How to prevent and control infectious gummosis in peach trees

It is a disease caused by a fungus of the Ascomycota subphylum. It mainly harms branches and trunks. When it occurs on 1-year-old young shoots, small protrusions first appear centered on the lenticel layer, later forming tumor-like protrusions 1 to 4 mm in diameter, and no gum flows that year. By early April of the following year, the tumor skin cracks, exuding resin, initially colorless, semi-transparent, thin and sticky soft gum, which soon turns tea-brown, hardens in texture into a crystalline form, and swells into a colloid after absorbing water. The branch surface becomes rough and black, and gradually sinks centered on the tumor, forming circular lesions 4 to 10 mm in diameter, scattered with small black dots. After perennial branches and trunks are damaged, 1 to 2 cm blister-like swellings appear, and the pathogen harms within the epidermis of the branches and trunks, reaching as deep as the xylem.

The damaged areas turn brown and necrotic. When there are many lesions on the branches and trunks, a large amount of gum flows, causing the branches and trunks to die and the peach tree to decline prematurely. The pathogen overwinters within the damaged branches, and conidia are spread by rain and wind. On rainy days, a large amount of pathogen overflows from the diseased parts, flows down along the branches or splashes onto new shoots, invading through lenticels and wounds, becoming the main source of primary infection for new shoots. The activity of latent pathogens in the branches and trunks is related to temperature. When the temperature is around 14°C, gum exudes from the diseased parts, and as the temperature rises, the number of gumming points on the tree increases, and the disease gradually becomes more severe. There are two peak periods of disease occurrence in 1 year, respectively from late April to late June and from early August to mid-September, and gumming stops after winter begins. The pathogen can lurk in the cortical tissue and xylem of the damaged branches, producing pycnidia and conidia in the dead cortex, becoming a source of infection. The most favorable time for pathogen invasion is during the gradual lignification of branch cortical cells and after lenticel formation. Prevention and control should be carried out during the vigorous growth period of new shoots (when lenticels form), and spraying for protection gives the best effect.