D After Application Research Articles

Comparison of Trifloxysulfuron and Pyrithiobac in Glyphosate-Resistant and Bromoxynil-Resistant Cotton

Field studies were conducted in 2000 and 2001 at Rohwer, AR. Trifloxysulfuron (5.3 and 8 g ai/ha) and pyrithiobac (70 g ai/ha) were applied preemergence (PRE) and postemergence (POST) broadcast at the two- to three-leaf (EP) and three- to four-leaf (MP) cotton growth stages. Both materials were also applied POST in combination with glyphosate at 560 g ae/ha or bromoxynil at 560 g ai/ha at both growth stages. Trifloxysulfuron applied EP or MP at 8 g/ha provided greater control of sicklepod and pitted morningglory 28 d after application (DAA) than trifloxysulfuron at 5.3 g/ha or pyrithiobac at 70 g/ha; however, control of prickly sida was greater with pyrithiobac than with trifloxysulfuron at either rate. Glyphosate alone controlled sicklepod, prickly sida, and pitted morningglory greater than 80%. The addition of trifloxysulfuron at 8 g/ha and pyrithiobac at 70 g/ ha increased control of all species over glyphosate alone 28 DAA. Bromoxynil at 560 g/ha controlled pitted morningglory and hemp sesbania at all application timings; however, sicklepod and Palmer amaranth control was less than 50% with bromoxynil applied alone. When bromoxynil was applied in combination with trifloxysulfuron at either rate, control of sicklepod and Palmer amaranth increased to 80% or greater at all application timings. Trifloxysulfuron has the potential to complement both the glyphosate-resistant and bromoxynil-resistant weed control programs by providing control of less susceptible weeds and by providing residual control to both programs.

Remote Sensing to Detect Herbicide Drift on Crops

Glyphosate and paraquat herbicide drift injury to crops may substantially reduce growth or yield. Determining the type and degree of injury is of importance to a producer. This research was conducted to determine whether remote sensing could be used to identify and quantify herbicide injury to crops. Soybean and corn plants were grown in 3.8-L pots to the five- to seven-leaf stage, at which time, applications of nonselective herbicides were made. Visual injury estimates were made, and hyperspectral reflectance data were recorded 1, 4, and 7 d after application (DAA). Several analysis techniques including multiple indices, signature amplitude (SA) with spectral bands as features, and wavelet analysis were used to distinguish between herbicide-treated and nontreated plants. Classification accuracy using SA analysis of paraquat injury on soybean was better than 75% for both 1/2- and 1/8× rates at 1, 4, and 7 DAA. Classification accuracy of paraquat injury on corn was better than 72% for the 1/2× rate at 1, 4, and 7 DAA. These data suggest that hyperspectral reflectance may be used to distinguish between healthy plants and injured plants to which herbicides have been applied; however, the classification accuracies remained at 75% or higher only when the higher rates of herbicide were applied. Applications of a 1/2× rate of glyphosate produced 55 to 81% soybean injury and 20 to 50% corn injury 4 and 7 DAA, respectively. However, using SA analysis, the moderately injured plants were indistinguishable from the uninjured controls, as represented by the low classification accuracies at the 1/8-, 1/32-, and 1/64× rates. The most promising technique for identifying drift injury was wavelet analysis, which successfully distinguished between corn plants treated with either the 1/8- or the 1/2× rates of paraquat compared with the nontreated corn plants better than 92% 1, 4, and 7 DAA. These analysis techniques, once tested and validated on field scale data, may help determine the extent and the degree of herbicide drift for making appropriate and, more importantly, timely management decisions.

Comparison of chlorophyll fluorescence and whole‐plant bioassays of isoproturon

Summary The response to aqueous solutions of isoproturon was examined on intact plants of Matricaria perforata, Apera spica‐venti and Sinapis alba in greenhouse tests, comparing visual estimates of shoot phytotoxicity at 30 d after application (DAA) with measurements of fast chlorophyll fluorescence induction at 10 DAA on leaves of the same treated plants. The sensitivity was greatest from pre‐emergence application to intact plants of M. perforata and A. spica‐venti, whereas post‐emergence sprays were relatively more active on S. alba. The use of fluorescence induction was investigated further in Petri‐dish experiments on excised M. perforata leaf segments. The Petri‐dish bioassay enabled detection of isoproturon at concentrations above 9 × 10−7 M within 96 h after herbicide exposure. The potential for using chlorophyll fluorescence assays for the determination of isoproturon content in soil extracts is discussed.

Quantification and Remediation of Pesticides in Runoff Water from Containerized Plant Production

AbstractDuring containerized plant production pesticides may move from application site in runoff water created by overhead irrigation systems. In this study, four pesticides, isoxaben {N‐[3‐(1‐ethyl‐1‐methylpropyl)‐5‐isoxazolyl]‐2,6‐dimethoxybenzamide}, trifluralin {(2,6‐dinitro‐N,N‐dipropyl‐4‐trifluoromethylaniline}, chlorpyrifos {O,O‐diethyl O‐3,5,6‐trichloro‐2‐pyridyl phosphorothioate) and thiophanate‐methyl {dimethyl 4,4−‐o‐phenylene bis(3‐thioallophanate), were applied at a commercial plant nursery. Overhead irrigation after application generated runoff water which was channeled into waterways of clay/gravel or hybrid bermudagrass [Cynodon dactylon (L.) Pers. × C. transvaalensis Burtt‐Davy]. Isoxaben was detected in runoff water through 4 d after application (DAA). Other pesticides were detected primarily on the day of application (DOA). Thirteen percent of applied thiophanate‐methyl was recovered from the clay/gravel waterway and 11% from the grass waterway. Total amounts of isoxaben lost were 23% of total applied in both treatments. Less than 0.01% of applied chlorpyrifos and trifluralin were detected. Isoxaben amounts recovered from the grassed waterway on the DOA were 16% lower than from the clay/gravel treatment. Thiophanate‐methyl amounts were 18% lower from the grassed treatment on the DOA. The results suggest that vegetated waterways can reduce pesticide losses from application site in runoff water.

Efficacy and Persistence of Heterorhabditis marelatus (Rhabditida: Heterorhabditidae) Against Root Weevils (Coleoptera: Curculionidae) in Strawberry

We compared the efficacy of Heterorhabditis marelatus Liu & Berry, a newly described species of entomopathogenic nematode, with that of H. bacteriophora Poinar against the root weevils, Otiorhynchus ovatus (L.) and O. sulcatus in strawberry. In the laboratory, H. marelatus was significantly more virulent than H. bacteriophora on O. ovatus and O sulcatus 7 d after nematode application at 14°C. In field experiments, H. marelatus applied at concentrations of 52 and 136 infective juveniles (IJs) per square centimeter, reduced root weevil larvae and pupae 75.3 and 77.4%, respectively, 20 d after nematode application. H. bacteriophora applied at concentrations of 128 and 379 IJs per square centimeter reduced root weevils 50.0 and 74.0%, respectively. Both nematode species were detected up to 30 dafter application by baiting with Galleria mellonella larvae in soil samples collected from the field.

Efficacy and Persistence of Steinernema carpocapsae (Rhabditida: Steinemematidae) Applied through a Center-Pivot Irrigation System Against Larval Com Rootworms (Coleoptera: Chrysomelidae)

We evaluated control of natural and artificially infested populations of larval com rootworms (Diabrotica virgifera virgifera LeConte and D. barberi Smith & Lawrence) in corn ( Zea mays L.) treated with entomopathogenic nematodes, Steinernema carpocapsae (Weiser); All strain, applied after planting through a center-pivot irrigation system at 2.5 and 1.2 x 109 infective juvenile nematodes per hectare. We compared control achieved with nematodes with that achieved with planting time applications of terbufos (Counter 15G [granular]; 9.9 kg [AI]/ha) and chlorpyrifos (Lorsban 4E [emulsion]; 1.12 kg [AI]/ha) applied after planting through an irrigation system, and with an untreated (water only) control. In 1989 studies with natural rootworm populations, chlorpyrifos and both nematode rates provided significantly lower root damage ratings than terbufos and the untreated control. Chlorpyrifos was significantly more effective than the low nematode rate. In 1990 studies with a natural rootworm infestation, the high nematode rate, terbufos, and chlorpyrifos provided Significantly lower root damage ratings than the untreated control. Effectiveness of the low rate of nematodes was not significantly different from that of the untreated control. In both years, all treatments were generally less effective under higher rootworm pressure in artificially infested plots. In 1989, the high rate of nematodes significantly reduced adult western corn rootworm emergence compared with terbufos, the low rate of nematodes, and the untreated control. In 1990, all treatments significantly reduced western com rootworm adult emergence compared with the untreated control. In 1989, viable nematodes were commonly found 1-3 d after application and at low levels 28 d after application. However, in 1990, no viable nematodes were found >7 dafter application.

Crop Responses to Hexazinone, Imazapyr, Tebuthiuron, and Triclopyr

Field investigations were conducted for 2 yr to characterize the responses of wheat, kidney bean, field corn, squash, okra, potato, and banana to soil-applied hexazinone, imazapyr, tebuthiuron, and triclopyr at rates used for control of woody perennial plants. Test species were planted at seven selected intervals through the first and second years after herbicide applications to assess residual herbicide activity. Tebuthiuron treatments of 2.2 kg ai ha−1were not tolerated by any bioassay species planted 436 d after application (DAA). Only potato was tolerant of residual hexazinone 436 DAA. All species except banana generally tolerated residual imazapyr and triclopyr by the second growing season. Indigenous plants repopulated all herbicide-treated areas, except those treated with tebuthiuron, by the third growing season. Plots treated with tebuthiuron were 90% free of indigenous plants 40 mo after herbicide application.

Suppression of Frankliniella bispinosa (Thysanoptera: Thripidae) and the Fungal Pathogen Colletotrichum gloeosporioides, with Pesticides During the Bloom Cycle and Improved Fruit Set on ‘Navel’ Orange in Florida

Four field experiments were conducted in two ‘Navel’ orange groves in southwest Florida between 1988-1990. Insecticides were applied alone, in combination with the fungicide benomyl, or benomyl was applied alone during ‘Navel’ orange flowering cycles between February and April. The duration and intensity of flowering differed each year. Population densities and peak activity of Frankliniella bispinosa (Morgan) differed by year and by site during the same year. Fifty-unit samples of small (5-9 mm), medium (10-13 mm), and large (≥14 mm) floral buds, open flowers, and fruitlets were evaluated to determine the optimal stage of floral development for sampling adults and larvae of F. bispinosa . All floral stages were infested but open flowers consistently had the highest numbers of both adults and larvae and were used to assess treatment differences in thrips populations after 1988. Results showed a positive relationship between population suppression of F. bispinosa during the flowering cycle and subsequent ‘Navel’ orange fruit set in late June or early July. Chlorpyrifos, dimethoate, and formetanate hydrochloride were effective in suppressing numbers of F. bispinosa , with activity lasting 3-7 dafter application. Two or more applications of benomyl resulted in fruit set increases each year in the four field experiments compared with fruit set increases in three of four experiments where insecticides only were applied. The fungal pathogen, Colletotrichum gloeosporioides Penzig, was identified previously as the causative organism for postbloom fruit drop disease on citrus. This study demonstrated that there are two potential factors ( F. bispinosa and C. gloeosporioides ) involved in reduced fruit set on ‘Navel’ orange during the flowering cycle in Florida.

Insecticide Treatments Used Against a Rice Bloodworm, Chironomus tepperi (Diptera: Chironomidae): Toxicity and Residual Effects in Water

The toxicity and persistence in water of six organophosphate insecticide treatments used for control of Chironomus tepperi Skuse was evaluated. Each insecticide was applied to three rice bays (20 by 4 m) at the maximum recommended field rate. Fourth-instar C. tepperi were tested with water samples taken at various intervals after insecticide application. All treatments caused high (>97%) initial mortality of larvae with the exception of diazinon (0.13 ppm; average initial mortality, 47.3%). Temephos (0.06 ppm) showed the least residual activity, with no mortality occurring 5 d after application. Chlorfenvinphos (0.27 ppm) had the longest residual effect in water, resulting in 61.5% mortality 15 dafter application but only nominal activity at 20 d. The remaining treatments, diazinon, chlorpyrifos (0.08 ppm), trichlorfon (0.47 ppm), and malathion (0.32 ppm), provided <10% mortality after 7 d.

Resistance to Pyrethroid Insecticides in Soybean Looper (Lepidoptera: Noctuidae) in Mississippi

Recommended rates of pyrethroid insecticides failed to give adequate control of soybean looper, Pseudoplusia includens (Walker), on soybean in some areas of the alluvial plain (Delta) region of Mississippi in 1987. Permethrin provided 53.0% control 5 dafter application in an area of the Delta where permethrin control failures had been suspected in 1985 and 1986. This was lower than the 87.5% control reported in another area of the Delta where no permethrin control failures were suspected during these years. Numbers of soybean looper larvae were 69.4 and 73.4% lower in methomyl treatments and 58.5 and 56.2% lower in acephate treatments than in the untreated control in the Delta within and outside areas of suspected pyrethroid control failures, respectively. Compared with LD50’s for a laboratory strain susceptible to pyrethroids, LD50’s for permethrin applied to soybean loopers collected in the Delta were 10.4 and 21.1 times higher for two strains established from larvae collected in soybean fields treated with permethrin, 3.5 times higher for a strain from an untreated soybean field, and 7.3 times higher for a strain established from adults collected in an ultraviolet light trap. The levels of resistance of the Delta strains to cypermethrin and fenvalerate were similar to those for permethrin. LD50’s of cypermethrin and permethrin for a strain established from the northeastern (Hill) region of Mississippi were not different from the LD50, of the susceptible strain. LD50’s for methomyl applied to field strains were variable but were not different from the laboratory strain. The same was true for methyl parathion, except that a Delta strain collected from a soybean field treated with methyl parathion showed some evidence of resistance.

The Influence of Application Timing and Posttreatment Irrigation on the Fate and Effectiveness of Isofenphos for Control of Japanese Beetle (Coleoptera: Scarabaeidae) Larvae in Turfgrass

During 1984, isofenphos 1.5 and 5% granular and 2 flowable (2.24 kg [AI]/ha) applied 11 April to golf course turfgrass in Canal Fulton, Ohio, resulted in 92% average reduction of overwintered Japanese beetle, Popillia japonica Newman, larvae 48 dafter application. Of treatments applied April through August, only August applications significantly reduced summer larvae. Analysis by gas/liquid chromatography for isofenphos and oxyisofenphos residues in samples taken 6 August from the April, May, June, and July treatments showed that 79, 92, 94, and 97%isofenphos, respectively, remained in the thatch. Mean oxyisofenphos residues at this time were 54, 45, 54, and 63%, respectively, of total residue. Oxyisofenphos residues 5–6 d after the 11 April and 14 August applications were 7 and 15%, respectively, of the total. Immediate posttreatment irrigation, plus regular subsequent irrigation and rainfall, did not improve isofenphos penetration into the soil or enhance larva control.