Rose Disease and Pest Identification
Today's sharing of small experiences: topics about roses, identification of rose diseases and pests, let's learn about it together.
Roses are famous for being "medicine jars," but many flower enthusiasts don't know how to identify rose diseases and pests. This article summarizes some common rose disease and pest identification images along with corresponding control methods, which is very helpful for rose lovers!
1. Rose Powdery Mildew: Rose powdery mildew is a fungal disease that affects roses and other flowering plants in the Rosaceae family. The initial infection occurs in mid-to-late May, and it spreads in June and July. After infection, a white powdery substance appears on the leaves and young shoots. In severe cases, the leaves turn yellow and fall off, severely affecting plant growth and flowering.
Medication: Alternate the use of 500-800 times the concentration of mancozeb, chlorothalonil, carbendazim, and thiophanate-methyl during the spring growing period. During the outbreak period, spraying 70% thiophanate-methyl at a concentration of 1000 to 1500 times has a good control effect. After spraying, the white powdery layer on the affected parts turns dark gray, dries up, and disappears. The peak periods of the disease are during the plum rain and the autumn rain. In hot and humid summers, the disease is also very severe, and the interval for application should be shortened during this period. Spraying should be done between 8 am to 10 am and 4 pm to 7 pm on sunny, windless days. Note: Prevention is more effective than treatment, so it's best to spray the fungicides every 7-15 days.
2. Rose and Rose Black Spot (Black Star Disease): This disease is a fungal disease. The pathogen overwinters on diseased residues and spreads through rain or sprinkler water splashes or by insects. The optimal temperature for the disease to occur is around 26 degrees Celsius. In rainy seasons, the host plants are severely affected, especially newly transplanted or weakened plants. In Beijing, the disease occurs in mid-May and peaks from July to September. There are two peaks of the disease in the Yangtze River Valley, from May to June and from August to September.
Regularly clean up fallen leaves, remove diseased leaves to reduce the source of infection, prune heavily for severely affected plants in winter, remove overwintering pathogens from the stems, avoid placing potted plants too close together or directly on the ground to prevent excessive soil moisture, and place them on tiered plant stands. Improve watering methods and time, pour water from the edge of the pot, and avoid overhead watering. Do not water at night to prevent leaves from staying wet and becoming prone to infection.
Medication: DuPont Fuxing at a concentration of 1000 times, alternate or mix with mancozeb every 7 days, spray both sides of the leaves, and burn the diseased leaves.
3. Rose Aphids: Aphids cause direct and indirect damage. Direct damage includes absorbing nutrients from the young shoots, causing leaf and bud deformities and affecting photosynthesis. Indirect damage includes spreading bacteria and viruses through their mouthparts, increasing the chances of various diseases.
Aphid control is very simple, spray the plant surface with 800-1000 times the concentration of imidacloprid every 7 days, 2-3 times.
4. Rose Spider Mites (Tetranychidae): Spider mites are a common pest in flower cultivation. These tiny creatures are less than 1 millimeter in size, round or oval, and orange or reddish-brown. Due to their small size, they are not easily detected, and by the time their damage is noticed, the plants are often already severely affected. They pierce the leaves to suck sap, destroying the chlorophyll and causing grayish-yellow spots or patches on the leaves, which turn yellow and may fall off. Spider mites reproduce rapidly, with a generation time of about 5 days. They thrive in hot and dry conditions, reproducing rapidly and causing severe damage in such climates.
Medication: Use Ecarzine or Jinmianzhi at a concentration of 1000 times, spray both sides of the leaves and branches alternately twice to easily control the problem.
5. Rose Downy Mildew & Blight: These two diseases usually occur together. They can occur at any stage from seedlings to harvest, with the mature plants being more severely affected. They mainly affect the leaves, developing from the base to the upper leaves. Initially, light yellow round to angular spots form on the leaves, which can easily lead to angular leaf spot. When the air is humid, a downy mildew layer can develop on the underside of the leaves, sometimes spreading to the upper surface. In the later stages, the spots die and become brown, and in severe cases, all outer leaves turn yellow and die, similar to wilt.
Routes of transmission and conditions for disease occurrence: The pathogen overwinters in the form of mycelium in seeds or on winter crops and can also overwinter in the form of oospores in diseased residues. It is mainly spread through air, watering, agricultural activities, and insects. The optimal temperature for spore germination is 6-10°C, and the optimal temperature for infection is 15-17°C. Low temperatures and high humidity favor disease development. Overcrowded planting and severe disease can cause mass death with a very high mortality rate.
Treatment methods: 1. Move the roses to a well-ventilated, dry, and sunny area. 2. Remove all diseased leaves and destroy them (important). 3. Alternate or mix the use of Yikuaijing 1000 times liquid (T-J) 1000 times liquid and Yin Fala (Fenarimol) 1000 times liquid every 7 days, for 3 consecutive times.
6. Thrips: Thrips are insects that feed on plant sap and belong to the Thysanoptera order. Larvae are white, yellow, or orange, while adults are brown or black. Feeding can cause damage to leaves and flowers.
Harm: Thrips feed on the sap of young plant tissues (shoots, leaves, flowers, fruits, etc.), causing the young leaves and shoots to harden, curl, and wither, and the plant to grow slowly.
Note: Thrips are jumpers and are active at night, making them difficult to detect. The presence of the disease can only be inferred from the shape of the young leaves.
Treatment: Spray the leaves and backs with 800-1000 times the concentration of imidacloprid or acetamiprid 2-3 times. Additionally, due to the smooth surface of rose leaves, the adherence of water or fertilizer is poor, so organic silicon can be added as an adhesive when spraying or applying foliar fertilizer.
The above introduction to rose disease and pest identification (images) is for reference and suggestion only!