1. Leaf spot
(1) symptom characteristics
The disease mostly occurs in dry or aging leaf tissue, and produces dead spots at the tip or edge of the leaf, accounting for 1/3 ~ 3/4 of the leaf area. Black mildew spots are densely distributed on the front of the diseased spots in the later stage. Conidia germinate at high humidity and 10 ~ 20℃, and invade from stomata, causing diseases.
(2) Prevention and control methods
Careful maintenance, increased application of phosphorus and potassium fertilizer, make plants grow healthily and enhance plant disease resistance. Spray 50% chlorpheniramine wettable powder 1000 times or 75% dyclonine (chlorothalonil) wettable powder, 50% thiophanate-methyl suspension concentrate and 65% thiophanate-methyl wettable powder.
2. Pseudocercospora brown spot disease
(1) symptom characteristics
The disease mainly occurs on leaves, both on the front and back of leaves. At first, it was a brown patch, and then it gradually expanded, forming irregular large spots due to the restriction of veins; In the later stage, the center of the lesion becomes shallow, grayish white or light brown, with brown edges and yellow halo around it. Black mold was scattered on the spot. Pathogens overwinter in hyphae on diseased leaves and fallen leaves. In the next spring, when the temperature and humidity are suitable, conidia are produced and spread through airflow and wind and rain. It can happen in spring and autumn. In high temperature, high humidity and rainy weather, the disease is serious and the leaf lesions are dense, which leads to yellowing and shedding (Figure 14).
Fig. 14 strawberry brown spot disease
1. symptom 2. Spores and conidia
(2) Prevention and control methods
Remove diseased leaves in time and burn them centrally. When the seedlings in seriously ill areas leave the nursery, they should be disinfected by spraying potassium permanganate 1000 times. Branches and leaves should not be too dense, combined with crown shaping, sparse branches and leaves should be thinned to make them ventilated and transparent. Spraying 50% thiophanate-methyl sulfur suspension or 27% copper expensive suspension 800 times, 12% green milk copper emulsifiable concentrate and 20% prochloraz suspension 500 times at the initial stage of the disease.