Jaime E. Araya 1. The toxicity of an insecticide formulation containing triazamate and alpha-cypermethrin and Both insects were collected on alfalfa, Medicago sativa L. The eggs and pupae of H.
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Jaime E. Araya 1. The toxicity of an insecticide formulation containing triazamate and alpha-cypermethrin and Both insects were collected on alfalfa, Medicago sativa L. The eggs and pupae of H. The mobile stages of both insects were set on the leaflets once they had dried at room temperature to prevent them from escaping. Mortality during the growth stages of H. The LC 50 for both insects was determined by Probit analysis. The LC 50 s for adults, eggs, larvae, and pupae of H.
Therefore, the commercial dose could be reduced to this amount and still control A. Ambos insectos se colectaron en alfalfa Medicago sativa L. Los huevos y pupas de H. La mortalidad de los estados de desarrollo de H. Las CL 50 para los adultos, huevos, larvas, y pupas de H. Most adults and larvae of ladybirds have a beneficial action and feed mainly on mites, aphids and other insects, contributing to their natural and biological control. If their prey are at low density, the adults and larvae of ladybirds also feed on moth and beetle eggs, mites, thrips, and other small arthropods, as well as pollen and nectar.
Aphis craccivora Koch is an important vegetable pest that can have many host plants Prado, This aphid is 1. Its feeding produces abundant honeydew, which promotes the growth of black soot, reducing photosynthesis. Pest control with insecticides is widely used in the world to avoid pest damage to crops Aguilera, However, the use of conventional insecticides also affects natural enemies and their populations, particularly ladybirds Obrycki and Kring, , although this can result in variable effects Hassan, ; Kaakeh et al.
In the short term, the intensive and careless use of insecticides has produced biological imbalance and increased environmental contamination Saini, This insecticide has been withdrawn from the market, but it was registered in Chile when the study was conducted.
It was recommended for the control of thrips, caterpillars, meloid beetles, aphids, and others that have developed resistance to other insecticides AFIPA, This study validates a method to evaluate the effect of insecticides on both the aphid and the ladybird.
The sequential scheme of this process tries to achieve the least number of products before proceeding to field trials, as these are the most difficult to establish. The initial tests are designed to evaluate the effects of only one type of pesticide exposure, by contact, while beneficial organisms have three sources of exposure in the field: direct sprays, persistent residues on surfaces, and oral intake of contaminated food Longley and Stark, Based on these tests, the IOBC has classified pesticides in four toxicity categories depending on the degree of mortality they cause to beneficial organisms Hassan, , as summarized in Table 1.
Rearing methods. Adults of both the ladybird H. These insects were reared separately in the laboratory in Flanders batteries and on Vicia faba L. The amount of insecticide mixture was calculated by surface based on the recommended dose to apply in the field. The treatments were applied by spraying 0. Treatments for the eggs and pupae of H. Treatments for mobile stages larvae and adults were applied to alfalfa leaflets, and the insects were placed on them when the residues had dried in order to prevent the individuals from escaping during sprays.
The dish covers had vent holes covered with cloth to avoid a lethal chamber inside. Mortality of the predator by contact with insecticide residues was recorded 24 and 48 h after treatment application both larvae and pupae alive moved when touched slightly. The same insecticide doses were tested on the aphid, while the control insects were sprayed with distilled water Schiess, Experimental design and statistical analysis. A randomized complete block design was used, with 4 replicates for treatment 5 , plus a water control.
The experiment unit was a Petri dish with 20 individuals. The results corresponding to the dose applied were adjusted to a Probit model Busvine, , which allowed estimating LC 50 values to evaluate susceptibility of H. Results of the bioassays. The concentration used on each H. From those tests, thenLC 50 values were significantly different for each growth stage of both the ladybird and the aphid Table 2 , which resulted very susceptible to the insecticide formulation.
The ladybird eggs exhibited the lowest level of susceptibility. This result is in agreement with Croft , who states that the eggs of predators are immune even to direct applications; the tolerance of a particular stage can be due to physiological, behavioral, and chemical factors. The pupae stage not mobile followed the egg stage in susceptibility, which is also in agreement with Liu and Stansly The Chi 2 values obtained indicate that the mortality rate fitted the insecticide mortality-dose curve Ulloa, Mortality rates for the four growth stages of H.
Results for adults of H. The LC 50 for adults was 0. Molina conducted laboratory studies with cypermethrin sprayed on H. In a study by Peckman and Wilde , Inglesfield evaluated alpha-cypermethrin on beneficial arthropods, including coccinellids.
Studies on fenvalerate, which is another pyrethroid, conducted by Wilkinson et al. Mizell and Schiffhauer found high toxicity of fenvalerate to Cycloneda sanguinea L. Results for eggs of H. In addition, these eggs produced larvae that continued living 48 h later.
For more accurate results, the eggs were defined as not viable when they presented dehydration and a dark shell. These effects were observed 48 h from the spray. The LC 50 was Results for larvae of H.
The highest mortality occurred in larvae compared to the other growth stages of H. The LD 50 obtained was 0. To the effect of an insecticide, that of cannibalism observed between larvae must be added, despite that the Petri dishes were provided abundant aphids for the predators to have more than sufficient prey.
This behavior was observed 24 and 48 h after treatment. It has been described for many coccinellids Hodek, , Obrycki and Kring, , and allows the survival of some larvae when the aphid density is low Sundby, Mass rearing of H. Polis states the cannibalism is a mechanism for reducing the number of potential competitors.
Therefore, larvae should be separated individually after sprays. Results for pupae of H. Mortality of pupae was defined as follows: if pupae moved the abdomen slightly when touched with a hair brush they were considered alive; no movement indicated they were dead. When reducing. The LC 50 obtained was 1. Some pupae survived and produced adults that were observed 48 h after application.
However, those adults developed only the characteristic color of the species but later died. Results for adult aphids. The LC 50 was 0. Inglesfield observed that alpha-cypermethrin at 20 g i.
Wiles et al. The egg stage was less susceptible to the insecticide formulation than the other growth stages of H. Further studies are required to evaluate longer time periods. Larvae were the most susceptible in case of H. Thus, when they predominate in the field, lower doses of the insecticide should be used.
Aphids of A. This would allow applying the insecticide in at reduced doses in integrated management programs against A. Abbott, W.
A method of computing the effectiveness of an insecticide. Manual Fitosanitario Aguilera, A. Resistencia de las plagas a los insecticidas. Simiente 51 Artigas, J. Busvine, J. Recommended methods for measurement of pest resistance to pesticides. FAO, Rome, Italy.
Di Masi, D. Magdalena, E.
Manual Fitosanitario AFIPA A.G. (en este mismo contexto)
Thank you for your understanding. More information. The influence of these herbicides on root length, plant height, crown diameter, shoot and root dry weights, shoot phytotoxicity and root injury were studied at two application rates. Variable responses in the growth parameters were observed throughout the experimental period. Herbicides did not affect root length. Bentazon reduced root dry weight while the other herbicides had no effect.
Plaguicidas y fertilizantes
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