Control Methods for Several Diseases of Phalaenopsis

Anthracnose is severe under high temperature and high humidity, forming brown-black round spots that gradually expand outward. Spray evenly with Previcur 800 times solution, once every 5 days, for 2 to 3 consecutive sprays, to bring the disease under control.

Soft rot symptoms are rot at the leaf base, rot of the pseudobulb, with a musty bacterial odor. Control method: spray agricultural streptomycin sulfate 4000 to 5000 times solution at the early stage of disease, once every 7 days, for a total of 2 to 3 sprays.

Sclerotinia disease symptoms first appear at the leaf base, with light brown, water-soaked lesions that rot and can spread to the whole leaf. Later, black round or nearly round small sclerotia form under the epidermis. Control method: treat diseased plants with 50% carbendazim wettable powder 1500 times solution.

Slugs and snails both prefer tender parts with high water content, causing plants to form irregular notches and holes, and leaving white mucus trails where they have crawled. Control method: during their larval stage, evenly scatter 2 bags of Mita per greenhouse, with excellent results and a trap-kill rate above 98%. Or choose 6% metaldehyde granule 500 g, mix with 15 kg of dry sand and evenly scatter on the bed surface. Or use 10 to 20 kg of quicklime per greenhouse and scatter it evenly.

Red spider mite control method: spray with 20% dicofol 800 times solution, once every 5 days, for 2 to 3 consecutive sprays, with good results; if combined with Nissorun 1500 times solution, the effect is even better; Comite 1000 times solution also works well; or spray with 25% Bieleba wettable powder 1000 to 2000 times solution. During the pest outbreak period, spray evenly with 20% fenpropathrin emulsifiable concentrate 2000 to 3000 times solution, all of which can control it.

For scale insects, spray with omethoate, phoxim (or high-penetration phoxim), 1605 emulsifiable concentrate, or Nongbeile 800 to 1000 times solution; note that applying the pesticide at the early larval stage gives the best results.

Root diseases

(1) A large number of roots grow above the potting medium. Cause: improper planting method.

(2) Roots grow out of the pot. Cause: no repotting.

(3) Roots grow upward, even beyond the pot rim. Cause: too much watering, potting medium too dense.

(4) Roots die off, with more in the upper layer than the lower layer, and stems and leaves shrink and wilt. Cause: excessive fertilisation or high salt content in the water causing saline-alkali damage.