ORNAMENTAL HORTICULTURE RESEARCH

WEED CONTROL IN ONE-GALLON AZALEAS

OBJECTIVES:

In recent years growers in the Southeastern United States have reported difficulties concerning use of preemergence applied herbicides on newly potted azalea liners. There appears to be some species that are more sensitive to herbicides than others. Also, growers have questioned the use of dinitroaniline herbicides (DNA's) and their impact on growth of these newly potted plants. The objective of this experiment is to evaluate commonly used preemergence herbicides for weed control in container-grown azaleas.

PROCEDURE:

Rooted 72-cell liners of selected azalea cultivars were potted on April 29, 1997 into trade gallon containers using a 3 pine bark:l peat moss growing medium amended with 1.5 lb Micromax and 6 lb dolomitic limestone. Plants were fertilized with 14 lb/yd3 Osmocote 17-7-12 incorporated at transplanting. Herbicide treatments were applied on April 30, 1997. Herbicide treatments were initiated after two irrigations. Treatments will be repeated at 90 day intervals for a total of three applications.

TREATMENTS:

1. Regal Ronstar AC 4 lb aia
2. Regal 0-0 3 lb aia
3. OH-2 3 lb aia
4. RegalStar II 2.4 lb aia
5. Snapshot 2.5 TG 4 lb aia
6. Ronstar 2G 4 lb aia
7. Nontreated control ----------

PLANT MATERIAL:

Coral bells
Delaware valley white
Pink pearl
Sherwood red

COMMENTS:

Phytotoxicity seems to be associated with heat around the time of application. Temperatures were unseasonably cool after the initial application.

DATA:

Weed # per container
Weed control rating
Visual rating of plant quality
Growth indices