Section 5: Nursery and plant hygiene - World Agroforestry Centre

NURSERY AND PLANT HYGIENEdifficult to control. The best way is probably to issue to staff boots and workclothes to wear during work in the nursery and to install a dip basin with 10%household bleach solution at the entrance of the nursery through which staffand visitors have to walk to disinfect their shoes, especially when they comefrom fields where soil-borne diseases or nematodes are present.Section 5Methods ofsurface sterilizationheatchlorinefungicidesFor seeds, tubers and roots, hot water soaks(40–55°C) are recommended. Temperature andduration depend on the species. You can find thebest range with simple experimenting, forexample by soaking material at two differenttemperatures for half an hour, two hours and fourhours.Dipping cuttings into a 10% household bleachsolution for 20 minutes is a practicerecommended for some hardwoods but it shouldbe tested for phytotoxicity on all species first.Seeds or cuttings can be coated with a dust orslurry of fungicides. Captan ® and Benlate ® arethe most commonly used fungicides for seedtreatment. Captan ® is a contact fungicide whichkills pathogens present on the seed coat;Benlate ® is a systemic fungicide whichpenetrates into the seed and has an effect on theembryo during germination, giving the seed alonger-lasting protection. However, mostfungicides have a high toxicity to seeds and theyoften act only on one of the number ofpathogensthat are usually present. Recent work suggeststhat coating the seed with a bacterialformulation, esp. Trichoderma harzianum orPseudomonas spp., would be helpful. However,for the time being, this technique is out of reachfor most institutions in developing countries.61