Control of Root-Knot Nematode Disease in Balloon Flower
Along with the adjustment of the industrial structure, the balloon flower planting area in our district has been continuously expanding. However, due to years of continuous cropping, the occurrence of root-knot nematode disease has shown a spreading trend, causing balloon flower to lose its commercial value and reducing economic returns.
1 Disease symptoms
After balloon flower is infected by root-knot nematodes, when the disease is mild, the symptoms on the aboveground parts of the plant are not obvious; when the disease is severe, the aboveground parts show poor growth, stunting, yellowing, and wilting, resembling symptoms of nutrient or water deficiency or fusarium wilt. During drought or when evaporation is intense, the plants wilt at noon. After pulling up severely diseased plants, tumor-like root knots can be found on the rhizomes or fibrous roots, generally spherical, the size of mung beans or soybean seeds. When the root knots are cut open and examined under a microscope, many tiny milky-white nematodes can be seen hidden inside. On top of the root knots, slender new roots may grow, which become infected again and form root-knot tumors.
2 Disease occurrence pattern
The root-knot nematode of balloon flower overwinters as eggs and larvae in the soil, on hosts, and on diseased plant residues. It mostly survives at a soil depth of 5-30 cm. The optimum temperature for survival is 25-30°C. When the temperature is above 40°C or below 5°C, it is rarely active. Its activity is inhibited in dry or excessively wet soil. It is mainly spread through diseased soil, diseased seedlings, diseased plant residues, soil-mixed manure, irrigation water, farm tools, and weeds. When conditions are suitable, overwintering eggs hatch into larvae in the root knots. The first-instar larvae remain inside the eggs, while the second-instar larvae emerge from the eggs into the soil, infect young new roots, and stimulate host cells to expand, forming root knots.
3 Control methods
3.1 Agricultural control First, rational crop rotation. In terms of commercial value, balloon flower needs to grow for 2-3 years, so it is easily rotated once every 2-3 years with wheat-summer corn (or summer sorghum). Second, strengthen field management. Thoroughly dispose of diseased plant residues by centralized burning or deep burying or soaking in water to reduce sources of infection. Third, apply fertilizers with caution. Apply organic fertilizers that do not contain diseased plant residues or that are fully decomposed to reduce sources of infection. Fourth, deep winter plowing. Carry out tillage in winter to turn the nematode larvae remaining in the soil up to the surface, using low temperatures to freeze them to death and reduce sources of infection.
3.2 Chemical control First, soil disinfection. When preparing the land, apply 4-6 kg of 3% Miral granular formulation per mu, or 3-4 kg of 5% aldicarb granular formulation, or 3-4 kg of 5% fenamiphos granular formulation mixed with 25 kg of dry fine soil and broadcast evenly, first broadcasting and then plowing. Alternatively, before sowing, apply 450-500 ml of 1.8% Beinong Aifuding emulsifiable concentrate per mu, mix with 20-25 kg of fine sandy soil and broadcast evenly, then deep-plow 10 cm. The control effect is relatively good, reaching over 90%, with no soil pollution and no residual toxicity to balloon flower.
Second, root irrigation. In the early stage of disease occurrence, irrigate the roots with a 1000-fold dilution of 1.8% chlorfenapyr emulsifiable concentrate, once every 10-15 days, which can effectively control the occurrence and damage of root-knot nematode disease.