Control Methods for Phytophthora Disease in Fig Cultivation

Fig Phytophthora disease is an important disease of figs in suburban areas in recent years, occurring commonly and causing serious damage. In years when the disease is epidemic, 80%-90% of the fruit can be affected and rot, and large numbers of branches and leaves wither.

[Symptoms of damage] The disease mainly damages fruit, new shoots and leaves, and can also infect buds. When fruit is affected, water-soaked round spots first appear on the fruit surface, then rapidly expand into slightly sunken, irregular-shaped rotting spots. When the spots extend to cover more than one half of the whole fruit, the fruit will drop. After diseased fruit falls to the ground, it shrivels into a mummified fruit.

When leaves are affected, irregular round water-soaked brown spots appear, with concentric rings, spreading very quickly, with indistinct edges; when the weather is humid, sparse white mold grows on the surface. When the weather is dry, the spots dry up and the diseased leaves fall early.

When new shoots are affected, water-soaked brown spots appear; when the spots encircle the shoot, the new shoot dries up and dies.

[Disease development pattern] The pathogen overwinters as oospores in the diseased host residue left on the ground. In the following spring and summer, it is spread by rain to new shoots and fruit near the ground, and germinates and infects them to begin causing damage. Afterwards, sporangia and zoospores are produced on the spots and, with wind and rain as the vector, cause repeated infection, until oospores are formed in autumn and overwinter.

In this region, affected new shoots and fruit are generally seen in late May, and the plum rain season is the peak period of disease occurrence. In the field, branches near the ground usually become diseased first, then it spreads to the whole tree. Where orchards are low-lying, poorly drained, with low, densely clustered trunks and overly dense, closed canopy branches, the disease is more severe.

[Control methods]

(1) Clean the orchard and eliminate overwintering sources of inoculum. In winter and spring, carefully carry out orchard cleaning, prune out dead branches and diseased and residual branches, sweep up fallen leaves and diseased and residual material on the ground, burn them in a centralized manner, and spray 3-5 degrees Baume lime sulfur mixture.

(2) Chemical protection. From late May until 20 days before fruit harvest, spray once every 15-20 days. Chemicals that can be used include 40% meiyijing wettable powder at 300 times dilution, or 50% ridomil wettable powder at 800 times dilution, or 58% ridomil MZ wettable powder at 800 times dilution; 1:1:200 Bordeaux mixture also has a good control effect, and can be used for protection in the early stage, with ridomil and the like used for control after the disease occurs. In addition, 50% ziram wettable powder at 400-500 times dilution can also be used for control.

(3) Strengthen field management, do a good job of ditching and drainage, reduce field humidity, thin out overly dense branches, appropriately raise the fruiting position, and improve the ventilation and light penetration conditions of the canopy.