Seven common disease and pest control methods

Brown spot is a worldwide disease, which often leads to a large number of withered and yellow leaves.

The pathogen of symptomatic brown spot is a kind of fungus, which mainly invades the tip of leaves and distinguishes brown from healthy parts. Later, disease spots will also appear on the edge and middle of the leaves, and usually the lower leaves begin to develop, and then gradually spread to the upper part. In the initial stage, the lesions were of different sizes, round or oval, and the upper and lower ends were quickly yellowed. When the disease spot occurs, it causes the leaf to twist. In the later stage, the diseased part ruptured, and when it was wet, the diseased part was dense with dark brown dots, and gushed out a dirty yellow, followed by a fleshy red conidium pile. When the disease is serious, the disease spot becomes patchy, and the whole leaf turns yellow quickly and falls off ahead of time.

The living habit pathogen overwinters in the diseased leaves in the form of mycelium or conidia, produces conidia in the following year and spreads to new parts with the wind. The old leaf is seriously ill. It is easy to cause wounds when the leaves collide with each other when the plants are planted too densely. Brown spot generally begins to occur in early summer and is serious in high temperature and rainy days. The lower leaves are more susceptible to infection than the upper leaves.

Prevention and treatment methods after the disease was found in horticulture, the diseased leaves should be cut off and the diseased plants should be removed in time to reduce the source of infection. Timely elimination of stagnant water after rain, no partial application of nitrogen fertilizer, strengthen cultivation management, shaping and pruning, so as to make the plant ventilated and transparent.

3000 times of tebuconazole, 6000 times of flusilazole, 3000 times of prochloraz or 70% methyl thiophanate were sprayed. Apply the medicine for the first time after seeing the spot, once in the next 20 days, spray 3 times.

Powdery mildew is a fungal disease, and most plants are important targets. It occurred in Sichuan, Yunnan, Jiangsu, Beijing, Tianjin, Qingdao, Hebei and Shandong, and seriously occurred in Beijing and Chongqing.

After the onset of symptoms, the leaves and tender stems of the plant are often distorted and covered with a layer of white powder, and the powdery mildew layer turns gray in the later stage. These leaves are more purple than normal leaves, infected plants will become short, young leaves twisted, deformed, withered, leaves do not develop, serious flowers can not open normally, leaves withered and yellow, shedding, directly affect the tree potential and ornamental effect.

Regular powdery mildew occurs when mycelium overwinters on diseased buds, diseased leaves and diseased branches. The disease is closely related to the air temperature. The disease can occur at 15 ℃, which starts in March and April and is prevalent from May to July. The disease varies with varieties, and bare-leaf, trailing and multi-flowering varieties are more resistant to disease. The disease is easy to occur when partial application of nitrogen fertilizer and potassium is insufficient. Powdery mildew occurs seriously in the rainy season or under the condition of high relative humidity, and it is easy to occur when planting is too dense or poor ventilation and light transmission.

Control methods Horticulture Control first of all, select disease-resistant varieties. In addition, after cutting off all the branches in winter, spraying 3-degree stone-sulfur mixture to kill the overwintering bacteria, and focus on burning the diseased branches, thoroughly remove the source of the disease. Ventilation and light after the onset of the disease, do not have too high humidity. Control the planting density, strengthen the management, increase the application of phosphorus and potassium fertilizer, control the amount of nitrogen, and improve the disease resistance of the plant.

Spraying 3 to 4 degrees of stone sulfur mixture before sprouting, spraying 80% Dysen zinc 500 times, or 70% methyl topiramate 3000 times or spraying 25% tebuconazole 3000 times, 40% flusilazole 6000 times, 45% imipramine 3000 times, once a week, three times in a row.

Aphids and aphids belong to Homoptera and Aphidoidea, which are major pests in the world and are distributed all over the country. There are more than 300 kinds of hosts, which can transmit at least 55 kinds of viruses.

The morphological characteristics of adult winged parthenogenetic aphids grow 2.1 mm, dark green in spring and autumn and yellow in summer. The body and back are striped, and the ventral tube tail is black. The wingless parthenogenetic aphid is 1.9 mm long, and the body is green to yellow, mostly yellow.

The egg is orange when it is first laid, and then it is painted black and shiny. The nymph is yellowish at first birth, then yellowish green, and blue-gray in spring and autumn.

Life habits can reproduce 30 generations a year, overwintering with eggs in the armpits of weeds or brocade, hibiscus, pomegranate and so on. The fastest breeding season can complete one generation every five days and three generations in half a month. The maximum fecundity of one aphid is 100, which can increase the total number of aphids in a very short time. When the temperature drops after autumn, it will fly back to the brocade belt to mate with aphids from elsewhere and survive the winter.

Harmful characteristics aphids often cause branch and leaf deformation, slow growth stagnation, serious leaves and even death. When plants are damaged by aphids, there are some amino acids in their saliva. After injection into plant tissues, auxin increases or decomposes and decreases, resulting in spots, curling leaves, wrinkles, galls, tumors and other injuries. at the same time, their excreta often induce coal fouling disease. Another major harm of aphids is that they can carry hundreds of plant virus diseases and other diseases, causing serious indirect harm.

The control methods use natural enemies such as ladybugs and lacewings, which can be released in time after a large number of artificial feeding, and aphids and molds can also be artificially cultured and diluted and sprayed. These live potions are already available for sale in some areas.

The above three agents can be diluted to 8 to 1200 times, 20% dichlorophenyl ether and pyrethroid 3000 to 4000 times, 40% methamidophos 1000 times, 40% omethoate 2000 times. Spray once every 5 weeks, three or four times in a row. 40% omethoate 100 times liquid coating stem. The root application of 3% furan granule not only cured the aphids, but also protected the natural enemies.

Brown soft scale, also known as wax scale, Homoptera, Coccidae. Distributed in North China, Northeast, Central China, Sichuan, Shaanxi and other places, and widely distributed in the tropics, subtropics, Europe and the United States, Oceania and many other areas, has become an important pest of garden plants.

The morphological characteristics of the female adult are flat, oval, close to the surface of the plant, and the back colors are light yellow, brown, yellow, brown and so on. The male adult is about 1 mm long. The egg is oval, yellowish, about 0.20 mm long. The nymph is oval, yellowish and thin after secreting wax.

Life habits occur for four or five generations a year, and all plants damaged by scale almost often have adults, eggs and nymphs. The algebra that occurs every year varies from place to place, 2 generations a year in Beijing, 3 generations in Shanghai and 4 generations in Shandong. Scale breeds quickly in a warm and humid environment. Scale overwinters include fertilized females, second instar nymphs or eggs, usually in cracks in the branches. The nymph hatching period is from the first ten days of June to the middle of July, and from the middle to late August to September every year, and the nymph of the first generation is damaged at the end of March and the beginning of April.

The harmful characteristics of nymphs are mostly parasitic at the base of stems and tender leaves. Adults cluster in branches, leaf back, leaf axils and other places, live and reproduce in a shady environment, resulting in poor plant growth, coal fouling disease, fecal matter is many and sticky, each drop can breed mold, it is not easy to remove after accumulation into stains, seriously affecting the ornamental value.

Prevention and cure method horticulture prevention and cure early artificial brushing. In the case of low injured plant rate, small insect population density and small area, spraying detergent water or manually scraping off hard objects such as brushes or bamboo slices can also be effective without damaging the plant soft skin tissue.

Strengthen the daily maintenance and management so as not to make the branches and leaves too dense. Reasonable pruning, combined with winter shaping and pruning, remove pest branches and concentrate on burning.

Spraying 50% monocrotophos 1000 times, 40% omethoate 1000 times, or 50% fenitrothion 800 times, once every week for 4 times in a row. Fenitrothion, omethoate and monocrotophos can be mixed with 2 or 3 kinds of agents. Mixed method: 1 part A plus 1 part B, and then add 2000 parts of water or 1 part of A, B and C plus 3000 parts of water. The effect of mixed use is better than that of single use and is safer for plants.

Biological control "pest control with insects", the use of natural enemies, the protection of red ring lady beetles to control shell insects.