The effects of drip-applied 1,3-dichloropropene (1,3-D) and chloropicrin on fumigant soil gas levels and growth of vegetable seedlings were investigated in three separate tests in Tifton, Ga. Tests were conducted in Spring 2002, Fall 2002, and Spring 2003. Phytotoxicity of 1,3-D + chloropicrin was induced in the 2002 tests by applying progressively higher rates (0 to 374 L·ha–1) of drip-irrigated InLine (an emulsifiable formulation (EC) containing 60.8% 1,3-D and 33.3% chloropicrin) and planting vegetable seedlings within four days after application. Vegetables evaluated were tomato, pepper and cucumber (Spring 2002), and tomato and squash (Fall 2002). In Spring 2003, the effects of 1,3-D formulation (InLine versus Telone EC, an EC containing 94% 1,3-D), plastic mulch type [low density polyethylene (LDPE) versus virtually impermeable film (VIF)] and drip tape configuration (one versus two drip tapes) on fumigant soil gas levels and growth of tomato were investigated. Tomato was planted after the recommended 3-week waiting period. Fumigant concentrations in soil were measured using Gastec detection tubes at 1 to 4 days after drip fumigation in all three tests. Measured fumigant soil gas concentrations were correlated with fumigant application rates in Spring 2002, but not in Fall 2002. Vegetables were visibly affected by residual fumigant levels in the soil and showed symptoms such as leaf chlorosis (cucumber, squash and pepper), leaf bronzing (tomato) and stem browning and stunting (all crops). Fumigant soil air levels were negatively and linearly correlated with different plant growth parameters, in particular plant vigor. The cucurbit crops showed an immediate response and high mortality within 1 week after planting. Surviving plants recovered well in fall. The solanaceous crops showed a more delayed response and lower mortality rates. However, phytotoxic effects with tomato and pepper were more persistent and plants did not seem to recover with time. Overall, fumigant residue levels and potential phytotoxicity were greater in spring than in fall. Greater fumigant soil concentrations were measured under VIF as compared to LDPE plastic mulch. The effect of drip-tape configuration varied with the type of plastic mulch that was used. The double-tape treatment resulted in lower fumigant levels at the bed center under LDPE mulch, and higher fumigant levels at the bed shoulder under VIF mulch. The formulation containing 94% 1,3-D resulted in higher soil fumigant levels as compared to the formulation containing 61% 1,3-D and 33% chloropicrin, especially with VIF mulch. Early plant vigor of tomato was negatively correlated with fumigant soil gas levels, and was especially poor following drip fumigation with 94% 1,3-D under VIF mulch.
Abstract
Trials in the greenhouse and growth chambers were performed to evaluate the influence of fertilizer level and temperature on sensitivity of Spathiphyllum cv. Clevelandii to acephate insecticide. Plant quality was not influenced consistently by fertilizer level in all tests, although highest-quality plants usually were produced with recommended fertilizer levels (3 g/15-cm pot Osmocote 19N-6P-12K). Plants were grown at fertilizer levels up to 15 g/15-cm pot with those grown between 22° and 27°C undamaged, while those grown at 32° had severe foliar necrosis and were stunted. Increases in either fertilizer level or temperature resulted in increased levels of phytotoxicity when plants were sprayed with recommended rates (0.4 g/liter) of acephate insecticide. An interaction occurred between temperature and fertilizer level in growth chamber trials.
Abstract
A 20% dichlorvos impregnated polyvinyl chloride (PVC) resin strip (6.3 × 15.9 × 0.7 cm) per 28.3 m3 interior room significantly reduced the number of mealybugs (Phenacoccus solani Ferris) 48 hour posttreatment. Greenpeach aphid (Myzus persicae Sulzer) and twospotted spider mite (Tegranychus urticae Koch) populations were not suppressed. Exposure of pests to a stake label with an attached dichlorvos impregnated PVC strip produced the same effects as the room fumigation test. Placement of a 20% dichlorvos PVC resin strip per 25.4 × 70 cm polyethylene bag with infested plant material for 12 or 24 hr reduced populations of M. persicae, P. solani and T. urticae, however, 3 exposures at 7-day intervals were more effective in maintaining low populations. Fumigation in bags produced phytotoxic effects with specific plants.
Abstract
No appreciable signs of phytotoxicity were observed for 4 days following fumigation of plants (including begonias, petunias, snapdragons) with ozone of up to 80 parts per hundred million (pphm) or sulfur dioxide of up to 400 pphm for 2 hr. Thereafter, there was considerable necrosis, particularly on begonias fumigated with the highest concn of the pollutants. Growth suppression was reflected in reduced shoot and flower wt, and to a lesser degree in reduced flower number. Overall, begonias and petunias were the most sensitive. Coleus and snapdragons were moderately sensitive, while marigold, celosia, impatiens and salvia were tolerant. ‘White Tausendschon’ was the most sensitive begonia cultivar while blue-flowered ‘Capri’ was the most sensitive petunia. Mixed color petunias exhibited varying degrees of tolerance. ‘Scarlet Rainbow’ coleus was more sensitive than ‘Pastel Rainbow’. Measurements of growth alterations in plants were found very useful in determining latent forms of air pollutant injury.
Twenty-two preemergent herbicides were applied at their maximum labeled rates and twice those rates to determine their safety and effectiveness on areca palm [Dypsis lutescens (H. Wendl.) Beentje & Dransf.], pygmy date palm (Phoenix roebelenii O'Brien), and mexican fan palm (Washingtonia robusta H. Wendl.). Two products, dichlobenil and metolachlor showed consistent phytotoxicity on all three species. Several of the remaining products caused death of the apical meristem in mexican fan palms and reduced growth rates in pygmy date palms, but most caused little damage to areca palms. Herbicides applied as sprays generally remained effective for 2 to 4 months, whereas granular products, especially those containing oxyfluorfen plus another chemical, were effective for up to 8 months.
Hydrogen cyanamide (CY) induced earlier, more uniform, and a higher percentage of budbreak in poplar (Populus alba × P. gradidentata, N C 5339). c y was phytotoxic at 0.5 M or higher concentration. Percent budbreak increased and percent dieback decreased when plants were treated with a mixture of CY and Cys. No difference was found in percent budbreak or dieback between plants treated with CY alone and a mixture of CY and Ser. Mixing CY with Cys concentrations in vitro reduced the percentage of the cyano group, and mixing of Cys with CY concentrations decreased the percentage of the SH group remaining in the mixture. Mixing CY with Ser concentrations in vitro had no effect on CY level. These studies suggest that the SH group reacts with CY directly and the improvement of budbreak and toxicity caused by mixing CY and Cys may be due to the reduction of CY concentration.
Field research was conducted to evaluate pre-transplant (PRE) applications of sulfentrazone (0.20 or 0.41 kg·ha-1 a.i.) and flufenacet (0.045 kg·ha-1 a.i.), or early postemergence (EPOST) halosulfuron (0.027, 0.036 or 0.054 kg·ha-1 a.i.) on phytotoxicity and yield of field-grown chili (var. Sonora), jalapeño (var. Grande) and bell (var. Giant Belle) peppers (Capiscum annuum) in Texas. Crop injury recorded 15 days after sulfentrazone treatments (DAT) showed minor stunting at the low rate, but moderate stunting and temporary leaf malformation when applied at 0.41 kg·ha-1 a.i. Increased stunting occurred 37 DAT at both rates; however, new leaf growth was not affected. Flufenacet did not result in crop injury to any of the three types grown. Phytotoxicity from halosulfuron recorded 7 DAT gave significantly higher ratings for stunting/chlorosis for broadcast EPOST treatments when compared to EPOST-directed applications. Injury from halosulfuron was temporary and considered minor with all EPOST treatments by 22 DAT. Pepper yield data showed that EPOST halosulfuron treatments were statistically equivalent to the untreated controls for each of the three types, but there was a trend for lower yields with rates higher than 0.027 kg·ha-1 a.i. All peppers treated with flufenacet gave excellent yields. Sulfentrazone applied at the high rate gave the greatest yield losses in all three types, and this was significant in the jalapeños. The results indicate that all three herbicides have potential for use in commercial pepper production in Texas. However, more research is needed to evaluate these and other herbicides for improved crop safety in peppers.
Imidacloprid is a long-term systemic insecticide that is currently labeled under the trade name Marathon (imidacloprid, 1-[(6-chloro-3-pyridyl)methyl-4,5-dihydro-N-nitro-1-H-imidazol-2-amine, 1% granular on fritted clay, Bayer Corp., Kansas City, Mo.) for ornamental crops grown in greenhouses. The company that markets Marathon is seeking to expand its label to greenhouse-grown vegetable crops, although the rates they plan to label have not yet been divulged. Marathon was applied to cucumber (Cucumis sativus L. `Turbo') and tomato (Lycopersicon esculentum Mill. `Rutgers') at 0, 1/8, 1/4, 1/2, 3/4, and 1 tsp (0, 5, 10, 20, 30, and 40 mg a.i.) per 4.5-inch (550-mL) pot. Both species developed phytotoxicity symptoms of leaf chlorosis of the oldest leaves and distorted growth and marginal necrosis of newer leaves within 1 week after application. By the end of the experiment, even the lowest rate caused phytotoxicity symptoms. The symptoms were similar in appearance to Ca deficiency but cucumber foliar analysis revealed no difference in Ca, Zn, Fe, or Co across imidacloprid rates, however, Mg and B decreased whereas K and Mn increased linearly across imidacloprid rates. P, Cu, and Mo varied quadratically with 1/2 tsp (20 mg a.i.) per pot having the lowest P and Mo, and Cu increasing at the higher rates. These data indicate that imidacloprid can alter plant nutrition. The rates of imidacloprid applied here are not recommended for use on greenhouse-grown cucumber and tomato under similar growing conditions as in this study.
must consider potential phytotoxic effects on these plants if treated water is used to irrigate landscape species. Topramezone and bispyribac-sodium provide aquatic resource managers with alternate modes of action to control fluridone-resistant hydrilla
Abstract
Eight herbicides were evaluated for phytotoxicity to field grown ‘Candidium’ caladiums (Caladium × hortulanum Birdsey) in 1983. The 4 most promising or currently used herbicides were evaluated for weed control and phytotoxicity in 1984. During 1984, 4 applications of 2.24 kg/ha alachlor, 2.24 kg/ha simazine, 1.68 kg/ha oryzalin, and 0.56 kg/ha oxyfluorfen, all in combination with 1 postemergence application of 0.28 kg/ha fluazifop-butyl, were applied to caladiums. Alachlor and oxyfluorfen provided poor weed control and reduced plant vigor, tuber weights, and tuber size in 1984. Simazine provided good weed control, but reduced plant vigor and yield. Oryazlin provided excellent weed control without crop injury. Chemical names used: 2-chloro-N-(2,6-diethylphenyl)-N-(methoxymethyl)acetamide (alachlor); 6-chloro-N,N’-diethyl-1,3,5-triazine-2,4-diamine (simazine); 4-(dipropylamino)-3,5-dinitrobenzene sulfonamide (oryzalin); 2-chloro-l-(3-ethoxy-4-nitrophenoxy)-4-(trifluoromethyl)benzene (oxyfluorfen); butyl-2-[4-[[5-(trifluoromethyl)-2-pyridinyl]oxy] phenoxy] propanoate (fluazifop-butyl).