Field‐scale experiments were conducted in 2005 and 2006 on three cooperative farms in DPR Korea to evaluate the potential of Trichogramma ostriniae releases to reduce tunnel damage of maize plants caused by the Asian corn borer, Ostrinia furnacalis, and increase grain maize production. When released three times against the first generation of the pest at nominal densities of about 150 000 parasitoids/ha each and another two times against the second generation (in total 750 000 parasitoids/ha), significant effects on all assessed parameters were obtained. In the release plots, a mean parasitism rate of 61% was found, significantly different from the 21.8% found in non‐release (control) plots. Furthermore, the number of larvae was significantly reduced in release plots compared to control plots by 63.5% over all farms and both study years. Feeding tunnels caused by the Asian corn borer were reduced in length in the release plots by 64.1%. Finally, we found that fresh yield of maize ears was significantly higher in the release plots compared to control plots. For all farms and both years, the increase in fresh yield was 28.2%. In this paper we are for the first time presenting data in an international journal on the effect of Trichogramma releases on maize production in DPRK. Although T. ostriniae releases at high host densities observed in the present study were not able to completely suppress damage by the Asian corn borer, the yield increase of more than 1 ton/ha indicate that T. ostriniae releases may contribute significantly to stabilize the country’s maize production as well as support community efforts to avoid reversion into a food emergency situation.
Athetis lepigone (M€ oschler) is a new insect pest that feeds on corn seedlings in summer corn region of China. It is an omnivorous insect, which not only infests corn, soya bean, peanut and other crops, but also feeds on fallen and decaying leaves of some crops and weeds. Effects of host plants, corn, cotton, peanut, wheat and soya bean, on larval and pupal development and survival, and the fecundity of adults of A. lepigone were studied under laboratory conditions. The developmental time from egg to adult was the shortest (30.78 days) on germinating wheat kernels and the longest (40.13 days) on corn leaves. Larval survival was the highest (80%) on germinating wheat kernels and lowest (55%) on soya bean leaves. Hatching rate was the highest (92.98%) where eggs were oviposited by the females developed from larvae that were fed on germinating wheat kernels. Similarly, fecundity was the greatest on germinating wheat kernels (337), while the lowest fecundity (145) was observed on cotton leaves. The highest intrinsic rate of increase (0.22) and net reproduction rate (181.39) were found on germinating wheat kernels. Germinating wheat kernels were recognized as the most suitable host plant for A. lepigone because of the shortest developmental period, highest survival and highest fecundity. The results correspond with the field habits of A. lepigone and clearly show differences in development and adaptability on the five tested host plants. The findings will serve as baseline information to better understand the biology of the pest, which can be utilized in an effective management programme.
In September 2010, grapevine {Vitis vinifera) trunk diseases were observed in several vineyards of Yantai District in Shandong Provinces and Changli County of Hebei Provinces of China. Characteristic symptoms of Botryosphaeria canker were apparent, including dark brown discoloration on the trunk (visible in cross-section), cob base shriveling, drying of fruit clusters, and berry falling (2). To identify the causal pathogen, culturing of fungi was attempted from 387 small pieces of tissue from the canker margins of 43 diseased plants. Samples were surface disinfected by placing them in 75% ethanol for 1 min and rinsing with sterilized water three times before culturing on potato dextrose agar (PDA) at 28°C for 7 to 10 days. Fungi isolated were single spored to obtain pure cultures. On the basis of colony characteristics on PDA, 18 isolates from the 387 tissue pieces were eventually identified as Botryosphaeria obtusa (1), Most of the other fungi isolated were B. dothidea. B. obtusa colonies were grayish white, becoming dark brown with age, and pycnidia were formed after incubation for approximately 7 days. Conidia measured 8 to 11 x 17 to 26 pm (n = 50). Two isolates were used for rDNA internal transcribed spacer (ITS) sequence analysis with primers ITSl and ITS4 (3). PCR products were separated by electrophoresis and bands were purified for legation with PMD-18T (Takara Company, Dalian, China) vector for sequencing. BLAST searches of two ITS sequences had 99 to 100% identity to B. obtusa. EFl-a and ß-tubulin sequence analysis gave similar results. Koch's postulates were completed in the greenhouse on grape shoots inoculated with two isolates of B. obtusa originally isolated from diseased plants in the field. Inoculations were made on green shoots of V. vinifera cv. Dunkelfelder T. Six shoots were inoculated per isolate by wounding with a 4-mm cork borer (2 mm deep) and placing a colonized agar plug from a 5-day-old culture on the wound and wrapping it with Parafilm. Controls were mock inoculated with an agar plug from sterile PDA. Inoculated shoots were incubated in the dark under moist conditions in the laboratory for 8 to 10 days at 25°C. Inoculated shoots had necrotic cankers after 8 to 10 days and B. obtusa was recovered from each canker margin. The results indicated that some grapevines in China with symptoms of Botryosphaeria canker were infected by B. obtusa. To our knowledge, this is the first report of this pathogen causing trunk disease on grapevine in China.Miscanthus sinensis Anderss., a perennial grass, is native to eastern Asia. It has been widely grown as an ornamental in temperate regions of the world, including the United States, and recently has become an important component of public and private sector bioenergy feedstock Miscanthus selection programs. In August 2008, stem rot and blight was observed on M. sinensis plants in two irregular patches, -2 to 2.5 x 1 to 1.5 m each in a trial plot that was preceded by corn, at the University of Illinois Energy Farm near Urbana, IL. At the time of the ...
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