11 research outputs found
Ação de inseticidas sobre os ovos e lagartas da broca-pequena-do-fruto do tomate, em bioensaio de laboratório
Eclosion time and larval behavior of the tomato fruit borer, Neoleucinodes elegantalis (Guenée) (Lepidoptera: Crambidae) Tempo de eclosão e comportamento de larvas da broca-pequena-do-tomateiro, Neoleucinodes elegantalis (Guenée) (Lepidoptera: Crambidae)
In several regions of Brazil, Neoleucinodes elegantalis (GuenĂ©e) is one of the most serious tomato pests. The moth lays eggs on the calyx or developing fruit, and shortly after eclosion larvae penetrate into the fruit, where they remain until pupation. Once larvae have entered the fruits, insecticides and biological control agents are relatively ineffective. Because N. elegantalis is most susceptible to conventional treatments when the larvae are outside the host tissues (or fruit), it would be advantageous to know the time required for egg development and the length of time that the larvae spend on the surface of the fruit. To answer these questions detailed behavioral studies were untaken. Eggs were collected from the field and maintained in an environmental chamber at 20°C, 75 ± 5% R.H., and a 12L:12D photoperiod. The time of egg eclosion was recorded with a video camera, whereas larval behavior and time required to enter the fruit were determined by direct observations. The majority of eggs (93%) hatched within the first two hours after the beginning of photophase. Larvae spent 51.1 ± 31.1 (mean ± SEM) min on the surface of the fruits. Once a suitable site was identified, larvae required an additional 23.8 ± 19.4 min to completely enter the fruit. Eighty-six percent of the larvae were successful in penetrating the fruit. Of the larvae that bored into the fruit, 42% selected the upper portion, 18% selected the middle portion, and 40% selected the lower portion.<br>Neoleucinodes elegantalis (GuenĂ©e) Ă© uma das pragas mais sĂ©rias do tomate em vĂĄrias regiĂ”es do Brasil. A fĂȘmea deposita seus ovos no cĂĄlice ou nos frutos em desenvolvimento, e logo apĂłs a eclosĂŁo a larva penetra no fruto, onde permanece atĂ© a pupação. Depois que a larva entra no fruto, inseticidas e agentes de controle biolĂłgico sĂŁo relativamente ineficazes. Como N. elegantalis Ă© mais suscetĂvel a mĂ©todos de controle quando a larva encontra-se no exterior do hospedeiro, seria vantajoso conhecer o perĂodo de tempo necessĂĄrio para o desenvolvimento dos ovos e quanto tempo a larva passa na superfĂcie do fruto. Para responder estas questĂ”es, detalhados estudos comportamentais foram conduzidos. Ovos foram coletados no campo e mantidos em cĂąmara ambiental a 20°C, 75 ± 5% U.R., e fotoperĂodo de 12L:12E. O horĂĄrio de eclosĂŁo foi registrado com uma cĂąmera de vĂdeo, enquanto que o comportamento da larva e o tempo requerido para que ela penetre no fruto foram determinados com observaçÔes visuais. A maioria dos ovos (93%) eclodiu dentro das primeiras duas horas da fotofase. Larvas passaram 51,1 ± 31,1 (mĂ©dia ± erro padrĂŁo) min na superfĂcie do fruto. Uma vez que sĂtios adequados eram identificados, as larvas necessitaram de 23,8 ± 19,4 min adicionais para entrar completamente nos frutos. Oitenta e seis por cento das larvas penetram com sucesso no fruto. Destas, 42% selecionaram a porção superior, 18% selecionaram a porção mĂ©dia, e 40% selecionaram a porção inferior do fruto
Dispersal patterns and chromatic response of Scaphoideus titanus Ball (Homoptera Cicadellidae), vector of the phytoplasma agent of grapevine flavescence doree
Nutrient Applications Reported by Farmers Compared with PerformanceâBased Nutrient Management Plans
Bravo-Ureta, B (Bravo-Ureta, Boris)2,3;2. Univ Connecticut, Dep Agr & Resource Econ, Storrs, CT 06269 USA
3. Univ Talca, Dep Agr Econ, Talca, ChileThis study had two main objectives: (i) to evaluate how well farmers implemented nutrient management plans (NMPs) by comparing the farmers' reported practices with the recommended management for manure and fertilizer; and (ii) to evaluate whether the management of manure and fertilizer had significant effects on the nutrient status of soil and corn tissue tests. The analysis relied on data from four dairy farms that had 5 to 7 yr of records at the field level. The farmers chose to apply the recommended amount of fertilizer P from 50 to 100% of the fields. The amount applied was often only 10 to 20 kg P2O5 ha(-1) different from the recommended amount. The farmers applied the recommended amount of fertilizer N from 40 to 71% of the fields when the pre-sidedress soil nitrate test (PSNT) was used for the recommendation, but only 1 to 21% of the fields received the recommended amount when the yield goal method was used. These data suggest that the farmers trusted a fertilizer recommendation developed from a soil test more than they trusted a nonsoil test recommendation. Only a small percentage of fields (3-37%) received the recommended amount of manure N and P. Variability in the amount of residual N available from previous manure applications caused great variation in the PSNT and corn stalk nitrate values (CSNT). This variation in N availability in fields indicates that a number of years of data are needed before the PSNT and the CSNT can be used to objectively evaluate the performance of an NMP