THE EFFECTS OF SUB-LETHAL DOSES OF MCPA ON THE MORPHOLOGY AND YIELD OF VEGETABLECROPS

Summary. The effects of sub-lethal doses of MCPA-sodium on the morphology and yield of red beet, turnip and onion and on the morphology of spinach were studied in field and glasshouse experiments. Epinastic responses of beet were seen at 0.003 lb/ac a.c., but no serious formative effects or yield reductions occurred below 0–07 lb/ac and plants were only killed by doses above 0–1 lb/ac. Spinach was affected at 0–06 lb/ac, the lowest dose used, but the plants were not killed at 0–33 lb/ac. Epinasty in turnip occurred at 0–002 lb/ac, and at 0–01 lb/ac many of the roots were abnormal, while spraying with 0–1 lb/ac and above resulted in severe distortion or death of the plants. Onion was the least affected of all the crops studied. When a welting agent was included in the spray epinasty occurred at 0–3 lb/ac, but there were no serious formative effects or yield reductions below 1–0 lb/ac. The symptoms of injury in onion were often transitory because the affected parts were replaced as the bulb developed.
Effets de doses sub-léthatles de MCPA sur la morphologie et If rendement des cultures légumiéres. V. Betteraves, Epinards, Navets et Oignons     

THE EFFECTS OF SUB-LETHAL DOSES OF MCPA ON THE MORPHOLOGY AND YIELD OF VEGETABLE CROPS

Summary. The effects of sub-lethal doses of MCPA-sodium on the morphology, yield and maturity of French beans, and on the morphology of broad beans, were studied in field and glasshouse experiments. Epinasty in French beans developed at 0.002 lb/ac a.e., but formative effects were not seen at less than 0–1 lb/ac. With doses up to 0.4 lb/ac there was no significant reduction in yield or haulm weight, but at 1.0 lb/ac and above, yield was reduced and some of the plants sprayed at an early stage of growth were killed. There were characteristic modifications of the roots and stems and of those leaves which were at a susceptible stage of development when sprayed. Broad beans were only slightly injured by 0.2 lb/ac but were generally killed by 2.0 lb/ac. Abnormalities were noted in the germination of seed produced by affected plants.
Effets de doses sub-léthales de MCPA sur la morphologic et le rendement des cultures légumières IV. Haricots verts et fèves     

THE EFFECTS OF SUB-LETHAL DOSES OF MCPA ON THE MORPHOLOGY AND YIELD OF VEGETABLE CROPS

Summary. The effect of sub-lethal doses of MCPA-sodium on the growth, yield and marketability of summer cabbage lettuce was studied in seventeen replicated field experiments.
Initial epinasty was produced by doses as low as 0.002 lb/ac a.e., and formative effects of the leaves developed at doses below 0.01 lb/ac. In plants treated at early or intermediate growth stages, two distinct types of formative effects occurred, With doses in the range 0.0025-0.03 lb/ac, a zone of characteristic abnormal leaves developed. This reduced the marketability of the crop and the maturity was delayed, but the weight per plant at harvest was not affected. At higher doses these a abnormal leaves were not evident but the whole plant became distorted, growth was suppressed and few marketable plants were produced. In plants treated at the hearting stage, plant weight and maturity were not affected, but the marketability was reduced at doses of 0.01 lb/ac and above. The effects produced by MCPA in cos and curly crisp lettuce were compared with those produced in cabbage lettuce.     

THE EFFECTS OF SUB-LETHAL DOSES OF MCPA ON THE MORPHOLOGY AND YIELD OF VEGETABLE CROPS

Summary. The effects of sub-lethal doses of MCPA-sodium on the morphology, yield and marketability of cabbage, cauliflower and Brussels sprouts were studied in field and glasshouse experiments. The epinastic and formative effects in all three crops were similar. Cauliflower was the most susceptible and cabbage the least, but the marketability of these two crops was adversely affected at lower doses (less than 0.06 lb/ac a.e.) than that of Brussels sprouts (not below 0.1 Ib/ac a.e.), where the damage to the apex had less effect on the economically important portion of the plant. Brussels sprouts also produced lateral shoots on which normal sprouts developed even when the main stem above had been killed. In all three crops, characteristic galls were produced on the stems, and these, together with the effects on the stem apices, the leaves and the roots, are described and contrasted with abnormalities caused by other agencies.
Effets de doses sub-létales de MCPA sur la morphologie et le rendement des cultures tégumières IL Choux, choux-fleurs et choux de Bruxelles     

THE REACTION OF TRIFOLIUM REPENS (L.) IN GRASSLAND TO 2,4-D, MCPA AND MIXTURES OF 2,4-D AND MCPB

Summary. Eight experiments were carried out on a range of pasture lypes under different management and in different years to lest the reaction of white clover ( Trifolium repens in grasstand to doses of up to 4 lb/ac of the herbicides MCPA-sodium or-potassium and 2,4-D-amine. The initial effect of the treatments was to reduce the amount of dover in the sward, the size of the reduction varying greatly from field to field for any one dose. In general, the higher the dose, the more severe was the depression of the clover 1 month after spraying. Both herbicides at 2 and 4 lb/ac caused substantial depressions on some of the fields. The growth of the treated clover was examined during the year following spraying. The ability of the clover to recover from the initial depression varied considerably in the different fields; on some, recovery started in the year of spraying and on others in the following year. Quick recovery was usually associated with a high initial resistance but there were fields in which the clover showed contrasting rates of recovery following similar depressions. The experiments produced no clear-cut evidence as to why the initial resistance and speed of recovery varied in different fields. In one experiment the effects of MCPB-sodium and 2,4-D-amine on white clover were compared separately and in a series of mixtures. An examination made 6 weeks after spraying showed that MCPB at up to 8 lb/ac had no significant effect on the clover, whereas 2,4-D at 1 lb/ac caused a 22% reduction. Mixtures containing up to 0.37 lb 2,4-D and up to 6 lb MCPB caused no reduction while those containing 0.75 lb 2,4-D and 4 lb MCPB were not significantly different from 1 lb 2,4-D alone.
Reaction de Trifolium repens (L.) en prairie au 2,4-D, au MCPA, et aux mélanges de1, 2,4-D et de MCPB     

SOME EFFECTS OF DROPLET SIZE AND POSITION ON THE RESPONSE OF LETTUCE TO SUB-LETHAL DOSES OF MCPA

Summary. Senescent, expanded or expanding leaves of lettuce plants were treated individually with MCPA. The subsequent development of auxin-induced symptoms throughout the plants was recorded. The number of leaves affected and the severity of the symptoms increased with application to the less mature leaves. In addition more leaves were affected when the application was made to larger plants than to smaller ones. These results were associated with absorption/translocation differences in the leaves of different ages, and in their spatial relationship to tissues at particularly susceptible stages of development. In further experiments, applications of similar weights of MCPA to lettuce plants in droplet sizes of approximately 100 μ and 500 μ were compared. There were consistent trends for the small droplets to produce greater effects.
Quetques effets de la taille des gouttelettes et de leur position sur la reaction de la laitue à des doses sub-létales de MCPA     

THE YIELD AND QUAEITY OF RED BEET SEED AS AFFECTED BY DESICCANT SPRAYS AND HARVEST DATE

Summary. Diquat and sodium monochloroacetate (SMA) were used to desiccate seed crops of red beet in experiments from 1963 to 1965. The seed plants became brown and dry about 7 days after spraying and were then judged suitable for combine harvesting, although this was not done in these experiments. Yields of seed 7 days after spraying were as good as those from the control plants, but were lower than the control yields when harvested 14 days after spraying. In laboratory tests in moist sand at 20° C the percentage of the embryos which germinated was not markedly affected by diquat or SMA treatment. The emergence of seedlings in the field, however, was affected adversely by treatment of the seed crop with 11 and 22 oz/ac of diquat ion in 1963 and by SMA at 20 lb/ac in 1964 and 1965. Diquat at 6·6 oz/ac in 120 gal/ac water in 1964 and 1965 had no serious adverse effects on embryo emergence. Residues of diquat ion in seed varied from 2 to 4 ppm, but the impairment of embryo emergence by diquat was believed to be due to the premature arrest of growth of the seed on the desiccated plants.
It is concluded that when harvesting conditions are poor, desiccants could be valuable.
Influence des traitements dessicants et de la date de récolte sur le rendement et la qualité de la sentence de betterave rouge     

OBSERVATIONS ON THE EFFECT OF HERBICIDES ON YOUNG COCONUTS

Summary. Phytotoxic effects of eight herbicides on young coconuts were assessed by recording visual symptoms of injury and growth following treatment. The growth-regulators 2,4-D, 2,4,5-T and MCPB were lethal at the normal doses used for annual weed control. Dalapon at 5–9 lb/ac applied in 100 gal/ac of water caused yellowing and necrosis of the foliage, reduced growth, and sometimes killed the whole plant, while doses down to 2.2 lb/ac caused some fusion of the pinnae. Monuron at 3.2 and 6.4 lb/ac resulted in serious frond damage and reduced growth, and some frond injury occurred at 1–6 lb/ac. Diquat at 0.25–1.0 lb/ac and paraquat at 1.0–l.5 lb/ac caused extensive necrosis of existing fronds but there was no appreciable reduction in new growth. Amitrole produced considerable chlorosis both at 3.1 and G.3 lb/ac, but only the higher dose caused a reduction in growth.
Essai d'herbicides sur jeunes cocotiers     

STUDIES OF THE RESPONSE OF PLANTS TO ROOT-APPLIED HERBICIDES

Summary. Applications of several herbicides -were made to roots and to the bases of shoots of peas, cucumber, mustard and barley grown in soil, sand or water culture.
Localized applications (variation horizontal) of atratone and MCPA to roots of peas and barley in soil produced effects similar to those observed in water euluire, described in Pan I. Airatone killed the plants whether available to the whole or to only a portion of the root system whereas MCPA affected only the roots with which it was in direct contact, and growth continued when a portion of the root system was in herbicide-free environment.
In water culture, MCPA was more effective when applied to the lower (younger) roots with the upper (older) roots kept dry than when twice the concentration was applied evenly to the whole root system in water. When all the roots were kept wet the effect of application to the upper roots was greater than the effect of application to the lower roots. The response of plants to atratone was not appreciably altered whether applications were made to the upper or lower parts of the root system in water culture. Variations in water level had little effect.
Even when the herbicide solution was confined to the stem or hypocotyl, atratone and DNOC were little, if any, less effective than when applied to roots. MCPA, both as ester and sodium salt, was significantly less effective.
Partial replacement of solution in the root zone by sand and air did not reduce the activity of atratone at a given concentration. Similar replacement in the zone of the stem or hypocotyl greatly reduced the effectiveness of all herbicides. When sand of low water content was used, atratone and MCPA-sodium became quite ineffective via the stem, but DNOC and MCPA-ethyl ester remained active.
Études sur les réactions de certaines plantes á des herbicides appliqués aux racines II. Observations nouvelles sur l'effet de l'application localisée.     

THE INFLUENCE OF IRRIGATION, FERTILIZING AND MCPA ON THE COMPETITION BETWEEN SPRING CEREALS AND WEEDS

Summary. The average air-dry yield of weeds on fallow plots was about four times as large (2660 kg/ha) as the yield of weeds which developed among spring cereal crops (740 kg/ha). Application of fertilizers increased the number of weeds and their average weight on both irrigated and non-irrigated plots. Treatment with MCPA reduced the weed yield to 36% on fallow plots and to 26% on weedy cereal plots. It was more effective on fertilized plots than on unfertilized plots, but irrigation made little difference to its effectiveness. The space left by the destroyed weeds was mainly occupied by Agropyron repens . Oats were better able to compete with weeds than were wheat and barley. On unfertilized and non-irrigated plots spraying with MCPA (1-26 kg/ha) at the beginning of shooting significantly reduced the yields of weed-free barley. The yields of sprayed oats and wheat were also below the yields from the unsprayed although the reductions were not significant at the 5% level. However, on a number of fertilized and irrigated plots, both weedy and hand-weeded , on which the plants had better growing conditions, MCPA resulted in a significant increase in the grain yield of barley and oats.
Influence de l'irrigation, de la fertilisation et du MCPA sur la compétition entre céréales de printemps et mauvaises herbes     

THE USE OF ADSORBENTS AND SIMAZINE ON NEWEY PLANTED STRAWBERRIES

Summary. A series of field trials was conducted to determine if the tolerance of newly planted strawberry runners to simazine could be increased by placing adsorbents in the vicinily of the root zone at planting time. Powdered steam-activated charcoal was found to be the most suitable of seven adsorbents tested. Dipping the roots of runners in charcoal before planting was more effective and practicable than placing a similar quantity of charcoal around each runner at planting time. No significant damage was recorded in several trials in which dipped runners were sprayed with simazine at 1 lb/ac within a few days of planting.
Although new roots are likely to take up the herbicide as they grow away from the charcoal-protected area around the plant, the protection provided by the adsorbent appears to be sufficient to enable the young plants to develop satisfactorily.
Utilisation d'adsorbants et de simazine sur des fraisiers récemment plantés     

THE CONTROL OF WEEDS IN TEA BY HERBICIDES IN MAURITIUS

Summary. Weed control experiments carried out in tea plantations showed that diuron at doses 2·4, 3·2 and 4·8 lb/ac a.i. resulted in better and more persistent weed control than siamazine.
Shoot absorption experiments carried out on three tea jats, dark, medium and light, showed that the tea jats differed in their tolerance to both diuron and simazine, the light one being the most susceptible.
A difference IN the expression of phytotoxic effects between leaf and root absorption was observed for diuron only. At equivalent doses, 2-year-old plants were in general more susceptible to diuron than to simazine.
Diuron and simazine used alone at 2·4, 3·2 and 4·8 lb/ac a.i. or with addition of sodium chlorate at 6 lb/ac to improve the kill of emerged weeds, did not affect yield of either pruned unpruned 6-year-oId tea. Dalapon, on the other hand, at 6 lb/ac significantly reduced the yield of unpruned tea but not of pruned lea.
Le désherbage chimique du théè l'lle Maurice     

THE EFFECTS OF SUB-LETHAL DOSES OF MCPA ON THE MORPHOLOGY AND YIELD OF VEGETABLE CROPS

Summary. The effects of 2,4-D, 2,4,5-T, mecoprop and 2,3,6-TBA were compared with those of MCPA on the morphology and yield of lettuce, cabbage, cauliflower, Brussels sprout, carrot, parsnip, French and broad bean, red beet, spinach, turnip and onion. Although the relativie phytotoxicity of MCPA, 2,4-D, 2,4,5-T and mecoprop varied according to the crop, the morphological abnormalities produced by the different compounds were essentially similar, except that in lettuce and cabbage sperilic foliar symptoms appeared to be associated with 2,4-D. 2,3,6-TBA caused less epinasty and usually fewer root and stem abnormalities, but in some crops, notably French and broad bean, red beet and spinach, it produced severe injury symptoms which were different from those produced by the other compounds.
Effets de doses sub-léthales de MCPA. sur la morphologie et le rendement des cultures légumirres VI. Comparaison avec le 2,4-D, le 2,4,5-T, le micoprop et le 2,3,6-TBA     

CHEMICAL CONTROL OF FERTILE SPARTINA TOWNSENDII (S.L.) ON THE CHESHIRE SHORE OF THE DEE ESTUARY I. FIELD TRIALS ON SPARTINA SWARD

Summary. Trials with dalapon, paraquat and fenuron in 1963 and 1964, and with bromacil and amitrole-T in 1964, were carried out on mature Spartina sward. Dalapon, paraquat and fenuron all gave complete kill on some plots in 1963. In 1964, paraquat gave variable results and lower percentage kills than in 1963, whereas dalapon and fenuron were more consistent. Fenuron allowed a greater degree of regeneration than dalapon and was uneconomic at the high dose (60 lb/ac) required for complete kill. Dalapon gave the best results and with 100 lb/ac there was 98–100% kill 2 years after treatment. At 50 lb/ac results were initially good, but there was more regeneration in the second season after spraying. Bromacil at 5 and 20 lb/ac and a mixture of 5 lb/ac bromacil and 4 lb/ac amitrole-T maintained more than 99% kill lor 2 years after application.
La lutte chimique contre les formes fertiles de Spartina townsendii (s.l.) sur la cóte du Cheshire dans l'esluaire de la Dee I. Essais au champ sur des pelouses de Spartina     

THE EFFECTS OF MCPA AND 2,3,6-TBA ON GLASSHOUSE CUCUMBERS

Summary. The effect of sub-lethal doses of MCPA-sodium and 2,3,6-TBA-sodium on young cucumber plants was studied in three replicated experiments. The materials were applied either to the leaves of plants in pots or as a soil drench. Epinastic and formative effects were observed. Formative effects included leaf inrolling and blistering, stem and petiole proliferation, and root modification. The symptom pattern resulting from application of each material was described.
Les effets du MCPA et du 2,3,6-TBA sur Us concombres cultivés en serre     

CHEMICAL AND BIOLOGICAL PROPERTIES OF TWO NEW HERBICIDES—IOXYNIL AND BROMOXYNIL

Summary. The preparation of ioxynil, bromoxynil, and their salts is described, and information on solubilities and stability to storage is summarized. Although the toxicology of the herbicides is to be reported in greater detail, a preliminary statement is made here. Evidence of herbicidat activity under glasshouse conditions is indicated briefly, and supports the conclusion that both compounds are effective when applied to the foliage of a wide range of dicotyledon weed species. Seedlings of some weed species resistant to the phenoxy alkanoic acids are controlled under glasshouse conditions at doses as low as 0.125 lb/ac, and ioxynil has a wider range of activity than bromoxynil at these low doses. Graminaceous species tolerate 4–8 lb/ac of both herbicides without injury, and certain leguminous crops tolerate one or other herbicide at doses of 0.5–0.75 lb/ac. The contact action of the herbicides is rapid, there are also slower systemic effects, and seed germination is inhibited. In susceptible species the level of post-emergence activity is shown to be influenced by the growth stage of the weed, the distribution of herbicide on the foliage, and environmental factors of which light intensity appears to be most important.
Propriétés chimiques et biologiques de deux nouveaux herbicides: ioxynil et bromoxynil     

COMPARISION OF RATES OF PARAQUAT PRIOR TO DIRECT-DRILLING CEREALS

Summary. Trials were conducted in East Anglia to compare direct-drilling following paraquat at 1 and 2 lb/ac with normal cultivations for both winter wheat and spring barley. The three treatments were compared at two levels of nitrogen.
With direct-drilled winter wheat, yields were higher after using paraquat at 2 lb/ac and at this rate there was little difference between direct-drilling and normal cultivations when 100 units of nitrogen were applied in spring. When only 50 units were given the results were more variable, with direct-drilling significantly outyielding normal cultivations in one trial, being outyielded in another and showing no difference in the third.
Yields of spring barley were slightly higher after paraquat at 2 lb/ac as compared with 1 lb/ac, but not significantly so. The time of application of paraquat influenced yield; when applied in December yields from direct-drilling and normal cultivations were similar, but when applied in February higher yields were recorded with normal cultivations.
Comparaison des doses de paraquat a utiliser avant un semis direct de dreales     

THE EFFECT OF MCPA ON THE AMINO ACID AND SUGAR COMPOSITION OF VICIA FABA LEAVES

Summary. The effect of spraying Vicia faba leaves with 5000 ppm MCPA is described. Three to 4 days after spraying, a marked increase (× 5 approx.) was found in the concentrations of leucine iso -leucine and valine in the leaves. No significant changes were detected in the other amino acids. Treatment with MGPA also caused a significant increase (× 4 approx.) in the glucose and fructose content of the leaves. Detached leaves (sprayed and unsprayed), when kept in a moist atmosphere for 3–4 days, exhibited very similar increases in amino acids and sugars to sprayed intact plants. Experiments using ¹⁴CO₂ revealed that in short term photosynthesis (30 min) of sprayed and unsprayed plants, 80–90% of the radioactivity was incorporated in sucrose, with about 5% in each of glucose and fructose. Over photosynthelic periods of 4 days, glucose and fructose were found to be almost as heavily labelled as sucrose in sprayed plants, but in the controls the distribution of radioactivity was similar to that in short term photosynthesis. It is suggested that the build up of amino acids and sugars in plants treated with MCPA is due to an interruption of the translocatory flow from the leaves, and that this build up of metabolites may be a contributory factor in the toxic action of this herbicide.
Effet du MCPA sur la composition en amino-acides et en sucre des feuilles de Vicia faba     

THE EFFECT OF JULY APPLICATIONS OF DALAPON ON THE GROWTH AND BOTANICAL COMPOSITION OF AN AGROSTIS/LOLIUM PASTURE

Summary. Dalapon–sodium at 3.3–7.5 Ib ac/a.e. was applied in early, mid– and late July 1964 to an Agrostis/Lolium pasture for selective control of the weed grasses Agrostis stolonifera, Poa trivialis and Holcus lanatus. These species were significantly more susceptible than Lolium perenne to dalapon at all doses regardless of the time of spraying. The most promising treatment was 33 lb/ac applied on 4th July, which increased the ground cover of L. perenne and substantially reduced Agrostis stolonifera and Poa trivialis. The total yield of herbage 12 weeks after spraying was only 50% of that from the unsprayed control, but the yield of Lolium perenne was not affected. When cut on 21st May and 5th August 1965, total yield was only slightly reduced and that of L. perenne was increased by 60–90%. The successful practical utilization of this selectivity is likely to depend largely on the spacing of the plants of L. perenne in the pasture. Simazine at 0.75 Ib/ac applied to half of each plot 3–4 weeks alter dalapon treatment had no lasting beneficial effect on the composition of the sward.     

STUDIES OF THE RESPONSE OF PLANTS TO ROOT-APPLIED HERBICIDES

Summary. Peas, barley and linseed were grown in water-cuture. Roots were divided into two portions and contained in separate vessels. The effect of herbicides applied to one-third of the roots was compared with their effect when applied to the whole root system.
Propham, chlorpropham, atratone and 2,3,6-TBA killed the plant whether application was to one-third or all of the roots. Roots in direct contact with propham, chlorpropham and 2,3,6-TBA were deformed or killed, while roots in uncontaminated solution remained healthy. The effect of atratone and high concentrations of chlorpropham on a portion of the roots was transmitted to roots not in the toxic solution.
Certain concentrations of MCPA and DNOC applied to the whole root system killed the plant while three times the concentration to one-third of the roots caused local damage but had little effect on the plant as a whole. Sufficient herbicide may be taken up by one- third of the roots from high concentrations to kill the whole plant.
TGA gave variable results with respect to the health of the aerial portion of the plant but had no obvious direct effect on root growth.
Propham, chlorpropham, atratone and 2,3,6-TBA reduced transpiration rates whether applied to part or whole root systems. MCPA and DNOC prevented water uptake by roots with which they Were in direct contact.
Etudes sur les réactions de certaines plantes à des herbicides appliqués aux racines I. Effet d'une application localisée