Northern highbush blueberry is an important fresh market product in New Jersey where the plant was first domesticated in the early 20th century. Because of the short period for safely and timely applying postemergence (POST) herbicides, reliance on residual herbicides that provide season-long control of weeds is essential for blueberry growers to minimize the detrimental effect of weed competition on berry yield and quality and bush growth. Field studies were conducted from 2018 to 2020 in Chatsworth, New Jersey, on ‘Bluecrop’, ‘Duke’, and ‘Elliott’ blueberry cultivars growing on sandy acidic soil to evaluate weed control and crop tolerance in response to repeated annual applications of indaziflam at 73 or 146 g ai ha−1 applied in fall or spring. The efficacy of indaziflam treatments were compared to those of fall-applied dichlobenil at 3,300 g ai ha−1 or a spring-applied mix of diuron at 1,800 g ai ha−1, oryzalin at 3,360 g ai ha−1, and mesotrione at 210 g ai ha−1. Indaziflam at the currently labeled rate of 73 g ai ha−1 provided ≥85% and season-long control of horseweed, Canadian toadflax, and large crabgrass with fall applications on dormant blueberry, whereas spring applications were less effective. Whereas minor (≤8%) and transient leaf crinkling was noted in response to spring-applied indaziflam at 146 g ai ha−1, a fall application never caused leaf crinkling greater than that observed in the nontreated weedy and weed-free controls, regardless of rate. No negative effects on plant growth or fruit production were observed from indaziflam applied at 73 or 146 g ai ha−1 in fall or spring. Findings of this study suggest that indaziflam applied at 73 (1× commercial use rate) and 146 g ai ha−1 is safe to use on blueberry grown on New Jersey sandy acidic soils despite restrictions for using this herbicide on such soils.

Several chemicals were evaluated in the laboratory for their ability to inhibit growth of hydrilla [Hydrilla verticillata (L.f.) Royle] from tubers. Fenac [(2,3,6-trichlorophenyl)acetic acid] and dichlobenil (2,6-dichlorobenzonitrile) were effective in controlling regrowth in outdoor aquaria. In field tests, hydrilla regrowth was controlled for over 13 months by single applications of 34 kg/ha rates of fenac and over 48 months in one of three replicates treated with 11 kg/ha dichlobenil. Regrowth occurred in controls within 2 to 6 months. There were no differences in the number of viable propagules found in hydrosoil before and 13 months after treatments. Regrowth occurred from root-stocks and from tubers. Regrowth was associated with disappearance of the herbicides from water.

Mitotic disrupters from higher plants have been studied for their effects on animal cells, but their effects on plant cells have been studied less. The plant-derived compounds have counterparts among herbicides with respect to cellular effects and, in some cases, mode of action. Cellular effects in common are arrested prometaphases (colchicine, dinitroanilines), multipolar divisions (Vinca alkaloids, carbamates), and production of binucleate cells (caffeine, dichlobenil). The potential of these natural compounds, either directly or as the basis of new chemistries for herbicides, has remained largely untapped.

Greenhouse and field herbicide evaluation, flooding, and soil saturation studies were conducted to investigate the control of oldfield cinquefoil in cranberry. Chlorimuron ethyl and dichlobenil were found to be promising herbicides for control of this weed in both greenhouse and field studies. The number of leaves, leaf area, shoot, root, and total dry weight of oldfield cinquefoil were reduced by dichlobenil at 1.1 to 4.5 kg ha-1 and chlorimuron ethyl at 17.5 to 35 g ha-1, at 12 wk after treatment. The higher rate of dichlobenil, however, caused reduction in cranberry height and total dry weight. Field treatment at time of cinquefoil emergence did not provide adequate weed control. Postemergence application to cinquefoil of 4.5 kg ha-1 dichlobenil, 35 g ha-1 chlorimuron ethyl, and 2.2 to 4.5 kg-1 ha terbacil reduced the number of leaves and shoot dry weight. Only terbacil at 4.5 kg ha-1 reduced cranberry shoot and fruit fresh and dry weight. Flooding for up to 72 h did not affect oldfield cinquefoil growth. At 22/18 C, 4 wk of soil saturation reduced runner development and fresh and dry weight of oldfield cinquefoil. At 13/9 C, no runners developed in either saturated or control soils, and there was no effect of soil saturation on fresh and dry weights. This suggests that oldfield cinquefoil grows better in an unsaturated soil condition, but needs a relatively warm climate to develop.

Applications of 2,4-D [(2,4-dichlorophenoxy)acetic acid] at 1.1 kg/ha at the start of each growing season severely damaged established alfalfa (Medicago sativa L. ‘Beaver’) and reduced seed yield 32% over a 4-yr period. Dandelion (Taraxacum officinale Weber) populations were reduced but perennial sowthistle (Sonchus arvensis L.) increased in frequency. Dichlobenil (2,6-dichlorobenzonitrile) applied at 2.1 kg/ha controlled both dandelion and perennial sowthistle. Alfalfa was damaged initially but rapid recovery resulted in an increase in seed yield in 2 yr out of 4. Terbacil (3-tert-butyl-5-chloro-6-methyluracil) applied at 1.1 kg/ha also controlled dandelion and perennial sowthistle. No alfalfa damage was evident and seed yields were increased 34% over a 3-yr period. Seed yield increased 30% where asulam (methyl sulfanilylcarbamate) was applied at 4.5 kg/ha, but there was no visible effect on the growth of either alfalfa or weeds. Simazine [2-chloro-4,6-bis (ethylamino)-s-triazine], propham (isopropyl carbanilate) + PCMC (p-chlorophenyl-N-methyl carbamate), pronamide [3,5-dichloro(N-1,1-dimethyl-2-propynyl)benzamide], and diuron [3-(3,4-dichlorophenyl)-1,1-dimethylurea], did not affect alfalfa seed production significantly, although simazine and diuron did reduce dandelion populations.

The long-term effect of repeated late-fall versus early-spring imazethapyr, hexazinone, terbacil, metribuzin, dichlobenil, or chlorsulfuron treatments, when applied on dormant stands of alfalfa was investigated at three sites for weed management of alfalfa grown for seed. Dichlobenil applied at 1.2 to 2.4 kg ha−1 and chlorsulfuron applied at 11 to 22 g ha−1 in fall or spring were the only herbicides to injure alfalfa at one location. Hexazinone provided the most consistent weed control of the herbicides evaluated. Average control of Canada thistle, catchweed bedstraw, dandelion, perennial sowthistle, quackgrass, Russian pigweed, and scentless chamomile was 80%. When averaged over three sites, weed control by hexazinone resulted in a 33% increase in seed yield.

Enzymatically isolated American pondweed (Potamogeton nodosus Poir.) epidermal tissues were exposed to 14C-labeled dichlobenil (2,6-dichlorobenzonitrile), diquat (6,7-dihydrodipyrido[1,2-α: 2′, 1′-c] pyrazinediium ion), silvex [2-(2,4,5-trichlorophenoxy) propionic acid] or 2,4-D [(2,4-dichlorophenoxy)acetic acid] at concentrations of 5 × 10−4, 5 × 10−5, and 5 × 10−610M, and the amount of herbicide crossing the tissue layer was measured. Rates of herbicide movement were compared to those found when copper sulfate pentahydrate was added as a potential synergist at concentrations of 5 × 10−5 M (12.5 ppm), 5 × 10−6 M (1.25 ppm), and 5 × 10−7 M (0.125 ppm). Copper sulfate at 5 × 10−6 M increased the rate of movement of all herbicides. However, diquat and dichlobenil exhibited the most enhanced movement in the presence of copper sulfate. Without copper sulfate, 0.1 nmoles of 5 × 10−6 M 14C diquat penetrated the tissue within 24 h, compared to 1.3 nmoles following the addition of 5 × 10−7 M of copper sulfate.

Bamboos are grass species that can escape cultivation and invade lawns, landscapes, and other areas. Limited information is available on ways to control invasive bamboo species. Greenhouse and field studies were initiated to determine the level of bamboo control provided by a single application of selected PRE and POST herbicides. Bamboo species included in the study were golden bamboo in greenhouse experiments and red-margined bamboo in field experiments. In greenhouse trials, MSMA, quinclorac, dithiopyr, clethodim, fenoxaprop, and sethoxydim did not control either species. Glyphosate, glufosinate, and fluazifop significantly reduced bamboo-shoot fresh weight, although regrowth occurred after a single application. In field trials, bamboo control with dichlobenil in the 2002 and 2004 experiments was less than 23%. For the study initiated in 2002, glyphosate and imazapyr provided 76% and 98% bamboo control, respectively, at 58 wk after treatment (WAT). By 161 WAT (approximately 3 yr after treatment), bamboo-control ratings were 40% with glyphosate and 85% with imazapyr. For the study initiated in 2004, at 61 WAT, glyphosate and imazapyr provided 46 and 88% control of bamboo, respectively.

To address grower concerns that repeated use of dichlobenil could negatively affect cranberry productivity, field studies were conducted at two commercial farms in either high weed density (HW) or low weed density (LW) areas. Data from 4 yr of repeat annual applications of 0, 1.8, and 4.5 kg ai/ha dichlobenil indicated minimal negative impact on cranberry vines. Herbicide application did not affect upright productivity, leaf biomass production, percent fruit set, or other yield parameters adversely; in addition, no improvement in these parameters was noted. Although the interaction of herbicide application with weed density on cranberry root length varied with sampling date, no consistent trend (adverse or positive) was seen. The presence of weeds, rather than herbicide application, was the important determinant of yield. Vines in LW areas produced more marketable fruit and had higher percentage of fruit set than vines growing in HW areas. Repeat annual applications of dichlobenil on commercial cranberry beds may be considered as part of a viable integrated weed management program with no adverse effect on crop growth or yield.