University of Maryland Extension

What Crops Up on Pansy?

What is pH and Why is it Important to Know it?

When growing a pansy crop, remember to track the pH levels to avoid problems with iron. Keep the pH between 5.6 and 6.0 because above 6.0, iron deficiency (intervienal chlorosis on younger leaves) becomes a problem. If the pH level goes higher, iron deficiency can become a problem. Iron may be present in the substrate, but not available to the plant. Use a foliar spray of iron chelate (4 oz per 100 gallons) to reduce foliar yellowing. Be sure to rinse off the iron chelate from the foliage to avoid foliar burn. To lower the pH of the substrate, drench seedlings at 10 day intervals with 1 to 3 lb per 100 gallons of iron sulfate.

               Invterveinal chlorosis on pansies
               The pH was 6.8. Interveinal chlorosis is due to iron deficiency.
               The roots looked good.

Thielaviopsis: At higher pH levels, plants are also susceptible to the root rot pathogen, Thielaviopsis (black root rot), which also causes yellowing of the foliage so checking the roots to see if they are healthy or not is necessary in addition to measuring pH levels. If you find damaged roots, get a plant sample to an Extenion office or University plant diagnostic lab to confirm if a root disease is the problem.
Management: Be sure to check plugs when they arrive for any disease symptoms such as chlorosis and uneven plant growth.  Black root rot spores can survive for up to several months on benches and plug trays and even longer on plant debris under benches. Maintain good sanitation in the greenhouse and do not reuse substrate or pots to prevent or reduce the spread of this disease. Fungicides for control include Banrot, Medallion, Hurricane, thiophanate methyl products, and Terraguard.

                      Black root rot on roots of petunia
                      If pansy roots look like these petunia seeding roots which
                      are infected with Thielaviopsis and the pH is above 5.8 - 6.0,
                      take a sample to a plant pathologist to check for Thielaviopsis.

 
Aphids

                             Aphid cast skins and honeydew covering pansy
                             Pansy covered in cast skins and some sooty
                             mold and honewdew.

Aphids are an insect commonly found on pansy in the greenhouse and the landscape.  Aphids cause distorted, curled tip growth on many greenhouse ornamentals, and they produce honeydew that is a food source for sooty mold which reduces plant vigor and can make plants unsalable. Also look for the characteristic white cast skins on the plants.

Several beneficial insects can be released to control aphids in greenhouses. The parasitoid, Aphidius colemani, can be released for control of green peach aphids. A. colemani also parasitizes melon aphids. This parasitoid does not go into diapause (a ‘resting’ stage) so it remains active in late winter and early spring.

Aphid mummies on leaf

 

 

 

 

 

These aphid 'mummies' indicate parasitism
by an Aphidius wasp.

Adult Aphidius parasitic wasp

 

 

 

 

 

 

A parasitic wasp (Aphidus sp.)

Aphidoletes midge feeding on an aphid

 

 

 

 

Aphidoletes aphidimyza, a predaceous midge, is a generalist predator that feeds on many species of aphids. It does go into diapause during the winter so it would not be effective early in the growing season.

Banker plants can be used for rearing parasitic wasps for release into greenhouses.


Variegated Fritillaries

In late summer, look for this caterpillar on pansy plants in the greenhouse and nursery.  They can be a problem on fall produced pansy crops. In 2013, we also had reports of the caterpillar on plants in the landscape. This caterpillar overwinters as an adult in the southern states.

Variegated fritillary caterpillarVariegated fritillary butterfly
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