Bernard H. Zandstra

Beneficial Effects of Weeds in Pest Management — A Review

Abstract Weeds sometimes play an important role in pest management systems and when specific weeds are not present, biological control of certain insects is often impossible. Examples are given of weeds which serve as food sources for alternative hosts of insect predators and parasites or for the parasites themselves. The implications of these relationships for weed and insect control and for crop production are discussed.

Flame Weeding Effects on Several Weed Species

Flaming can be an effective nonselective, nonchemical method of weed control. It has been more effective against broadleaf weeds than grasses. Experiments were conducted with a conveyor bench burner apparatus to evaluate flaming to kill broadleaf and grass seedlings at the 0- to 2- and 2- to 4-leaf stages. Most 0- to 2-leaf green foxtail seedlings were killed when flamed at 2, 4, and 6 km/h conveyor speed. A few plants survived when flamed at 8 km/h. Green foxtail seedlings at the 2- to 4-leaf stage were more tolerant to flaming than 0- to 2-leaf green foxtail, and substantial numbers of plants survived at all flaming speeds except 2 km/h. Barnyardgrass was more tolerant to flaming than green foxtail, and many 0- to 2- and 2- to 4-leaf seedlings survived after flaming. However, fresh weight of the live plants at 14 d after treatment was reduced. Some large crabgrass plants survived flaming at both growth stages. Flaming at 2 km/h reduced seedling number and fresh weight, but there was significant regrowth. Common ragweed was more susceptible to flaming at the 2- to 4-leaf stage than at the 0- to 2-leaf stage. Redroot pigweed and common lambsquarters were susceptible to flaming at both 0- to 2- and 2- to 4-leaf stages. Nomenclature: Redroot pigweed, Amaranthus retroflexus L. AMARE, Common ragweed, Ambrosia artemisiifolia L. AMBEL, Common lambsquarters, Chenopodium album L. CHEAL, Large crabgrass, Digitaria sanguinalis L. DIGSA, Barnyardgrass, Echinochloa crus-galli L. ECHCG, Green foxtail, Setaria viridis L. SETVI

Evaluation of Flumioxazin and Other Herbicides for Weed Control in Gladiolus

Two studies were conducted near Bronson, MI, to determine gladiolus tolerance and weed control with flumioxazin and other herbicide treatments. The first study was conducted in 2002, 2003, and 2004 to evaluate weed control and gladiolus injury with flumioxazin and 14 other preemergence treatments. Crop injury over the 3-yr period was less than 6% and was considered commercially acceptable with flumioxazin, linuron, oryzalin, pendimethalin, prometryn, S-metolachlor, and sulfentrazone. Gladiolus stand count, height, and flower count were similar to those of the nontreated control with these treatments. Clomazone, halosulfuron, imazamox, imazapic, mesotrione, oxyfluorfen, rimsulfuron, and trifloxysulfuron resulted in unacceptable crop injury. Of the acceptable treatments, only flumioxazin controlled common ragweed, yellow nutsedge, and foxtail species at least 68%. The second study was conducted in 2003 and 2004. Flumioxazin was evaluated at four rates, in mixtures with S-metolachlor and oryzalin, and in comparison with isoxaben plus oryzalin. Gladiolus injury did not exceed 6%. Common ragweed, annual grass, and yellow nutsedge control were at least 63% with all flumioxazin treatments. Nomenclature: Clomazone; flumioxazin; halosulfuron; imazamox; imazapic; isoxaben; linuron; mesotrione; oryzalin; oxyfluorfen; pendimethalin; prometryn; rimsulfuron; S-metolachlor; sulfentrazone; trifloxysulfuron; common ragweed, Ambrosia artemisiifolia L. #3 AMBEL; giant foxtail, Setaria faberi Herrm. # SETFA; large crabgrass, Digitaria sanguinalis (L.) Scop. # DIGSA; purple robust foxtail, Setaria viridis var. robusta-purpurea Schr. # SETVI; stinkgrass, Eragrostis cilianensis (All.) E. Mosher # ERACN; yellow nutsedge, Cyperus esculentus L. # CYPES; gladiolus, Gladiolus spp. Additional index words: Crop tolerance, floriculture, herbicide efficacy. Abbreviation: WAT, weeks after treatment.

Arsenic and lead residues in carrots from foliar applications of monosodium methanearsonate (MSMA): A comparison between mineral and organic soils, or from soil residues

Carrot roots may absorb arsenic residues when grown in soil that has been treated previously with arsenical pesticides. Arsenic residues in crops also may result from the inappropriate application of post-emergence arsenical herbicides. To compare potential sources of arsenic residues, carrots were planted in mineral or organic soil and treated post-emergence with the herbicide monosodium methanearsonate (MSMA) at 0, 0.56, 1.12, 2.24, 4.48, or 8.96 kg ha−1. Arsenic concentration in all plant parts declined between 30 days before harvest and harvest. Arsenic concentration in peeled carrot roots ranged from less than the limit of detection (LOD) for untreated carrots to 0.963 mg kg−1 (fresh weight) at harvest for carrots treated with 8.96 kg ha−1 MSMA. In another study, carrots were grown in a greenhouse in soil collected from an old orchard site that had been sprayed with lead arsenate for many years. The old orchard site soil had an arsenic level of 110 mg kg−1, and similar non-orchard soil had an arsenic level of 1.97 mg kg−1. All carrot plant segments from plants grown in old orchard soil had higher arsenic concentrations than those from non-orchard soil. Peeled carrot roots from non-orchard soil contained 0.034 mg kg−1 arsenic, while the peeled roots from old orchard soil had 0.135 mg kg−1. Old orchard soil had a lead level of 496 mg kg−1, compared with 6.52 mg kg−1 for non-orchard soil. Peeled carrot roots from old orchard soil contained 0.885 mg kg−1 lead, and peeled roots from non-orchard soil contained 0.147 mg kg−1 lead.

The Effects of Depth and Duration of Seed Burial on Viability, Dormancy, Germination, and Emergence of Ivyleaf Speedwell (Veronica hederifolia)'

Experiments were conducted to investigate the effects of depth and duration of burial on seasonal germination, primary and secondary dormancy, viability, and seedling emergence of ivyleaf speedwell (Veronica hederifolia L.) seeds. The seeds were buried at 0, 5, 10, or 20 cm and retrieved from the field at monthly intervals. The exhumed seeds were germinated at 5 C. In the second experiment, seeds were stored in the laboratory after harvest and tested for germination at monthly intervals. In each experiment, nongerminated seeds were treated with triphenyltetrazolium chloride at monthly intervals to test their viability. The effects of stratification and burial depth on seedling emergence were observed for 1 yr. The seeds exhumed from the soil were dormant at the beginning of the experiment and exhibited dormancy/nondormancy/conditional dormancy cycling throughout the experiment. Depth of burial and time affected seed germination. Seeds retrieved from the soil surface germinated well initially, but germination decreased as depth of burial increased. In the dry storage experiment, seeds had a high level of primary dormancy, and viability decreased over time. Seedling emergence decreased when depth of burial increased. Seedlings emerged nonuniformly throughout the year and demonstrated typical winter annual characteristics. Nomenclature: Veronica hederifolia, Ivyleaf speedwell, #3 VERHE Additional index words: Primary/secondary dormancy, weed management, wheat, germination ecology. Abbreviations: TTC, triphenyltetrazolium chloride.

Influence of wheat seeding rate and cultivars on competitive ability of bifra (Bifora radians)

Bifra is an annual noxious broadleaf weed of winter-sown crops in the Central Anatolia and Middle Black Sea regions of Turkey. This species has become more prevalent in wheat fields in the past three decades because of poor chemical control. Field experiments were conducted in Havza and Kavak, Samsun, Turkey, to evaluate the effect of cultivar and seeding rate on the competitive interaction between bifra and wheat at four bifra densities. Wheat grain yield increased with seeding rate, either in the presence or in the absence of bifra in both locations. Decreasing the seeding rate from 250 to 200 kg/ha or 150 kg/ha decreased wheat yield in the presence of bifra in all cultivars. The percentage yield decreases were different according to cultivars, although yields decreased in all cultivars. On the basis of the analysis of yield variables, data suggest that the relative competitiveness was ‘Bezostaja’ > ‘Momtchill’ > ‘Kate A-1’ = ‘Panda’. Bifra biomass and seed numbers were reduced not only by an increase in the wheat seeding rate but also by cultivars. Bifra seed production in Bezostaja, Kate A-1, Momtchill, and Panda were diminished 60, 53, 54, and 46%, respectively, at the seeding rate of 250 kg/ha compared with bifra alone at a density of 350 plants/ m2. Nomenclature: Bifra, Bifora radians Bieb.; Winter wheat, Triticum aestivum L. ‘Bezostaja’, ‘Kate A-1’, ‘Momtchill’, ‘Panda’. Additional index words: Competition, weed management, wheat cultivars.

Physiological characteristics of linuron-resistant Portulaca oleracea

Abstract Studies were conducted to compare physiological characteristics of linuron-susceptible and -resistant Portulaca oleracea. The susceptible biotype had heavier seed and germinated more rapidly than the resistant biotype. Eight weeks after seeding, fresh and dry weights of susceptible P. oleracea plants were significantly greater than those of resistant plants. Susceptible P. oleracea had a significantly higher CO2 assimilation rate at 30 C, but was similar to that of resistant P. oleracea at 40 C. The susceptible biotype had a significantly higher CO2 assimilation rate at CO2 concentrations ≥ 600 ppm and at incident light levels ≥ 900 µmol m−2 s−1. The susceptible biotype had higher carboxylation and photochemical efficiencies. Nomenclature: Atrazine; cyanazine; diuron; linuron; prometryn; simazine; Portulaca oleracea L. POROL, common purslane.

Virginia Creeper (Parthenocissus Quinquefolia) and Wild Grape (Vitis spp.) Control in Fraser Fir

Abstract Virginia creeper and wild grape are troublesome perennial vines that often infest Christmas tree plantations. Field studies were conducted to evaluate Fraser fir injury and Virginia creeper and wild grape control with directed applications of triclopyr (1,680 g ai/ha) alone and in combination with 2,4-D (1,120 g ai/ha), clopyralid (280 g ai/ha), and halosulfuron (36 g ai/ha). Additional treatments included 2,4-D, clopyralid, glyphosate (1,120 g ai/ha), halosulfuron, hexazinone (560 g ai/ha), mesotrione (105 g ai/ha), and sulfometuron (71 g ai/ha) applied alone; and a mixture of hexazinone plus mesotrione. In the triclopyr-containing treatments, Fraser fir injury ranged from 6 to 13% at 1 mo after treatment (MAT) and was 4 to 8% at 11 MAT. Leader growth was not impacted by the herbicide treatments. At 11 MAT, all triclopyr-containing treatments controlled Virginia creeper 93 to 98% and wild grape 98 to 100%, which was greater than the control observed with glyphosate at 63 and 59%, respectively. Virginia creeper and wild grape control with 2,4-D was 88 to 90%. Clopyralid, halosulfuron, hexazinone, hexazinone plus mesotrione, mesotrione, and sulfometuron provided less than 66% control of both perennial vines. Directed applications of triclopyr-containing treatments or 2,4-D were effective management tools for selective removal of wild grape and Virginia creeper from Fraser fir Christmas tree plantations. Additional research is needed on the potential sensitivity of other commonly grown Christmas tree species to triclopyr-containing treatments. Nomenclature: Clopyralid; glyphosate; halosulfuron; hexazinone; mesotrione; sulfometuron; triclopyr; 2,4-D; Virginia creeper, Parthenocissus quinquefolia (L.) Planch. PRTQU; wild grape, Vitis spp. VITSP; Fraser fir, Abies fraseri (Pursh) Poir

Postemergence Weed Control in Onion with Bentazon, Flumioxazin, and Oxyfluorfen

Field experiments were conducted in 2008 and 2010 to determine crop tolerance and weed control efficacy of the POST herbicides bentazon, flumioxazin, and oxyfluorfen applied to direct-seeded dry bulb onions on organic soil. Postemergence application of oxyfluorfen at 0.071 kg ai ha-1 resulted in less than 20% onion injury when applied at the 2 and 4 onion leaf stages and provided good control of ladysthumb and common lambsquarters. Oxyfluorfen EC caused slightly higher visual injury than oxyfluorfen SC, but there was no difference in onion yield among the treatments. Application of flumioxazin at 0.036 of 0.072 kg ai ha-1 alone or in combination with pendimethalin ACS resulted in minimal onion injury and no yield reduction. Combining flumioxazin in a tank mix with pendimethalin EC, dimethenamid-P EC, or S-metolachlor EC resulted in significant onion injury and yield reduction. Flumioxazin plus S-metolachlor, dimethenamid-P, or pendimethalin improved ladysthumb control in one of two years. Bentazon applied at 0.56 kg ai ha-1 produced moderate onion injury and did not control yellow nutsedge adequately. Bentazon applied at 1.12 kg ai ha-1 provided good control of yellow nutsedge but caused serious onion injury and yield loss. Nomenclature: Bentazon, dimethenamid, flumioxazin, oxyfluorfen, pendimethalin, S-metolachlor, common lambsquarters, Chenopodium album L., hairy nightshade, Solanum physalifolium Rusby, ladysthumb, Polygonum persicaria L., redroot pigweed, Amaranthus retroflexus L., yellow nutsedge, Cyperus esculentus L., onion, Allium cepa L.