Adequate papaya nutrition aims to prevent important diseases in the crop

Papaya is affected by diseases such as lethal yellow and ring spot. For the plant to express greater resistance, it is essential to nourish it properly.

14.09.2016 | 20:59 (UTC -3)

Papaya can be affected by various pests and diseases, which result in a drop in production or even make commercial planting unfeasible in certain regions (Ramos, 2008). Its productivity in the Tabuleiro de Russas region, in Ceará, has been negatively affected by diseases such as ring spot (Papaya ringspot virus, PRSV) and the lethal yellow of the papaya tree (Papaya lethal yellowing virus, PLYV).

O PRSV It produces yellowing of the youngest leaves in the upper third of the crown, lightening of the veins and also an intense mosaic on the leaves (with yellowish and other greenish areas). The leaves can become deformed and, often, the leaf blade practically disappears, being reduced to the central vein (shoe thread). Round spots appear on the fruits that form rings. The leaf petiole has oily or watery streaks extending to the stem. Leaf symptoms can be confused with those caused by mite attack. Depending on the strain of virus present, death of infected plants may occur. Production losses are variable, reaching up to 72% (Embrapa, 2006).

O PLYV in papaya it causes yellowing of the leaves in the upper third of the plant and twisting of the pointer. Over time, the leaves wither and die, causing the plant to die. There are longitudinal depressions on the petioles and the veins have necrotic lesions on the lower surface. In other varieties, the symptoms are similar without the tip twisting and death of the infected plants. The fruits show circular light green spots that turn yellow over time, with the pulp becoming hard and with delayed maturation (Jaimes & Andrade, 2004).

Achieving good productivity and fruit quality is directly linked to balanced nutrition. Likewise, it is known that a properly nourished plant has greater resistance to diseases and can reach its productivity potential. However, in Brazil, the behavior and nutritional requirements of the main papaya cultivars are not known (Oliveira, 2004). In foliar fertilization with sources of potassium (K), several applications are necessary to increase the K content in the leaves. An important aspect is the effect of the K ion or cation companion to be applied, as it may be related to greater plant resistance to diseases and provide maximum economic productivity.

Experiment

With the objective of studying the effect of sources and doses of foliar fertilization with potassium (K) on diseases and survival of Formosa papaya, cultivar Tainung no 1, in the edaphoclimatic conditions of Russas, Ceará, a test was conducted on a farm belonging to the company Frutacor. Papaya seedlings, cultivar Tainung n, were used.o 1. After 30 days of sowing, the seedlings were transplanted in groups of four seedlings per linear meter, for future selection of hermaphrodite plants. After 72 days of transplanting, sexing was carried out, leaving only one of the four transplanted plants.

The experimental area was divided into 13 treatments containing four plots, each with an area of ​​144m2 (12x12), with 20 plants. The 14 plants around each plot were used as a border, leaving six useful plants in each plot.

The treatments (Table 1) consisted of four sources of K applied via foliar (potassium nitrate, potassium sulfate, potassium chloride and potassium silicate) with three doses (1%, 2% and 4% of the solution concentration). The applications began after sexing the plants, and were carried out monthly using an Arbus 2000 turbo atomizer. From the eighth month onwards, production was evaluated and at 16 months the percentage of survival of the papaya trees was examined. A completely randomized design was used, for treatments in a factorial arrangement (4x3) plus a control treatment, totaling 13 treatments with four replications. The data were submitted to Anova and the Tukey test was applied at 5% significance, using the “Saeg/UFV 9.1' software.

Result

The highest productivity (75,3mg/ha) and survival (100%) was observed in plants to which potassium silicate was applied, with no significant difference between doses. The lowest productivity (35,3mg/ha) and survival (11,1%) was observed in treatments in which potassium chloride was applied (Table 2).

Conclusion

The better behavior of silicate is mainly explained by the lower incidence of diseases that favored the larger population.

Table 1 - Composition of treatments

Treatment

Amount of K applied via fertigation

Concentration of the K source in the foliar applied solution

1

240g of KCl.planta-1.month-1

No amount of foliar fertilizer

2

1% potassium nitrate

3

2% potassium nitrate

4

3% potassium nitrate

5

1% potassium sulfate

6

2% potassium sulfate

7

3% potassium sulfate

8

1% potassium chloride

9

2% potassium chloride

10

3% potassium chloride

11

Potassium silicate 1%

12

Potassium silicate 2%

13

Potassium silicate 3%

Treatment

Amount of K applied via fertigation

Concentration of the K source in the foliar applied solution

1

240g of KCl.planta-1.month-1

No amount of foliar fertilizer

2

1% potassium nitrate

3

2% potassium nitrate

4

3% potassium nitrate

5

1% potassium sulfate

6

2% potassium sulfate

7

3% potassium sulfate

8

1% potassium chloride

9

2% potassium chloride

10

3% potassium chloride

11

Potassium silicate 1%

12

Potassium silicate 2%

13

Potassium silicate 3%

Table 2 - Effect of sources and doses of foliar fertilization with K on the production and survival of Formosa papaya cultivar Tainung no 1

Treatment

Production (Mg.ha-1)

Survival (%)

1

40,8 BCD

27,8 DEF

2

62,5 BC

22,2EF

3

63,4 BC

27,8DEF

4

60,8 E

27,8 DEF

5

40,8 E

66,7 ABCDE

6

42,6 E

77,8 ABC

7

54,3 D

72,2 ABCD

8

36,1 E

44,4 BCDEF

9

35,4 E

33,3 CDEF

10

35,3 E

11,1F

11

A 75,3

A 100

12

A 75,3

A 100

13

66,9 AB

88,9 AB

Treatment

Production (Mg.ha-1)

Survival (%)

1

40,8 BCD

27,8 DEF

2

62,5 BC

22,2EF

3

63,4 BC

27,8DEF

4

60,8 E

27,8 DEF

5

40,8 E

66,7 ABCDE

6

42,6 E

77,8 ABC

7

54,3 D

72,2 ABCD

8

36,1 E

44,4 BCDEF

9

35,4 E

33,3 CDEF

10

35,3 E

11,1F

11

A 75,3

A 100

12

A 75,3

A 100

13

66,9 AB

88,9 AB

Papaya production (Box)

Papaya (Caricapapaya L.) is distributed in several tropical and subtropical countries (Ramos 2008). Brazil, in 2010, produced around 1.871.295 tons of papaya (IBGE, 2010), with the domestic market consuming most of the total production, with a small portion destined for export (Rodrigues 2001). The largest producer of the fruit is the state of Bahia, with around 48,64% of the country's total production, followed by Espírito Santo with 32,80% and Ceará 5,5% (IBGE, 2010).

The most explored cultivars in Brazil are: Solo (e.g. Sunrise Solo and Improved Sunrise Solo cv 72/12) and Formosa (e.g. Tainung nº 1 nº 2). The Tainung no 1 cultivar is a highly productive hybrid, with a fruit from a round and elongated female flower and a long hermaphrodite flower with an average weight of 900g, with a light green skin and orange-reddish pulp. It has an average productivity of around 60t/ha/year (Embrapa, 1995).

Click here to read the article in issue 80 of Revista Cultivar Hortaliças e Frutas.

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