What are the control methods for goji root rot?

Goji root rot occurs commonly and causes serious damage; plants killed by the disease account for 3%-5% each year, causing great losses to goji production.

According to research by Lu Zhankui and others at the Ningxia Academy of Agriculture and Forestry Sciences, root rot symptoms fall into the following two types:

(1) Root decay type. Roots or the root crown show varying degrees of decay and peeling, the stem vascular bundles turn brown, and in damp conditions a white or pink mold layer grows on the diseased area. It can further be divided into two types: small-leaf type and yellowing type.

① Small-leaf type: leaf emergence in spring is delayed, leaves are small, branches are stunted, flower buds and fruits are thin and small, buds often drop, and in severe cases the whole plant dies.

② Yellowing type: leaves turn yellow, with both wilting and non-wilting phenomena, often with heavy leaf drop, and in severe cases the whole plant dies; some also sprout new leaves after leaf drop, and die after this repeats many times.

(2) Rot type. The cortex of the root crown or branches turns brown or black and rots, and the vascular bundles turn brown. Leaf tips first turn yellow, then gradually scorch and curl upward; when the rotting cortex encircles the trunk, all leaves above the diseased area drop and the trunk dies, while in some cases the leaves suddenly wilt and die but the dead leaves still hang on the tree. This phenomenon mostly occurs in the high-temperature season of July-August.

The various types above often also appear as disease and wilting on half the crown, or disease and wilting of only one branch. In some cases the trunk dies of disease, while new sucker shoots grow from the root crown.

The pathogen overwinters with surviving diseased plants, and can also overwinter and spread with diseased plant residues in the topsoil and soil and with diseased fruit seeds. The pathogen invades plant tissues directly through wounds or by penetrating the tissue cortex, causing disease. Different pathogens and different infection methods have different incubation periods for the disease. At 20°C, Fusarium oxysporum has a disease incubation period of 3 days when the host has wounds, but 19 days when unwounded; Fusarium solani is 5 days and 19 days respectively; Fusarium concolor has a disease incubation period of 5 days when the host has wounds. Waterlogging in the field is an important reason for increased incidence. Soil with poor aeration has an increase of 9%-22.5% compared with well-aerated sandy loam; root damage caused by intertillage operations facilitates pathogen invasion.

The control methods are: improve cultivation conditions, change flat planting to ridge planting with soil mounding, reduce water accumulation in the goji root zone, and avoid root injury during cultivation; drench the roots with a 500-fold dilution of 45% amobam, using 10-15 kg of the solution per plant.