Effects of application of three insecticides (imidacloprid, pymetrozine and lufenuron) on host searching and oviposition behavior of Neochrysocharis formosa (Westwood), a larval parasitoid of the American serpentine leafminer Liriomyza trifolii (Burgess), were investigated in the laboratory. Female wasps spent more than 89% of their time on a leaf of host-infested kidney bean when introduced into a container containing the leaf treated with each insecticide or distilled water. However, wasps spent more time resting near or away from hosts and less time foraging for hosts on the leaves treated with imidacloprid than the other treated leaves. As a result, they encountered, oviposited and fed on hosts less frequently with imidacloprid treated leaves than any other treated leaves. The numbers of host findings, ovipositor insertions and host feedings were also significantly lower on the leaves treated with lufenuron than the control. These results suggest that imidacloprid and lufenuron reduced wasp host searching efficiency.

Vietnam is the world's fifth largest rice producing country. Since methane (CH 4 ), a potent greenhouse gas (GHG), emission from the rice cultivation accounts for 14.6% of the national anthropogenic GHG emission, developing and disseminating mitigation options are the urgent need. Alternate wetting and drying (AWD) is the irrigation technique, in which a paddy field encompasses several soil-drying phases during the growth period, thereby reducing the CH 4 emission. However, field trials of the AWD's feasibility in Central Vietnam are limited so far. We therefore carried out a 3-year experiment in a farmer's field both in winter-spring season and summer-autumn season. CH 4 and nitrous oxide (N 2 O) emissions were compared among the three treatments of water management: continuous flooding (CF), AWD, and site-specific AWD (AWDS) that changed the degree of soil drying depending on the growth stage. The total water use including irrigation and rainfall was significantly (p < 0.05) reduced by AWD (by 15%) and AWDS (by 14%) compared to CF, but rice grain yield did not differ among the three treatments. The seasonal cumulative CH 4 emission was significantly reduced by AWD (26%) and AWDS (26%) compared to CF, whereas the seasonal cumulative N 2 O emission did not differ among treatments. The resultant global warming potentials (GWPs) of CH 4 and N 2 O under AWD and AWDS were 26% and 29% smaller than that under CF, respectively. The GWP of N 2 O was only 0.8% of the total GWP of CH 4 + N 2 O. The yield-scaled GWP and water productivity (i.e., the ratio of grain yield to water use) were also improved by AWD and AWDS. No significant differences in the measured items between AWD and AWDS were attributed to similar variation patterns in the surface water level. The results confirm the AWD's performance as a mitigation option for paddy GHG emission in Central Vietnam. ARTICLE HISTORY

Soil fertility regulates invasive herbivore performance and top-down control in tropical agroecosystems of Southeast Asia The International Center for Tropical Agriculture (CIAT) believes that open access contributes to its mission of reducing hunger and poverty, and improving human nutrition in the tropics through research aimed at increasing the eco-efficiency of agriculture. CIAT is committed to creating and sharing knowledge and information openly and globally. We do this through collaborative research as well as through the open sharing of our data, tools, and publications.

Amaranth (Amaranthus tricolor L.) is a plant that is rich in vitamins, minerals, and phytochemicals. It is grown as a leafy vegetable in marginal environments, but high salinity levels in the soil can have a detrimental effect on its growth. These deleterious effects of salinity can be alleviated by exogenously applying signaling compounds such as salicylic acid (SA) and calcium (Ca), which can improve plant adaptation to stressful conditions. The present study evaluated the physiological and phytochemical responses of red amaranth (Amaranthus tricolor L.) to foliar-applied salicylic acid (SA; 0.005 mM) and calcium (CaSO 4 •2H 2 O; Ca, 2.5 mM) either alone or in combination (SA + Ca) under conditions of 100 mM NaCl salinity. The setup was placed under greenhouse condition from May to October 2017. Treatments without salinity and applied with SA or Ca were used as controls for comparison. Salinity stress reduced the growth and biomass, total chlorophyll contents, and increased electrolyte leakage with Na + and Cl − accumulation in shoot and roots. Nonetheless, exogenous applied SA and/or Ca 2+ reduced the adverse effects of salinity by modulating growth, Na + exclusion from roots, and increased total phenolics, flavonoids, and antioxidant activity in red amaranth. The combined application of salicylic acid and calcium can be a better strategy for improving the salinity tolerance of amaranth under salt-stressed conditions.

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