Greenhouse - Prepare for Spring Pansy Production

Greenhouse growers are in the midst of poinsettia sales season now. The next major production plant for many growers will be spring pansies. The following is information on pansy problems to avoid.

Growers will be once again starting their spring pansies in December. Just a few reminders on what to watch out for on your pansy crop:

Root rots- look for stunting, wilting, and yellowing. Roots rots are promoted by cold, cloudy weather when soils tend to stay wet for longer periods of time which is a very common situation as we move into January and February.

Examine roots for Pythium. AGDIA of Indiana produces on-site serological testing kits that can be used to detect Pythium and Rhizoctonia. If Pythium is detected, materials for control include Subdue Maxx, Alude, Aliette, Truban, and Banrot.

For Thielaviopsis (black root rot) controls include Terraguard, Cleary’s 3336, and Banrot. However, it is recommended that infected plants be discarded. It should also be noted that cleaning used pots or trays with bleach is not enough to protect against Thielaviopsis; you must either steam sterilize them or use fresh ones.

Botrytis- remove spent blooms, water as early in the day as possible, and increase air circulation. Controls include Decree, Daconil, Cleary’s 3336, and Chipco 26019.

Leaf spots- insufficient nitrogen can lead to Alternaria or Colletoctrichum in cold weather and Cercospora in hot weather.

Fungus gnats- can spread root rots. Monitor with potato slices. Controls include IGRs like Adept and Distance. Biocontrols include Bacillus thuringiensis serotype 14 (=israeliensis), available as Gnatrol, and beneficial nematodes (Steinernema feltiae), applied as a drench.

Fertility and pH- the EC should be around 0.5-1.0 microseimens. Maintain a lower pH of 5.8-6.2 to avoid problems with Thielaviopsis and nutrient deficiencies.

Iron deficiency causes interveinal chlorosis on the new leaves and can be corrected with iron sulfate at 2 lbs/100 gallons or sulfuric acid at 1 oz/ 100 gallons.

Boron deficiency makes the leaves thick and puckered and can be corrected with Borax at 0.5 oz/100 gallons or Solubor at 0.25 oz/100 gallons.

Magnesium deficiency can cause symptoms of interveinal cholorosis that look much like iron deficiency. Magnesium can compete with calcium to create a magnesium deficiency that appears on the middle leaves rather than the new leaves. It can be corrected with Epsom salts at 1-2 lbs/100 gallons.

Excess phosphorus and ammonia will cause plants to stretch and become floppy.

Information reprinted from the December 8, 2006 edition of the Greenhouse TPM/IPM Weekly Report from the University of Maryland Cooperative Extension