Common Pests and Diseases of Geraniums
Today, the editor will explain to you about the knowledge of geraniums, such as common pests and diseases of geraniums, as follows:
Geranium pests and diseases mainly include two categories, namely, diseases and insect pests. In daily maintenance, such situations basically occur, and different treatment plans are adopted according to the size of the situation and the degree of impact. Most of them are home gardening plants, so the varieties are mixed. The probability of occurrence of pests and diseases is basically alternating infections! For example, the common hybrid planting of roses and geraniums, the place is limited, it is impossible to achieve exclusive area planting alone.
The common pests of roses will infect geraniums, such as aphids and red spiders. These two are common pests. Aphids are easy to manage, and red spiders are almost incurable for most people. Therefore, for these common pests and diseases in daily life, we should take early prevention and timely treatment for a small number of occurrences.
1. Fungal Leaf Spot Disease of Geraniums
The main fungal leaf spot diseases of geraniums caused by fungi are black spot disease and brown spot disease. Black spot disease mainly occurs on the lower old leaves of the plants, initially small water-soaked spots, gradually expanding into necrotic spots. The lesions have concentric rings and a small amount of black mildew-like substances. In severe cases, the lesions merge, the leaves wrinkle, turn black and die. The leaves affected by brown spot disease initially produce needle-like yellow spots, which gradually develop into brown round spots. The edge of the lesions on the front of the leaves is slightly raised, and the corresponding part on the back of the leaves is slightly concave. The severely affected leaves turn yellow and are easy to fall off, with light black mildew-like substances on both sides.
1.1 Pathogen and Epidemiology: Black spot disease is caused by Alternaria, and brown spot disease is caused by Pseudomonas coccinea. Both pathogens belong to the Deuteromycetes. The disease is more serious under warm and humid conditions.
1.2 Control Methods: Strictly control the frequency and amount of watering, ventilate and remove moisture in time, and pay attention to improving lighting conditions. Remove diseased leaves in time, remove diseased residues and burn them together. Spray 50% carbendazim wettable powder 1000 times, or 75% chlorothalonil wettable powder 800 times, or 70% methyl thiophanate wettable powder 800~1000 times, or 80% mancozeb wettable powder 500 times, or 1:1:100 Bordeaux mixture.
2. Gray Mold Disease of Geraniums
Mainly causes flower withering, leaf spots, and cutting rot. When the flower is affected, the middle small flowers are first infected, and the flowers wither and fall off in advance. When the weather is humid, a gray mold layer appears on the diseased part, and the rotten small flowers are stuck together. Irregular water-soaked brown spots appear on the leaves, which become soft rot and gray mold layer, and later become dry and wrinkled. When the stems and petioles are affected, water-soaked brown spots with unclear edges and rotten spots appear, and rot occurs.
2.1 Pathogen and Epidemiology: Caused by Botrytis cinerea. It occurs more in cool and humid environments. The most important cause of the disease is frequent watering at low temperatures.
2.2 Control Methods: The pot soil used for planting diseased flowers must be replaced or disinfected before use. Remove diseased flowers and leaves in time, pull out severely diseased plants, and destroy them together to avoid spreading. When planting, apply enough base fertilizer, appropriately increase the application of phosphorus and potassium fertilizer, and control the amount of nitrogen fertilizer. Avoid watering on cloudy and rainy days and at night, it is best to water in the morning on sunny days, and ventilate and remove moisture after watering. Do not water too much at a time, and try not to pour water on the leaves. In the early stage of the disease, the pesticides can be selected from 50% procymidone wettable powder 2000 times, or 50% pyrimidine carboxamide wettable powder 1500 times, or 70% methyl thiophanate wettable powder 800~1000 times, or 50% carbendazim wettable powder 1000 times, or 50% nylar wettable powder 1500 times, or 65% metalaxyl wettable powder 1500 times, for foliar spraying. Spray once every two weeks, and continue to spray for 3~4 times. If conditions permit, 10% Green Emperor emulsion 300~500 times or 15% Green Emperor wettable powder 500~700 times can be used.
3. Rust Disease of Geraniums
The geraniums affected by rust disease have red-brown vesicular spots on the leaves, petioles, and stems, and the leaves turn yellow and fall off when the disease is severe.
3.1 Pathogen and Epidemiology: The pathogen is a kind of rust fungus. The spores can survive for 6 months on the diseased parts, and can infect when conditions are suitable.
3.2 Control Methods: Remove diseased leaves and even diseased plants in time when the disease occurs, and burn them thoroughly. In the early stage of the disease, spray 15% triadimefon wettable powder 1000 times, or 40% triadimefon wettable powder 4000 times, or 80% mancozeb wettable powder 500~700 times, or 30% terbuthylazine wettable powder 2000 times, or 20% propiconazole emulsion 500 times, or 25% tebuconazole emulsion 3000 times, or 40% fuberidazole emulsion 9000~10000 times. Spray once every 10~15 days, and continue to spray for 3~4 times.
4. Sclerotinia Stem Rot of Geraniums
This disease mainly occurs at the base of the stems of geraniums. Initially, the lesions are light brown, water-soaked, slightly sunken, and then expand upwards, and the diseased tissue rots. When it is humid, white mildew-like substances appear on the diseased parts. In the later stage, white mildew-like substances in the stems produce black rat feces-like sclerotia.
4.1 Pathogen and Epidemiology: The pathogen of Sclerotinia stem rot of geraniums is Sclerotinia sclerotiorum. The temperature of about 20℃ and relative humidity of more than 85% are conducive to the growth and development of the pathogen. The pathogen overwinters in the diseased tissues and soil in the form of sclerotia. Under suitable conditions, the sclerotia germinate, and the ascospores are spread by wind and rain, or by the growth and spread of hyphae. Heavy and wet soil, excessive application of nitrogen fertilizer, dense planting, low temperature, and high humidity can all aggravate the occurrence of the disease.
4.2 Control Methods: Flower pots should not be placed too densely to improve ventilation and lighting between plants, strengthen fertilizer and water management, apply fully decomposed organic fertilizer, increase the application of phosphorus and potassium fertilizer, and avoid excessive application of nitrogen fertilizer to improve the disease resistance of plants.
Before and in the early stage of the disease, apply wood ash and quicklime, mix them in a ratio of 4:1, and sprinkle them on the soil surface in the middle and lower parts of the plants and the base of the stems. In the early stage of the disease, spray pesticides in time, such as 40% carbendazim-sulfur suspension agent 600~700 times, or 70% methyl thiophanate wettable powder 500~600 times, or 50% mixed sulfur suspension agent 600 times, or 40% sclerotinia fungicide wettable powder 500 times, or 50% benomyl wettable powder 1500 times, or 50% procymidone wettable powder 1000~1500 times.
5. Bacterial Leaf Spot Disease of Geraniums (different from the first fungal leaf spot disease)
Also known as bacterial blight of geraniums, it mainly damages the leaves, and also infects the stems and branches. After the leaves are infected, there are initially water-soaked brown spots, which later expand into dark brown round or irregular spots. In severe cases, the spots become pieces, the leaves necrotize and dry. When the stems and branches are affected, the vascular bundles turn brown or black, the stems and branches turn black and contract, showing dry rot, and the leaves on the stems wither and fall off, and the dead spots are polygonal.
5.1 Pathogen and Epidemiology: This disease is caused by a species of Xanthomonas. Bacteria can spread and spread through the contact of cuttings, the splashing of water droplets, and the migration of insects. Plants that are densely cultivated and overgrown are prone to disease. High temperature and humidity, improper fertilization also contribute to the occurrence of the disease. The lower old leaves of the plant are seriously affected. Different varieties have different resistance to the disease. Big flower geraniums are highly resistant, while shield leaf geraniums are highly susceptible.
5.2 Control Methods
The flower pots can be soaked in 10% bleaching powder solution for 10~30 minutes, and the soaking solution should be prepared and used immediately, or 40% formalin can be diluted with water to prepare a 2% solution, and the flower pots can be soaked for 10 minutes. Remove all diseased leaves and branches, and the plants should not be too dense. Control the temperature and humidity properly. The watering method and time should be reasonable, and do not spray water directly on the plants to avoid the spread of the disease by splashing water droplets. In the early stage of the disease, spray 50% copper sulfate (DT) wettable powder 500 times, which cannot be used with other drugs. Or 60% DTM wettable powder 500 times, or 77% copper sulfate wettable powder 400 times, or 70% chlorothalonil wettable powder 500~600 times, or 72% streptomycin sulfate 4000 times, or neomycin 4000 times, for foliar spraying, and apply the drug once every 7~10 days, and continue to spray for 3~4 times.
6. Crown Gall Disease of Geraniums
Also known as crown gall disease, it mainly occurs at the root and stem of geraniums, and some also occur at the stem and branches. Initially, small tumor-like substances can be seen, which gradually expand and harden, with cracked and rough surface, grayish white to fleshy color, varying in size, and many hairy substances often grow on the surface of the tumor. Diseased plants become stunted, the leaves produced are small and often chlorotic, flowering is less, the flowering period is short, and in severe cases, leaf shedding and branch drying, and even death of the whole plant occur. This disease is caused by Agrobacterium tumefaciens, the pathogen survives on the surface of the tumor and in the soil, and is transmitted by rainwater, irrigation water, and enters through wounds. The root and stem parts of the plant are easily infected. Continuous cropping and wounded root and stem parts are more likely to get sick.
6.1 Control Methods:
When the seedling infection rate is high or diseased plants are found, soak the base of the seedling stems in 1% copper sulfate for 5 minutes, and then soak in 2% lime water for 1 minute. In the early stage of the disease, cut off the diseased tumors with a knife, and then apply lime sulfur mixture or 1:1:100 Bordeaux mixture, 25% thiabendazole 400~500 times, 90% streptomycin 2000~3000 times to the wounds. In addition, injection of penicillin and streptomycin is also very effective.
7. Edema Disease of Geraniums
Edema is a physiological disease, which is more common in hanging series varieties. When the plant absorbs a lot of water and cannot evaporate in time through the leaf surface, such symptoms will appear. Initially, the symptoms appear on the underside of the leaves, showing blisters. When the plant is subjected to environmental stress such as water, light, and pH, the blisters will burst. The symptoms are similar to those caused by spider mite damage. The following operations can be performed during the growth process to effectively control the occurrence of this disease and ensure that the plant does not lack water and dryness, especially when the environmental temperature is relatively high, in January and February, do not overwater the plants, try not to use flower pot trays, ensure sufficient air circulation, maintain relative humidity below 75%, heat and ventilate when the humidity is high; provide shade treatment to avoid sudden strong light; maintain the pH value between 5.6~5.7, and the substrate should not be iron deficient; water in the morning, and regularly supplement calcium nitrate fertilizer.
Insect Pests
1. Black Dot Silver-striped Moth
Larvae: The body length of the last instar larvae is 32mm. The head is brown, with black spots on both cheeks; the body is yellow-green, with 8 light-colored longitudinal stripes on the back, and the anal line is light yellow; there are 3 pairs of black thoracic legs, 2 pairs of abdominal legs, and 1 pair of yellow-green anal legs.
Adults: About 17mm, wing expanse 34mm, black-brown, with brown hair tufts on the back of the posterior chest and the 1st and 3rd abdominal segments. The central part of the forewing has a prominent silver spot and U-shaped silver stripe; the hindwing is light brown, with black-brown outer edge. The eggs are hemispherical, yellow-green, with longitudinal and transverse grids on the surface.
Control Methods
1.1 Use black lights and other methods to trap adult insects during the occurrence period of adult insects.
1.2 Spray 90% imidacloprid water agent 4500 times, or 75% laverone 4000 times, 10% imidacloprid wettable powder 2500 times, 5% chlorpyrifos 3000 times, 5.7% cyhalothrin 3000 times.
2. Whitefly
It has a piercing and sucking mouthpart. The adults and nymphs suck plant juice, causing the leaves to turn yellow, wither, and even the whole plant to die. In addition, due to its strong reproductive ability, fast breeding speed, large population, and clustering damage, it secretes a large amount of honeydew, seriously polluting the leaves and plants. Morphological characteristics: The adult body is about 0.9-1.4mm long, light yellowish white or white, both males and females have wings, and the whole body is covered with white wax powder. The female is larger than the male, and its ovipositor is needle-like. The eggs are oblong, about 0.2-0.25mm long, initially light yellow, then turning blackish brown, with egg stalks, laid on the back of the leaves. The larvae (or nymphs) are elliptical and flat, light yellow or dark green, with uneven wax filaments on the body surface. The pupae are elliptical, about 0.7-0.8mm long, slightly convex in the middle, yellow-brown, with 5-8 pairs of uneven wax filaments on the back.
Control Measures
2.1 Pesticides can be sprayed for control, such as 600-800 times of chrysanthemum louse net, chrysanthemum louse 1+1, acetamiprid, 0.30% (matrine), thiamethoxam, nitenpyram, fenvalerate, cypermethrin, fenpropathrin, or fenpropathrin.
3. Aphids
Plants infested by aphids have various symptoms, such as reduced growth rate, leaf spots, yellowing, poor development, leaf curling, reduced yield, wilting, and death. The extraction of juice by aphids leads to the lack of vitality of the plant, and the saliva of aphids is also toxic to the plant.
Control Measures
Select and use the series products of imidacloprid according to the instructions, which is relatively easy to control.
The above () introduces the experience and knowledge of common pests and diseases of geraniums (figures) for you, hoping to bring you some help after reading this article!