Effect of exotic invasive old world climbing fern (lygodium microphyllum) on soil properties

Old World climbing fern (Lygodium microphyllum) has become one of the most serious ecological threats to the integrity of the greater Everglades ecosystem of south Florida. In this study, we analyzed the effects of Old World climbing fern on surfacesoil characteristics at invaded sites in Florida. We compared soil characteristics of six invaded and adjacent uninvaded plots at three different locations. Our results show that the fern can grow and thrive in a wide range of soil types and the impact on the soil was site specific with effects being more prominent in sites with low nutrient status. Additionally, there were significant differences in the soil nutrient status and microbial population in the invaded and uninvaded sites. Sites with Old World climbing fern had significantly higher nutrient concentrations that correlated with higher soil organic matter. Overall our results indicate that this exotic pest plant can potentially alter its below ground environment to its own benefit by enhancing the soil nutrient status by adding soil organic matter

Native and non-native plant species differentially affect arthropod community dynamics with consequences for crop production in Lower Rio Grande Valley

In agricultural ecosystems, arthropods play critical roles- including biocontrol, pollination services, and as herbivores. While herbivory negatively affects crop production, the recent decline in beneficial insect numbers have created a global concern, and consequently have led into multiple lines of conservation strategies. Agroecological practices that can provide sustenance, nesting, and refuge for beneficial organisms are considered as some of them, except we lack a better understanding of how seasonal and crop specific variation can affect their community dynamics. In this study, we examined this by investigating how native and non-native plants, when incorporated into a vegetable agroecosystem in Lower Rio Grande Valley in south Texas can influence arthropod community over their life cycle. We used a combination of different trapping systems and the following species: four species native to Texas: Ratibidia columnifera, Helianthus anuus L., Desmanthus virgatus var. and Pappophorum bicolor. We then compared these results to the non-native species Lobularia maritima (L.) Desv. We found that among the arthropods trapped, pests accounted for 66.3%, and were significantly more prevalent than beneficials. More specifically, we found that sampling time and feeding guild, also affected arthropods, but not plant species or their native/ invasive status. Detailed analyses also revealed that Eulophidae was the most abundant parasitoids family, and Aleyrodidae was the most abundant herbivore family. We followed the experiment by also examining whether these differences had any consequences for eggplant, the cash crop planted post cover, although we found no significant effects. Collectively, we show that arthropod community response to vegetation is variable, and a single species may not create the interactive dynamics to meet the benefits desired in food production and needs to be examined further

Soil Nematode Trophic Group Composition and Influence on Growth of Amaranthus palmeri and Parthenium hysterophorus

Weeds have a significant impact on agricultural systems. They not only cause a loss in crop yield by competing with them for resources, but they can also serve hosts for several pests and parasties such as plant parasitic nematodes casusing additional crop loss. The aim of this study was to analyze plant-nematode feedback in two major weeds, Amaranthus palmeri S Watson and Parthenium hysterophorus L. First, a field survey was conducted to determine the rhizosphere nematode trophic groups associated with these two plants in the summer of 2020 and 2021. Then a 6-week greenhouse study was conducted where the two weed species were treated with nematode communities extracted from their respective rhizospheres. Results from this study show that both weeds harbored a high number of herbivore nematodes, followed by fungivore and bacterivore nematodes. Total number of these nematodes were highly influenced by total sol carbon, pH and salinity. Under greenhouse conditions, the nematode treatment did not have any impact on the growth of P. hysterophorus but A. palmeri plants treated with nematodes had significantly higher above ground biomass. In conclusion, plant-nematode relationships are complex. Given the extent of direct damage caused by these weeds and plant parasitic nematodes in global crop production, the weeds-nematode feedback warrants further detailed studies

Cover crops for weed suppression in organic vegetable systems in semiarid subtropical Texas

Economic losses due to weeds are exceptionally high in organic agriculture particularly in tropical and subtropical growing regions where weeds are persistent year-round. For organic vegetable growers, weed control accounts for the largest portion of labor effort to produce crops. The use of cover crops during fallow period has gained popularity among organic growers who cannot use synthetic herbicides on their farms for weed management. We conducted a 2-year study in a certified organic vegetable farm in the semiarid subtropical region of south Texas. We compared cover crop canopy closure, cover crop and weed biomass, and subsequent weed emergence in cash crops after cover crop termination for four different cover crop treatments: sudangrass (Sorghum × drummondii), sunn hemp (Crotalaria juncea), cowpea (Vigna unguiculata), and a mix of the three species. Sudangrass produced the highest biomass followed by the three-species mix in 2017, while cowpea treatments had the lowest total cover crop biomass in both years. Weed biomass was the highest untreated fallow (control) and there was no significant difference among the four cover crop treatments. When followed by subsequent cash crops, the weedy fallow plots had significantly higher weed biomass in both years, and in 2018, sunn hemp plots had the lowest weed biomass. Overall, our results indicate that cover crops, especially those with the ability to grow quickly and develop a closed canopy or known to have allelopathic properties, have the potential to control weeds in organic vegetable farms in semiarid subtropical Texas