Occurrence and Integrated Control Methods of Gummosis in Goji Berry

Brown lesions appeared on the branches and trunks after 15 d, along with a grayish-white mold layer, while no disease developed from the other inoculated fungi. This result is consistent with the findings of the Ningxia Academy of Agricultural Sciences. Based on the field symptom characteristics and isolation results, it is considered that Clonostachys is the pathogenic fungus causing gummosis, while Alternaria and Fusarium are saprophytic fungi of secondary infection.

3 Disease occurrence patterns

3.1 Overwintering of the pathogen and transmission routes

In November, diseased goji branches and trunks with lesions were placed on the field surface and in soil at 20 m-30 cm underground respectively, then retrieved in April of the following year for isolation and culture. The results showed that the goji gummosis pathogen can overwinter with diseased residues in soil at 20-30 cm, with a survival rate of 20%-30%, indicating that this fungus can overwinter both on diseased plants in the field and with diseased plant residues in the soil, becoming the most important source of primary infection.

3.2 Relationship between soil and disease occurrence

Generally, the disease incidence is lower when planted in sandy loam soil than in saline-alkali land. According to surveys, the incidence of goji in sandy loam soil was only 3.2%, while in saline-alkali land the incidence reached 37.5%, and especially in newly reclaimed saline-alkali land, the incidence could reach as high as 73.8%.

3.3 Relationship between climatic conditions and disease occurrence

Generally, the disease is more severe in spring and autumn, which is related to the climatic conditions of the northwest region. In spring, when the temperature is between 15-25°C, it is unfavorable for pathogen growth, and the disease incidence is relatively low. In autumn, when goji enters the fruit ripening stage, the temperature is 22-25°C, and rainfall is greater than in spring and summer, resulting in a relatively high disease incidence. Therefore, abundant rain and suitable temperature are the main factors affecting disease occurrence.

3.4 Relationship between other pests and diseases and disease occurrence

According to surveys, trees with high population densities of goji gall mites, aphids and scale insects had weaker tree vigor and more wounds on the tree body, and gummosis occurred severely, often mixed with other diseases. At the same time, it was found in the field that goji trees with severe powdery mildew and anthracnose had severe gummosis in the middle and late growth stages. Therefore, the occurrence of other pests and diseases leads to weakened tree vigor and a greatly reduced disease resistance, which is also a major predisposing factor for gummosis.

4 Integrated control techniques

4.1 Selecting suitable orchard sites

Goji is tolerant to salinity and alkalinity, but when salinity and alkalinity are too high, or the soil is heavily clayey with poor drainage and a high groundwater table, the disease incidence is high, so such soils are not suitable for planting. Generally, sandy loam soil with a salt content below 0.33% is preferable.

4.2 Cultivating strong seedlings and enhancing tree vigor

4.2.1 Rational fertilization Goji is sensitive to water and fertilizer. To fully decompose the fertilizer in the soil and bring its fertilizer effect into play early, various decomposed farmyard manures are generally applied from late October to mid-November. That is, on one side of the tree at a distance of about 0.3-0.5 m, a semicircular ditch is dug, fertilizer is applied, covered with soil, and watered. In the second year, a ditch is opened on the other side of the tree for fertilization. From May to June, nitrogen fertilizer needs to be top-dressed 2-3 times, about 150-100 g per plant.

4.2.2 Rational turning of the orchard and intertillage To prevent the orchard soil from becoming compacted, the orchard is turned and the soil is sun-dried twice a year to increase soil aeration and moisture retention capacity and promote root development. The first time is in early spring after the land thaws, with shallow digging of 12-15 cm; the second time is before winter irrigation or in August, with deep turning of 21-25 cm. During the growing season, attention should be paid to intertillage and weeding, with an intertillage depth of about 6-10 cm.

4.2.3 Rational pruning Enhancing tree vigor is a key measure for disease resistance. Generally, after the plants sprout in April and new shoots begin to grow, spring pruning is carried out, mainly to prune dead branches; from May to August, summer pruning is carried out, mainly to prune excessive water sprouts, intermediate branches and dense branches, and appropriately cut off the first and second batches of fruiting branches to facilitate the cultivation of new fruiting branches and ensure a bumper autumn fruit harvest. From October to November, autumn pruning is carried out to cut off dead branches, diseased and pest-infested branches, and excessive water sprouts.

4.3 Scraping tree bark

When goji gummosis lesions develop to the canker stage, scrape off the bark and then apply 10% Shuangxiaoling stock solution or a 12.5% solution of 900@L Yekuning; the treatment efficacy reaches 75.3% and 70.8%.

4.4 Chemical spray control

In the early stage of disease occurrence, use a 100@t solution of 64% Sandofan, a 10% solution of 50% Tuzet wettable powder, and a 2%-10% solution of 50% carbendazim to smear on the lesions, then combine with spraying a 0.125% solution of 64% Sandofan, a 0.1% solution of 50% Tuzet wettable powder, and a 0.125% solution of 50% carbendazim on the leaves and branches; the control efficacy can reach over 85%. At the same time, after goji sprouts in spring, spray a 0.1%-0.15@1 solution of 40% dimethoate emulsifiable concentrate or a 0.1%-0.05% solution of 50% malathion to control gall mites and aphids, so as to improve tree vigor and enhance disease resistance.