Gabino Alberto Martínez-Gutiérrez

Mechanical production of pellets for the application of entomopathogenic nematodes: effect of pre-acclimation of Steinernema glaseri on its survival time and infectivity against Phyllophaga vetula

ABSTRACT The low survival time and diminished infectivity by entomopathogenic nematodes (EPNs) from granular formulations limit their efficiency against agricultural insect pests. This study determined the benefit of pre-acclimating infective juveniles (IJs) of Steinernema glaseri (NJ-43 strain) on extending their mean survival time (STm) in diatomaceous earth (DE) pellets and increasing their infectivity against Phyllophaga vetula. The IJs were reared in Galleria mellonella larvae placed in Petri dishes containing plaster of Paris (PP) or modified White traps (WTs). Pelletisation was performed in a machine operating on the principle of laminar flow using DE Celite® 209. Pellets were stored at room temperature (23 ± 3°C) and high relative humidity (96–100%). IJs harvested from WTs between the 3rd and the 5th days after the onset of emergence were more infective on P. vetula and pre-acclimation of S. glaseri in PP increased significantly its STm in the pellets; from 23.1 to 34.5 days, compared with non-pre-acclimatised IJs from WTs. However, juveniles with or without pre-acclimation formulated in DE pellets failed to achieve significant control of P. vetula. These results are discussed in light of the relationship between EPN survival and host infection by EPNs with possible effects of the formulation in DE pellets.

Productivity under Shade and Different Nutrient Solution of Hydroponic Watercress (Nasturtium officinale R. BR.)

Commercialization of watercress in the Sierra Norte mountain range in Oaxaca, Mexico principally relies on harvesting plants growing on riverbanks; however, semi-intensive cultivation throughout the year could be established as an alternative for the region. With this as an objective, the present study was carried out using the laminar flow of nutrients technique to evaluate four solutions of different macronutrients and four shade percentages. Treatment distribution was formulated according to a bifactorial arrangement. Four harvest periods were employed, in April, June, September, and November of 2010. Yields and vegetative growth of watercress decreased linearly with increasing shade levels. The best results were obtained with a nutrient solution using an electrical conductivity (EC) of 0.90 dS m−1. Shade cloth percentages higher than 10% caused a significant decrease in total cycle production; the use of shade cloth is not recommended during seasons with low incident radiation.