Using Analytical Techniques and Cole Crop Field Responses to Quantify 2,4-D plus Glyphosate Removal from the Surface of Plastic Mulch

Planting cole crops and leafy greens in plastic mulch free of summer and winter annual broadleaf weeds is challenging. Because these crops are often grown as a second or third crop on mulch, weeds emerge in previously punched plant holes, tears in plastic, and row middles. Without the ability to use tillage and with limited herbicide options available for weed control, achieving a weed-free planting window is not often feasible. Additional herbicide options are needed, but their interaction with plastic mulch must be understood. Therefore, research has determined the persistence of preplant applications of 2,4-D tank-mixed with glyphosate applied over plastic mulch. Analytical laboratory analyses of plastic samples from field experiments, in conjunction with bioassays using broccoli (Brassica oleracea var. botrytis L.) and collard (Brassica oleracea var. viridis L.), evaluated herbicide dissipation. Analytical studies determined that 0.5 cm of irrigation after herbicide application and 1 day before planting removed 99% of 2,4-D, and 100% of glyphosate from the plastic mulch. Waiting an additional 14 days after application and irrigation further reduced the amount of 2,4-D on the plastic mulch 88% to 95%. For the field bioassay, preplant applications of 2,4-D tank-mixed with glyphosate resulted in 7% or less visual broccoli or collard injury without influencing crop growth, biomass, early season yield, or total yield as long as the mulch was washed with 0.5 cm of irrigation before planting. These studies also demonstrated there were no differences between the 1× and 2× use rates with respect to all response variables measured. Results suggest that 2,4-D and glyphosate can be effectively removed from the surface of plastic mulch with irrigation or rainfall before planting broccoli and collard.

Olive Fruit Fly, Bactrocera oleae (Diptera: Tephritidae), Attraction to Volatile Compounds Produced by Host and Insect-Associated Yeast Strains

The olive fruit fly, Bactrocera oleae (Rossi), is one of the most damaging insect pests of olives worldwide, requiring the use of insecticides for fruit protection in many orchards. Olive fruit flies are attracted to volatile composunds, including a female-produced pheromone, and host-plant and bacterial volatiles. Preliminary laboratory bioassays were conducted for olive fruit fly attraction to over 130 yeast strains from among 400 that were isolated from B. oleae adults and larvae or other insects, infested olives, and potential feeding sites. Kuraishia capsulata, Scheffersomyces ergatensis, Peterozyma xylosa, Wickerhamomyces subpelliculosus, and Lachancea thermotolerans appeared to attract B. oleae as well or better than did torula yeast pellets (Cyberlindnera jadinii; syn. Candida utilis). Volatile compounds emitted by these yeast strains were chemically identified, and included isobutanol, isoamyl alcohol, 2-phenethyl alcohol, isobutyl acetate, and 2-phenethyl acetate. The behavioral response of B. oleae adults to these volatile compounds at three concentrations was tested in a laboratory Y-tube olfactometer. The same volatile compounds were also tested in the field. Isoamyl alcohol was more attractive than the other compounds tested in both laboratory and field bioassays. Isobutanol was not attractive to B. oleae in either laboratory bioassay or field bioassay. Identifying yeast volatiles attractive to the olive fruit fly may lead to development of a more effective lure for detection, monitoring, and possibly control of B. oleae.

Initial Location Preference Together with Aggregation Pheromones Regulate the Attack Pattern of Tomicus brevipilosus (Coleoptera: Curculionidae) on Pinus kesiya

Research Highlights: We found that the initial attack location together with the aggregation pheromones played an important role in mediating the aggressive behavior of T. brevipilosus on P. kesiya. Background and Objectives: T. brevipilosus was identified as an aggressive species, which possesses the ability to kill live, healthy P. kesiya. In this scenario, we study the top-down attack pattern of T. brevipilosus on P. kesiya during the entirety of the reproductive period. Materials and Methods: We investigated the phenology of trunk attack on P. kesiya over a period of three years in Pu’er City, China. The hindguts extracts of the females and males T. brevipilosus were analyzed by coupled gas chromatography-mass spectrometry (GC-MS). The candidate aggregation pheromone compounds of T. brevipilosus were determined through electrophysiology experiments (electroantennographic detection, EAD and electroantennography, EAG), laboratory olfactometer bioassays, and field trapping. Results: we found that the pioneer beetles preferentially infested the crown of P. kesiya at the early stage of attack following spring flight with the later arriving beetles selectively attacking the lower area of the trunk to avoid intraspecific competition and better utilize limited resources, which exhibits a top-down attack pattern. During gallery initiation, the beetles release aggregation pheromones to attract conspecifics to conduct a mass attack. The chemical analyses indicated that the hindgut extracts of gallery-initiating beetles contained a larger amount of myrtenol, cis-verbenol, trans-verbenol, and verbenone. Myrtenol and trans-verbenol were identified as candidate aggregation pheromone compounds. In addition, a blend of these two components with S-(−)-α-pinene and S-(−)-β-pinene attracted more T. brevipilosus individuals in a field bioassay. Conclusions: We concluded that the preference for the initial attack location together with the aggregation pheromones played an important role in mediating the top-down attack pattern of T. brevipilosus on P. kesiya.

Respostas eletroantenográficas e comportamentais de abelhas africanizadas, Apis mellifera (Linnaeus), ao feromônio de Nasanov e ao óleo essencial de capim-limão

Resumo. O objetivo do estudo foi avaliar as respostas eletrofisiológicas e comportamentais de abelhas africanizadas, Apis mellifera (Linnaeus), em duas idades, ao feromônio de Nasanov sintético (FNS) e ao óleo essencial de capim-limão (OCL), e verificar a porcentagem de ocupação de enxames em caixas de papelão com iscas de FNS comercial (Swarm Catch Lure®) ou OCL formulado em emulsão de parafina. Foram observadas as respostas eletroantenográficas (mV) e comportamentais de abelhas operárias nutrizes e campeiras (1-5 e 20-30 dias de idade, respectivamente) aos referidos compostos, em olfatômetro de dupla escolha. Os bioensaios de campo foram conduzidos em Eldorado do Sul e Minas do Leão (Brasil, RS), utilizando-se doze caixas com dois caixilhos contendo uma tira de cera alveolada cada e iscadas com OCL ou FNS ou sem tais tratamentos (controle). Não foram observadas diferenças nas respostas eletrofisiológicas e comportamentais entre operárias jovens e velhas submetidas aos voláteis de FNS e OCL. O limiar de resposta para o feromônio foi de 0,1 mg/mL e para o óleo, 10 mg/mL. O feromônio de Nasanov e o óleo de capim-limão desencadearam resposta quimiotáxica positiva nas abelhas. Caixas com FNS atraíram mais enxames que as com OCL e controle.Electroanthenographic and behavioral responses of Africanized bees, Apis mellifera (Linnaeus), to nasanov pheromone and lemongrass essential oilAbstract. The study aimed to evaluate and compare the electrophysiological and behavioral responses of africanized honey bees (workers), Apis mellifera (Linnaeus) at different ages, to synthetic Nasanov pheromone (SNP) and to lemongrass essential oil (LGO), as well as, to verify occupancy percentage of swarms in baited cardboard boxes with SNP commercial (Swarm Catch Lure®) or LGO formulated in paraffin emulsion. Tests were conducted to observe electroantennographic responses (mV) and chemotactic behavior of nurse and forage workers bees (1-5 and 20-30 days old, respectively), to those compounds, in two choice olfactometer. The field bioassay was conducted by using twelve cardboard boxes with two bee wax sheet foundation placed in each frame, baited with SNP or LGO or without these treatments (control), in Eldorado do Sul and Minas do Leão (Brazil, RS). The mean number of swarms found in all treatments, were checked weekly. It was not observed electrophysiological and behavioral difference responses between young and old workers subjected to SNP and LGO odors. The threshold to Nasanov synthetic pheromone was 0.1 µg/µL and to lemongrass essential oil, 10 µg/µL. Synthetic Nasanov pheromone and lemon grass oil triggered positive chemotaxis in bees. Cardboard boxes with commercial SNP were more attractive to swarms than those baited with LGO and control treatment.

Queen's Genetically Engineered Machine Team (QGEM): Nemoremediation

Synthetic biology is a rapidly growing field that tries to simplify genes into “biobricks” and use these to push the limits of what is possible in genetic engineering. The Queen's Genetically Engineered Machine Team competes annually at the International Genetically Engineered Machine Competition, one of the largest undergraduate research conferences on the planet. Last year’s project focused on modifying the nematode worm, C. Elegans to chemotax, or seek out and degrade pollutants, such as naphtalene. We have produced genetic constructs with protein receptors from M. musculus, R. norvegicus, and H. sapiens intended to enhance the worm's ability to chemotax towards naphthalene and other pollutants. We also worked on a field bioassay based on fluorescent proteins that will indicate the presence of naphthalene in a soil sample. The goal is to have a population of green fluorescent worms chemotaxing toward and a population of red fluorescent worms chemotaxing away from the napthalene in the soil sample. Finally, we have added the P. putida gene, nahD, to the biobrick registry, which encodes a degradative enzyme as part of a naphthalene catabolic pathway.

Halosulfuron-Methyl Degradation from the Surface of Low-Density Polyethylene Mulch Using Analytical and Bioassay Techniques

Vegetable injury and yield loss has occurred when applying halosulfuron to low-density polyethylene mulch (LDPE) prior to transplanting. Research determined vegetable crop response to halosulfuron applied over LDPE mulch from 1 to 28 d prior to transplanting using (1) temperature effects in aqueous solution in laboratory experiments, (2) analytical evaluation of degradation from LDPE under field conditions, and (3) a field bioassay. Halosulfuron stability was evaluated on a thermal gradient table for temperatures at 10 to 42 C for 15 d. Half-life was inversely related to temperatures ranging from 38.5 d at 20 C to 3.2 d at 42 C, with little to no degradation at temperatures of 11 and 15 C. Analytical data indicated that the field half-life of halosulfuron at 26 or 52 g ha−1applied to LDPE mulch under dry conditions was 2.6 and 2.8 d, respectively. Given the changes in the microclimate effects at the mulch surface by absorption of solar radiation, daily thermal energy quantified halosulfuron degradation (at the same rates) to be 51 and 55 MJ m−2, respectively. At 21 d after treatment (DAT), 90% of halosulfuron had dissipated from the mulch, with none detectable 35 DAT under dry conditions. When watermelon or yellow crookneck squash was transplanted into mulch previously treated with halosulfuron at 79 g ha−1, plant growth and development were equal to nontreated controls as long as there was a 14 d prior to transplant (DPT) interval accompanied by 13.5 cm of rain, or a 17 DPT interval accompanied by 6.2 cm of rain. However, at 79 g ha−1applied at 9 or 1 DPT in 2013, and 1 DPT in 2014, halosulfuron injured yellow squash and reduced yield and fruit number. Halosulfuron at 79 g ha−1applied 1 DPT significantly reduced watermelon yield in 2013, which was confirmed by vine length and plant biomass reductions in 2014. Halosulfuron POST controlsCyperusspp. in mulch vegetable production, but time and rainfall are required for dissipation to occur in order to prevent injury and yield loss.