Correspondence

Abstract

Twenty-seven different herbicides were tested at the AUB Agricultural Research and Education Center in the Beqa'a, Lebanon, to determine their effects on weeds in wheat, barley, maize, onion and sugar beet. Each herbicide was tested at three different rates as pre-emergence and post-emergence applications. Unweeded and hand-weeded check plots were included. Data on yield, quality and other agronomic characteristics of the crops tested were recorded.

Concentrations of 1,000 and 10,000 ppm of 2, 4–D caused a significant decrease in the height and grain yield of wheat and barley when sprayed at the 3-leaf stage. At the 5-leaf stage, injury to wheat and barley occurred only when sprayed at 10,000 ppm, whereas an increase in the grain yield was obtained at 1,000 ppm of 2, 4–D acid equivalent (1 kg a.i./ha).

Pre-emergence treatments of atrazine and simazine at 2.5 kg a.i./ha caused a significant increase in the forage and grain yields of maize as compared to unweeded check plots. Wheat, oats, vetch and sugar beet were injured when planted after triazine-treated maize, whereas onions and soyabeans were tolerant. Other promising herbicides tested on maize were C 3095 (N–3–trifluoromethylphenyl–N'–methyl–N'–methoxyurea) and BV– 201 (1–(3′, 4′–dichlorophenyl)–3–methylpyrrolidin–2–one) applied as a pre-emergence spray at 1 and 2 kg/ha respectively.

Pre-planting treatment of EPTC and pre-emergence treatment of pebulate at 2 kg/ha gave a slight increase in the yield of roots of sugar beet. BV–201 and BV–207 (1–(3–chloro–4–methylphenyl)–3–methylpyrrolidin–2–one) were phytotoxic to beet.

In onions, nitrofen, BV–201 and BV–207 at 1–2 kg/ha were promising as pre-emergence and post-emergence sprays. DNOC and dinoseb at 1.5 kg/ha and ioxynil at 0.5 kg/ha sprayed post-emergence increased the yield of onions significantly over the check. No significant effects of these herbicides were observed on the bulb index, moisture content and total soluble solids of onions.     

Sodium 2,2,3,3-tetrafluoropropionate,a New Herbicide for Jute Field Weeds

Abstract

Sodium 2,2,3,3-tetrafluoropropionate (TFP) was tested as pre-planting and post-emergence applications on jute heavily infested with grasses and sedges. The herbicide was applied by two methods, at several rates and at different times before sowing. As a post-emergence application it was sprayed over a three week old crop. The best results were obtained when the herbicide was incorporated into the soil ten days before sowing at 3–4 kg a.i./ha. This practice controlled all grasses and sedges except nutsedge, which was only reduced by 30–40%, although higher rates gave better control. No phytotoxic effects on jute were observed with this rate and method of application.     

Insect Pests of Cotton – Western Herbaceum Region of India

Abstract

Pre-plant and pre-emergence herbicides were tested for effective weed control in a seed crop of okra during 1974–75 and 1975–76. All treatments significantly decreased the weed population and increased the seed yield as compared to the unweeded control. Fluchloralin (0.90 and 1.20 kg a.i./ha pre-plant), alachlor (2.50 kg a.i./ha pre-em) and EPTC plus alachlor (3.75 kg a.i./ha pre-plant and 1.25 kg a.i./ha pre-em) proved to be the most effective and economical treatments. No residual effects were observed with any herbicide on the succeeding crops of radish, carrot, turnips, peas and spinach.     

Herbicide Performance in Rainfed Cabbage

Abstract

The effectiveness of butralin (2.0 and 4.0 kg a.i./ha pre-plant, 2.0 and 4.0 kg a.i./ha pre-em), chlorthal-dimethyl (10.0 and 12.0 kg a.i./ha pre-em), trifluralin (0.6 and 1.1 kg a.i./ha pre-plant) chloramben (2.0 kg a.i./ha pre-em) and nitrofen (2.0 kg a.i./ha pre-em) in controlling weeds in transplanted ‘Kono Cross’ cabbage and the influence of these treatments on the yield and quality of marketable heads and on the economics of weed control were evaluated in three replicated field experiments on River Estate loam soil in Trinidad during the wet seasons of 1976 and 1977. While herbicides did not affect the size of the cabbage plant population or the date to maturity of the crops, they reduced the cost of weed control by over 30% and increased the net returns relative to the clean-weeded control by over 9%. Butralin at 4.0 kg a.i./ha pre-plant and pre-em and the trifluralin treatments were superior to nitrofen which gave good weed control up to five weeks and higher yields than the clean-weeded control. Chlorthal-dimethyl gave encouraging results but caused slight, temporary stunting. The application of one of these treatments followed by one hand weeding at about four weeks should give full-season weed control and an acceptable yield of marketable heads with increased financial returns. Chloramben was the least effective herbicide tested and its use may not be justified under similar conditions to those of this study.     

Chemical Control of Phalaris minor and Avena ludoviciana in Wheat

Abstract

In field experiments conducted at the Punjab Agricultural University, Ludhiana during 1973–74 and 1974–75, pre-emergence application (one day after sowing) of methabenzthiazuron (1.05 kg a.i./ha), metoxuron (1.6 kg a.i./ha) and chlortoluron (0.75 kg a.i./ha) gave effective control of Phalaris minor and Avena ludoviciana in wheat without any phytotoxic effect on the crop. Methabenzthiazuron, metoxuron and chlortoluron gave 1410, 1420 and 1090 kg/ha, respectively, more grain than the unweeded crop and 590, 600 and 270 kg/ha more than the crop hand-weeded twice. Nitrofen (1.25 kg a.i./ha) applied pre-emergence was effective against P. minor only and gave substantial increase in grain yield. Terbutryne, dichlormate and linuron, while effective against P. minor, also had a phytotoxic effect on the crop.     

The Coconut Rhinoceros Beetle Oryctes rhinoceros (L)[Coleoptera: Scarabaeidae: Dynastinae]

Abstract

Field experiments were conducted during two dry seasons in northern Nigeria to identify suitable pre‐transplant herbicides for weed control in irrigated tomatoes. At Samaru in the northern Guinea savanna, diphenamid at 1.5 kg a.i./ha followed by supplementary hoe‐weeding, metribuzin at 0.5 kg a.i./ha, diphenamid at 3.0 kg a.i./ha, metolachlor plus metobromuron at 1.0 + 1.0 kg a.i./ha and two or three hoe‐weedings, resulted in higher tomato yields than the untreated controls, and most of these treatments reduced weed infestations significantly in both years. At Bakura, in the Sudan savanna zone, metribuzin at 0.25 and 0.5 kg a.i./ha, diphenamid at 3.0 g a.i./ha and chloramben at 1.5 kg a.i./ha plus supplementary weeding consistently resulted in yields that were similar to two hoe‐weedings and higher than the untreated controls. Three kg a.i./ha of chloramben depressed yields in all the trials. At both sites hoe‐weeding once six weeks after transplanting gave unacceptably low crop yields, but similar high yields were obtained with two or three hoe‐weedings. Supplementary hoe‐weedings were unnecessary with the application of metribuzin at 0.5 kg and metolachlor plus metobromuron at 1.0 + 1.0 kg a.i./ha. Uncontrolled weed growth resulted in a 53–67% reduction in tomato fruit yield.     

Possible Methods for Controlling Ischaemum afrum (J. F. Gamel) Dandy,in Fallow

Abstract

Different mechanical cultivations and herbicide treatments were compared for controlling Ischaemum afrum in a heavily infested fallow area. Of the mechanical cultivations, disc ploughing to a depth of more than 15 cm, following removal of tufts and watering, was found very effective (83% reduction). Incorporated pre-emergence triluralin (1.90 kg a.i./ha) alone or in tank mixtures with oxadiazon (0.95 + 0.95 kg a.i./ha) was also found promising (79 and 76% reduction respectively). Three applications of dalapon (8.09 kg a.i./ha), as post-emergence, at two weekly intervals or two applications followed by another application at 4.05 kg a.i./ha gave almost complete eradication of Ischaemum afrum seedlings for about 12 weeks (99% reduction).     

Efficiency of Different Herbicides for Weed Control in Peas

Abstract

A field experiment was conducted for two years during 1977–78 and 1978–79 to evaluate the efficiency of methabenzthiazuron, terbutryn and metoxuron in controlling weeds in peas (Pisum sativum) at the Punjab Agricultural University, Ludhiana, India. Pre-emergence application of methabenzthiazuron at 1.05 and 1.40 kg a.i./ha gave efficient weed control and gave comparable yields to two hand hoeings. Post-emergence application of methabenzthiazuron proved inferior. Terbutryn pre-emergence showed promise but as a post-emergence application it was ineffective. Metoxuron both pre- and post-emergence showed phytotoxic effects on the crop.     

The Institute of Phytopathological Research

Abstract

Further work with the herbicide C 19490 (S-(2-methyl-1-piperidyl-carbonylmethyl)-O,O-di-N-propyl dithiophosphate) in the mixture C 288 with the triazine C 18898 in the ratio 4:1, and with 2,4-D isopropyl ester (2,4-D IPE) in the ratios 2:1 and 3:2 have been completed. New toxicological data show that the risk of toxicity hazards to the user or to other mammals by contamination is low. Residue work shows that C 19490 leaves very low or undetectable residues in rice grain and soil, though C 18898 was detected in both, but never at more than 0.28 ppm in soil or more than 0.04 ppm in grain. There was no interaction between either C 19490 or C 288 and commonly used insecticides. Uptake of the products by plants was shown to be preferentially through emerging shoots, and less through roots.

Field trials resulted in recommendations for around 2 kg C 288 total a.i./ha in Japan, optimum timing depending on the prevailing temperature. Successful control was achieved in Taiwan with C 288 at 1 kg a.i./ha in both the cool and warm season crops, applied 7–12 days after transplanting. In equatorial Asia, mixtures worked well: C 288 at 0.75–1.25 kg a.i./ha, C 19490 at 0.75–1.0 + 2,4-D IPE at 0.5 kg a.i./ha and the 3:2 mixture at 0.75 + 0.5 kg a.i./ha (granular), applied four DAT on dense weed stands, but up to ten DAT on stands comprising predominantly moderate infestations of Echinochloa crusgalli, Monochoria vaginalis and annual Cyperus spp. These recommendations resulted in yields which were never significantly different from those of hand-weeded areas. On light, permeable soils, e.g. in Pakistan, C 288 at 1.0–1.25 kg a.i./ha, 8–10 DAT was less harmful to the crop than lower rates applied earlier, and was better than the 2,4-D IPE mixture for weed control. In Egypt, C 19490 + 2,4-D IPE at only 0.375 + 0.25 kg a.i./ha was successful, because of the susceptible weed flora.     

Chemical weed control in rainfed upland rice in Nigeria

Abstract

Two field experiments on chemical weed control in Faro 41 upland rice (Oryza sativa L.) variety were conducted at a rainforest site near the National Cereals Research Institute, Amakama Substation in 1989 and 1990. The herbicides tested were a coformulated mixture of pretilachlor and dimethametryne at 1.5, 2.0 and 2.5 kg a.i./ha, a co‐formulated mixture of piperophos and propanil applied at 3.16 and 3.95 kg a.i./ha, and Oxadiazon at 1.0 kg a.i./ha. Two hand weedings and a ‘no weeding’ treatment were included. The herbicides were applied 5 days after planting. All were safely selective to the crop. Most provided adequate weed control through 8–12 weeks after planting. Weeds controlled included Cynodon dactylon, Commelina benghalensis, Dlgitaria horizontalis, Eleusine indica, Panicum maximum and Pennisetum purpureum as grass weeds. The broadleaf weeds were Emilia sonchifolia, Ageratum conyzoides, Portulaca oleraceae, Richardia brasiliensis and Ipomoea Involuncrata. The sedges Mariscus alternifolius and Cyperus esculentus were encountered in the plots. Pretilachlordimethametryne at 2.5 kg a.i./ha had the best weeding score. Twoyear average grain yields of 1.7–2.6 t/ha were obtained from the herbicide treatments. With only 0.4 t/ha from the unweeded treatment, yield losses of more than 80% were recorded.     

Herbicide Research on Groundnut and Sorghum under Farmer Conditions in the Indian Semi-arid Tropics

Abstract

Plots 17 × 5 m were laid out in farmers' fields in three villages. Treatments (replicated thrice) included atrazine (0.5 or 1.0 kg a.i./ha) on sorghum and nitrofen (0.75 and 1.5 kg a.i./ha) on groundnuts with or without hand-weeding or farmers normal weed control. Groundnuts were unfertilized, sorghum received 20 or 80 kg N/ha. Cooperating farmers were allocated plots for traditional weed control, other operations were carried out by research staff. Some plots were discounted because farmers withdrew cooperation or did not participate correctly or because of flooding. In groundnuts nitrofen alone was inferior to nitrofen + one hand-weeding. In sorghum there were no differences between high and low fertilizer regimes. Atrazine gave superior yields to farmers' weed control. All treatments were better than the unweeded control. Generally farmers fields had low weed populations due to good, timely control and low soil fertility. Herbicides are not economic at present. Problems associated with research in farmers fields included: selection of farmers who would participate correctly, variability between different farmers' weeding practices and between different fields due to previous crops and cultural practices; lack of control of farmers weeding operations and the distance of experimental plots from the research station. The authors suggest that small experiments with only 4-6 treatments are easier for participating farmers to comprehend, selecting suitable size and shape of plots is important and that if many farmers are involved the number of replicates can be reduced.     

Recent Developments in the Use of Herbicides in Rubber and Oil Palm

Abstract

Recent developments in the use of herbicides during the establishment of leguminous cover crops and the mature phases of rubber and oil palm plantings are discussed. Results of 12 semi-commercial and commercial scale trials showed that chemical weeding using paraquat and diuron post-emergence or oxyfluorfen pre-emergence with supplementary manual or chemical control was considerably cheaper than exclusive manual weeding during the six months following the sowing of legumes. Reductions in weeding costs ranged from 6 to 66%. In the mature phase a wide range of herbicide treatments involving extensively used herbicides such as paraquat, MSMA, 2, 4-D amine and sodium chlorate for the suppression of weed growth along rubber tree rows and in oil palm circles and harvesters' paths were compared. Results indicate that there are several suitable alternatives to sodium arsenite, a formerly widely used herbicide which is now banned for general weed control. In both crops, the most cost effective treatments for controlling mixed vegetation were Ustinex Special (MCPA + diuron + amitrole, 2:3:6) at 1.48 kg a.i.ha + Gramoxone (paraquat) at 0.22 kg a.i./ha and Paracol (paraquat + diuron, 1:1) at 0.56 kg a.i./ha + DMA Amine (2, 4-D) at 0.50 kg a.e./ha.     

Response of transplanted rice to nitrogen fertilization under different weed management practices

Abstract

Rice yield increased significantly and consistently up to 120 kg N/ha when weeds were not controlled. But when weeds were effectively controlled by two hand weedings (20 and 40 days after transplanting) or by use of thiobencarb at 1–0 kg a.i./ha rice yield increased significantly up to 80 kg N/ha. The optimum dose of N for transplanted rice under mid‐hill conditions of Himachal Pradesh (Palampur) was 82 kg/ha when two hand weedings were done and 86 kg/ha when weeds were managed using thiobencarb. The yield response per kg of N in the respective treatments was 20 and 24 kg of grain. The weed dry weight was significantly lower in thiobencarb and hand weeded plots compared with unweeded check though the difference in weed dry weight due to the former two treatments was not significant.     

Studies on very-low volume (VLV) water-based sprays for the control of cotton pests

We evaluated, water-based very-low volume (VLV) sprays of various pyrethroids at different dosage levels, comparing these with ultra-low volume (ULV) sprays for the control of cotton pests in the Nampula province of Mozambique. The results showed that karate (lambda-cyhalothrin) 2.5% SG at a dosage level of 15 g a.i./ha applied as VLV gave a significantly higher yield than karate 0.8% ULV (28 g a.i./ha). Also, karate 3.75% WG (12 and 15 g a.i./ha) gave a similar yield to that of karate 0.8% ULV (28 g a.i./ha). Karate 5% EC (15 and 20 g a.i./ha) gave a yield similar to Karate 0.8% ULV (28 g a.i./ha). Baythroid (cyfluthrin) 5% EC at 15, 22.5 and 30 g a.i./ha gave a yield similar to baythroid 1.2% ULV (36 g a.i./ha). Bulldock (beta-cyfluthrin) 12.5% SC at dosage levels of 6, 9 and 12 g a.i./ha gave a similar yield to that using baythroid 1.2% ULV (36 g a.i./ha). In all four trials, water-based VLV sprays gave a yield of cotton and degree of pest-control similar to those obtained with the ULV formulations at comparatively lower dosage levels. Integrated with other pest management practices, these could play an important role in the cost effective management of insect pests of cotton on small-scale farms in many countries.     

Efficiency of Paraquat as a Weed Control Chemical for Rubber Nurseries

Abstract

Three rates of the post-emergent herbicide paraquat, 0.7, 0.35 and 0.175 kga.i./ha in 560 //ha were applied to weeds between rows of rubber seedlings. At each rate of paraquat, spray drift caused some defoliation of the seedlings but this was considerably higher at 0.7 kg a.i./ha than at the two lower rates. Death of individual seedlings was negligible at 0.175 kg a.i./ha. Weed control increased with dosage, but 0.175 kg a.i./ha gave acceptable control, which was also completely safe to budgrafts. At this rate, bud development was not affected and growth was comparable to the hand-weeded control.     

A World-Wide Organization to Promote the Development of Biological Control

Abstract

Three experiments were conducted to evaluate the efficacy of metribuzin in tea fields. These were a field trial in plots infested with a wide range of weeds, a pot experiment using Paspalum conjugatum and a microplot experiment with 100 Ageratum conyzoides plants/plot. Metribuzin at 0.70, 1.05, 1.40 and 2.10 kg a.i./ha was applied in 450 l water/ha. All rates were satisfactory after 1 week but residual activity increased with application rate; metribuzin at 2.10 kg a.i./ha was significantly superior after 6 weeks. Control after 8 weeks was reduced due to the presence of resistant species. Against Paspalum conjugatum metribuzin at 1.40 kg/ha gave good control for 8 weeks but 2.10 kg/ha was necessary for 12 weeks control. All rates compared favourably with dalapon (4.48 kg a.i./ha). Against Ageratum conyzoides metribuzin at all rates gave good control for up to 12 weeks and significantly better than 2, 4-D at 1.12 kg a.i./ha. Most other grass and broadleaved weeds were satisfactorily controlled at 1.40 kg a.i./ha. Metribuzin with its marked post-emergent effect and prolonged soil residual activity from 6-12 weeks after application, depending on weed species, may become an important tool in pre-monsoon weed control programmes in tea fields. It did not induce any phytotoxic symptoms on mature tea.     

Effects of Herbicides on Horticultural Characteristics,Yield and Quality of Onions

Abstract

Seven different herbicides were tested in 1967, and two of these chemicals were further evaluated in 1969 for their efficacy in onions grown in Lebanon. Chloroxuron at 6 kg a.i./ha and Sindone at 1.5 kg/ha gave a significant increase in the bulb weight and yield of onions over unweeded plots. Significant reductions in yield were observed from pre-em. applications of chlorbromuron at 3 kg/ha, propachlor at 6 kg/ha, Sindone at 0.5 kg/ha, and prometryne at 1 and 1.5 kg/ha. Good weed control was obtained as a result of pre-em. application of all herbicides tested.

With post-em. application, weed control was not effective. With the exception of prometryne at 1.5 kg/ha which injured the onions and reduced the yield, the post-em. applications of herbicides tested gave no significant effect on onion yield.

None of the treatments, in both pre-em. and post-em. applications, had any significant effect on leaf length, bulb index, bolting and splitting percentages, dry matter content, total soluble solids, or pungency of onions.     

Chemical control of perennial nutsedge (Cyperus rotundus L.) in tropical upland rice

Five herbicides were tested in the dry and in the wet season for their effectiveness in conlrolling perennial nutsedge (Cyperus rotundus L.) in direct-seeded upland rice in the tropics. K-223 [N-(α,α-dimethylbenzyl)-N'-P-tolyl urea] gave the best results. When broadcast sprayed at 8.0 kg a.i./ha in the dry season and 10 kg a.i./ha in the wet season and immediately mixed into the soit just before drilling, K-223 gave excellent perennial nutsedge control with no visible crop damage and increased the grain yield. Bentazone at 2.0 kg a.i./ha applied 7 days after crop emergence was highly selective and gave fair control of nutsedge without being toxic to the crop. MBR 8251 [1.1,1-trifluoro-4′-(phenylsulfonyl) methane-sulfono-o-toluidide] at 2.0 kg a.i./ha, mecoprop (MCPP) at 1.5 kg a.c./ha and fenoprop (silvex) at 1.0 kg a.e./ha applied 7, 14 and 7 days, respectively after crop emergence provided a fair degree of nutsedge control. Fenoprop and MBR 8251 caused slight and mecoprop moderate initial toxicity, but the injury sustained did not significantly affect crop yield.     

Studies on the Efficacy of Various Insecticides Against Mustard Aphid [Lipaphis erysimi (Kalt)]

Abstract

An experiment was designed to test the efficacy of various insecticides for the control of mustard aphid (Lipaphis erysimi (Kalt)) on mustard (Brassica juncea), variety RL 18 at the Research Farm of the Haryana Agricultural University, Hissar (India). Out of the 13 insecticides tried, each at two levels, it was found that methyldemeton 250 ml and menazon 250 g a.i. gave the maximum control of mustard aphid. Maximum yield of 1111 kg/ha was obtained with methyldemeton 250 ml (a.i./ha) against 360 kg/ha of the control.     

Suppression of Cyperus rotundus L. in carrots with night applications of nitrofen or herbicidal oil*

Selective control or suppression of Cyperus rotundus L. in carrot (Daucus carota L.) was investigated in Brazil using post-emergence applications of nitrofen (2,4-dichlorophenyl 4-nitrophcnyl ether) or a herbicidal oil (11–7% aromatics). Night applications of nitrofen in water, nitrofen in the herbicidal oil and the herbicidal oil alone were more effective in suppressing the growth of C. rotundus foliage than day applications. Nitrofen and the herbicidal oil were, respectively, 50 and 30% more active in suppressing C. rotundus during the warm, wet season (October to March) than the cool, dry season (April to September) in Viçosa. Night applications of nitrofen (1, 2 and 4 kg/ha) in water and the herbicidal oil alone (100, 200 and 400 1/ha) suppressed C. rotundus by 60% or more, and resulted in similar carrot yields to the hand-weeded control. Combinations of nitrofen in the herbicidal oil were more effective in suppressing C. rotundus than either herbicide applied alone, but the combinations tested were toxic to the carrots. Elimination du Cyperus rotundus L. dans les cultures de carrottes au moyen d'applications nocturnes de nitrofène ou d'une huile herbicide..