How to prevent and control pests and diseases in home-grown Dracaena fragrans

Dracaena fragrans is a foliage plant of the genus Dracaena, native to Guinea and widely distributed in the tropical regions of Asia and Africa. It was introduced to Guangzhou in the 1980s in China and became popular in Beijing after the 1990s. Just as more and more Dracaena fragrans plants were entering the homes of ordinary Chinese people, several pests and diseases that severely harm Dracaena fragrans were also brought into China.

1. Scania moth (Opogona sacchari) The Scania moth mainly bores into the fleshy cortex of Dracaena fragrans as larvae. When damage is light, tunnels appear and a small amount of frass is expelled; when damage is severe, the fleshy part beneath the epidermis is entirely eaten out and replaced with frass. Pressing the epidermis with the hand gives a soft feeling, and peeling back the epidermis for inspection reveals it is already full of frass. The adult Scania moth specifically chooses wounds on Dracaena fragrans to lay eggs, so any trunk with wounds suffers more severe damage. In particular, the saw cuts on the top of the trunk, if not tightly sealed with wax or sealed with white wax, suffer heavier damage. In Beijing, the Scania moth has the habit of burrowing down into the soil to overwinter. At present, the Scania moth has caused serious losses in flower production, with loss rates for Dracaena fragrans reaching as high as 50%, and at some bases it can even wipe out the entire crop of Dracaena fragrans. For Dracaena fragrans kept in homes, even if there are only one or two pots, Scania moth infestations can still occur.

2. Stem rot Caused by Thielaviopsis basicola. Symptoms mostly appear on the stem, forming irregular black lesions on the phloem, with a grayish-white or black mold layer on the lesions. In severe cases the phloem peels off completely and black rot develops, the affected wood becomes water-soaked and slightly brown, and after the pathogen invades the xylem it rapidly spreads upward and downward, causing decay, with large amounts of black mold forming at cut surfaces or wounds. Symptoms can also occur on leaves, mostly starting from leaf margins or wounds, initially as small brown spots, which in humid conditions rapidly expand into irregular long blackish-brown lesions with water-soaked edges, and in severe cases cause the leaves to wither and die. At present, stem rot has caused great losses in production. It often occurs together with the Scania moth, and stems that have been bored by insects are often more prone to the disease.

3. Bark beetle There have been reports abroad of Dracaena fragrans being severely harmed by a type of bark beetle. In 1997, a bark beetle was found harming Dracaena fragrans in Guangdong Province, China, and was identified as Xyleborus perforans. The damage symptoms are basically similar to those of the Scania moth, but the insect body is smaller, the frass is slightly finer, and it usually occurs together with the Scania moth. 4. Home control methods First, attention should be paid to prevention. When purchasing Dracaena fragrans, be sure to select carefully and choose pest-free and disease-free plants. During cultivation, inspect frequently to detect pest problems early. Once damage is found, carry out control promptly. 1. Clean up the affected parts Once pests or diseases are found, clean up first. Remove frass, crush larvae promptly when found, and remove the parts that have discolored or died after being affected. 2. Summer protection measures Summer is the peak period for Scania moth occurrence, so extra attention should be paid. Insecticides can be sprayed for protection; 20% fenpropathrin-fenvalerate emulsifiable concentrate at 2000 times dilution or 20% fenvalerate emulsifiable concentrate at 2500 times dilution gives better results. Adult Scania moths are nocturnal, so in combination with household mosquito fumigation, place the Dracaena fragrans near a mosquito repellent device to repel and kill the adults that emerge at night to lay eggs.