Binomial sampling of Paraleyrodes Quaintance pos. bondari (Hemiptera: Aleyrodidae) in Persea americana Mill.

Fresno (Tolima), in Colombia, is a notable avocado producer, with 36% of the national production. In this paper, two sampling methods are presented to assess natural populations of Paraleyrodes Quaintance pos. bondari attacking avocado trees of Hass and Lorena cultivars under field conditions. The presence/absence of whitefly nymph colonies on 30 leaves located at the high, medium and low strata per host plant from both cultivars was evaluated. Visual estimations were performed to count the number of whitefly nymphs on 1.25 cm2 of five leaves/bud in low and medium strata per tree to evaluate the spatial distribution of whitefly population in accordance to Poisson distribution, Negative Binomial distribution and b parameter of Law of Taylor. Significant differences in percentages of infestation (P≤0.03) from leaves that belonged to the low avocado tree strata were found between the Lorena (31.88±1.2%) and Hass (15.64±1.8%) cultivars. Natural populations of P. pos. bondari were located on the abaxial leaf side, showing an aggregate distribution in avocado tree from orchards located at different altitudes. Our findings recommend entomological surveillance for Paraleyrodes sp. pos. bondari in Fresno (Tolima), sampling four branches from the medium and low avocado tree strata through inspection of five buds/branches/tree throughout each branch with the presence/absence method to count whitefly nymph colonies on the abaxial side of pre-basal leaves. In total, the sampling involved five leaves/branch (20 leaves/strata or 40 leaves/tree) on 13 avocado trees per hectare

Efecto de Corythucha gossypii sobre las hojas de higuerilla: criterios para su muestreo y control con insecticidas

The lace bug, also called the “cotton or bean lace bug”, Corythucha gossypii (Fabricius) (Hemiptera: Tingidae) is a common pest from cotton. However it has been reported in another twenty four plant hosts including castor bean (Ricinus communis L.). This work aimed to establish if this insect pest can reduce the life-period of leaves, to assess which is the leaf surface that best represents the total pest population for sampling and to test the efficacy of six insecticides for C. gossypii control in a castor bean crop. The life-period of leaves was negatively affected by the presence of the insect, the larger the number of C. gossypii, the shorter their leaf life. The lower surface best represented the entire population of lace bug with a mean ± standard error of 55.10 ± 4.76, with a 99.60% of correlation, a R2=0.99 and a p < 0.0001; compared to 3.44 ± 0.57, with a 66.32% of correlation, a R2=0.44 and a p < 0.0001 for the upper surface. Efficacy of control after three days of insecticide application was: thiamethoxam + lambdacyhalothrin (0.00%), spinetoram, (0.00%), malathion (20.35%), thiamethoxam (38.62%), dimethoate (86.94%) and imidacloprid (87.33%). After seven days of insecticide application the efficacy was thiamethoxam + lambdacyhalothrin (0.00%), spinetoram (21.46%), malathion (38.77), thiamethoxam (50.84%), dimethoate (86.14%) and imidacloprid (90.37%). Results obtained after 16 days lacked many sampling unit leaves, which made their analysis meaningless, after that period of time. El chinche de encaje, Corythucha gossypii (Fabricius) (Hemiptera: Tingidae), es un insecto plaga del algodón, pero ha sido reportado en más de veinticuatro hospederos, incluyendo higuerilla (Ricinus communis L). El objetivo de este trabajo fue evaluar si esta plaga disminuye el periodo de vida útil de las hojas, establecer la superficie de muestreo de la hoja que mejor representa las poblaciones de esta plaga y la eficacia de seis insecticidas para su control en higuerilla. La vida útil de las hojas fue negativamente influenciada por la presencia del insecto plaga; a mayor número inicial de insectos, menor fue el tiempo para la pérdida de hojas. La superficie del envés fue la que mejor representó la población de C. gossypii con un promedio ± Error Standard (ES) de 55,10 ± 4,76 de individuos y una correlación con la población total de 99,60%, R2 =0,99 y p < 0,0001; comparado con 3,44 ± 0,57 individuos y una correlación de 66,32%; R2=0,44 y p < 0,0001 para la superficie del haz. El orden de eficacia de control para 3 días después de la aplicación de los tratamientos fue tiametoxam + lambdacihalotrina (0,00%), spinetoram, (0,00%), malation (20,35%), tiametoxam (38,62%), dimetoato (86,94%) e imidacloprid (87,33%); para 7 días fue tiametoxam + lambdacihalotrina (0,00%), spinetoram (21,46%), malation (38,77), tiametoxam (50,84%), dimetoato (86,14%) e imidacloprid (90,37%). Los datos de muestreo, a partir de 16 días, presentaron una gran pérdida de unidades experimentales, lo que imposibilitó el análisis de los resultados, después de ese tiempo. 

Binomial sampling of <i>Paraleyrodes</i> Quaintance pos. <i>bondari</i> (Hemiptera: Aleyrodidae) in <i>Persea americana</i> Mill.

Fresno (Tolima), in Colombia, is a notable avocado producer, with 36% of the national production. In this paper, two sampling methods are presented to assess natural populations of Paraleyrodes Quaintance pos. bondari attacking avocado trees of Hass and Lorena cultivars under field conditions. The presence/absence of whitefly nymph colonies on 30 leaves located at the high, medium and low strata per host plant from both cultivars was evaluated. Visual estimations were performed to count the number of whitefly nymphs on 1.25 cm2 of five leaves/bud in low and medium strata per tree to evaluate the spatial distribution of whitefly population in accordance to Poisson distribution, Negative Binomial distribution and b parameter of Law of Taylor. Significant differences in percentages of infestation (P≤0.03) from leaves that belonged to the low avocado tree strata were found between the Lorena (31.88±1.2%) and Hass (15.64±1.8%) cultivars. Natural populations of P. pos. bondari were located on the abaxial leaf side, showing an aggregate distribution in avocado tree from orchards located at different altitudes. Our findings recommend entomological surveillance for Paraleyrodes sp. pos. bondari in Fresno (Tolima), sampling four branches from the medium and low avocado tree strata through inspection of five buds/branches/tree throughout each branch with the presence/absence method to count whitefly nymph colonies on the abaxial side of pre-basal leaves. In total, the sampling involved five leaves/branch (20 leaves/strata or 40 leaves/tree) on 13 avocado trees per hectare