Integrated control of anthracnose of growing citrus

After damage, it causes leaf spot, fruit drop, branch wither, tree vigor weakening, even whole plant death, which has great influence on citrus yield and tree vigor. In particular, the heavy rain and lack of light in autumn last year caused serious ponding in some orange orchards, poor root growth and weak tree vigor, resulting in anthracnose bacteria "taking advantage of the weakness" and a large base of overwintering pathogenic bacteria; the strong cold current invasion in early spring this year also caused some orange orchards to be frozen and their disease resistance decreased; the continuous low temperature and rainy climate since spring has been conducive to the massive spread and invasion of anthracnose bacteria. Therefore, citrus bases should attach great importance to the prevention of citrus anthracnose in time.

Symptoms of anthrax

When the leaf is damaged, the disease spot often occurs at the edge or tip of the leaf, nearly round or irregular, slightly depressed, the edge of the disease spot is brown to dark brown, the center is grayish brown, and there are many small black dots scattered or arranged in a ring pattern. The diseased spot on the branch tip was long prismatic and slightly concave. If the diseased spot developed to a week around the branch, the diseased tip was gray and dead from top to bottom, with many black small dots scattered above. The leaves of the diseased tip were often curled and dried, and did not fall for a long time. Young fruit damage, initially dark green oily irregular spots, after the expansion to the whole fruit, spots depression black, causing a large number of fruit drop or dehydration stiff fruit hanging on the branches. The disease spots of mature fruits were round, brown, slightly sunken leathery dry scar type or brown rotten fruit rot type.

2. Comprehensive control measures Strengthening cultivation and management, strengthening tree vigor, improving tree disease resistance and spraying timely are the key measures to prevent this disease.

1. Eliminate the source of disease combined with spring shearing, cut off dead branches of diseases and pests, remove, pick up fallen leaves, drop fruits, and burn them intensively. At the beginning of March, spray 2-3 degree stone sulfur mixture or 45% crystal stone sulfur mixture 300-500 times, or 20% 45 copper Shuai 2000 times, thoroughly eradicate pathogenic bacteria.

2. Spraying timely to protect the growth of spring shoots and July to September is the peak period of citrus anthracnose infection. Spraying early to protect can play a good control effect. Green citrus base can choose 2% Junke 200-300 times, or Dasheng M? 45, 1000 times; or 60% citrus pesticide 1500 times; or 4% agricultural antibiotic 120, 1000 times; or Zhongshengmycin 1000 times, alternate spraying, continuous spraying 2? Three times.

3, scientific management, enhance tree vigor (1) heavy application of winter fertilizer, timely recovery of tree vigor.

I am rich in orange orchard part of the orange farming imbalance,"big and small year" phenomenon is serious,"big year" tree yield of more than 10,000 jin, tree body serious nutrition "deficit", but not timely supplement, tree potential is too weak, disease resistance is poor. We should improve traditional farming habits, pay attention to winter fertilizer, and apply it in time and in sufficient amount. Fertilization in this period should reach more than 60% of the total amount of fertilizer in the whole year, mainly organic fertilizer, appropriate amount of quick-acting fertilizer, applied within a week before and after fruit picking, in order to restore tree vigor and promote flower bud differentiation. This is like a pregnant woman postpartum nutrition supplement, recharge, restore vitality.

(2) Deep ploughing and soil improvement, increasing organic fertilizer.

Most of our flat land and paddy field orange garden neglect deep ploughing, long-term partial application of N fertilizer, soil serious hardening,"ventilation" poor, nutrition imbalance, extremely partial "thin", tree disease resistance is poor, fruit floating skin phenomenon is serious. Therefore, according to soil characteristics, soil moisture and fertilization period, tilling and heavy application of organic fertilizer should be carried out in citrus bases. The concrete method comprises the following steps of: opening a ditch with different depth and width of 30- 40cm outside the tree crown drip line, and mixing organic fertilizers such as compost, cake fertilizer, green manure and the like with N, P and K according to a proportion with soil into the ditch.

(3) Scientific pruning to prevent tree crown from being blocked.

Orange orchard planting too dense, especially more than 220 trees per mu orange orchard, after the garden crown closed cross, conducive to the breeding of diseases and insect pests, and difficult to control. Therefore, fruit growers in dense planting gardens should strictly implement the new technology of "light transmission pruning to cut and determine yield": that is, properly thinning "open skylight" for crowded backbone branches; distinguishing temporary plants from permanent plants in orange gardens planted with more than 220 trees per mu, adopting the pruning method of "one promotion and one control, one advance and one retreat" to overcome "big and small years" and control yield to achieve stable and high yield. Generally, the yield per mu of orange orchards above 7 years old should be controlled at 3000-3500 kg.

(4) Remove accumulated water to prevent root hypoxia. According to the climate characteristics of more rainy autumn in our country, in the future, paddy fields and flat orange orchards should especially strengthen the construction of drainage and irrigation channels. Paddy field garden construction should be ridged planting, flat orange garden should be dug according to the terrain 40 cm deep crisscross drainage ditch, in order to effectively prevent "flood irrigation" and autumn rain caused by "standing water" harm.