Wild carrot is becoming a serious weed problem in Michigan continuous no-tillage crop production. Greenhouse and field research was conducted to identify effective management strategies for wild carrot control in no-tillage cropping systems. In the greenhouse, PRE applications of acetochlor plus dichlormid (5.8:1 w:w), cyanazine, linuron plus chlorimuron (18:1), and metribuzin plus chlorimuron (10:1) and POST applications of bentazon, CGA-152005, clopyralid, cyanazine, and MON 12000 provided the greatest control of wild carrot seedlings. In the field, PRE and POST treatments containing chlorimuron consistently controlled overwintered wild carrot greater than 71% at 30 d after the POST application in no-tillage soybean. Atrazine, MON 12000, nicosulfuron, and primisulfuron applied POST consistently controlled overwintered wild carrot greater than 78% at 30 DAT in no-tillage corn. Glyphosate at 0.84 or 1.68 kg ae/ha applied in October to established wild carrot provided greater than 74% control the following spring. Early preplant (EPP) applications of glyphosate at 0.84 kg/ha in no-tillage soybean gave 95 and 24% control of overwintered wild carrot in St. Clair and Lenawee Counties, MI, respectively, at 70 DAT. PRE applications of glyphosate at 0.84 kg/ha controlled overwintered wild carrot less than 69% at 58 DAT in no-tillage corn and soybean. Fall applications of 2,4-D ester at 1.12 kg ae/ha provided 18 and 88% control of wild carrot the following spring in Clinton and Lenawee Counties, respectively. EPP applications of 2,4-D ester at 1.12 kg/ha provided 7 and 72% control of overwintered wild carrot in St. Clair and Lenawee Counties, respectively.

Field and growth chamber experiments determined the efficacy of temporal glyphosate applications on velvetleaf. Glyphosate was applied postemergence to velvetleaf periodically before and during light and after dark. In 1999, glyphosate at 840 g ae/ha applied before sunrise and after midday provided 54 and 100% velvetleaf control, respectively. In 2000, glyphosate at 840 g/ha applied before sunrise, midday, and after sunset provided 69, 100, and 37% velvetleaf control, respectively. In the growth chamber, glyphosate at 840 g/ha applied before or after light reduced velvetleaf biomass 15 to 20% or 32 to 47%, respectively, and reduced velvetleaf height 24% or 45 to 54%, respectively. Velvetleaf control was consistently greater with glyphosate applications during light compared with dark, regardless of constant air temperature and relative humidity (growth chamber), dew absence or presence (field and growth chamber), or leaf blade orientation (growth chamber) with natural light–dark movements or a fixed horizontal position.

Differential response of wild carrot to 2,4-D was found in seeds collected from 10 locations in Michigan, three in Ohio, one in Illinois, and one in Ontario, Canada. Greenhouse studies were conducted on plants grown from the collected seeds to confirm resistance of wild carrot to 2,4-D, and to study variations among and within populations. The differential response of wild carrot to 2,4-D in field research was due to resistant individuals. Among the 14 locations, wild carrot control with 2,4-D ranged from 18 to 91%. Wild carrot varied in its response to 2,4-D among and within populations as well as within individual umbels. In 69% of the tested samples, at least one wild carrot plant was resistant to 2,4-D.

Potato exhibits adequate tolerance to preemergence applications of sulfentrazone at rates up to 0.28 kg ai ha−1. Sulfentrazone also controls several troublesome weeds such as common lambsquarters but may be less effective against jimsonweed. Laboratory experiments were conducted to investigate differential tolerance to root-absorbed [14C]sulfentrazone by potato, common lambsquarters, and jimsonweed. Common lambsquarters and jimsonweed absorption of [14C]sulfentrazone g−1 fresh weight was more than twofold that in potato after 24-h exposure. After 48-h exposure, sulfentrazone absorption by common lambsquarters was nearly twofold that in jimsonweed and nearly threefold that in potato. Sulfentrazone movement from roots to shoots was also greater in common lambsquarters than in jimsonweed and potato after 6 h. Both weed species exhibited nearly a twofold increase in sulfentrazone translocation from roots to shoots compared with potato after 12, 24, and 48 h. Minor differences in sulfentrazone metabolism in roots were noted among species after 6 h. Metabolism in roots and shoots was similar in all species after 12, 24, and 48 h. Because the enzyme on which sulfentrazone acts, protoporphyrinogen oxidase, is located in shoot tissue, translocation to shoots is essential for sulfentrazone toxicity. Therefore, differential root absorption and differential translocation of sulfentrazone from roots to shoots are the proposed primary mechanisms of differential sulfentrazone tolerance among potato, common lambsquarters, and jimsonweed.

Anecdotal reports suggest waterhemp is becoming more difficult to control with glyphosate. Waterhemp accessions collected primarily in Illinois before 1996, in 1998 to 1999, and in 2003, were evaluated for differential responses to glyphosate treatment. The pre-1996 group consisted of 10 accessions, whereas the 1998 to 1999 and 2003 groups consisted of 45 accessions each. Plants 10 to 12 cm in height from each waterhemp accession were treated with 0 or 220 g ae ha−1 glyphosate. Although shoot dry biomass 14 d after treatment, expressed as a percentage of the untreated, varied within and among accessions, the mean responses of the three groups were similar. However, when glyphosate responses were divided into 10 arbitrary classes (0 to 10, 11 to 20, …, and 81 to 90; > 91% of untreated), the number of plants within each class differed among groups. Most notably, the proportion of plants in the range of 0 to 30% of the untreated control decreased with time when progressing from the pre-1996 to the 2003 accessions. The relative frequency of waterhemp plants that were ≥ 100% of the untreated plants (i.e., uninjured by glyphosate) in the pre-1996, 1998 to 1999, and 2003 groups were 5, 6, and 5%, respectively. In a separate trial, waterhemp populations that exhibited the least sensitivity to glyphosate at 220 g ha−1 were controlled by 870 g ha−1 glyphosate. These results suggest that waterhemp, as a whole, within Illinois has not become less sensitive to glyphosate over the past few years. However, the proportion of plants that are most sensitive to glyphosate may be decreasing within populations.

Benthic nematode and macrofaunal communities are regularly utilized in impact studies. However, very few studies are carried out utilizing both communities. A literature search using the search engine Scopus (www.Scopus.com) covering the last twenty years, using the keywords ‘Macrofauna’ and ‘Disturbance’ then ‘Meiofauna’ and ‘Disturbance’ and finally ‘Macrofauna and Meiofauna’ and ‘Disturbance’, gave 210, 115 and 36 hits respectively. To assess the differential response of meio- and macrofauna to in situ burial a replicated random block designed field experiment was carried out over a 9-month period on an intertidal mud flat. In situ burial was achieved by spreading 4 cm of anoxic mud on top of each treatment plot at two different intensities. Differences in the response of the two faunal communities over time were assessed using both univariate and multivariate techniques. Clear differences in community behaviour over time and in response to the different intensities of disturbance were observed. Overall macrofauna were found to be more sensitive to physical disturbance than meiofaunal nematodes, although, attributes of meiofaunal nematode communities were more sensitive to the initial impacts of disturbance. The observed community-specific responses and sensitivities of meiofauna and macrofauna to the physical disturbance associated with in situ burial highlights the importance of using both faunal types in the assessment of the effects of seabed disturbance in the marine environment.