What are the methods for preventing and controlling flower diseases and pests in spring?

Common flower diseases and pests in spring include powdery mildew, rust, black spot, leaf curl, and chlorosis, as well as pests such as longhorn beetles, aphids, scale insects, and scarab beetles.

Prevention and control methods

<1> Powdery mildew: Commonly seen on flowers such as Impatiens, cineraria, dahlia, Chinese rose, and hall crabapple. It mainly occurs on leaves, and also harms tender stems, flowers, and fruits. At the initial stage, multiple faded diseased spots first appear on the leaves, but there is no obvious edge around them, and later the small spots merge into large spots. As the disease develops, the diseased spots become covered with white powder, the leaves shrink, affected flowers cannot bloom normally, and affected fruits stop developing. The occurrence period of this disease can extend from early spring through summer until autumn. Its prevention and control methods include: at the initial stage, promptly remove diseased leaves to prevent spread; when the disease is severe, spray 0.2 to 0.3 degree lime sulfur mixture, or 1000 times 70% thiophanate-methyl solution.

<2> Rust: The flowers and trees most prone to this disease are mostly Rosaceae plants such as Chaenomeles speciosa, including roses and hall crabapple. In addition, peonies and carnations are also susceptible to this disease. It occurs in early spring. Initially, spotted chlorosis appears on young leaves, and later small black dots densely form on them. Initially, yellow round patches appear on young leaves, and grayish-white wool-like matter emerges from the underside. From August to September, yellow-brown powdery matter is produced and spreads with the wind to juniper trees. In early spring of the following year, it again spreads with rainwater and harms the above flowers, so this disease must pass through parasitic damage on these two types of plants to continue, and in plant disease and pest theory it is called a heteroecious disease. When the damage is severe, it causes defoliation; when lighter, it causes diseased spots, affecting appearance and photosynthesis. Its prevention and control methods are: try to avoid planting alternate host plants such as juniper nearby; in early spring, around mid-March, begin spraying 400 times 20% carboxin emulsifiable concentrate or 50% Tuzet wettable powder, then spray once more after about half a month until early April. If spring has little rain or is dry, one spraying may be omitted.

<3> Leaf curl: It mainly occurs on the leaves of Rosaceae plants such as plum and peach. When leaves first unfold in early spring, affected leaves are deformed and swollen, and the color turns red. As the leaves grow, they curl toward the underside, the diseased spots gradually turn white, and powdery matter appears on them. Because the leaves are damaged, tender shoots cannot grow normally and may even die. If leaf damage is severe, they fall off, affecting tree vigor and reducing flower quantity. Its prevention and control methods include: at the initial stage, promptly remove diseased leaves showing early symptoms to reduce the spread of the pathogen; before bud break in early spring, spray 3 to 5 degree lime sulfur mixture to eliminate the pathogen overwintering inside and outside bud scales and on diseased shoots. If this can be done for two or three consecutive years, the disease can be controlled relatively thoroughly. For severely affected potted flowers, increase fertilizer application and strengthen management to restore tree vigor so they can bloom more.

<4> Aphids: Also known as honey insects. Many potted flowers are harmed by aphids, such as peach, Chinese rose, flowering almond, plum blossom, and cherry blossom. Aphids mostly gather on the underside of leaves and feed on leaf sap. Because they reproduce quickly, as early spring temperatures rise, affected leaves cannot unfold normally, new shoots cannot grow, and in severe cases leaves fall off, affecting flowering. When summer temperatures are high, some aphids fly to other plants such as vegetables, and only in early spring do they fly back to trees to lay eggs and overwinter. Its prevention and control methods include: after bud break and before leaf unfolding, spray 1000 times 40% dimethoate emulsifiable concentrate to kill newly hatched young aphids; alternatively, do not spray pesticide first, to protect natural enemies such as ladybugs and let them eliminate aphids, and only consider using pesticide when population imbalance means natural enemies cannot control the aphids. When using this method, it must still be combined with the auxiliary method of manually pinching aphids to death.

<5> Scale insects: Scale insects are the most numerous among pests in terms of types and the number of flowers and trees they harm. Tortoise shell scale, white lipid, round. Mulberry white scale, white, pointed. Oyster shell scale, dark brown, males elongated, females round. Armor scale, dark brown, round, shaped like armor. Plants susceptible to scale insect damage include camellia, pomegranate, oleander, azalea, hibiscus, cherry blossom, plum, peach, crabapple, and Chinese rose. The larvae first feed on sap on leaves, causing chlorosis, and as adults they mostly feed on sap on branches and trunks, severely weakening tree vigor and affecting flowering. Its prevention and control methods include: pinch them to death by hand or scrape them off leaves and branches with a small knife, and during the larval stage spray 1000 times 40% dimethoate emulsifiable concentrate once or twice, with an interval of 7 to 10 days.

<6> Red spider mite: A type of mite. The body is small and almost indistinguishable to the naked eye. They mostly gather in groups and reproduce extremely quickly. Many plants are susceptible, such as Chinese rose, rose, flowering peach, cherry blossom, and azalea. The mites gather on the underside of leaves and feed on sap, first causing chlorosis, and ultimately causing leaf drop and death of new shoots. In severe cases, small trees weaken in growth and may even die. Its prevention and control methods include: at the initial stage, spray 1000 times 40% dimethoate emulsifiable concentrate, or 1000 to 1500 times 40% trichlorfen emulsifiable concentrate; when spraying to kill them, it must be thorough and dense. When summer temperatures are high, the pest reproduces fast and control is often too late, so pesticide should be sprayed early and continuously 3 to 4 times, with an interval of about 7 days, and do not use a single pesticide repeatedly to avoid resistance.

<7> Nematodes: Nematodes harm plant roots, causing abnormal plant development. Affected plants include orchid, carnation, narcissus, and peony. When the pest damage is light, it is often hard to notice. When severe, plants grow poorly and bloom weakly. Because there are many kinds of nematodes in soil and the bodies are small and almost invisible to the naked eye, prevention should be the main approach. For each kilogram of planting soil, add 20 to 30 granules of 3% furadan granules, which slowly release through soil dissolution to eliminate nematodes.

<8> Caterpillars: Including tent caterpillars and boat-shaped caterpillars. They have very mixed feeding habits and harm almost all plants, appearing in outbreaks. Control should be carried out early. Manual capture can mainly be used, and when necessary spray 1000 times 40% dimethoate emulsifiable concentrate.

<9> Carpenter moths: The larvae bore and feed inside branches and trunks, commonly seen on peach, plum, and cherry blossom. In severe cases, they can break off large branches 2 to 3 years old, affecting tree shape. Its prevention and control method is: usually observe carefully. When there are bore holes on branches or trunks and small granular frass is excreted from the bore holes, use an iron wire to dig out the pest from the bore hole, or cut off the branch to kill the pest. The insect itself is reddish-brown, with hairs on the head and each segment of the body, clearly different from the milky white of longhorn beetles. This method is also used to control longhorn beetles. You can also use 150 times 80% dichlorvos emulsifiable concentrate, inject it with a syringe from the frass opening of the insect tunnel, then seal the insect tunnel with wet mud to kill the pest.#p#Pagination title#e#

<10> Scarab beetles or beetles: Omnivorous pests that feed on leaves or flowers. Roses and others are susceptible. Manual capture is the main prevention and control method.

<11> Underground pests: White grubs, that is, scarab larvae, white. Cutworms, green-black. In the soil, they feed on plant roots or root crowns and often cause plant death. The prevention and control method is to promptly dig them out from the holes where they enter the soil.