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Populations of MCR of commercial field corn from Arenal, Jalisco were exposed to nine insecticides of organophosphorous (OP), cabamate, organo chlorinated and pyrethroid groups. Larvae were collected from the roots of corn plants daily, and confined in polyethylene black bags of two kg capacity with humidity and germinated corn as food for larvae. Insects were taken to the laboratory of Sanidad Vegetal in Guadalajara, Jalisco. Dilutions of the insecticides tested were prepared using acetone from 500 to 5000 ppm (6 to 9 dosage/product). For this study 20 larvae of last instar were selected and 1 u, liter of the solution was placed topically on the thorax, after this, each larva was placed in a petri dish with a moistened paper towel and the petri dishes confined in a cardboard box to eliminate light. Mortality counts were carried out at 24 hours. Percent mortality was corrected by Abbott’s formula. The mortality data were analyzed by probit to obtain LC50 and LC,5 values for each insecticide.

The response of potato tuberworm to ten doses of acyl-urea, diflubenzuron and triflumuron was evaluated in a series decreasing in halfs (e.g. 2,000, 1,000, 500 ppm, etc.). Potato tubers were submerged in the desired concentrations, put on paper to dry and then placed in one liter plastic containers. Over each tuber, 10 larvae were placed per replication, with four replicates/dose (40 larvae), and a total of 400 larvae per insecticide trial was used. A water-treated check was used. Larvae were obtained from Navidad, Nuevo Leon, Mexico and were maintained 30 d at 25 ± 2°C. Two samples at 10 and 15 d post-treatment were made to check mortality, and at 30 d for adult survival. The final analysis was based on adults because differences in mortality among stages was low. The mortality data were analyzed by probits to obtain LC50 and LC95 values for each insecticide.

Materials were applied on 28 Mar on 4m furrow plots (20 plants); 7 acaricides in a randomized complete block design with an untreated furrow buffer strip around each plot. Acaricides were applied at a rate of 600 liter/ha, using a motorized sprayer 121 liter capacity. ‘Chandler’ strawberry variety was used when plants had 250 days post transplant under irrigation at El Valenciano ranch and there were no unusual conditions during the test, temperatures were generally warm without rain. There were 8 samples post treatment every 3 days. The number of mites were counted from 5 randomly chosen plants and 5 leaves/plant for each replication (100 leaflets/treatment). Natural populations of spider mites were high and reasonably well distributed. Data were analyzed by Duncan’s multiple range test, and by comparing pretreatment means with post-treatmenlt means using the Henderson and Tilton formula. The spider mite species present during the test was identified by mounting them on a glass slide for microscopic examination.

The responses of second instar nymphs and adults of fowl tick to chlorfenvinphos, diazinon, coumaphos, trichlorfon and lindane in commercial formulations were measured after 48 h in laboratory bioassays. Ticks were collected from La Aurora, Saltillo, Coahuila, Mexico. Vials, measuring 5 cm high X 6 cm diameter, were treated with 1 ml of water solution and rotated until dry. Ten to 15 ticks were placed inside each vial, and plugged with cotton cloth, with a total of 40 ticks used in each trial. Five doses of each product were evaluated. Vials were held at 25°C ± 2°C and mortality was recorded after 48 h. Ticks were considered dead if they failed to respond to touch. Mortality data were subjected to probit analysis to derive LC50 and LC95 values.

We evaluated the response of fourth-instar PTW to methamidophos and methyl parathion from five potato growing areas (states). Larvae were collected in the field the day of the experiment and exposed to toxicants by the residual technique in a 100 ml glass recipient. One μ, liter of each toxicant dosage, using acetone as solvent was deposited on each larvae. Each bioassay was carried out with 6 or 7 doses of insecticide; varying from 5 to 100 ppm in methamidophos and from 50 to 400 ppm in methyl parathion. Forty larvae per dose were used. An acetone check was included. The data were compared with a population from Navidad, Nuevo Leon maintained in the laboratory for 28 generations free of insecticides. Mortality was observed after 24 hours.

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