Horticulture Week
 https://www.hortweek.com/pest-disease-management-nursery-hygiene/ornamentals/article/1452693

How to create an effective hygiene programme that will support profitable growing.

Pests and diseases occur on nurseries because cultivated plants are more susceptible than their wild relatives. Growing large numbers of the same species close together can encourage disease-causing organisms and pests to establish and spread rapidly.

Many plants are specifically bred for their foliage and flowers rather than disease resistance, and commercial crop production can create environmental conditions that favour particular pathogens and/or pests.

Infectious organisms are part of the environment. The management of some crops, particularly those for same season sales, can lead to stress and susceptibility. Understanding the crop that you are growing — the normal growth habits and the normal variability of plants — will help you to recognise unusual conditions as early as possible.

An effective hygiene programme is important to succeed in growing plants profitably. Successful hygiene management is based on accurately diagnosing any problem that may occur and its cause as well as having some knowledge of the pest/pathogen and its life cycle.

Understanding the effects of the environment on crops and their potential pest/pathogen is essential. Being able to evaluate the cost and practicability of any actions taken is also important.

Reducing problems on-site
Nursery hygiene is the principal means of reducing pest/pathogen introduction and has the ability to reduce the most difficult-to-control problems. It is more cost-effective to prevent pathogens from being introduced into the production cycle than attempting to suppress diseases in infected plants.

All activities should be aimed at eliminating or reducing the amount of disease/pest present in the environment and preventing their spread to healthy plants. An effective programme needs to fit well with your nursery situation and has the ability to change through the entire production cycle according to environmental conditions.

Following good nursery hygiene advice will help to reduce:

• Physical disorders.
  
• Pathogen build-up on dead or dying plants.
• Carry-over and spread of pests/pathogens on tools, benches, pots and hoses.
• Carry-over and spread of pests/pathogens from one crop to another.
• Contamination of healthy plants with infested soil/water and contamination of clean pots, growing media and so on.Well-spaced crops in appropriately ventilated protected structures can reduce Botrytis, downy mildew, leaf spot and rust infections. This is also true of subirrigation, where possible.

Clean trays, pots, benches and floors can reduce weed seedling re-emergence as well as Rhizoctonia, Pythium, Phytophthora, Fusarium and Sclerotinia. Clean water, well-drained growing media, healthy 
stock plants and removing debris will reduce the risk of Pythium, Phytophthora, Fusarium, viruses, Rhizoctonia, Sclerotinia, mildews, rust and Botrytis.

Five key control methods
Exclusion Making sure plants, seeds and cuttings are free from pests and pathogens; maintaining a disinfection regime; limiting the number of people handling stock; taking strong healthy cuttings; avoiding water splash; treating irrigation water; controlling weeds around growing areas; checking new plant sources thoroughly — set up a quarantine area if unsure. Take the time to learn what a real plant passport should look like and what information it should contain.

Protection Uniform, timely applications of pesticides, ringing the changes to avoid resistance; knowing when a pest/pathogen is likely to attack;  growing resistant cultivars where possible and biological controls where appropriate.

Prevention Prevent conditions that favour infection, disease development and pest attack; keep leaf surfaces dry, avoid over-watering; use growing media with good drainage; clean up growing areas and keep a routine going even if no pest/pathogen is present.

Eradication Through chemical application. Observe techniques and timing when applying products; remove dead/diseased plant parts; rotate crops; plant green manures. Monitoring Conduct this throughout the year and step it up to three-day intervals during the growing season to enable the designated crop walker/spray team member to stay in touch with what is happening on the nursery and identify problems early on. Check systems — irrigation, fertiliser regimes, etc — and carry out an environmental assessment to record weather, temperatures, irrigation applications, etc.

Train staff to be able to easily identify the key pests and diseases that can attack the crops you grow. Use a combination of experienced staff and BASIS-registered advisers to carry out this training. When an issue arises, approach it in this order and ask: "What can we do to change things culturally, environmentally, biologically — predators, parasitoids, biorationals — and, lastly, chemically using selective pesticides?"

A large number of weed types can act as alternative hosts when a vulnerable crop is not present, particularly for aphids, whitefly, rusts and powdery mildews.

Use a hand lens to accurately identify the pests and diseases attacking a crop. This is particularly important when checking for spider mites and the life stages present on foliage, where successful control depends on applying the right predators and/or the right selective pesticides to target the right life stages for successful control.

For fungicides applied to control diseases such as powdery mildew, a check must be carried out a few days post-spraying to see whether the product is working well. This cannot be done accurately enough with the naked eye, especially where the disease is attacking plants that have tight foliage.

All corrective actions need to be quickly implemented to minimise plant damage and losses. A timely programme is always better than a knee-jerk reaction.