ANTI-RESISTANCE METHOD

Abstract

The decrease in soybean rust control using fungicide mixtures (DMAs+QoIs) reached very low levels for the harvest of 2012/13 (an average of 37% for the three main mixtures). This decrease is due to a decrease in Pp sensitivity to individual DMIs and QoIs, and mixtures thereof. Anti-resistance strategies have not been introduced in Brazil for preventing/delaying the development of resistance of the fungus that is the casual agent of rust (Phakopsora pachyrhizi) in soybean [plant form the family Fabaceae, Glycine max (L.) Merr.] and of the fungus that is the casual agent of yellow leaf spot (Drechslera tritici-repentis) in wheat [plant of the family Triticea, Triticum aestivum L.], as well as other disease complexes that attack the main crop plants in Brazil, such as corn, beans, cotton, inter alia. By means of said method it is possible to recover the efficiency of several mixtures (DMI+QoI and QoI+SDHI) due to a decrease in fungal sensitivity. The methods described by the present invention seek to increase the effective useful life of fungicides and increase grain yield.

Claims

1. An anti-resistance method, characterized by comprising the following steps: (i) add to the spray tank, mancozeb (manganese ethylene bis(dithiocarbamate)+Zn), mixtures of fungicides “QoIs+DMIs” or “QoIs+SDHI”; (ii) trigger the spray tank agitator; and (iii) once homogenized the syrup, apply it in the field.

2. The method according to claim 1, characterized in that mancozeb is added in the amount between 1.0 kg/ha and 5.0 kg/ha, preferentially between 1.0 and 4.0 kg/ha, most preferentially between 1.0 and 3.0 kg/ha, together with the fungicide (mixture of prefab “DMI+QoI” or “QoI+SDHI”) in all of their combinations and applications.

3. The method according to claim 1, characterized in that the addiction of the multi site protective is given with a first mobile penetrating fungicide (QoI) and subsequently with a second mobile penetrating fungicide (DMI or SDHI).

4. The method according to any one of claims 1 to 3, characterized in that it prevents or retards the development of resistance of the fungus that is the causal agent of Phakopsora pachyrhizi rust of soybean and the fungus that is the causal agent of yellow spot of the Drechslera tritici-repentis leaf of wheat, consisting in the addition of the protective multi-site fungicide mancozeb to mixtures of “QoIs+DMIs” or “QoIs+SDHIs.

5. The method according to any one of claims 1 to 4, characterized in that it rescues control levels between 80% and 90%, both of triazoles and strobilurin, isolated or in mixture.

6. The method according to any one of claims 1 to 4, characterized in that it preserves or retards the sensitivity reduction of P. pachyrhizi and Drechsiera tritici-repentis of the mixtures containing “carboxamides+QoI”, “prothioconazole+QoI”, “prothioconazole+QoI+carboxamide”, and “QoI+carboxamides.”

7. The method according to any one of claims 1 to 3, characterized in that it prevents or retards the development of resistance to fungi in cultures of corn, cotton and beans, consisting in the addition of the fungicide protective multi-site mancozeb to mixtures of “QoIs+DMIs” or “QoIs+SDHIs”.

Description

DESCRIPTION OF THE FIGURES

[0062] FIG. 1. Reduced soybean rust control by tebuconazole over eleven crops. (Source: Cooperative tests of fungicides).

[0063] FIG. 2. Control Reduction of soybean rust by cyproconazole+azoxystrobin mixture over six crops. (Source: Cooperative tests of fungicides).

[0064] FIG. 3. Control Reduction of soybean rust by cyproconazole+picoxystrobin mixture over six crops. (Source: Cooperative tests of fungicides).

[0065] FIG. 4. Reduction control of soybean rust by epoxiconazole+pyraclostrobin mixture over six crops. (Source: Cooperative tests of fungicides).

[0066] FIG. 5. Average reduction of soybean rust control by mixtures of cyproconazole+azoxystrobin, cyproconazole+picoxystrobin and epoxiconazole+pyraclostrobin over six crops. (Source: Cooperative tests of fungicides).

[0067] FIG. 6. Control Reduction of soybean rust for azoxystrobin over six crops. (Source: Cooperative tests of fungicides).

DETAILED DESCRIPTION OF THE INVENTION

[0068] In order to solve some of the problems found in the prior art—that is, to rescue the control levels (between 80% and 90%) of triazoles, strobilurins, carboxamides, isolated or in mixture—the present invention developed a method for preventing/delaying the development of fungal resistance in some crops such as soybeans, wheat, cotton, corn and beans, specifically for the fungus that is the causal agent of rust (Phakopsora pachyrhizi) of soybean (plant of the Family Fabaceae Glycine max (L.) Merr.), and the fungus that is the causal agent of yellow leaf spot—(Drechsiera tritici-repentis) of wheat (plant of the Family triticeous Triticum aestivum L.) and all other disease complexes including these two crops and all other disease complexes of grain crops in Brazil such as corn, cotton, beans and other of minor importance.

[0069] By the said method it is possible to recover the efficiency of some mixtures (MDI+QoI) due to increased fungitoxicity of mixtures.

[0070] The fungus resistance retarding technique consists of:

[0071] add to the spray tank, mancozeb (manganese ethylene bis(dithiocarbamate)+Zn), multi-site fungicide, mixtures of demethylation inhibitor fungicides (DMIs), quinone outside inhibitors (QoI) and succinate dehydrogenase inhibitors (SDHI) currently in use. The amount of mancozeb can vary between 1.0 kg/ha and 5.0 kg/ha, preferentially between 1.0 kg/ha and 4.0 kg/ha, most preferentially between 1.0 and 3.0 kg/ha, together with the fungicide (mixture of prefab “DMI+QoI” or “QoI+SDHI”) in all of their combinations and applications;

[0072] trigger the spray tank agitator; and

[0073] once the syrup is homogenized, apply the syrup in crops.

[0074] The anti-resistance strategy of the present invention is the addition of the multi-site protective fungicide, e.g. mancozeb, mixtures of “DMIs+QoIs” or “QoIs+SDHIs” in control of soybean rust and yellow spot of wheat leaf and other diseases complexes in all crops. The addiction of the multi site protective is given with a first mobile penetrating fungicide (QoI) and subsequently with a second mobile penetrating fungicide (DMI or SDHI).

[0075] In the case of soybean rust, the facts showed that the resulting control of the mixtures use of 80% of two fungicides specific site (strobilurins+triazoles) was not durable. So much that, after five crops of continuous use, producers reported the failure of said control.

[0076] Experiments conducted at various locations in Brazil showed the efficiency of mancozeb (manganese ethylene bis(dithiocarbamate)) applied alone to control soybean rust and yellow spot of wheat leaf. However, its greatest contribution was proven when added to commercial blends bringing control to values of up to 80%, similar efficiency of mixtures “triazole+strobilurin” at the beginning of its use.

[0077] The results showed that the addition of mancozeb improved the performance of all the mixtures tested. Therefore, the present invention used the same strategy as the solution to recover the original control levels (>80%) and make the useful life of the fungicides longer in controlling the target disease of the invention. This is because, mancozeb, being a multi-site protective fungicide and presenting a broad spectrum of action, will also contribute to the control of other diseases in soybean and also in wheat.

[0078] It is important to note that the method of the present invention, although quite simple, should be understood as innovative and very important for the sustainability of soybean and wheat cultures in Brazil and worldwide. First, because until then, the control of soybean rust and yellow spot in wheat showed to be inefficient. Second, because with mixtures “triazole+strobilurin” it was the latter that made the control and technical scholars understood that it would not be feasible the development of resistance to strobilurins, which unfortunately ended up happening. This is because the fungus used a new biochemical mechanism, hitherto unknown, to face the fungicide (QoIs) and not be eliminated from the environment.

[0079] The method of the present invention aims at increasing the effective life of fungicides and increase grain yield.

[0080] It was clearly demonstrated, on the background of the invention, the use of the multi-site protective fungicide “manganese ethylene bis(dithiocarbamate)+Zn” as the mechanism of action for recovering the control efficiency of the mixtures that showed reduced efficacy due to reduced sensitivity of the fungus to these active ingredients.

[0081] Thus, in order to solve the prior art drawbacks related primarily to soybean and wheat, the present invention aims to provide a method for treating soybean rust and wheat yellow spot with the addition of multi-site fungicides to the existing commercial mixtures.

[0082] The multi-site fungicides, such as mancozeb, act at least in six biochemical mechanisms of the fungus cell, hampered or preventing development of resistance. This is the most reliable tool in the fight against the development of resistance of fungi to fungicides.

Examples

[0083] In Soybean.

[0084] A study was conducted to determine the contribution of the mancozeb addition to mixtures of “strobilurin+triazoles.” The experiments were conducted in the field, in nine different locations, where it was determined the fungi toxicity of mancozeb to soybean rust.

[0085] Two doses were tested (1.5 and 2.0 kg/ha) with various numbers of mancozeb applications. The effect of mancozeb (1.5 kg/ha), incorporated into commercial mixtures was also tested.

[0086] The experiments were conducted with soybean cultivar Monsoy 9144 RR. Mancozeb formulation 750 WDG (water dispersible granules) was used, commercially available, for application of mancozeb according to Tables 6 and 7.

TABLE-US-00006 TABLE 6 Control (%) of soybean rust by mixing “DMI + QoI” added or not mancozeb, applied three times in two groups of phenological stages of soybean, evaluated by the area under the disease progress curve (AUDPC). Rio Verde - GO Mancozeb Mixtures Without With RI Cyproconazole + Azoxystrobin 42.8 74.0 31.2 Cyproconazole + Pycoxistrobin 74.0 79.4 5.4 Tebuconazole + Pycoxistrobin 74.0 85.9 11.9 Average A 66.1  B 79.8  13.7 Severity in the control = 70%. CV = 4.60%. RI = Relative Increase of Control.

TABLE-US-00007 TABLE 7 Control (%) of soybean rust by mixtures “DMI + QoI” added or not mancozeb, applied three times at different growth stages and assessed by the severity in leaflet - Passo Fundo - RS Mancozeb Mixtures Without With RI Cyproconazole + Azoxystrobin 68.6 89.8 21.2 Epoxiconazole + pyraclostrobin 40.5 75.2 34.7 Tebuconazole + Pycoxistrobin 64.4 79.0 14.6 Average A 57.8  B 81.3  23.5 Severity in the control = 37.3%. CV = 6.45%. RI = Relative Increase of Control.

[0087] From the experimental results, we found that the addition of the fungicide protective target not only reduces the risk of resistance, but primarily reverts control to the original level of 80%, and achieve results also in the yield increase of soybean grain.

[0088] In wheat. Due to reduced sensitivity of Dtr, mainly to QoIs, control of leaf spot has been very low (15.5% as shown in Table 8).

[0089] With the addition of mancozeb, by using the method anti-resistance described in the present invention, the control has been quite improved (33.3% also as shown in Table 8).

TABLE-US-00008 TABLE 8 Control (%) of the wheat leaf spots mixtures of DMI + QoI with or without mancozeb added. Evaluation 14 days after the first application Mancozeb Fungicide Without With Cyproconazole + Azoxystrobin 0 30 Cipro. + azoxy + propiconazole 23 38 Epoxiconazole + pyraclostrobin 19 36 Tebuconazole + methyl crezoxim 15 39 Tebuconazole + trifloxystrobin 17 29 Prothioconazole + trifloxystrobin 17 28 Average 15.2 33.3

[0090] Thus, in view of the above reported tests, it was found that the addition of mancozeb increased control of rust and wheat yellow spot with the conventional fungicide “DMI+QoI”. This can also be extrapolated to other disease complexes in other crops as above mentioned.

[0091] In view of the foregoing it can be said that one advantage of the method described herein is to use the multi site fungicide mancozeb, since hitherto, there are known cases of fungi resistant to it. Therefore, it appears as an essential tool in the fight against soybean rust resistance to fungicides DMIs, QoIs, and mixtures thereof. It was further found that the lower the performance of the mixture in rust control, the greater the added benefit of mancozeb. Furthermore, the addition of the dithiocarbamate (such as mancozeb) resulted in better disease control and plant productivity. Therefore, said method is regarded as innovative and very important for the soybean crop sustainability in Brazil and worldwide.

[0092] It was concluded therefore that the addition of a fungicide multi site protective, such as mancozeb, for the combined products (registered for control of Asian soybean rust and wheat yellow spot) regains control and primarily prevents the future development of fungal resistance.

[0093] It is important to emphasize that although the present invention has exemplified its application in soybean and wheat cultures, the patent holder states that the method described herein may also be applied to other cultures, such as, for example, corn, cotton and bean.

[0094] The present invention is more specifically explained by the examples above. However, it should be understood that the scope of the present invention is not limited to the examples in any respect. It can be seen by one skilled in the art that although the present invention includes the previously reported examples, modifications and changes can be made within the technical scope of the present invention.