Phenotypic Plasticity of Life History Characteristics: Quantitative Analysis of Delayed Reproduction of Green Foxtail (Setaria viridis) in the Songnen Plain of China

Green foxtail （Setaria viridis L.） is a common weed species in temperate regions. Research on the effect of delayed reproduction on the phenotypic plasticity and regularity of the vegetative and reproductive growth is of vital significance for understanding population regulation and control of the weed in the growing season. Green foxtail seeds were sown every 10 days from 25 June to 24 August of 2004. The growth and production metrics were measured via harvesting tufts and statistical analysis was carried out. The results showed that the reproductive tillers, seed number, seed biomass and one thousand-seed weight of plants at the first sowing （25 June） approximately increased 28.8, 7 827.0, 1 104,0 and 12.3 times compared with that at the last sowing （24 August）, respectively. Total tillers, reproductive tillers and height increased linearly as the reproductive period delayed, however, biomass increased exponentially. Quadratic equations best explained the relationships between the delayed reproductive period and seed number, inflorescence length, one thousand-seed weight, seed biomass. Based on the quantity and quality of seed production, weeding young seedlings emerging before July can be the most effective weed-control strategy in the Songnen Plain.

Antifeedant Activity of Three Plant Extracts Including P. acinosa against Pieris rapae

[Objective] The research aimed to study antifeedant activity of Phytolacca acinosa Roxb., Setaria viridis （L.） Beauv and Viola yedoensis Makino extracts against Pieris rapae. [Method] Activity material was extracted from S. viridis （L.）, P. acinosa and V. yedoensis using acetone cold soak method, and non-selective antifeedant activity of extracts to Pieris rapae larva was determined by using lobular plate addition method. [Result] The results showed that the acetone leaching agent of P. acinosa had most obvious antifeedant effects on Pieris rapae. The antifeedant rate were 74.53% and 82.34% at 24 and 48 h respectively. With the concentration increasing, the antifeedant effect of P. acinosa extracts increased. The antifeedant rate of 0.050 g/ml treatment was the highest, being 74.53% and 82.34% at 24 and 48 h. [Conclusion] P. acinosa could be studied and utilized as potential botanical insecticide.

Benefit of Adding Ammonium Sulfate or Additional Glyphosate to Glyphosate in Corn and Soybean

Nine field trials (4 in corn and 5 in soybean) were conducted over 2 years (2014 and 2015) to determine if there is greater benefit of adding ammonium sulfate (AMS) (2.5 L·haˉ1) or an equal dollar value of glyphosate (406 g·ae·haˉ1) to glyphosate applied at 450, 675 or 900 g·ae·haˉ1 for weed control in corn and soybean. Glyphosate applied at 450 g·ae·haˉ1 controlled velvetleaf 90% to 98%, common ragweed 80% - 97%, common lambsquarters 91% - 99%, Eastern black nightshade 83% - 100% and barnyardgrass 73% - 97% in corn and common ragweed 37% - 89%, common lambsquarters 39% - 98%, barnyardgrass 90% - 98% and green foxtail 91% - 98% in soybean. The addition of AMS to glyphosate applied at 450, 675 or 900 g·ae·haˉ1 provided little to no added benefit for the control of velvetleaf, common ragweed, common lambsquarters, Eastern black nightshade, barnyardgrass and green foxtail in corn and soybean. There was a greater benefit in weed control efficacy by simply adding and equal dollar value of glyphosate (406 g·ae·haˉ1) than AMS (2.5 L·haˉ1) to glyphosate. There was no difference in corn or soybean yield among the herbicide treatments evaluated. Based on these results, addition of AMS to glyphosate at rates evaluated had little benefit on weed control efficacy or yield of corn and soybean.