Aglaonema Diseases

MANILA, Philippines - Aglaonema has been around for a long time. It is mainly used as indoor plant in the temperate countries. Aglaonemas are called Chinese evergreens and most of the plants in commerce are green with white speckles or have mottled leaves at best.

During the 80’s, Mr. Sittiporn of Pattaya Garden bred the first colored Aglaonema using Aglaonema rotundum as source of red or pink color. The cross was named “Balanthong” in Thailand. The interest in this breeding line started. With the help from the Kasetsart University through Dr. Surawit Wannakrairoj, the Thai ornamental plant farmers started training in breeding and doing their own breeding lines. New lines using Aglaonema cochinchinensis gave the interesting poinsettia colors while other species gave different results.

Gregorie Hambali in Bogor bred his famous Aglaonema xPride of Sumatra and Aglaonema xDonna Carmen using the Philippine Aglaonema commutatum. The two above mentioned hybrids are the only colored Aglaonema hybrids that can tolerate the low temperatures of the temperate households thus their popularity among the tissue culture companies in USA.

With the exciting new crosses in the market, the Aglaonema is starting to be a big seller and several nurseries world wide are propagating the colorful varieties at the fastest rate possible. Growing plants of the same genetic make-up in a limited area of course will result in new problems like diseases and other challenges.

Curvularia

The first case of Curvularia infection in Aglaonema was observed in Nakhon Chaisi. The Aglaonema plants started stretching the petiole downwards giving the plant a wilted effect. Closer examination shows that the stem and roots starts rotting after the leaves started to contort. 

Curvularia has been observed in Dendrobiums. This microorganism was not reported earlier on orchids until the big shipments of orchids came in from Bangkok around the end of the 80’s. The microorganism results in frog-eye disease and soft rot of Dendrobium stems.

Since the Aglaonemas were growing together with the Dendrobium cutflowers, samples of both Aglaonema and Dendrobiums were taken and they showed the same Curvularia spores under the microscope. More studies should be done on this pathogen as it can spread very fast when humidity is high (rainy season) and can wipe out susceptible varieties (e.g. Aglaonema xPride of Sumatra).

Anthracnose

Aglaonema infected with Anthracnose exhibit concentric brown lines on the leaves. The infection affects Aglaonemas during rainy season. Field-grown Aglaonemas are specially susceptible. Plastic-covered-greenhouse-grown Aglaonemas may get the infection also if water is injected or sprayed on to the plants at high pressure or when the leaves do not dry up after watering.

Practically all varieties are susceptible. Calcium deficiency aggravates the situation.

Spraying the foliage with Benomyl or Carbendazim solves the problem when coupled with separate Calcium nitrate application.

Chlorophyll Destruction

Although Chlorophyll Destruction is not an infective disease, it is a man-inflicted Physiological Disease. 

The young leaves of plants turn paler and paler until the whole leaf is white, pink or yellowish. There is a progressive loss of Chlorophyll on the new leaves. Roots are relatively normal except for the overall color of the plant. The plants get a bleached look. Leaves get thinner (mesophyll collapse) and sometimes are reduced to sword-shaped flags.

The symptoms are very similar to herbicide damage (Round up and 2,4-D) but the main culprit is either Doxytetracycline or Streptomycin antibiotics.

Overzealous nursery operators and hobbyists usually get the syndrome after 2 months of spraying antibiotics. 

Modern Agriculture does not recommend spraying of Antibiotics because it is ineffective and has phytotoxic reaction in plants. The bacteria have similar if not the same metabolic enzymes and physiology as the plants. 

Bacterial infection is a system defect. This means that the grower needs to correct the different cultural inputs to solve the bacterial problem. No amount of antibiotics can kill all the bacteria on the leaves, soil, roots and media.

Some causes of bacterial infections are: damp conditions, mechanical damage, Calcium deficiency, insufficient light, Manganese and Zinc deficiency and extreme growing temperatures.

Lichen

Lichen is an intermarriage of a fungous and an algae. The marriage of the two organisms resulted from need to survive. Although most Lichens are free-living and do not infect plants, this lichen infects Aglaonema xSnow White. The lichen infection was observed first in Thailand, then later in Indonesia and is already in Philippines for the past 10 years.

Wet conditions and high fertilizer feeding supports the infective lichen growth. The lichen spore settles on the leaf and creates a cancer-like lesion with dark green coloration on top. Tissues around the lesion turn yellowish and die off.

It is surprising that it has been observed to infect only Aglaonema x Snow White (a dwarf green and white variety).

Infection is easy to eradicate with Benomyl or Carbendazim spray followed by 5% chlorox with surfactant spray the day after. The plant should be kept dry for most of its growing cycle to prevent re-establishment of Lichen colonies.