10%, 2) Noctovi® 43sb, 3) Noctovi® 43sb + sugarcane syrup 10%, 4) Noctovi® OVI PLU 1-3 in the study with no chance of choice. For the toxicity study, the food attraction associated with insecticides was used: methomyl 2%, lambda-cyhalothrin 1%, chlorpyriphos 2%, spinosad 1%, chlorantraniliprole 2% and chlorfenapyr 2%. The experimental design was the completely randomized design (CRD) with chance of choice, without chance of choice and toxicity. The following parameters were evaluated: number of insects that fed; time in minutes that remained in the attractive food and mortality. The molasses (10%) and Noctovi® 43sb food attractiveness were significantly more efficient in relation to feeding time and the highest number of landings was observed in the Noctovi® 43sb treatment, both in females and total adults. Methomyl, lambda-cyhalothrin and spinosad insecticides associated with food attractiveness are promising toxic baits for the management of S. frugiperda.

Performance of Trichogramma pretiosum Riley (Hymenoptera: Trichogrammatidae) on eggs of Helicoverpa armigera (H\xfcbner) (Lepidoptera: Noctuidae)

Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) is a polyphagous pest with a wide geographic distribution. This pest first arrived in Brazil in 2013, and since then studies on possible control methods for it have been necessary. A possible method for the control of H. armigera is using the egg parasitoid Trichogramma pretiosum Riley (Hymenoptera: Trichogrammatidae). Therefore, the objective of this study was to evaluate the performance of T. pretiosum on H. armigera eggs, which are known to represent suitable hosts for the development of this parasitoid species in the laboratory. Parasitism and emergence rates and the duration of the egg-to-adult period of T. pretiosum were investigated following 24- and 48-h exposures of this parasitoid to H. armigera and Corcyra cephalonica (Stainton) (Lepidoptera: Pyralidae) eggs. The longevity of offspring after the 24-h exposure was studied, as well as the frequency of parasitism and emergence, host preference, and the emergence of offspring from eggs of different ages or oviposited by lepidopterans on different days. Parasitism was 14.4 and 34.9% more frequent on C. cephalonica than on H. armigera after 24 and 48 h of exposure, respectively. In C. cephalonica, parasitism was 27.2% higher after 48 h. Parasitism was more frequent on C. cephalonica eggs collected on the second day of oviposition (76.2%), and on H. armigera on the third day of oviposition (71.1%). Parasitism frequency was lower on 2-day-old C. cephalonica eggs (63.3%) and on 3-day-old H. armigera eggs (41.3%). When tested with a chance of choice between hosts, T. pretiosum preferred H. armigera, while in the test with no chance of choice there was no difference in preference. Thus, T. pretiosum may be considered a tool for the Integrated Pest Management (IPM) of H. armigera.

Entomopathogenic nematodes for the control of Gryllus sp. (Orthoptera: Gryllidae) under laboratory and field conditions

ABSTRACT: Entomopathogenic nematodes are effective in controlling soil insects and they are used in agricultural systems. The virulence of entomopathogenic nematodes on crickets (Gryllus L.) (Orthoptera: Gryllidae) was evaluated under different conditions in order to select populations for application in the field. Virulence tests with Heterorhabditis amazonensis RSC05, H. amazonensis MC01, Steinernema carpocapsae All (Weiser) and H. amazonensis GL were performed. Evaluations were then made of the concentrations of infective juveniles (100, 200, 400 and 600 infective juveniles per insect); feeding preference with or without choice; and field tests using traps to evaluate insect sampling. All isolates were found to cause mortality in Gryllus sp., and H. amazonensis MC01 and S. carpocapsae All were selected; an increase in concentration resulted in increased insect mortality. Regarding the feeding preference tests, after 16 h there was no feeding in any of the treatments. In treatments with a chance of choice, it was verified that the crickets fed, independently of the presence of the nematodes. In the field tests, 19 live crickets were found in the traps, and, after application of entomopathogenic nematodes in aqueous suspension, 2 live crickets were found. Results suggested that H. amazonensis MC01 was promising in the control of Gryllus sp. under the tested conditions.

Essential Oils from the Leaves and Flowers of <i>Callistemon viminalis</i>: Chemical Characterization and Evaluation of the Insecticide and Antifungal Activities

The chemical compositions of the essential oils from the leaves and flowers of Callistemon viminalis and their insecticide and fungitoxic activities were determined. The essential oil was extracted by the hydrodistillation method using a modified Clevenger apparatus. The chemical characterization was performed by GC-MS and GC-FID. The evaluation of the insecticidal activity was performed with the Myzus persicae aphid, and the antifungal potential was determined via the inhibition of the mycelial growth of Alternaria alternata, Fusarium oxysorum and Botrytis cinérea phytopathogenic fungi. The principal components of the essential oils from the leaves and flowers were eucalyptol (84.60% and 61.47%), α-pinene (10.28% and 21.48%) and α-terpineol (2.59% and 2.79%), respectively. The use of a 0.5% concentration of the essential oil from the flowers influenced the preference of aphids and their reproduction. The number of adult aphids decreased within a period of 48 hours in the presence of the essential oil from the leaves. In the test with no chance of choice, the mean number of adults decreased with both oils within 48 hours. No inhibition of the mycelial growth of the A. alternate microorganism was observed in any of the treatments with the two essential oils. However, the growth of F. oxysporum and B. cinerea fungi was inhibited. The mycelial growth of F. oxysporum was inhibited with the concentration of 100 μL·Lˉ1 of the oil from the flowers and 250 μL·Lˉ1 of the oil from the leaves. The inhibition of the growth of B. cinerea was observed at concentrations of 500 and 100 μL·Lˉ1 for the oils from the flowers and leaves, respectively. The essential oils presented insecticidal and antifungal potentials. However, further studies are needed for these oils to be used in integrated pest management.

Preferência para oviposição e ciclo de vida de mosca-negra- dos-citros Aleurocanthus woglumi Ashby em espécies frutíferas

Aleurocanthus woglumi Ashby conhecida popularmente como mosca-negra-dos-citros é considerada praga quarentenária A2 no Brasil e ocasiona prejuízo em diversas frutíferas, principalmente em citros (laranja, limão e tangerina). Poucas são as pesquisas relacionadas aos seus aspectos biológicos nas condições ambientais brasileiras. Nesse sentido, o objetivo da pesquisa foi verificar a preferência de oviposição e a duração do ciclo de vida de A. woglumi em diferentes hospedeiros. A pesquisa foi conduzida em casa de vegetação, durante o período de março de 2009 a março de 2010. Foram realizados testes de preferência sem chance de escolha em seis hospedeiros, simultaneamente, em períodos de 48 e 72 horas, além da biologia comparada em mangueira e laranjeira. Foram observados nos testes que A. woglumi apresenta preferência por ovipositar nas espécies cítricas (limoeiro, laranjeira e tangerineira), mantendo um padrão de não preferência em cajueiro e goiabeira. Os hospedeiros laranjeira e mangueira não interferiram no ciclo biológico da praga.

Efeitos do ácido silícico e do acibenzolar-S-methyl sobre Schizaphis graminum (Rondani) (Hemiptera: Aphididae) em plantas de trigo

The objective of this work was to evaluate the effects of silicon acid and acibenzolar-S-methyl (ASM) on biology and behavior of the aphid (greenbug) in wheat plants. The experiment involved a 4 factorial (no silicon, silicon on leaf, silicon in the soil and silicon in the soil + on leaf), x 2 (with and without acibenzolar-S-methyl), in a completely randomized design. A preference test with chance of choice was set in blocks randomized, with 10 replications. Silicon acid was used at 1% and ASM at 0.5%. The treatments were evaluated by means of preference tests with chance of choice (adult aphids in leaf sections of wheat plants were counted), biological studies (length of pre-reproductive, reproductive and post-reproductive periods, mortality rate during the pre-productive period, number of nymphs, longevity and population growth rate were determined) and colonization of aphids (number of adult aphids and nymphs were determined). In the preference test, plants that received ASM were not chosen by the aphids. The application of the silicon or ASM reduced significantly the number of nymphs, the population growth rate, the post-reproductive period and the longevity of the greenbug. A significant reduction of the number of aphids was observed during aphids colonization when ASM or silicon were applied. The addition of silicon acid, mostly in the soil, or of ASM is promising as a control method in the integrated management of aphid in wheat.

What chance of choice?

Choice is the key word when it comes to health care nowadays, but just how realistic is the choice of health care provision being proffered by both the major political parties in the months foreshadowing the next election? I am profoundly sceptical that any of the alternatives on offer have any real substance. Behind the choice word, the patient is faced with a lottery.