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Tropentag, September 20 - 22, 2017 in Bonn

"Future Agriculture: Social-ecological transitions and bio-cultural shifts"

Ecofunctional Management Strategies for Diaphorina citri on Organic Orange Orchards

Lea Forster1, Carlos Castillejos Cruz2, Salvador Garibay3

1University of Kassel / University of Goettingen, Germany
2National Autonomous University of Mexico, Botany, Mexico
3Research Institute of Organic Agriculture (FiBL), Dept. for International Cooperation, Switzerland


This study was conducted to develop eco-functional management strategies on organic citrus orchards. The citrus Huanglongbing (HLB) or greening disease is considered as the most destructive and devastating citrus disease worldwide. The bacteria Candidatus Liberibacter is the causal agent for the disease and mostly disseminated by the Psyllid Diaphorina citri. Therefore, this research explores potential difference in the quantity of natural enemies of D. citri in two different weed-management systems for organic citrus production. The weed management included i) an alternate weeding, ii) and a frequent and low weeding, both within the tree rows. The on-farm study was conducted in Mexico, Veracruz on a 2 years old organic orange (var. Valencia) orchard under a systematic line sample design. Data was taken from 5th of February till the 18th of March. Measurements were conducted in total 3 times for the weed composition and 5 times concerning Arthropode diversity. Along transects randomly ten square metre of floral composition were determined on species level. Afterwards the alpha and beta biodiversity are calculated with the Shannon-Wiener index, the evenness and the beta biodiversity with the Jaccard's index. D. citri, Coccinellidae and Crysopidae were observed on 4 sprouts of each 3 selected tree/treatment with a magnifying glass. With an insect net, the arthropod populations on the ground between the trees were caught and placed into polyethylene bags with alcohol 70%. Afterwards, the insects were counted and divided into the different orden level. Preliminary results show that there was no difference in the weed composition concerning family level. The species number was on the second and third observation date higher in the treatment with alternate weed management, 57 and 51 species against 53 and 45 in the low weed management but the Shannon index was higher for the low mowing weed management. D. citri population was not significantly different among treatments (correlation of 0.34). However, the amount of D. citri was lower in the alternate weeding compared with the frequent weeding. That is in contrast to the other arthropods, which were abundant in higher numbers in the alternate weed management.The amount of natural enemies decreased strongly after the second observation and was the same for both treatments.

Keywords: Beneficial insects, Diaphorina citri, eco-functioning, Huanglongbing, management

Contact Address: Lea Forster, University of Kassel / University of Goettingen, Witzenhausen, Germany, e-mail: legafo@riseup.net

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