Detailed Explanation of Common Pests and Diseases of Gerbera and Their Control Methods
Gerbera is a perennial evergreen herbaceous plant with fleshy roots, suitable for environments with warm winters and cool summers, good air circulation, and ample sunlight. So what pests and diseases can appear when cultivating gerbera? And how should they be controlled?
Stem Rot
1. Symptoms and Damage
Leaves show dehydration and wilting, gradually turning purplish-brown and dying. When the root crown is parted, the stem is found to be black, with blocked vascular bundles and vessels, while the root system remains normal. This is a soil-borne disease caused by Fusarium, mainly invading through plant wounds, and once it occurs it is difficult to cure completely.
2. Disease Characteristics
The pathogen overwinters in the soil, and chlamydospores survive for many years. It spreads through water flow and invades through wounds. Rainy weather, heavy watering, and waterlogged soil are conducive to the occurrence of this disease. In protected cultivation it occurs from April to August, and in greenhouses it occurs year-round.
3. Control Methods
3.1 Disease Prevention through Cultivation Techniques
Keep soil moisture moderate; do not let it alternate between dry and wet. Adopt a cultivation method of 6 ridges with 1 deep furrow, or dig deep furrows around the greenhouse (in areas with a high groundwater table). Drain promptly after rain, and avoid excessively damaging roots during intertillage and other farming operations.
3.2 Chemical Control
75% Dexon at 3-4 kg per mu can be applied with irrigation water to flush into the root zone for prevention. Use 50% Root Rot Remedy at 800 times dilution plus NEB root-promoting agent for drenching, at 5 d intervals, for 2-3 consecutive applications.
Gray Mold
1. Symptoms and Damage
When the disease is severe, leaves dry up and die. Lesions mostly occur at the leaf margins, appearing as water-soaked, brown small spots, which after expansion become semicircular or irregular brown lesions. In the later stage of the disease, lesions turn yellowish-brown with purplish-brown margins and inconspicuous concentric rings. On petals, the disease appears as brown necrotic spots, elongated or irregular in shape. Under high humidity, a gray mold layer forms on the necrotic petals.
2. Disease Characteristics
The pathogen overwinters in diseased plants or in the soil, and sclerotia survive for many years. The pathogen spreads through airflow and water droplet splash. High humidity (above 90%) and rising temperatures on sunny days after several consecutive rainy days (nighttime temperature of 15-20°C) can cause disease outbreaks. Abundant diseased residual flowers and leaves, or faded flowers falling on leaves, will aggravate the disease. Using water spraying to control spider mites often aggravates the disease.
3. Control Methods
(1) Disease prevention through cultivation techniques: promptly remove diseased leaves, diseased flowers, or faded flowers; if a gray mold layer has formed, the flowers must be bagged before picking. The method of spraying water to control spider mites is absolutely inadvisable. After consecutive cloudy days, the greenhouse must be ventilated on sunny days to lower temperature and dehumidify (reduce to below 80%), and outdoors, drainage must be prompt after rain.
(2) Chemical control: Pyrimethanil 30% water-dispersible granules can be used, with each 20 g bag diluted in 15-25 kg of water, at 5-7 d intervals; or 18% Bao Zhi Da at 20 ml diluted in 15-30 kg of water for control.
Mites
1. Symptoms and Damage
Mainly including tarsonemid mites and carmine spider mites, which reproduce quickly and are difficult to control.
2. Control Methods
(1) Disease prevention through cultivation techniques: ① Promptly clean up dead leaves and residual branches to reduce pest sources; ② Plant pest-free seedlings.
(2) Chemical control: 2% Abamectin at 1000 times dilution, 40% Dicofol at 1000 times dilution, 20% Manke emulsifiable concentrate at 1000-2000 times dilution, 15% Fenpyroximate emulsifiable concentrate at 1500-2000 times dilution, etc., can be used alternately.
Aphids
1. Symptoms and Damage
Adults and nymphs usually gather on the undersides of leaves and on new leaves and young flower buds to pierce and suck sap, causing the affected leaf surface to lose its luster and curl. Affected flower buds are mostly deformed and unable to bloom normally. Affected plants show slow growth and may even wilt and die.
2. Control Methods
(1) Disease prevention through cultivation techniques: Keep the cultivation site and surrounding environment clean to reduce pest sources; plant pest-free seedlings; use insect traps for trapping and killing.
(2) Chemical control: Spray insecticides during the damage period, once every 5-7 d, for 3-4 consecutive times. There are many insecticides for killing aphids, mainly including 10% Imidacloprid wettable powder at 3000-4000 times dilution, 50% Menazon emulsifiable concentrate at 1000-1500 times dilution, 50% Pirimicarb wettable powder at 1500-2500 times dilution, etc.
Thrips
1. Symptoms and Damage
The insects are relatively small, dark brown, slender, and highly active; on damaged flowers they can be observed by tapping with the hand. Damage symptoms include leaves becoming slender and hardened, leaf margins curling inward, and many yellowish-white small spots or elongated streaks appearing on petals.
2. Control Methods
(1) Disease prevention through cultivation techniques: Eliminate overwintering pest sources. Remove weeds, dead branches and fallen leaves, in combination with the control of other pests; blue sticky boards or other trapping devices can be used;
(2) Chemical control: 23% Phoxim-Fenpropathrin emulsifiable concentrate at 1500 times dilution mixed with 10% Imidacloprid at 1000 times dilution, or 10% Nitenpyram at 1000 times dilution can be used for control.
Leafminers
1. Symptoms and Damage
Adults are relatively small, resembling flies, and lay eggs beneath the epidermis on the upper leaf surface. After hatching, the larvae feed on mesophyll cells within the leaf tissue, producing white winding tunnels that are easily noticed. However, their occurrence and damage are very rapid, so close observation and timely control are necessary.
2. Control Methods
(1) Disease prevention through cultivation techniques: Remove field weeds, damaged old leaves, dead branches and fallen leaves; use yellow plastic boards coated with sticky oil to trap and kill adults; install insect-proof nets on greenhouse vents.
(2) Chemical control: 75% Qianke wettable powder at 1500 times dilution, 40% Omethoate emulsifiable concentrate at 1000 times dilution, 20% Fenvalerate emulsifiable concentrate at 2000-4000 times dilution, and other agents can be used alternately for control.
Pests and Diseases of Gerbera and Their Control
Diseases of Gerbera and Their Control
Leaf Spot Disease
Leaf spot disease is a bacterial disease. It is generally caused by pathogens spread through rain and insects. When leaf spot disease occurs, diseased leaves should be promptly removed, and a solution of Thiophanate-methyl wettable powder should be sprayed for treatment.
Mosaic Disease
Gerbera can also suffer from mosaic disease. Mosaic disease causes the leaves of gerbera to fade in color, become deformed, develop patches, and affects flowering or causes plant death. When mosaic disease occurs, pesticides should be sprayed promptly for treatment.
Powdery Mildew
When powdery mildew breaks out on gerbera, it mainly damages the leaves, causing white lesions that gradually expand. Powdery mildew on gerbera is mostly caused by pathogens, and outbreaks are likely when temperatures are high and ventilation is poor. When powdery mildew occurs, the growing environment should be promptly improved and pesticides sprayed, such as 70% Thiophanate-methyl at 1500 times dilution.
Leaf Blight
Leaf blight is also a common disease of gerbera, and it also causes lesions on the leaves. Leaf blight is generally caused by environmental factors, such as insufficient light or poor drainage. When leaf blight occurs, Carbendazim can be used for spraying.
Gray Mold
Gray mold is also caused by pathogens and is relatively harmful, occurring easily under high humidity. Humidity control is key to prevention and control; ventilation can be strengthened, and in the early stage of the disease, Thiophanate-methyl solution should be used for control.
In addition, gerbera can also suffer from root rot, viral diseases, sclerotium disease, phytophthora blight, etc. Treatment should be carried out according to the disease situation.
Pests of Gerbera and Their Control
Whiteflies
Whiteflies are a common pest of gerbera. When pests are found, the growing environment of gerbera should be promptly cleaned up, and appropriate pesticides should be selected and applied correctly to avoid poor control results due to pesticide resistance.
Thrips
Thrips are also a common pest of gerbera. When thrips are found, fumigation with pesticides is a good method. Dichlorvos or Imidacloprid can be used for spraying and killing.
Cabbage Caterpillars
The damage of cabbage caterpillars is mainly divided into damage by larvae and older larvae. Pests should be sprayed promptly, with multiple sprayings, to prevent further spread of the damage.
Control of Gerbera Leaf Spot Disease
When gerbera is cultivated in protected facilities year after year, the warm, humid environment with poor airflow easily leads to the occurrence of pests and diseases. Among them, one of the most common diseases is gerbera leaf spot disease, which is a disease caused by fungi.
Symptoms: Small purplish-brown spots appear on the leaves, gradually expanding into large spots with concentric rings (2 mm to 5 mm in diameter). In the later stage, the flower center rots, with sparse grayish-brown dusty fungal threads on the surface.
Disease pattern: Generally, the lower leaves are affected first. Excessive nitrogen fertilizer application easily triggers the disease. Heavy clay soil and poor drainage are also important conditions that induce the disease.
Control methods:
(1) Soil treatment: Chloropicrin fumigation can be used to effectively kill pathogenic bacteria and reduce the accumulation of pathogen sources in the substrate.
(2) Regulate temperature and humidity: The optimal temperature for gerbera growth is 20°C to 25°C, maintained above 10°C at night. Under conditions of low temperature and low humidity, the disease is less likely to occur.
(3) Spray fungicides once every 7 to 10 days, such as 75% Chlorothalonil at 500 times dilution, 50% Captan at 500 times dilution, 70% Thiophanate-methyl at 1000 times dilution, with obvious control effects. (Gao Shangshi) .