Preliminary Study of the Presence, Damage Level, and Population Dynamics of Mexican Pod Weevil (Apion sp.) in Bean Genotypes (Phaseolus vulgaris L.), in the Highlands of Guatemala. Julio C. Villatoro* 1, Jessica Moscoso 1, Karen A. Agreda 1, Juan M. Osorno 2, Phillip M McClean 2 and Luz De Maria Montejo 2 1 Instituto de Ciencia y Tegnologia Agricolas ICTA 2 North Dakota State University, Dept. of Plant Sciences. Livingstone, Zambia March 2016
Lowlands Monoculture Highlands Intercropping (Milpa)
Intercropping (Milpa) System in the western Highlands of Guatemala
INTRODUCTION The Mexican pod weevil (picudo de la vaina): Coleoptera: Curculionidae. Apion spp. (~500 species) Main pest in common bean production in Central America. Main production problem in the highlands of Guatemala. Up to 95% seed damage. Limiting factor in the production due to the direct damage that it causes to bean seed. No information regarding levels of prescence and damage. Insecticides are partially effective but very few farmers have access to agronomic inputs.
Two species have been identified affecting common bean: Apion godmani and Apion aurichalceum. A. godmani is the most common. Females oviposit one egg per bean seed in the young pods A. aurichalceum oviposit in the terminal stage of the pods finding up to 65 larvae in the space of two seeds. A. godmani A. aurichalceum
GENERAL OBJECTIVE To determine the presence of bean pod weevil and its damage level in the bean crop in the Guatemalan highlands. SPECIFIC OBJECTIVES To estimate the presence of Apion spp. and the level of damage in farmer s fields. To determine the level of damage and the population dynamics in two genotypes of climbing beans and two of bush beans.
METODOLOGY Survey at farmer s fields: 30 pods where randomly chosen every 3m from experimental parcels at farmer s fields across 10 locations. Damage was estimated by opening the pods and counting the damaged and healthy seeds, and expressed as percentage. Field Experiment at ICTA-Labor Ovalle Station: 2 bush-type varieties: ICTA Hunapú y Bayo Azteca 2 climbing varieties: ICTA Texel, ICTA Utatlán 100 m 2 per variety, 3 replications Population dynamics: 16 weekly counts of adults starting 11 and 78 days after planting for bush and climbing types, respectively. Damage level: 7 seed samples were made at physiological maturity. Damage expressed as %.
Survey at Farmer s fields expressed as % damage (10 locations) Locations
RESULTS: In determining the damage level in farmer s fields, in three climbing bean genotypes: ICTA Texel, ICTA Labor Ovalle & Criollo (local landrace), damage was found between 14% and 99% and an average of 45%. CONCLUSION From the above information we can deduct that Apion spp. is spread over the productive areas from the highlands, causing serious damages to the climbing bean.
Seed damage (%) in 4 varieties at physiological maturity 100.00 Climbing C Nivel de daño (%) 75.00 50.00 Bush A A B 25.00 0.00 Hunapú Precóz Bayo Azteca ICTA Utatlán ICTA TEXEL variedad Seed damage ranged between 35% and 38% and in the climbing genotypes between 67% and 83%. In the climbing genotypes the damage percentage was a higher rate probably due to the longer cycle.
Numero de adultos por muestreo semanal 40 35 30 25 20 15 10 5 0 Population Dynamics of Apion sp. in 4 Bean Varieties Across 16 weeks jul. 01 jul. 08 jul. 17 jul. 24 jul. 31 aug. 6 aug. 14 aug. 21 aug. 28 sep. 04 sep. 10 sep. 18 sep. 25 oct. 2 oct. 09 oct. 16 Weekly sampling of Apion sp. adults Sampling started 11 and 78 days after planting for bush and climbing types, respectively. Utatlán Texel Hunapú Bayo Azteca
CONCLUSIONS: The data obtained reveals the presence Apion spp. signicantly affecting seed yield and quality, showing that the damage caused to the seed in some cases is very high (up to 99%). Seed damage is 2 times higher in climbing beans than in bush-types, suggesting that the longer growing cycle of the climbing-types may be prefereed by the insect. The presence of adult weevils in the pods starts at flowering stages of the crop, increasing its population during pod developing, and decreasing when the pods are close to their physiological maturity.
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