Association of host plant growth and weed occurrence with armyworm(Mythimna separata) damage in corn fields

To clarify association between armyworm（Mythimna separata） damage level and the corn growth and weed occurrence, we investigated corn plant height, stem diameter and vigor as well as weed coverage and biomass. The investigations were conducted at three locations of Shaanxi Province, China which were suffered seriously from armyworm. Significant correlations were found between the parameters analyzed. At stunted corn growth and presence of plenty of weeds, the armyworm damage tended to be heavy; oppositely, when corn grew well and weed density were low, armyworm harm was the minimal. Therefore, corn growing status and weed density can significantly affect armyworm damage level. Our results imply that promoting corn growth and timely removal of weeds are conducive to reducing armyworm occurrence.

Preparation of 55% MCPA-isooctyl and Ametryn EC and Its Field Efficacy

[ Objective] The purpose was to supply experimental base for preparing new types of high efficient and safe mixture herbicide for sugarcane field. [ Method ] The associated function of MCPA-isooctyl and ametryn on Digitaria sanguinalis and Celosia argentea was evaluated by co-tox. icity coefficient method by potting experiment. [ Result] When active ingredient of MCPA-isooctyl and ametryn was mixed in the proportion of 9： 5, there was obvious synergistic effect on D. sanguinalis and C. argentea, while the co-toxicity coefficients reached 156.24 and 140.40. Proportion method and bisection method were used to confirm the optimum proportion of various ingredients in mixture of MCPA-isooctyl and ametryn, and the optimum proportion was as follows： 35.4% MCPA-isooctyl, 19.6% ametryn, 10.0% emulsifier and the rest were solvents. The stability test indicated that each index of this EC was consistent with standard for pesticide EC. Field efficacy test of 55% MCPA-isooctyl and ametryn EC showed that most weeds in sugarcane field could be effectively controlled with the dose range of 1 073 -2 310 g （a. i. ）/hm^2. [ Conclusion ] Mixture product of ametryn and MCPA-isooctyl with high content was successfully developed, which had the advantages including high efficiency, broad spectrum, good economy and convenient utilization, etc.

Chemical Weeding in Dry Direct Seeding Fields of Single Cropping Middlelate Rice

Chemical weeding in dry direct seeding fields of single cropping middle-late rice was studied in Huida vegetable farm of Huizhou City in 2012. The main treatment was herbicide（ pretilachlor ＋ bensulfuron-methyl,Yangguo and butachlor）,and the sub-treatment was application method（ soil treatments,seedling treatment and integrated treatment）. The results showed that 80 g pretilachlor ＋ bensulfuron-methyl（ 36% pretilachlor ＋ 4% bensulfuron-methyl） diluted with 50 kg water could be sprayed or 200 g Yangguo（ 23. 9% butachlor ＋ 1. 1% bensulfuron-methyl） mixed with 15 kg sandy soil could be broadcasted per 667 m2 on the sowing day or the second day under moist condition of soil,which could effectively control weeds in dry direct seeding fields of single cropping middle-late rice.

Prevention Effects of Pyrazosulfuron-ethyl·Quinclorac 50% WP on Stem and Leaf of Dry Direct Seeded Rice

[Objective] The aim was to explore the prevention effects of pyrazosul-furon-ethyl·quinclorac 50% WP on stem and leaf of dry direct seeded rice. [Method] Totaling 7 drug doses were set in the test and the effects were observed 5, 10, 15 and 30 d after drug application, with the remained weeds surveyed 15 and 30 d after drug application. [Result] The test showed pyrazosulfuron-ethyl·quinclorac 50%WP was safe to rice as treatment agent of stem and leaf, and rice yield increased dramatical y, with the growth rate in 2.1%-49.3%. After the drug application, the prevention effects on Echinochloa crusgal i, Ludwimlia prostrata, Monochoria vamli-nalis, and Zong grass were 92.2%, 96.6%, 93.5%, and 94.8%, and the effects on fresh weight were 94.8%, 97.1%, 93.3% and 94.9%, respectively. [Conclusion] Pyra-zosulfuron-ethyl·quinclorac 50% WP can be taken as treatment agents of stem and leaf of dry direct seeded rice.