Get integrated

Many processes can be used to produce woody ornamentals in a nursery, from propagation to pest control. Many woody crops produced in nurseries are propagated using cuttings from either stock plants or plants that have mature growth. Trees can start from seed, grafting or cuttings, and perennials can be propagated by division of stock plants and started from seed or cuttings.

Given these different methods of propagation, growers who want to develop an Integrated Crop Management (ICM) program could easily become overwhelmed.

Let’s cover two methods of liner production propagated by cuttings of common woody ornamental species.
 

Implementing ICM

The initial process for implementing an ICM program includes proper sanitation.

• Remove all weeds and disinfect propagation area.
• New trays or pots are best, but if they are being reused, they must be cleaned, disinfected and free of all growing media.
• Carefully scout stock plants for disease and pest issues and properly treat them prior to taking cuttings.
• Use chemistries that are compatible with biological control agents (BCAs).
• Use chemistries that target the disease or pest present on the stock plants.
• Make chemical applications early enough before the cuttings are taken so the product has time to work.
• Follow all label instructions, such as re-entry interval (REI) and use rates.
• When cuttings are being prepared for sticking, inspect for insects and discard any that are infested.
• Do not put cuttings on bare ground or soil that is covered only with plastic.
  
   

Sticking and irrigation

For woody cuttings, the liner container size can be anything from a cell pack, to trays of various sizes, to a 4-inch pot. In the nursery industry, there is no set rule to define what is referred to as “a liner.” In some types of woody production, liners are produced in ground beds and newly stuck cuttings are irrigated multiple times throughout the day on a regular schedule. This type of irrigation is referred to as misting, but is not exactly the same as misting in bedding plants or other herbaceous greenhouse production. Depending on the plant and environmental conditions, irrigation is gradually reduced when the cuttings have started to root.
 

Method A

Liners that remain in the greenhouse for six weeks

During the stage before sticking, if diseases or insects have been an issue on the stock plants or in the propagation area, cuttings may be dipped using a labeled product such as a disinfectant, fungicide or insecticide.

Once cuttings are stuck into the growing media these steps can be taken to protect against pest pressure:

To prevent Rhizoctonia and Phytophthora, a drench or direct spray of fungicides such as mefenoxam + fludioxonil (Subdue Maxx + Medallion WDG) should be applied when new roots start to appear. In 3-4 weeks, rotate with active ingredients in different mode of action (MOA) classes that are labeled for greenhouse use. Avoid fungicides that impact rooting in propagation until roots have established. The best results have been obtained by scheduling fungicide applications from the time cuttings have rooted until the finished plants ship.

Fungus gnats feed on newly emerging roots and can spread disease. To control fungus gnats, use the BCA Steinernema feltiae. S. feltiae are nematodes that prey on insect pests only and do not damage plants.

If you apply a high rate of nematodes the first week of propagation, it may be all you need to control fungus gnats. However, a second application at a medium rate may be necessary for slower rooting plant species.

If fungus gnat populations are high, an insect growth regulator can be used alone or with S. feltiae for control, with applications on a seven-day interval.

When cuttings are rooted, they are either moved to outside blocks for finishing or they remain in the greenhouse for three to eight months where they are transplanted into larger pots or sold as liners to commercial growers. The transplanted linersvcan stay on outside blocks from six months to two years, while larger containers stay even longer.
 

Method B

Liners that remain in the greenhouse for three to eight months

When cuttings have established roots and irrigation has been reduced to maintenance levels, preventive fungicide applications such as mefenoxam + fludioxonil (Subdue Maxx + Medallion WDG) rotated with mandipropamid + azoxystrobin (Micora + Heritage) fungicides should continue on a regular schedule to prevent Rhizoctonia and Phytophthora stem and root rot diseases.

Botrytis can be a problem on soft new growth in greenhouse conditions. It is important to scout and pay attention to environmental conditions so timely fungicide applications can be made. Recommended treatments include cyprodinil+ fludioxinil, azoxystrobin and chlorothalonil (Palladium, Heritage and Daconil) fungicides.

Many holly species are susceptible to Thielaviopsis. If there is a history of this disease in the greenhouse or the plant species is known to be susceptible, make preventive fungicide applications such as azoxystrobin or fludioxonil (Heritage or Medallion WDG).

The major insects and mite pests in this type of production include aphids, spider mites and, in certain crops, whiteflies.

Aphids are often found in new terminals where soft succulent growth is present. Unlike whiteflies, aphids are often found in groups and not scattered across the crop.

Chemical controls for aphids include Endeavor, Flagship and Avid insecticides, all of which can be compatible with BCAs.

BCAs for aphid control include Aphidius ervi (Aphiline e) and Aphidius colemani (Aphiline c), which contain parasitic wasps. Aphidoletes aphidimyza (Aphildoline a) contains a midge that feeds on 60 species of aphids.

Spider mites are often hard to control in liner production because of spray coverage. The leaves on these small plants are often thick and waxy, which makes it difficult to get proper coverage and harder for translaminar products to penetrate the leaf tissue.

Avid is effective on spider mites and can be used with BCAs. Phytoseiulus persimilis (Phytoline p) and Amblyseius andersoni (Amblyline aa) biological control agents are effective for mite control. These products contain predacious mites that feed predominately on spider mites.

Endeavor, Flagship and Avid, which are compatible with most BCAs, provide effective control of whiteflies that can be a pest on certain woody crops propagated in greenhouses.

BCAs for whitefly control are the parasitic wasp Eretmocerus eremicus (Eretline e) and a predacious mite Amblyseius swirskii (Swirskiline as).

With proper sanitation, scouting and pest control, ICM can be a practical solution for your nursery.

Marla Faver is technical service manager for Syngenta. She can be reached at marla.faver@syngenta.com.

Author note: Bioline biological control agents are tested for compatibility with Syngenta Plant Protection products. Compatibility with other chemistries, even with the same active ingredient, cannot be claimed because of formulation differences.

Photos courtesy of Marla Faver