Forecast of the Occurrence of Diseases and Pests in Shanghai's Two Crops of Wheat and Barley and Their Control Methods

Based on the occurrence base of diseases and pests in the two crops of wheat and barley in each district (county), and in combination with analysis of weather conditions, the occurrence trend of diseases and pests in the two crops of wheat and barley in this city this year is expected to be moderate. Among them, @#@245@#@ scab will occur moderately, with severe occurrence in some areas; the small brown planthopper will occur severely, with outbreaks in some areas; wheat aphids will occur moderately, wheat powdery mildew and barley scab will occur relatively lightly, and armyworms will occur lightly. In order to effectively control the damage of diseases and pests and secure a bumper harvest of summer-ripening crops, all districts (counties) are requested to conscientiously carry out disease and pest control work for summer-ripening crops in accordance with their own production conditions.

I. Analysis of Occurrence Trends

(1) Scab

1. Occurrence degree

Wheat will occur moderately, with a natural diseased ear rate of 13-18%, and over 20% in heavily affected fields; barley will occur moderately to lightly, with a natural diseased ear rate of 7-15%.

2. Forecast basis

(1) Inoculum source: Rice stubble perithecia were found on March 20 (Qingpu, Jiading), and in other districts (counties) on April 5, with the occurrence period delayed by more than 10 days compared with the usual March 10. On April 14, the fungal carryover rate of rice stubble perithecia per hill was 22%, the diseased plant rate was 4.43%, and the perithecium maturity index was 41.25%. The peak period of ascospore release is expected to be April 20-25, coinciding with the heading stage of wheat and some late barley.

(2) Weather: According to forecasts by the meteorological department, from April 20 to May 20 this year (from wheat flowering to late grain filling), the total rainfall will be 101.5 mm, ranging from 73 to 130 mm, slightly less than the usual 137.6 mm, with 11.5 rainy days, basically similar to the usual 12.9 days. During the period from late April to mid-May, there will be 4-5 days of warm and humid weather, which is relatively favorable for the occurrence of scab.

(3) Wheat and barley varieties and their growth trends: This year the city's total wheat and barley planting area is about 800,000 mu (including the Farm Bureau), of which wheat is 670,000 mu. The main varieties planted are Yangmai-158, Yangmai-11, Yangmai-12, Yangmai-15, Yangmai-16, Jiamai No. 1 and Luomai No. 8. These varieties all have moderate resistance to scab. The barley planting area is 130,000 mu, with the main varieties being Hua 22, Hua 30, Rudong No. 7, Shenmai No. 1 and Humai No. 16. According to the seedling survey in early April, this year's wheat growth period was delayed by 7 days compared with usual years. Among them, barley began heading in early April and reached full heading before April 10; wheat began heading on April 12, reached full heading around April 20, and entered the flowering stage (susceptible stage) on April 23-26.

(2) Small brown planthopper

From March 26 to 28, a citywide general survey was conducted on 576 fields of wheat, rapeseed, weeds, green manure and rice stubble, with an average of 13,600 insects per mu, ranging from 1,300 to 52,500, a decrease compared with 17,300 in the same period of 2006 and 51,000 in the same period of 2007. On April 14, a general survey was conducted in 10 districts and counties citywide on 362 fields of four types: wheat, rapeseed, weeds and green manure, with an average of 20,600 insects per mu (48,700 in the same period last year). The peak hatching period of the first generation of small brown planthopper is expected to be around April 25, with an occurrence of 250,000-400,000 per mu, and the occurrence degree will be moderate to severe, up to outbreak level.

(3) Wheat aphid

According to systematic surveys of wheat aphids by plant protection stations in each county (district), on April 14 the average rate of aphid-infested plants was 9.33%, ranging from 2.0 to 12.0%, with 38.0 aphids per 100 plants, ranging from 14.0 to 98.0, slightly fewer than the 165 in the same period in previous years. It is expected that after wheat heading, as temperatures rise, wheat aphids will increase markedly, with a moderate occurrence degree.

(4) Powdery mildew

Wheat powdery mildew was found on April 5, making this a late-occurrence year. On April 14, the average diseased plant rate in affected areas was about 20%, with a maximum of 31%. As temperatures rise, the rise of powdery mildew is expected to accelerate from late April, with a moderate to light occurrence degree.

II. Control Recommendations

At the heading stage of wheat, the control focus is wheat scab, while also controlling the small brown planthopper, wheat aphid and powdery mildew. For armyworms, each area may formulate measures according to the actual field pest situation. The main purpose of controlling the small brown planthopper is to effectively reduce the field base of the small brown planthopper in wheat fields and minimize the number of first-generation small brown planthoppers migrating to rice fields.

1. Selection of pesticides: (1) 25% Chimeiqing wettable powder 105 g per mu (1.5 packets) + 25% pymetrozine wettable powder 20 g per mu. (2) 25% Chimeiqing wettable powder 105 g per mu (1.5 packets) + 10% imidacloprid wettable powder 40 g, sprayed with 50 kg of water. For armyworm control, 25% Kuishaling (phoxim and fenvalerate emulsifiable concentrate) can be used at 100 mL per mu. For some varieties susceptible to powdery mildew, fenarimol should be added separately.

2. Suitable control period and frequency: For scab control, a full application should be made once from full heading to early flowering, around April 20-26. After that, depending on the weather trend and the actual occurrence of the small brown planthopper in the field, a second control should be carried out. For areas with tender and green late growth, as well as high-yield demonstration areas, a second control must be ensured.

3. If continuous rainy weather occurs during the suitable control period, seize sunny days for emergency control and do not miss the suitable control period.

III. Precautions:

1. In areas with bee release, @#@234@#@, and @#@235@#@, organophosphorus pesticides should be used with caution.

2. When applying pesticides, spray the solution onto the entire plant of the crop.