Yolanda D. Ortiz-Hernández

Biological Control of Phyllophaga vetula (Horn)1, and Lethal Concentrations and Times of Entomopathogenic Nematodes

Abstract. Numbers of Phyllophaga vetula (Horn) (Coleoptera: Melolonthidae) larvae killed after application of nematodes Steinernema glaseri Steiner, Heterorhabditis bacteriophora Poinar, and Steinernema feltiae Filipjev at five concentrations (50, 100, 200, 500, and 1,000 nematodes per larva) in aqueous suspension were compared. Lethal concentrations and times for each species were determined. The difference between the treatments was very significant. The nematode most effective for pest control was S. glaseri at a dose of 1,000 per larva that killed 97.5%. H. bacteriophora at the same dose killed 87.5%, and S. feltiae killed 60.0%. With 500 per larva, all three nematodes were statistically the same. S. glaseri at any concentration had the lowest lethal concentration (LC50 and LC95) and lethal time (LT50 and LT95), followed by H. bacteriophora and S. feltiae. The three species of nematodes showed a positive dose-response relationship.

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.

Effect of phosphate-solubilizing bacteria isolated from semiarid soils on pitahaya seedlings (Hylocereus undatus)

espanolLas bacterias solubilizadoras de fosfato (PSB) son un grupo de organismos que solubilizan formas insolubles de fosforo haciendolas disponibles para el desarrollo vegetal. Se estudio el efecto de tres cepas PSB denominadas PSBMi, PSBHc y PSBVa sobre el desarrollo de plantulas de pitahaya (Hylocereus undatus), bajo condiciones de camara de crecimiento. Los resultados indicaron que el mayor diametro del tallo, altura de planta, peso seco y longitud de raiz se encontraron en las plantulas de pitahaya inoculadas con PSBMi, el incremento en estas variables fue de 52.40, 34.71, 23.31 y 30.14% respecto del control no inoculado. Este estudio mostro el potencial de las PSB sobre el desarrollo de plantulas de pitahaya. Sin embargo, se necesita mas investigacion para entender los mecanismos especificos involucrados en el efecto positivo de las PSB sobre el desarrollo de plantas de pitahaya asi como verificar estos resultados bajo condiciones de campo. EnglishPhosphate-solubilizing bacteria (PSB) are a group of organisms that solubilize fixed forms of phosphorus, making it available for the plant growth. The effect of three PSB strains, called PSBMi, PSBHc and PSBVa, on growth of pitahaya seedlings (Hylocereus undatus) was studied in a growth chamber. The results indicated that plant stem diameter, plant height, plant total dry weight and root length were greatest in pitahaya seedlings inoculated with PSBMi. The increase in these plant growth variables was 52.40, 34.71, 23.31 and 30.14% with respect to the control pitahaya seedlings not inoculated. The present study showed the potential of P-solubilizers on pitahaya seedling growth. However, further research is needed to understand the specific mechanisms involved in the positive effects of PSB on pitahaya plant growth and to verify these results under field conditions.

Relationship between Scyphophorus acupunctatus Gyllenhal Damage and Nutrient and Sugar Content of Agave angustifolia Haw

Abstract In Oaxaca, Mexico, Agave spp. is produced as the main raw matter of the mezcal (distilled alcoholic beverage) industry. Agave weevil, Scyphophorus acupunctatus Gyllenhal, in adult agave plants causes rot and death, which in turn affects production and quality of mezcal. Five amounts of damage by the agave weevil were analyzed in relationship to total reducing sugars and nitrogen-phosphorus-potassium nutrient content of mature A. angustifolia Haw plants. A significant (p ≤ 0.05) relationship was found between the amount of damage to a mature plant and numbers of lesions (r = 0.981), adult insects (r = 0.908), and larvae (r = 0.994). Severely damaged agave plants had more lesions on the leaves (33.2) and more agave weevil larvae (40) and adults (30.5). Likewise, the greater the amount of damage, was reduced 52 % the weight of the plant, and 68% total reducing sugars. Nutrient content (NPK) in severely damaged plants were 0.7, 0.36 y 2.37 % in contrast to healthy plants was 2.8, 0.60 y 3.48 % respectively.

Carbon exchange rate of pitahaya (Hylocereus undatus L. Harwort) in contrasting seasons and irrigation regimes

The aim of this investigation was to evaluate the effect of two contrasting seasons (fall and spring) and irrigation regimes (well-watered and drought-stressed plants) on the carbon exchange rate (CER) of pitahaya grown in a cold greenhouse in the Valley of Mexico. Carbon exchange rate (CER) of one-year-old stems of pitahaya was studied over two periods of 24 h (November and April), in well-watered plants (every 15 days) and drought-stressed plants (irrigation suspended for four and five months before CER measurements in November and April, respectively). In November, when the relative humidity (RH) during the night was between 65 and 85%, watered plants with 88% of relative water content (RWC) showed two maximum CER peaks. The first CER peak declined slowly when the air temperature dropped from 11 to 7.4 °C and sharply at 6 °C. The second CER peak was reached when the air temperature was 12.2 °C. Drought-stressed plants (RWC = 60%) also showed two maximum peaks but at different times. The first one was w...

Agronomical, physiological, and cultural contributions of pitahaya (Hylocereus spp.) in Mexico

In the last two decades, the cultivation area of pitahaya from the Hylocereus genus has increased around the world due to its fruit attributes, production level, and economic returns. The plants stems, fruits, and flowers are used in food, and in medicine. Here we present the contribution of Mexico to the agronomical, physiological, and cultural knowledge of this species and its current situation.