Technical Solution of Rainfastness toward Protectant Fungicide

Rainfall is one of the necessary conditions for the growth and development of crops, but rainfall after pesticide application may have adverse effects on agricultural production, mainly reflected in:

1. Washing away the active ingredients from the surface of the plant and weakening the efficacy.

2. Pesticide flowing into the soil and water sources, causing environmental pollution.

Protectant fungicide are applied onto plant before infection occurs, by forming a permeable, breathable and transparent protective barrier, which inhibit germination and invasion of spores, thus achieving disease prevention. 

Additionally, Protectant fungicide are mostly formulated as wettable powders, water-dispersible granules, and suspension concentrate. The mode of action and formulation type showing defects like poor spreading on leaf, less adhesion and penetration, susceptible to being washed off from plant by rain as well as short duration of drug efficacy. Especially in high-temperature and rainy areas, rainfall can  remove most of drug droplets on the plant surface, dramatically destroying control effect.  

Sinvochem’s solution on Rainfastness 

The rainfastness of a pesticide can be improved by introducing adjuvants such as spreader-stickers. SP-TM07, a rainfastness adjuvant be developed by Sinvochem has a high molecular weight and contains hydrophobic groups and viscous chemical groups. 

The hydrophobic groups interact to form various adsorbed micelles on the surface of the active ingredient through dispersion forces, while the viscous groups adhere to the target leaf surface. The hydrophobic chains form a solvated film on the crop, effectively enhancing rainfastness of the formulation.

The adjuvant is suitable for non-solvent formulation like suspension concentrate, wettable powders, and water-dispersible granules, positively works on different types of protectant fungicide containing copper, dithiocarbamate, substituted benzene, diketimine etc..

Rainfastness Performance Trial 

Applied case 1: Image Processing Analysis Test

Wind tunnel laboratory was used to simulate rainfall condition;

Microscope imaging and digital software analysis was combined so as to compare residual ratios of drug spots before and after rainfall. 

Pesticide : 80% Mancozeb WP (Table 1, fig 1), Benchmark grade and 3 of commercial grades , 800 fold in dilution

Tank mix adjuvant: SP-TM07, 10000 fold in dilution 

Table 1. Experimental data on the rainfastness performance of 80% mancozeb WP

Fig 1. Fluorescence images of mancozeb spots before and after leaf wash

Through visual observation and data analysis, the treatment with the rain-resistant aid SP-TM07 was found to significantly enhance the fluorescence on the leaves compared to the base sample without the aid. There was no significant difference in the residual amount of mancozeb on the leaves compared to the market benchmark treatment.

Through visual observation(fluorescence on leaf) and data analysis(residue ratio), it demonstrates that active ingredient residue from treatment with adjuvant SP-TM07(3#,5#,7#) is obviously higher than treatment without SP-TM07(2#,4#,6#), also similar to the effect of benchmark treatment(1#)

Applied case 2: HPLC Test

Pesticide: 40% Chlorothalonil SC(commercial sample 1)

Adjuvant: SP-TM07 

Target plant: Green ivy / Broad bean 

Treatment 1#: 40% Chlorothalonil SC in 40 fold dilution 

Treatment 2#: 40% Chlorothalonil SC in 40 fold dilution, including SP-TM07 in 8000 fold dilution 

Fig 2. Fluorescence images of mancozeb spots before and after leaf wash

We can visually observe the washed-off traces( 1#) on the leaves of the green ivy and broad bean. On the leaves of the green ivy, the drug spot was washed away by nearly 50%, while there was no significant difference as for treatment with adjuvant (2#). On the leaves of the broad bean, drug spot was washed away by more than 70%(1#), but the synergistic sample still had a 60-70% residual(2#).

Fig 3. The residual chlorothalonil on the washed broad bean leaf tested by HPLC

To further quantitatively analyze the drug residual amount after washing, a high-performance liquid chromatography method(HPLC) was used to determine the residual amount of chlorothalonil on the leaves of broad beans. With value of chlorothalonil concentration as the horizontal axis and value of peak area as the vertical axis, the concentration of the extracted sample after washing was calculated. The results showed that without the adjuvant SP-TM07, the chlorothalonil residual amount was 51.97ml/L, while with the adjuvant SP-TM07, the chlorothalonil residual amount was 92.91ml/L, representing a 78.78% increase in the residual amount ratio. This further demonstrates that adjuvant SP-TM07 can effectively enhance the leaf retention of chlorothalonil active ingredients by it’s rainfastness ability.  

Applied case 3:  Field Trial

Pesticide: 40% Chlorothalonil SC( Benchmark grade and one commercial grade ) 400 fold in dilution

Adjuvant: SP-TM07, in 10000 or 20000 dilution fold 

Disease: Cucumber downy mildew

A field trial of 40% chlorothalonil SC against cucumber downy mildew was conducted during a period of heavy rainfall. The trial data showed that the efficacy of the benchmark(treatment 1# ) was better than treatment 2#. Treatments with addition of different dosage of SP-TM07(3# and 4#) may significantly increase efficacy after 7 days. Also, by using 20000 fold dilution of SP-TM07 can achieve the same efficacy as the benchmark. This indicates that adjuvant SP-TM07 can effectively improve adhesion ability of pesticide droplet, contribute to resistance of active ingredients to adverse environments like rainfall, prolong the duration of pesticide efficacy. 

Sinvochem adheres to a research and development strategy that is customer application-oriented. In response to the impact of safety and environmental policies, there is a growing demand for sustainable pesticide rainfastness technology in both domestic area and abroad. Sinvochem’s technology can enhance the rainfastness properties of various formulation types, assisting you to a sustainable future.