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1.

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.  相似文献   

2.
Abstract

Major insect pests and their natural enemies were sampled on cowpea in monocrop and cereal intercrop plots in southern and northern Nigeria. Populations of flower thrips, Megalurothrips sjostedti (Trybom), were reduced by 42% and predators, mostly Orius spp. (Anthocoridae), by 23% on cowpea in maize intercrop plots at Ofiki in the south. Infestation by pyralid pod borer, Maruca testulalis Geyer, was unaffected by cropping system. The results suggest that tasselling maize attracts flower‐eating beetles (Meloidae) to intercrop plots, and that pod‐sucking Hemiptera were increased by cereal intercrops at Yankara in the north. Three u.l.v. applications of permethrin at 150 g a.i./ha to monocrop cowpea reduced pest populations by 50 to 85% in the south and increased yield sevenfold. However, the sprayed crop in the north was lost due to a heavy infestation of pod‐sucking bug, Clavigralla tomentosicollis Stål, and outbreaks of Aphis craccivora Koch on sprayed plots in both localities suggested damage to natural enemies. It is concluded that the pest management potential of intercropping is variable and dependent on environmental factors, but it is recommended that intercropping be used in integrated pest management systems with the progressive decrease in insecticide use.  相似文献   

3.
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.  相似文献   

4.
Legumes have evolved effective defences against many pests by accumulating high levels of poisonous or indigestible compounds, pubescence and vigorous growth. These defences are greatly reduced in many cultivars of cowpea and common bean, which are susceptible to a succession of pest complexes. Stem pests and defoliators may kill seedlings but well-established plants tolerate heavy insect damage to leaves, flowers and green pods before pod or grain yields are reduced; virus vectors and root-knot nematode may be of greater importance. Generally, pod-borers, pod-sucking bugs and seed beetles are the main key pests. Control programmes are based on post-flowering treatments with broad spectrum insecticides. Battery-powered, controlled-droplet application machines are ousting knapsack sprayers in small-scale farming and competing with tractors and aircraft in larger units; subsistence cropping is still predominant and most legume crops remain unsprayed. Consequently, current emphasis is placed on developing cultivars with high yield potential and multiple pest and disease resistance. Insect infestations are lower in most other major legume crops largely due to pubescence (e.g. soybean, blackgram, greengram), fruiting in the dry season (e.g. pigeonpea, chickpea) or geocarpy (e.g. groundnut). Future entomological research will presumably concentrate on assessing the status of pests on resistant cultivars and introducing integrated control methods for the key pests.  相似文献   

5.
Abstract

Malathion seed treatments were evaluated as a means of protecting aerially‐sown rice from attack by Chironomus tepperi Skuse and other chironomids in New South Wales, Australia. Four treatments were examined: malathion applied to seed at 150, 300, and 450 ga.i/ha, and malathion applied directly to water at 300 ga.i./ha. Chironominae were significantly suppressed for 10 days by all treatments, but populations were often significantly above control levels at 20 and 25 days post‐treatment. None of the treatments significantly reduced other chironomids(predominantly Tanypodinae) at any stage of the trial. Emergence trap data from control and water treatment bays showed that there was, in practical terms, only a single generation of C. tepperi during crop establishment, and that malathion applied directly to water at 300 ga.i./ha almost completely eliminated adult emergence in this species. Bioassays of field‐collected water samples showed that malathion dissipates readily from seed into the water column. Toxicity profiles over time for the 150 and 300 g a.i./ha seed treatments were statistically similar to that for the 300 ga.i./ha water treatment. Although the 450 ga.i./ha seed treatment provided slightly longer residual toxicity, control was not enhanced sufficiently to justify an increase in the existing application rate of 300 ga.i./ha.  相似文献   

6.
Abstract

A method for assessing the damage by insect pests to cowpeas is presented. A crop life table for cowpeas grown in northern Nigeria shows the estimated losses due to insect attack at various stages of growth of the plants. The potential loss in yield due to insects is over 90%, with 70% of this loss occuring during the flowering and pod formation stages.  相似文献   

7.

Field trials were conducted during the rainy seasons of 1993/94 for chemical control of groundnut leaf spot using a single spray. A fungicide mixture ofcarbendazim 0.05%+mancozeb 0.2% was applied once in different treatments. Spray timings varied from 30 d.a.s. to 80 d.a.s. at 10-day intervals. Spray application reduced the percent disease index in all treatments. A statistically significant increase in pod yield was obtained in treatments sprayed up to 50 d.a.s. in 1993. The yield data were not significantly different in 1994. Sprays at 40 d.a.s. in 1993 and 50 d.a.s. in 1994 gave maximum returns. The cost of treatmentdid notvary significantly. The benefitto cost ratio oftreatments ranged from 1.1 to 8.1 in 1993 and 4.1 to 5.5 in 1994.  相似文献   

8.

Studies were carried out to evaluate the efficacy of various nematicides: aldicarb (Temik 10G), and carbofuran (Furadan 3G) at 3 kg a.i./ha, mocap (Ethoprop 10G) at 5 kg a.i./ha and oilcakes ofcastor ( Ricinus communis L., 4.2% N), groundnut ( Arachis hypogea L., 7% N), linseed ( Linum usitassimum L., 4.7% N), neem ( Azadirchta indica Juss, 5.4% N) and mustard ( Brassica compestris L., 4.8% N) at 1 g N/kg of soil in the form of soil amendments for the management of Meloidogyne incognita (Kofoid & White) Chitwood infesting Egyptian henbane ( Hyoscyamus muticus L.). All the treatments resulted in a significant increase in length, fresh and dry weights ofhenbane plants as compared with untreated inoculated plants. The maximum improvement in plant growth parameters was observed in plants treated with mocap followed by neem cake, aldicarb, carbofuran, castor, mustard, groundnut and linseed cakes respectively. Application of nematicides and oilcakes suppressed the pathogenic effect of M. incognita on Hyoscyamus muticus and resulted in significant reduction in gall intensity and population density ofroot-knotnematode in roots and soil. In comparison to untreated inoculated plants the highest reduction in root-knot index was noted in plants treated with mocap, whereas the lowest reduction was observed in plants treated with linseed cake.  相似文献   

9.
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.  相似文献   

10.
A large number of pests are associated with groundnut but not all are economically important. The distribution of, losses and damage caused by groundnut pests are discussed, along with a variety of control measures and methods for their integration for effective pest management. Disease resistant/tolerant varieties, including Girnar 1, ALR 1, ICGV 87160, ICGV 86590, DH 8, TG 3, MH 16, ICGS 37 and TAG 24 from India have been released for general cultivation and could be used in integrated pest management (IPM) programmes. A large number of advanced breeding lines possessing resistance to major diseases and insect pests have been identified. Biocontrol agents have been used successfully for insect and disease control. Intercrops such as pearlmillet and soybean suppress thrips, jassids and leaf miner; castor suppresses jassids and Spodoptera, and pigeonpea suppress early leaf spot, late leaf spot and rust. These plants act as traps or barriers for reducing pest incidence. The use of pheromone traps for gram pod borers, tobacco caterpillars and leaf miners, and the use of neem products against major insect pests and diseases, are novel approaches that may reduce the cost of groundnut production. If pest control measures are integrated in an optimum proportion and pest surveillance activity is strengthened further, maximum returns could be realized  相似文献   

11.
Abstract

Helicopter applied insecticides used for tsetse control were investigated for their potential to reduce populations of Simulium damnosum s.l. in riverine forest in the Guinea savanna zone of southwestern Upper Volta. Populations of aquatic stages and biting females were sampled before and after spraying. Deltamethrin applied at 12·5 g a.i./ha to a 30 km length of riverine vegetation almost eliminated adults for a period of about nine days. Residues which fell into the water killed all larvae in the river. Endosulfan at 100 g a.i./ha applied to a similar stretch of vegetation caused a reduction of over 60% in biting adults for 11 days, but residues falling into the river killed only young larvae. Neither dieldrin at 400 g a.i./ha, endosulfan at 10 g a.i./ha nor deltamethrin at 12.5 g a.i./ha applied to a 5 km insecticide barrier between the experimental blocks and the untreated river appeared to have much effect. This suggests that most S. damnosum were traversing the barrier without coming into contact with the insecticides.  相似文献   

12.
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.  相似文献   

13.
The application of granules containing 10 % phorate at 1.12,2.24 or 4.48 kg a.i./ha in a narrow slit together with carrot seed significantly reduced seedling emergence in both a mineral and peat soil. When the granules were applied at 2.24 or 4.48 kg a.i./ha in a narrow slit 2.5 cm below the seed, seedling emergence was adversely affected only at the higher rate in the mineral soil. Phorate granules applied with the seed in the peat soil gave a significantly lower plant density than when applied below the seed, but subsequent carrot yields were unaffected because much larger roots were produced. All phorate treatments gave effective reduction of carrot fly larval damage to the roots. On the peat soil, there were significant increases in total phorate residues present in mature carrots with increasing rate of phorate granules placed with the seed. Placement of the granules 2.5 cm below the seed resulted in a 50% reduction in total residues of phorate in whole carrots compared with placing the granules with the seed. Residues resulting from 1.12 kg a.i./ha with the seed or 2.24 kg a.i./ha 2.5 cm below the seed were not significantly greater than residues in untreated carrots.  相似文献   

14.
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.  相似文献   

15.
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.  相似文献   

16.
Abstract

Metsulfuron methyl (Ally‐Dupont), a sulphonylurea herbicide, was tested at rates of 0.5–2.0 g a.i./ha for the control of Striga hermonthica (Del.) Benth. in two cultivars of sorghum in pot experiments. There was good to excellent Striga control at 1.0–2.0 g a.i./ha applied either pre‐emergence or post‐emergence to CSH‐1 or N‐13 sorghum. The herbicide was unacceptably toxic to the Striga‐susceptible CSH‐1 cultivar when applied pre‐emergence, thus eroding any benefits of Striga control. In the Striga‐tolerant N‐13 cultivar there were considerable increases in the growth of infected plants. The herbicide was better tolerated from post‐emergence applications by both cultivars, and CSH‐1 plants recovered enough growth from Striga infection to produce grain yields at 1–5 and 2.0 g a.i./ha. Herbicide application at 4 weeks after planting sorghum was less damaging than at 2 weeks. Herbicide safening with 1,8‐naphthalic anhydride did not provide any additional benefits with post‐emergence application. The efficacy of the pre‐emergence herbicide was similar with surface or incorporated application.  相似文献   

17.

Studies conducted during the winters of 1997 - 98 and 1998 - 99 (December - March) at the Regional Research Station, Tamil Nadu Agricultural University, Vridhachalam, India, revealed the usefulness of polyethylene film mulching in arresting weed growth and maximizing pod yield in groundnut. Among the various treatments, two (1) crop grown under polyethylene film mulching and (2) pre-planting incorporation of fluchloralin in the flat-bed system of sowing registered the lowest weed numbers at harvest (106.7 and 113.7/plot of 27 m 2 in 1997 - 98 and 1998 - 99 respectively), the lowest weed dry-matter production (51.2 and 54.5 g/plot of 27 m 2 ), maximum weed control efficiency (62.1 and 57.4%) and weed control index (83.0 and 81.1%), the highest number of matured pods/plant (17.6 and 18.0), 100 kernel weight (48.6 and 48.7 g), percentage shelling (72.6 and 72.8) and a dry pod yield of 2451 and 2468 kg ha -1 when compared with non-mulched plots. The net return and benefit:cost ratio was also highest with the same treatment in both the study periods.  相似文献   

18.
Abstract

A field trial was conducted to study the magnitude of quinalphos residues in and/or cauliflower (Brassica oleracea Var Botrytis. The cauliflower crop was sprayed once with quinalphos 25 e.c. at 0.25 and 0.5 kg a.i./ha 104 days after transplanting. The samples of cauliflower drawn at different time intervals were analysed colorimetrically. The initial deposits of quinalphos on cauliflower were found to be 5.79 and 9.52 ppm, an the half life values 1.61 and 2.12 days, respectively, at 0.25 and 0.5 kg a.i./ha. The waiting periods determined were 11 days at the higher and 7 days at the lower dose of quinalphos.  相似文献   

19.
Abstract

The effects of aerosol dosages of different categories of insecticide were tested against Glossina tachinoides when applied by helicopter to riverine forest habitats of the River Komoe, Upper Volta, West Africa. The method of application, droplet characteristics of the aerosols and meteorological conditions are described in accompanying papers. Comparative trials based on field dosages calculated initially from dosage mortality curves obtained from topical application studies in the laboratory were carried out. Endosulfan applied at 5.4 g a.i./ha and 9.0 g a.i./ha reduced G. tachinoides populations (determined by Challier/Laveissière traps) by more than 90% in all age and sex categories and evidence is presented which indicates a residual effect at the higher of these dosages. Good results were also obtained with the synthetic pyrethroid decamethrin at a dosage of 0.36 g a.i./ha; another synthetic pyrethroid, permethrin, gave promising results at a dosage of 1.9 g a.i./ha. At the higher dosage of 4.3 g a.i./ha disappointing results were obtained, which were considered to be more attributable to a weakness in the application technique under challenging field conditions, than to a limitation of the insecticide. The organophosphate compounds tested, fenthion, azamethiphos and tetrachlorvinphos although known from laboratory tests to be appreciably toxic to G. tachinoides, performed poorly under field conditions. This was thought to be due to the formulations employed and the authors feel that further small-scale field testing of different formulations of these compounds is warranted. The compounds considered most worthy of larger scale field evaluation were endosulfan and permethrin. Although decamethrin was also very toxic to G. tachinoides it was considered inadvisable to field test this compound on a larger scale, until more information was available on its impact on aquatic food chains. The trials demonstrated that it is not always possible to extrapolate from laboratory-obtained comparative dosage/mortality data (in ng/fly) the field dosages of insecticides (in g a.i./ha) required to produce a certain level of mortality in target populations of G. tachinoides.  相似文献   

20.

Rust control and ethylenebisdithiocarbamate (EBDC) residues in green beans ( Phaseolus vulgaris L. 'Morgan') were evaluated in two seasons of 1993 in Dschang, Cameroon. Four weekly applications of mancozeb (2.8 kg ha- 1), sulphur (2.24 kg ha- 1), or mancozeb+sulphur (1.4+1.12 kg ha- 1) were initiated from initial rust symptoms. In both seasons, treatments with mancozeb alone resulted in a low area under pustule count progress curve (AUPPC) and a significant increase in leaf area index, and pod and green fodder yields. Pod yields were negatively correlated with AUPPC. Pod yield loss was estimated at 61% and 32% in the early and late seasons, respectively, while losses in green fodder yields were 57% and 24% respectively. EBDC residue levels decreased significantly with a delay in pod harvestand when pods were washed in running tap water. Residue levels were high in the late season, possibly due to low rainfall. Pods exposed to the combined fungicidal treatments accumulated higher levels of residues than those sprayed with mancozeb alone, suggesting a potential risk of EBDC accumulation on pods when EBDCs are mixed with sulphur.  相似文献   

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