What are the methods for controlling pests and diseases of narcissus?

Narcissus is a common decorative flower on office desks and dining tables. Anyone who has grown narcissus knows that although narcissus is beautiful, it is prone to attack by certain pests and diseases during cultivation. The main pests and diseases of narcissus are: narcissus leaf blight, large brown spot disease, basal bulb rot, and narcissus stem nematode disease, etc. Below we analyze in detail the control methods for these four diseases:

Narcissus pests and diseases and their control methods

(1) Leaf blight

This disease mainly occurs on narcissus leaves, mostly starting from the leaf tip. The lesions are initially faded green yellow spots, expanding inward in a fan shape, with a yellow-green halo around the edges; in the later stage the leaves dry up and black granular bodies appear. The pathogen survives at the upper end of the bulb scales and infects the plant as new leaves emerge. When grown in pots, high room temperature and poor ventilation favor the occurrence and spread of the disease.
Control methods: ① Before planting, remove the dried scales and rinse 2-3 times with a dilute potassium permanganate aqueous solution. ② Pay attention to indoor ventilation and control the room temperature. ③ In the early stage of the disease, spray with 50% zineb 1500x solution, or spray 0.3% equal-amount Bordeaux mixture or 50% thiram 1000x solution; all have good control effects.

(2) Large brown spot disease

This disease begins to occur in late February, with the peak period from April to May. It mainly damages the leaves and stems of narcissus. In the early stage of the disease, yellow, red and brown spots appear; the lesions are mostly in the middle and at the edges of the leaves, spindle-shaped. When the disease starts from the leaf edge, it often causes the leaves to twist. The disease can also start from the leaf tip, which can lead to death of the leaf tip or the entire leaf. The pathogen survives at the top of the bulb scales. It is easily infected with the emergence of new leaves and when narcissus is subjected to early frost; warm and rainy conditions in the later stage favor the occurrence of the disease.

Control methods: In the early stage of the disease, spray with 75% chlorothalonil wettable powder 600-700x solution, spraying twice every 5-7 days, for 8-4 consecutive sprays, which can control the spread of the disease.

(3) Basal bulb rot

This is one of the important diseases of narcissus. It mainly occurs in the underground parts of the plant, and sometimes also in the aboveground stems and leaves. During the growth period of narcissus, the underground parts are infected first, the root system turns brown and becomes water-soaked and rots, and brown spots appear at the basal plate of the bulb and spread rapidly upward.

Control:

(1) Carefully select seed bulbs. Remove diseased bulbs, or peel off some of the diseased scales and burn them.

(2) Avoid causing wounds. This reduces the chance of pathogen infection. Dug bulbs need to be dried quickly and stored in a dry, ventilated, cool place.

(3) Chemical control. Before planting, soak the bulbs in 50% benomyl 500x solution for 15-30 minutes, or soak the bulbs in formalin 120x solution for 3.5 hours. According to experiments, the control effect after such treatment can reach 75.8%. When the disease has already occurred, benomyl or carbendazim 800x solution can also be used to drench the root area of the plant in time.

(4) Stem nematode disease

The pathogen of this disease is the sweet potato stem nematode. Besides damaging narcissus, it also damages tulips, gladiolus, campanula, primroses, etc. It mainly damages the bulbs, and can also damage the leaves. On the cross-section of infected bulbs there are 1 to several dark rings, and there are many milky white nematodes in the diseased bulb tissue. After the leaves are infected, light yellow blister-like spots appear, and they become deformed and twisted.

Control:

(1) Strengthen quarantine. Stem nematodes can often spread over long distances with narcissus bulbs. Therefore, strict inspection is required when introducing seeds to prevent the disease from being spread out. When retaining seeds, disease-free bulbs should be selected as propagation material.

(2) Soil treatment. Diseased plants and residues should be removed and destroyed in time. Carry out rotation with non-host plants, and disinfect the soil. For soil disinfection, aldicarb can be used at 1.2-5.6 grams per sq m, mixed evenly with an appropriate amount of fine soil and applied in the sowing furrow or planting hole; or try 80% dazomet wettable powder 500x solution, combined with drenching with 70% fenaminosulf (dazomet, dishuang) wettable powder 500x solution.

(3) Bulb treatment. Diseased bulbs can be soaked in hot water at 50-52°C for 5-10 minutes, or in warm water at 45-46°C for 10-15 minutes, which can kill the nematodes in each bulb.