Floriculture Greenhouse Update

Inspect Incoming Plants

Thursday, 02 February 2012 14:48

Vegetative plugs and seedlings are arriving (or will be soon) in greenhouses and it is important to prevent pest outbreaks right from the start. Inspecting incoming plants is probably the most important and effective way to monitor for pests and diseases. Inspecting incoming plants is often overlooked due to lack of time or the assumption that "I know my suppliers and they always provide me with excellent plant material". Yes, that is often true, but it may not always be the case, in spite of the best intentions. Often times, pests are suppressed, but not completely eradicated, leaving overlooked one or two small aphid nymphs or a few two spotted spider mite eggs or larvae or thrips when plants are shipped. If you see whitish spray residue, yes, that means the plants were sprayed, but how well did the spray actually work? Did they obtain thorough plant coverage or were the pests resistant?
Take the time to use a handlens and look on the underside of the leaves for:

• Two Spotted Spider Mites (larvae, nymphs or adults) and their eggs
• Aphid nymphs
• Immature whitefly nymphs
• Immature and adult thrips

You will need a hand lens (10 to 16X) to see these small insects, and mites.

If the incoming plugs are somewhat lush, tap the plant material over a sheet of white paper to help you detect aphids and thrips.

Don't forget to inspect the roots – to insure that they are white and healthy. Look for signs of disease (discolored, brown or blackened roots or if the outer cortex sloughs off leaving a central core.) Occasionally, root aphids and root mealybugs can also be introduced on plant material that appears healthy.

If you see symptoms that may indicate a disease such as downy mildew, try placing the leaves in a "moist chamber " or moistened plastic bag, overnight. The next morning, look for the characteristic fungal sporulation using a hand lens or microscope.

Leanne Pundt, UConn Extension
Tina Smith, UMass Extension

Overwintering Perennial Greenhouses

Thursday, 12 January 2012 11:16

It has been an interesting winter. Some growers are reporting they have not even closed up their overwintering perennial houses this year. Given the warm temperatures this year, growers are advised to open up overwintering greenhouses on warm days to ventilate. Either roll up sides, open doors, use fans, depending on the type of overwintering greenhouse. Ventilating will lower the relative humidity. Greenhouses that are closed up will result in moisture buildup and encourage plant diseases to develop.

The added protection of thermoblankets works best only during the very coldest of weather, so they should be rolled on over the plants and rolled off as needed. High - low thermometers placed at plant height can be useful to provide the temperature range of the air and soil thermometers are also useful.

Fact Sheet: Overwintering Container-Grown Ornamentals

Tina Smith and Paul Lopes, UMass Extension

USDA/APHIS Proposes Changes in Chrysanthemum White Rust Regulations

Thursday, 12 January 2012 11:09

Chrysanthemum White Rust (CWR) has been an issue for growers for the last few years. The weather conditions in the Northeast and Western Regions of the United States in certain years can be ideal for the development of CWR on the hardy mum crop. Many Massachusetts hardy mum growers have had to make management decisions concerning CWR and these decisions have had a dramatic impact on the cost of production.

In the fall of 2009 the Massachusetts Flower Growers’ Association and the Connecticut Greenhouse Growers’ Association proposed changes in CWR regulations to top administrators in USDA/APHIS. The process has moved slowly but has now progressed to where a meeting is tentatively scheduled for early winter 2012 to have growers discuss and review a proposal to change CWR regulations to a Regulated Non-Quarantine Pest or (RNQP). This change would allow growers to deal with CWR as a common disease pest. CWR regulations would continue to stay in place for propagators and imported plant material would still be subject to inspection at the US borders.

Growers, industry representatives, federal and state regulators and researchers will attend the meeting. The purpose of the meeting is to provide an opportunity for stakeholders to discuss their thoughts and propose options on how best to safeguard the United States industry from Chrysanthemum White Rust (CWR).

The Massachusetts Flower Growers’ Association will be represented at the meeting. If you have any questions or have comments on the matter please feel free to contact the MFGA office at 781-275-4811.

Paul Lopes, University of Massachusetts