Section 5: Nursery and plant hygiene - World Agroforestry Centre

NURSERY AND PLANT HYGIENEActions to preventnursery contaminationplant health statusplant densityhardeningresistant speciesor cultivarscleanliness invegetative propagationstaff trainingHealthy, well-fertilized and properly irrigated plants arebetter suited to withstand pest attacks. However, overfertilizingshould be avoided, especially excess nitrogen,which weakens plants and makes them more attractiveto many sap-sucking insects, such as aphids andpsyllids.Avoid very dense spacing in germination and nurserybeds, because diseases can spread easily. Closespacing can also lead to etiolated and weak plantswhich are susceptible to disease.Timely hardening of seedlings will produce strong andhealthy plants that are able to withstand a certainamount of pest or disease attack.If possible, grow resistant types or cultivars, or avoidsusceptible species altogether. For example, citrusshould not be propagated in areas with high incidenceof aphids, since aphids transmit citrus greening disease,and spraying against the aphids usually cannot checkthe problem to the necessary extent.When harvesting scionwood and cuttings, take care thatthey come from healthy stock plants that are notdepleted of nutrients or drought stressed, to enhancetheir resilience to diseases. Always sterilize knives andsecateurs with alcohol to avoid spreading virusdiseases, which are often transmitted on the tools.To keep pest and disease levels low, all employeesshould be trained to recognize and report pests.Workers who are in daily close contact with the plantsthrough watering, weeding etc., will probably more oftenencounter such problems than a nursery managerwould.62Section 5