Systems of weed control composed of (a) herbicides only, (b) herbicides plus cultivation, or (c) cultivation only were devised. The most effective systems, involving herbicide sequences plus one “non-dirting” layby cultivation, controlled twelve troublesome species of weeds with acceptable yields of peanuts (Arachis hypogaea L.). On Greenville sandy clay loam, a particularly effective and economical system of weed control consisted of (a) N-butyl-N-ethyl-α,α,α-trifluoro-2,6-dinitro-p-toluidine (benefin) used as a preplanting incorporated treatment, then (b) S-propyl dipropylthiocarbamate (vernolate) either incorporated into the soil before planting or injected at planting, and finally, (c) a layby cultivation 5 to 6 weeks after planting. A similarly effective system on Tifton loamy sand involved vernolate injected at planting, 2-sec-butyl-4,6-dinitrophenol (dinoseb) at “cracking”, and 4-(2,4-dichlorophenoxy)butyric acid (2,4-DB) as a postemergence treatment followed by the layby cultivation. The “non-dirting” layby cultivation, averaged over both years and herbicide sequences, significantly increased yields of peanuts on both soil types. None of the systems of weed control caused consistent differences in market grade, average weight per seed, germination, or organoleptic quality of the peanuts.

Grain sorghum (Sorghum bicolor (L.) Moench ‘RS 671’) was grown during 1969 and 1970 in competition with two other members of the same species, wild cane and Kansas Orange forage sorghum, transplanted at various densities along grain sorghum rows. All densities of wild cane and Kansas Orange significantly reduced both grain and fodder yields of grain sorghum. Grain yield was highly and positively correlated with leaf area, culm length, culms per plant, panicles per culm, seeds per panicle, and amount of light received at the grain sorghum canopy; and grain yield was negatively correlated with plant factors that benefited wild cane and Kansas Orange. Grain yield did not correlate with either plants per hectare or seed weight. Panicle size was most important in determining grain yield. Kansas Orange reduced grain yields more than did wild cane in 1969. During 1970, with less favorable rainfall, grain sorghum responded similarly to both transplanted weed types.

A laboratory procedure for evaluating the effect of pesticides on nitrification in soil proved to be simple to perform, reproducible, and offers a procedure for rapid screening of a large number of chemicals in a short period. The recovery of added nitrate by extracting with distilled water was essentially 100% complete. The conversion of added ammonium to nitrate by the soil microorganisms was nearly complete after the 2-week incubation period. Nitrification in soil treated with several different herbicides and insecticides was determined by our procedure. A nitrification inhibitor, N-Serve3 (2-chloro-6-trichloromethyl pyridine) was included as a standard. None of the herbicides or insecticides inhibited nitrification and the N-Serve completely inhibited nitrification during the 2-week incubation.

Species of green algae seldom grew as well in two-species cultures with other green algae, or with blue-green algae, as when cultured alone. Several species of algae apparently excreted one or more substances into the medium which inhibited the growth of the second species. Inhibition of growth of green algae was particularly great in two-species cultures with the blue-green algae, Oscillatoria rubescens Decandolle, Anabaena flos-aquae (Lyngbye) Breb., Microcystis aeruginosa Kutz., and Coccochloris peniocystis (Kutz.) Dr. and Daily. Green algae also failed to grow at normal rates in media prepared from filtrates of water from ponds which contained blooms of blue-green algae. Inhibitory substances are apparently an important factor in the development and persistence of relatively unialgal blooms of various species.

Twelve-day-old corn seedlings (Zea mays L. ‘Funk's G-83’) were exposed to thermal conditions (482 C for 125 msec) approximating those used for flame weed control. Tissue dehydration was evident within 1 min after flame application. One hour after flame exposure, the water content of shoot tissues was 6% less than in nonflamed shoots. Transpirational water loss 16 hr after flame application was reduced by 68% when compared to that of nonflamed seedlings. Assimilation of 14CO2 by flamed seedlings, while substantially decreased when compared with that of nonflamed seedlings, continued on a limited basis even in the most severely injured leaf tips.

Six vegetable crops were greenhouse-grown to maturity in three Maryland soils treated with up to 500 ppm of arsenic (As) added as sodium arsenate. Phytotoxicity of arsenic residues was highest on Lakeland loamy sand and lowest on Hagerstown silty clay loam. Correlations between available arsenic and plant dry weight indicated that crop sensitivity proceeded as follows: green beans (Phaseolus vulgaris L. ‘stringless greenpod’) > lima beans (Phaseolus linensis L. ‘Fordhook 242’) spinach (Spinacia oleracea L. ‘Longstanding Bloomsdale Savoy’) > radish (Raphanus sativus L. ‘Champion’) > tomato (Lycopersicon esculentum Mill. ‘F-7’) > cabbage (Brassica oleracea L. var. capitata L. ‘Jersey Wakefield’). Residues in the total dry plant at the available arsenic level at which growth was reduced 50% (GR50) were highest with radish (43.8 ppm) and spinach (10.0 ppm). Residues in the dry-edible portion increased to 76.0 ppm arsenic for unpeeled, washed radish at the GR50 point. The soil at the GR50 level for radish contained about 19 ppm of available arsenic from a 50 ppm arsenate treatment to Lakeland loamy sand and a 100 ppm treatment to Hagerstown silty clay loam and to Christiana clay loam.

Herbicide treatments were applied to established alfalfa (Medicago sativa L.) in 1969 and 1970 to determine winter annual weed control efficacy, crop tolerance, and influence on alfalfa yield and protein. Common chickweed (Stellaria media (L.) Cyrillo) was the predominant species in both years. Excellent weed control was achieved in 1969 with 2-sec-butylamino-4-ethylamino-6-methoxy-s-triazine (GS 14254) at 1.7 kg/ha, 2-[[4-chloro-6-(ethylamino)-s-triazin-2-yl]amino]-2-methyl-propionitrile (cyanazine) at 4.5 kg/ha, 2-chloro-4,6-bis(ethylamino)-s-triazine (simazine) at 1.7 kg/ha, and 3-tert-butyl-5-chloro-6-methyluracil (terbacil) at 1.1 kg/ha. Several other treatments also significantly reduced weed yields. All herbicides significantly reduced weed yields in 1970. First harvest alfalfa yields in 1969 were not increased significantly despite the excellent weed control afforded by several treatments. Second harvest alfalfa yields did not differ significantly, however, weeds were not a problem in the regrowth. In 1970 four of the 19 treatments did yield significantly more than control plots. Alfalfa protein was not altered by any of the treatments either year.

Roots of susceptible cucumber (Cucumis sativus L. ‘Chicago pickling’) and tolerant wheat (Triticum aestivum L. ‘Manitou’) seedlings were treated with 3,6-dichloro-o-anisic acid (dicamba) or (2,4-dichlorophenoxy)acetic acid (2,4-D) for either 10 or 46 hr. The roots were excised and nucleohistones were isolated and fractionated by polyacrylamide gel electrophoresis. In untreated cucumber roots there were four major nucleohistone fractions. Two of these fractions decreased or were not detectable 10 or 46 hr after treatment with dicamba or 2,4-D. In wheat, the nucleohistone fractions of the treated roots were similar to those of the controls. This suggests that in cucumber more of the DNA template is available for transcription. This suggestion was supported by the fact that the incorporation of 14C-adenine into RNA in cucumber roots 10 hr after treatment with dicamba was increased by 50%, whereas in wheat there was no difference. Furthermore, the incorporation of 14C-leucine into protein in cucumber roots 10 hr after treatment with dicamba was inhibited by 70%, indicating that the increased RNA produced was incapable of translating for protein synthesis. It is proposed that selective phytotoxicity of auxin-like herbicides is based on a differential alteration of RNA species and interference with protein synthesis.

Soybean [Glycine max (L.) Merr.] seedlings grown in the greenhouse in a Wisner loam soil showed a greater reduction in plant growth from an application of 2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine (atrazine) if fertilized with 224 kg/ha of P2O5. This interaction was not observed in tolerant corn (Zea mays L.) seedlings in any of the four soils studied. The injury in sand culture of high levels of atrazine to soybean, corn, pea (Pisum sativum L.), and sorghum (Sorghum vulgare L.) seedlings increased when high levels of P (phosphorus) were present. The high level of P did not increase atrazine uptake, and in corn atrazine did not increase 32P uptake. Plants receiving the atrazine-phosphate combination exhibited a higher rate of respiration providing a possible basis for the observed interaction. The high rate of P application slightly reduced atrazine metabolism by corn and pea but not by soybean and sorghum.

Corn (Zea mays L. ‘Funk's G-83’) seedling leaves exposed to flame-generated ultra-high temperatures produced in flame cultivation were fixed in glutaraldehyde, post fixed in osmium tetroxide, and embedded in Araldite. In the light microscope, bundle sheath cells of flamed tissue were more heavily stained with Azure II and less vacuolated than were nonflamed cells. Heated mesophyll cells contained swollen, disrupted, and granular chloroplasts. Examination of flamed tissue by electron microscopy revealed granular, dispersed cytaplasm and altered membrane systems. Chloroplast lamellar systems and envelopes, tonoplasts, and plasmalemmas were disintegrated in both bundle sheath and mesophyll cells.

Overseeded rough bluegrass (Poa trivialis L. ‘Danish common’) and Italian ryegrass (Lolium multiflorum Lam. ‘Gulf’) maintained under putting green conditions were more susceptible to benefin (N-butyl-N-ethyl-α,α,α-trifluoro-2,6-dinitro-p-toluidine) and DCPA (dimethyl tetrachloroterephthalate) than creeping bentgrass (Agrostis palustris Hud. ‘Penn-cross’), red fescue (Festuca rubra L. ‘Dawson’), or perennial ryegrass (Lolium perenne L. ‘Medalist II’). February applications of 1.68 or 3.36 kg/ha of benefin and 6.72 or 13.44 kg/ha of DCPA caused significantly more discoloration and reductions in density than equivalent rates applied in March or April. Benefin was more injurious than DCPA to all overseeded species as judged by quality or density. DCPA caused significant delays in the breaking of dormancy of bermudagrass [Cynodon dactylon (L.) Pers. ‘Tifdwarf’].

Established stands of alfalfa (Medicago sativa L. ‘Lahontan’) at six field locations were treated with soil-active herbicides during the dormant period for the control of winter annual weeds. Weeds and alfalfa were hand separated at the first harvest. This forage, which varied widely in weed content, was analyzed for protein. The percentage of protein correlated negatively with weed content in all cases. Analyses of covariance revealed that the direct effect of the herbicides on protein content was either small or absent and that the primary cause of the negative correlations was weed content.

Equimolar concentrations of 4-phenylsulfonyltrifluoromethanesulfono-o-toluidide (hereafter referred to as MBR-8251), S-ethyl dipropylthiocarbamate (EPTC), and 2-chloro-2′,6′-diethyl-N-(methoxymethyl)acetanilide (alachlor) were compared using a quartz gravel nutrient culture method for detecting toxicity to yellow nutsedge (Cyperus esculentus L.), okra (Hibiscus esculentus L.), cabbage (Brassica oleracia var. captata L.), cucumber (Cucumis sativus L.), and flax (Linum ustitatissimum L.). MBR-8251 was more active on yellow nutsedge than EPTC or alachlor, and MBR-8251 treated nutlets were controlled for a longer period. In general, crops were more tolerant of MBR-8251. Field studies comparing the effectiveness of MBR-8251 to EPTC, S-propyl dipropylthiocarbamate (vernolate), 2-chloro-4-(ethylamino)-6-isopropylamino-s-triazine (atrazine), 3-isopropyl-2,1,3-benzothiazinone-(4)-2,2-dioxide-6,7,8 (BAS-3510), alachlor, and 2-chloro-N-(ethoxymethyl)-6′-ethyl-o-acetotoluidide (MON-097) indicated that after 10 weeks yellow nutsedge control was excellent with MBR-8251, MON-097, and alachlor.

Movement of 2-chloro-N-isopropylacetanilide (propachlor) from a granule to the soil was classified as horizontal, below the granule, above the granule, and into an area within a 3-ppmw contour. The influence of depth of placement, moisture content, temperature, relative humidity, and exposure time on each of the movement classifications was determined. Horizontal movement increased as the temperature, moisture, and exposure time increased. Propachlor tends to move down into the soil under dry conditions and up when the soil is moist. The size of the soil area that contained 3 ppmw was greater for granules placed in the soil than for granules placed on the surface. The size of the area increased as the moisture increased.

Interspecific crosses were made between perennial sowthistle (Sonchus arvensis L.) and annual sowthistle (Sonchus oleraceus L.). Flower head size, leaf type, and creeping root growth of the hybrid were intermediate to those same morphological characteristics of the parents. Backcrosses to the parents produced plants which resembled annual or perennial sowthistle more closely than did the F1 hybrids. Annual sowthistle and backcrosses to annual sowthistle were more tolerant to (2,4-dichlorophenoxy)acetic acid (2,4-D) and 3,6-dichloro-o-anisic acid (dicamba) than were perennial sowthistle or backcrosses to perennial sowthistle. However, annual and perennial sowthistle were similar to each other in response to 4-amino-3,5,6-trichloropicolinic acid (picloram). Natural crosses between annual and perennial sowthistles may account for some of the variability in herbicide response found in perennial sowthistle.

Greenhouse and field studies were used to evaluate crop protectants with herbicides in order to obtain selective, broad-spectrum weed control in sorghum [Sorghum bicolor (L.) Moench ‘RS 626’]. Of the herbicides evaluated alachlor [2-chloro-2′,6′-diethyl-N-(methoxymethyl) acetanilide] was the only one causing sorghum injury that could be moderated with crop protectants. The crop protectant anhydride (1,8-napthalic anhydride) was most effective in reducing alachlor injury when applied as a seed treatment at 0.5% (w/w). Storage of anhydride-treated seed for 1 year did not increase anhydride damage to sorghum seedlings. Preplant applications of alachlor, incorporated into the soil, caused four times more injury to sorghum than did the same rate applied preemergence. Combinations of atrazine [2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine] and alachlor did not increase sorghum injury or alter the effects of the crop protectants. In the field, anhydride was the most effective crop protectant used. Crop protectant R-28725 (2,2-dimethyl-3-dichloroacetyloxazolidine) at 0.5% w/w to sorghum seed and at 0.6 kg/ha as a tank mix was effective in reducing sorghum injury at the lower alachlor rates. Crop protectant R-25788 (N,N-diallyl-2,2-dichloroacetamide) was the least effective of those studied; however, seed treatment at 0.5% w/w was more effective than the tank mixes.

Herbicidal oil emulsions and herbicidal naphthas were applied repeatedly as postemergence treatments to cotton (Gossypium hirsutum L., ‘Stoneville 7A’) in field investigations over a 4-year period. Postemergence directed applications of high aromatic oils emulsified with water were effective for selective weed control in cotton. Oil emulsions did not cause stem girdling when applied to cotton at any growth stage. Herbicidal naphthas effectively controlled weeds but caused stem girdling when applied after the cotton was 4 weeks old.

Hairy galinsoga [Galinsoga ciliata (Raf.) Blake] and smallflower galinsoga [G. parviflora Cav.] are widespread weeds in New York State. Freshly harvested achenes (seed) are not dormant and germinate in the field from early May until frost. Rate of germination but not final total percentage was stimulated by alternating temperature, with the fastest rate being at 30 C day and 20 C night and with a 16-hr photoperiod and 11,000 lux of light. Some seed in each seed-lot required light for germination. Both species were day-neutral with respect to flowering. Smallflower galinsoga produced its first flower after node seven and hairy galinsoga after node six on the main axis 6 to 8 weeks after germination. Decreasing light intensity 83% decreased fresh weight.

An endemic anthrocnose disease of northern jointvetch [Aeschynomene virginica (L.) B.S.P.] incited by the fungus Colletotrichum gloeosporioides (Penz.) Sacc. f. sp. aeschynomene was discovered in 1969 at Stuttgart, Arkansas. When grown on solid or in liquid media, the organism grew rapidly and sporulated abundantly. From 1970 through 1972 water sprays of the fungus spores at 2 to 15 million spores per milliliter in 94 to 374 L/ha controlled northern jointvetch grown in the growth chamber, greenhouse, and field. The fungus controlled plants ranging from 5 to 66 cm tall. The disease developed on northern jointvetch most rapidly at temperatures of 23 to 32 C and at relative humidities above 80%. An incubation period of 4 to 7 days and up to 5 weeks was usually required to kill the weeds. The fungus was specific for Aeschynomene species since it was very virulent on A. virginica and only slightly virulent on Indian jointvetch (A. indica L.). It did not affect rice (Oryza sativa L.), soybeans [Glycine max (L.) Merr.], cotton (Gossypium hirsutum L.), or 12 other common field, forage, and vegetable crops or 15 common weeds.

Only 24% of black seed of halogeton (Halogeton glomeratus (M. Bieb.) C. A. Mey.) germinated 2 weeks after collection in October. After 11 weeks of dry storage germination had increased to 60%. During the additional 12 weeks of pregermination treatment, germination did not vary significantly from 60% except for seed stored moist at low temperatures. Ninety to 95% of moist seeds stored at −6 C for 6 weeks or longer germinated within 48 hr; this rate of germination was superior to that of seed collected in December.