Effect of Pyripridone Suspension in Controlling Whitebacked Planthopper in Field
Cheng Jinsheng, Jiangxi Province Xinjian County Plant Protection & Phytosanitary Inspection Station, Wu Wei, Jiangsu Kesheng Group Co., Ltd.
Abstract: The 25% pymetrozine suspension was applied to control the whitebacked planthopper in paddy fields during the peak period of young nymphs. A dose of 24g per mu was used, and after two days, the control effect reached 78.29%. By day five, it increased to 92.55%, approaching the peak efficacy. After ten days, the control rate remained high at 97.96%. The product is safe for natural enemies.
Key words: Pymetrozine, suspending agent, whitebacked planthopper, control effect
Pymetrozine suspension, developed by Jiangsu Kesheng Group Co., Ltd., is a new insecticide designed to manage rice planthoppers. To evaluate its effectiveness against the whitebacked planthopper, field trials were conducted in June 2008. The results are detailed below.
Materials and Methods
1. Test Subject: Sogatella furcifera (whitebacked planthopper).
2. Test Agent: 25% Pymetrozine Suspension provided by Jiangsu Kesheng Group Co., Ltd.
3. Dose: Three treatments were tested: 16g, 20g, and 24g per mu.
4. Experimental Setup: There were 12 experimental plots, each 16.6m², with three replications arranged randomly. Small ditches separated the plots.
5. Test Site Overview: Located in Yujia Village, Shijie Town, Xinjian County. The site has double-season rice fields with medium to high fertility, good drainage, and irrigation. The early rice variety was Feiyou 98, with a water depth of 3–4 cm at application. Some alfalfa grass was present, and the soil was a Wuhuang muddy field with a pH of 6.5. The whitebacked planthopper population was moderate, mainly consisting of young nymphs.
Weather Conditions: The pesticide was applied on June 19. The weather was cloudy, with wind speed of level 2. The next day was partly sunny.
Application Method: Applied once on June 19 using a "Farm/Farmers 16" manual sprayer. Each treatment used 1.25 kg of water (equivalent to 50 kg per acre) for fine spray. No other pesticides were used.
Previous Pest Control: On May 2, 75% chlorpyrifos was used at 40g/30kg water for early rice pest control. On May 20, 5% Ruijin was sprayed at 50g/30kg water for the first generation of Huaihua.
Survey Records and Methods
1. Survey Times: Before application (June 18), 2 days post-application (June 21), 5 days (June 24), 7 days (June 26), and 10 days (June 29). Live insects were counted in each plot.
2. Survey Method: Using the parallel jump method, 10 points were surveyed with 2 clusters per point. A white porcelain plate was placed at the base of the rice plant, and the base was manually smashed three times from the opposite side. The number of planthoppers in the dish was recorded.
3. Efficacy Calculation:
Insect Reduction Rate (%) = (Pre-treatment Count - Post-treatment Count) / Pre-treatment Count × 100
Corrected Control Effect (%) = (Pre- and Post-treatment Reduction in Test Area / Pre- and Post-treatment Reduction in Control Area) × 100
4. Visual inspection of crops and non-target organisms.
Results and Analysis
1. According to Table 1, the control effect of 24g/mu of 25% pymetrozine suspension was 78.29% after two days, 92.55% after five days, and 97.96% after ten days. Increasing the dosage from 16g/mu to 24g/mu improved the control effect.
Table 1 Field Efficacy Test Results of 25% Pymetrozine Suspension Against Whitebacked Planthopper
Treatment
Before Medicine
(Head/20 Bundles)
2 Days After Medicine
5 Days After Medicine
7 Days After Medicine
10 Days After Medicine
Live Insects
Decrease Rate (%)
Correction Control Effect (%)
Live Insects
Decrease Rate (%)
Correction Control Effect (%)
Live Insects
Decrease Rate (%)
Correction Control Effect (%)
Live Insects
Decrease Rate (%)
Correction Control Effect (%)
25% Pymetrozine 16g/Mu
57.67
37
35.84
57.72
24.33
57.81
85.30
15
73.99
93.64
12
79.16
93.97
25% Pymetrozine 20g/Mu
43
23.67
44.95
63.73
13
69.77
89.47
8.67
79.84
95.07
6.33
85.28
95.74
25% Pymetrozine 24g/Mu
56.67
18.67
67.05
78.29
12.33
78.62
92.55
6.67
88.23
97.12
4
92.94
97.96
CK
41
62.33
51.76
--
117.67
187
--
167.6
308.95
--
141.67
245.5
--
2. Impact on Crops and Non-Target Organisms
At the recommended dose, the pymetrozine series had no adverse effects on the early rice crop or field spiders.
Conclusion and Discussion
1. The 25% pymetrozine suspension developed by Jiangsu Kesheng Group Co., Ltd. showed significant control over whitebacked planthoppers. Within five days, the control rate reached 92.55%, close to the peak efficacy. After ten days, the control rate remained at 97.96%. It is safe for crops and does not harm natural enemies, making it suitable for widespread use. For moderately to heavily infested years, a dosage of 18–20 g/mu is recommended. For years with reinfestation, 20–24 g/mu is advised.
2. The optimal time to apply the 25% pymetrozine suspension is during the peak period of 1st to 2nd instar nymphs of Sogatella furcifera, ensuring maximum effectiveness.
3. When spraying, maintain a water layer of 3–5 cm in the field to enhance the absorption and distribution of the insecticide within the plants.
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