POTATO LATE BLIGHT CONTROL WITH DIFFERENT COPPER FUNGICIDES

Abstract

Potato culture is very sensitive to the pathogen attack. Of these, the most frequently reported is Phytophthora infestans. Late blight can cause in favorable years a 40-50% loss of the harvest if the control measures are not applied. In our country, Potato late blight is frequent and dangerous in the area of cultivation, especially in the rainy years, when the production losses can reach 50% or more. The evolution of the attack degree in 2017 is explosive, after 20 days of the first reading. If the first two readings in July show a level below 3%, in the third decay of the month, the average attack exceeded 20%. One of the oldest substances used to control these pathogens is copper. This substance is still valid and still accepted in organic farming. Climatic conditions strongly influence the efficiency of copper fungicides. Also, previous studies claim that there are differences in efficacy between the three chemical formulations of copper. This paper aims to determine the effectiveness of different formulations of this substance. Thus, copper sulfate, copper hydroxide, and copper oxychloride were tested on three varieties of potatoes (red, white, and purple). For control of downy mildew, the most efficient was the oxychloride followed by copper hydroxide. In the variant treated with copper sulfate, the average attack rate exceeded 30%. The highest levels of the attack were recorded in the variants treated with CuSO4 in both the Sante and Red Fantasy varieties. The differences between these two variants and all others are significant. Comparing the varieties is observed that the least attacked by the Phytophthora infestans is the purple variety, the differences between this variety and the others are covered statistically. The most sensitive to the late blight attack was found to be the Sante variety. Of the fungicides tested, the highest efficiency we noted at the copper oxychloride.

Full text

Research Journal of Agricultural Science, 51 (4), 2019
127
POTATO LATE BLIGHT CONTROL WITH DIFFERENT COPPER
FUNGICIDES
Simina Alina PAȘCA, Vasile FLORIAN, Loredana SUCIU
1 University of Agricultural Sciences and Veterinary Medicine Cluj-Napoca, Calea Mănăștur nr.3-5,
Romania
Corresponding author: vasile.florian@usamvcluj.ro
Abstract. Potato culture is very sensitive to the pathogen attack. Of these, the most frequently
reported is Phytophthora infestans. Late blight can cause in favorable years a 40-50% loss of the harvest
if the control measures are not applied. In our country, Potato late blight is frequent and dangerous in
the area of cultivation, especially in the rainy years, when the production losses can reach 50% or more.
The evolution of the attack degree in 2017 is explosive, after 20 days of the first reading. If the first two
readings in July show a level below 3%, in the third decay of the month, the average attack exceeded
20%. One of the oldest substances used to control these pathogens is copper. This substance is still valid
and still accepted in organic farming. Climatic conditions strongly influence the efficiency of copper
fungicides. Also, previous studies claim that there are differences in efficacy between the three chemical
formulations of copper. This paper aims to determine the effectiveness of different formulations of this
substance. Thus, copper sulfate, copper hydroxide, and copper oxychloride were tested on three varieties
of potatoes (red, white, and purple). For control of downy mildew, the most efficient was the oxychloride
followed by copper hydroxide. In the variant treated with copper sulfate, the average attack rate exceeded
30%. The highest levels of the attack were recorded in the variants treated with CuSO4 in both the Sante
and Red Fantasy varieties. The differences between these two variants and all others are significant.
Comparing the varieties is observed that the least attacked by the Phytophthora infestans is the purple
variety, the differences between this variety and the others are covered statistically. The most sensitive to
the late blight attack was found to be the Sante variety. Of the fungicides tested, the highest efficiency we
noted at the copper oxychloride.
Keywords: potato, Phytophthora infestans, copper, fungicide
INTRODUCTION
Obtaining healthy production is the desire of any farmer. One of the quality indicators
is pesticide residue content. Thus, in this paperwork, we present some data related to the
efficiency of some fungicides used in the control of potato late blight. The present work aims
to establish, if appropriate, the best copper formulation of fungicides. The efficiency of copper
fungicides is strongly influenced by climatic conditions (TÖFOLI ET AL., 2014; SCHILDER, 2010;
HERMEZIU, 2014). Also, Large in 2008 states that there are differences in efficacy between the
three chemical formulations of copper.
Late blight can cause, in favorable years, a 40-50% threshold of the harvest if no
control measures are applied (STEVENSON ET AL., 2008). In our country, the potato late blight is
frequent and dangerous in the main area of cultivation, especially in the rainy years, when the
losses can reap 50% or more (BOȚOMAN, 2005; HATMAN ET AL., 1989; LAZĂR ET AL., 1977).
All aerial and underground organs of plants can be attacked, except for the roots. The
most common form of attack is on the leaves. These, as a result of the infection, have brown
spots with a diffuse contour, located mainly at the edge or tip of the leaflets. Over time, the
tissue near the spots becomes necrotic, and around them, a yellowish area is observed. On the
underside of the leaves, on the edge of the spots towards the healthy tissue, in wet weather or in
the mornings on the dew, there is a delicate whitish puff made up of the sporangia and the
sporangiophores of the pseudofungi (PÂRVU M., 2010; POPESCU GH., 1999; ULEA, 2003).

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Figure 1 Late blight on the leaves and tubers - Phytophthora infestans
On the stems and petioles of the leaves, the disease appears in the form of elongated
brown spots, which can produce browning and drying.
From the stems, the disease passes through stolons on the tubers. The tubers can also
be infected directly from the sporangia which falling from the leaves on the ground they are
driven with rainwater up to 6-8 cm, where they meet the potato tubers and infect them. The
tubers can also be infected by direct contact with the sick ones. In the early stages, the tubers
attacked do not differ on the outside from the healthy ones; in a more advanced stage, on the
surface of the tubercles appear brown-leaden sunken spots, which correspond inward with
areas of brown tissue. (HATMAN ET AL., 1989; PUIA, 2005).
Copper products can control, or slow down, potato late blight epidemics. Copper
products have no therapeutic activity (MANEA ET AL., 2017). Therefore, they need to be applied
to all plant surfaces before infection (STONE, 2019). They must be applied so that all plant
surfaces are covered, including the undersides of leaves where Phytophthora infestans
sporulates (STEVENSON ET AL., 2008 FLORIAN ET AL., 2012).
MATERIAL AND METHODS
The purpose of the paper is to establish the efficiency of some copper fungicides in
control of potato late blight.
In order to achieve the objective, an experimental field was placed in the village
Petreștii de Jos, Cluj County. The experimental field was established on April 18, 2017, with a
length of 18.5 m and a width of 4.5 m using three potato varieties: Red Fantasy (red potato),
Sante (white potato), and Albastru de Gălănești (purple potato). Each plot comprises two rows
of 1.5 m in length.
The treatments were differentiated with products based on copper: Bordeaux Mint
(copper sulfate), Champ (copper hydroxide), and Flowbrix (copper oxychloride). The doses
used are those recommended by the manufacturer (Manea et al., 2017). Alternative treatments
with the following products have been performed to combat the Colorado (Leptinotarsa
decemlineata): Calypso, Actara, and Mospilan
The first of the four treatments was performed on June 27, 2017, the second on July 7,
2017, the third on July 18, 2017, and the last on July 27, 2017. After each treatment, at an

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interval of approximately 7-10 days, we performed the notations in the experimental field
regarding the efficiency of fungicide used.
RESULTS AND DISCUSSIONS
As mentioned above, climatic conditions have an influence on the behavior of the
pathogen Phytophthora infestans. We can see that in the first two readings, the attack level is
very low; most of the variants registering an attack degree of less than 1%. In 04.07.2017, on
purple variety, no attack was observed in the variants treated with oxychloride and hydroxide
copper (Table 1).
Table 1
The efficiency of copper fungicides, in late blight control (04.07.2017)
Variety
Treatment
Attack degree
Duncan significance
White
Sante
Average
0.64Mt
Zeamă Bordeleză
CuSO4
0.23
A
Flowbrix
Cu2(OH3)Cl
1.00
A
Champ
CuOH
0.68
A
Red
Red Fantasy
Average
0.25Mt
A
Zeamă Bordeleză
CuSO4
0.16
A
Flowbrix
Cu2(OH3)Cl
0.53
A
Champ
CuOH
0.07
A
Purple
Albastru de Gălănești
Average
0.63Mt
A
Zeamă Bordeleză
CuSO4
1.87
A
Flowbrix
Cu2(OH3)Cl
0.00
A
Champ
CuOH
0.00
A
Mt-control
LSD (p 5%) – 2.10
DL (p 1%)- 2.95
DL (p 0,1%)- 4.17
DS 2.10
Ten days after the first observation (table 2), the degree of attack increases, revealing
the varieties treated with copper sulfate for the purple variety and the Sante variety. These
variants registered the highest attack value of over 3%, the differences between them, and the
other variants being statistically covered.
At 20 days after the first reading, the situation of the attack degree changes
dramatically. The level of this attack reaching, on average, the Red Fantasy variety at 17.21%,
and the Sante variety up to 15.74% (table 3). This fact is due to the climatic conditions that
have been characterized by alternating short rains with warm periods. Again we note the purple
variety with the lowest degree of attack, below 3% (table 3).
The highest levels of the attack were recorded in the variants treated with CuSO4
(over 20%) in both varieties: Sante and Red Fantasy. The differences between these two
variants are significant. If in the Red Fantasy variety, there are no significant differences
between the plots treated with copper hydroxide or oxychloride, in the purple variety, there are
no significant differences between the three treatment variants.

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130
Table 2
The efficiency of copper fungicides, in late blight control (14.07.2017)
Variety
Treatment
Attack degree
Duncan significance
White
Sante
Media
1.83Mt
Zeamă Bordeleză
CuSO4
3.74*
B
Flowbrix
Cu2(OH3)Cl
0.47
A
Champ
CuOH
1.28
A
Red
Red Fantasy
Media
0.85Mt
Zeamă Bordeleză
CuSO4
0.40
A
Flowbrix
Cu2(OH3)Cl
0.65
A
Champ
CuOH
1.50
A
Purple
Albastru de Gălănești
Media
1.36Mt
Zeamă Bordeleză
CuSO4
3.67**
B
Flowbrix
Cu2(OH3)Cl
0.26
A
Champ
CuOH
0.15
A
Mt-control
LSD (p 5%) – 1.39
DL (p 1%)- 1.95
DL (p 0.1%)- 2.75
DS 1.38
Table 3
The efficiency of copper fungicides, in late blight control (24.07.2017)
Variety
Treatment
Attack degree
Duncan significance
White
Sante
Media
15.74Mt
Zeamă Bordeleză
CuSO4
21.53***
E
Flowbrix
Cu2(OH3)Cl
8.28ooo
B
Champ
CuOH
17.41
D
Red
Red Fantasy
Media
17.21Mt
Zeamă Bordeleză
CuSO4
21.30**
E
Flowbrix
Cu2(OH3)Cl
14.43o
C
Champ
CuOH
15.89
CD
Purple
Albastru de Gălănești
Media
1.65Mt
Zeamă Bordeleză
CuSO4
1.79
A
Flowbrix
Cu2(OH3)Cl
0.50
A
Champ
CuOH
2.66
A
Mt-control
LSD (p 5%) – 2.71
DL (p 1%)- 3.81
DL (p 0.1%)- 5.38
DS 2.71

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131
Figure 2. Late blight attack degree
Comparing the varieties, we observe that the least attacked by the Phytophthora
infestans is the purple variety, with an attack degree below 15% (Figure 2). The difference
between this variety and the others is statistically covered. The most sensitive to the late blight
attack was found to be the Sante variety.
Figure 3 shows a comparison of the efficacy of the treatments. It is also recognized
this time as the most efficient the copper oxychloride, the differences from the other two
formulations, in terms of efficiency, being significant.
Figure 3. Efficacy of copper fungicides
On the last date of reading the degree of attack and comparing the interaction between
varieties and treatments regarding the late blight (Table 4), we can say that the purple variety
behaved best in the variant to which copper oxychloride was applied. The least resistant to the
late blight proved to be white variety, which in the variant treated with copper sulfate noted an
attack degree of 37.75%.

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Table 4
The efficiency of copper fungicides, in late blight control (05.08.2017)
Variety
Treatment
Attack degree
Duncan significance
White
Sante
Media
32.12Mt
Zeamă Bordeleză
CuSO4
37.75
E
Flowbrix
Cu2(OH3)Cl
27.22
CD
Champ
CuOH
31.38
DE
Red
Red Fantasy
Media
29.33Mt
Zeamă Bordeleză
CuSO4
36.55*
E
Flowbrix
Cu2(OH3)Cl
19.94oo
B
Champ
CuOH
31.50
DE
Purple
Albastru de Gălănești
Media
14.94Mt
Zeamă Bordeleză
CuSO4
20.62
BC
Flowbrix
Cu2(OH3)Cl
8.95
A
Champ
CuOH
15.26
AB
Mt-control
LSD (p 5%) – 6.61
DL (p 1%)- 9.28
DL (p 0.1%)- 13.10
DS 6.61
Figure 4 The relation between the production and late blight attack degree
As expected, production is influenced by the degree of attack of this dangerous
pathogen, but especially by the productive potential of the tested variety (Figure 4). In all the
plots cultivated with the variety Sante or Red Fantasy, the productions exceeded 25 t/ha. The
variants treated with copper oxychloride generally had high yields, except for the purple
variety where it seems that this treatment inhibited the development of plants, the yields being
for this variant below 6 t/ha, with 1 and 2 tons per hectare smaller than the other variants.

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CONCLUSIONS
Among the varieties tested, the most resistant to late blight attack in the conditions of 2017 was
the purple variety (local population). Of the fungicides tested, the highest efficiency was noted
to the one based on copper oxychloride. Copper treatments are still a viable alternative in the
control of potato late blight. Under the conditions of organic farming, we recommend the
application of any copper-based product for the first two treatments, and the next one's
treatments fungicides based on copper oxychloride. Research on the effectiveness of treatments
should be continued in the following year to eliminate the influence of climatic conditions on
their efficiency.
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