Precautions for Soilless Cultivation of Flowers and the Trend of Pest and Disease Occurrence in July and Their Control

According to surveys conducted at flower production bases and landscaping sites in Lunjiao, Beijiao, Chencun and Daliang, flower pests and diseases in July occurred at moderate levels, with locally heavy outbreaks. The main ones include: anthracnose, powdery mildew, viral disease, soft rot, whitefly, leaf miner, sugarcane stem borer (Opogona sacchari), and thrips. In addition, leaf spot, fusarium wilt, powdery mildew, nematode disease, aphids, red spider mites, curved-stripe purple hairstreak butterfly (Arhopala bazalus), and tobacco cutworm occurred to varying degrees.

I. Trends of Flower Pest and Disease Occurrence

Anthracnose: expected to occur at moderate levels, locally heavy, damaging shade plants such as orchids, cockscomb (Celosia) and banana shrub (Michelia figo);

Powdery mildew: expected to occur at moderate levels, locally heavy, damaging sun-loving plants such as orange jasmine (Murraya paniculata) and chrysanthemum;

Viral disease: expected to occur at moderate levels, locally heavy, damaging shade plants such as orchids and peace lily (Spathiphyllum);

Soft rot: expected to occur at moderate levels, damaging shade plants such as orchids and peace lily;

Whitefly: expected to occur at moderate levels, locally heavy, damaging shade plants such as African daisy (Gerbera) and cockscomb;

Leaf miner: expected to occur at moderate levels, locally heavy, damaging plants such as potted kumquat;

Sugarcane stem borer (Opogona sacchari): expected to occur at moderate levels, damaging plants such as money tree (Pachira aquatica) and Brazilwood (Dracaena fragrans);

Thrips: expected to occur at moderate levels, damaging plants such as orchids and banyan trees.

II. Basis

1. Pathogen base

According to the survey: the average diseased leaf rate of anthracnose was 25.8%; the average diseased leaf rate of powdery mildew was 24.7%; the average diseased leaf rate of viral disease was 17.5%; the average diseased leaf rate of soft rot was 6.3%; the number of whiteflies was 224 per 100 plants; the number of leaf miners was 136 per 100 plants; the number of sugarcane stem borers was 54 per 100 plants; the number of thrips was 207 per 100 plants.

2. Varieties and cultivation

Overcrowded planting, excessive watering, poor ventilation, high temperatures in shade houses, and lack of air circulation are the breeding grounds for diseases of shade plants.

3. Weather conditions

In June, average rainfall was high, and temperatures were on par with previous years. According to the meteorological observatory forecast, July will be affected by tropical disturbances, with heavy rain to rainstorms, which is conducive to the occurrence of pests and diseases.

III. Recommendations for Flower Pest and Disease Control

Promptly remove diseased plants and leaves and destroy them in a centralized manner, manage fertilizer and water rationally, and reduce the spread of pathogens. Pay attention to ventilation in greenhouses, control temperature and humidity inside, and suppress the occurrence and spread of diseases. Chemical control of flower pests and diseases is as follows:

1. Control of anthracnose: 70% thiophanate-methyl wettable powder (Topsin-M) 1000-1500 solution; 65% zineb wettable powder 600 solution spray can be used, spraying again after 7-10 days. For anthracnose occurring on other flowers, the control method is the same.

2. Control of powdery mildew: 50% thiram wettable powder 500-800 times solution spray can be used, with an interval of 7 days, for 2-3 consecutive applications; after onset, 70% thiophanate-methyl wettable powder (Topsin-M) 1500 times, as well as Tilt (propiconazole) 800 times, etc. can be sprayed.

3. Control of viral disease: enhance plant resistance; on the basis of eliminating piercing-sucking insects (aphids, scale insects), spray 8% ningnanmycin aqueous solution (Junkeduke) on plants in the early stage of disease.

4. Control of soft rot: from the early stage of disease, spray 72% agricultural streptomycin sulfate soluble powder 3000-4000 times solution; 14% copper ammonia complex aqueous solution 350 times; 30% copper succinate-glutarate wettable powder 500-600 times; 4000 IU/microliter Bacillus thuringiensis suspension concentrate 500 times, spraying once every 7-10 days, for 2-3 consecutive applications.

5. Control of whitefly: 25% thiamethoxam water-dispersible granules 16 g/mu; 1.8% abamectin emulsifiable concentrate 1000 times solution; 3% acetamiprid emulsifiable concentrate 80 mL/mu can be used, applied at the beginning of the peak period of tobacco whitefly.

6. Control of leaf miner: 25 g/L deltamethrin emulsifiable concentrate (Decis); 40% isocarbophos emulsifiable concentrate 800-1000 times; 18% dimehypo aqueous solution 400 times can be used; it is best to spray in the evening (because adults mostly mate and lay eggs at night).

7. Control of sugarcane stem borer (Opogona sacchari): 20% fenpropathrin emulsifiable concentrate 1500-2000 times solution can be used to brush tree trunks, drench tree trunks, and spray, once every 7-10 days, and later gradually extended to once a month; it can also be injected directly into the affected parts with a syringe.

8. Control of thrips: 40% dimethoate emulsifiable concentrate 800-1000 times; fipronil 2500 times solution; 30% acephate emulsifiable concentrate 1000 times solution; 98% cartap soluble powder (Padan) 1000 times solution; 2.5% rotenone emulsifiable concentrate 300-500 times solution; 45% malathion emulsifiable concentrate 3000-4000 times solution spray can be used.