摘要:

After the fumigation of stock, grain stores may be resprayed regularly with a residual insecticide to lower the rate of insect reinfestation. For financial justification, respraying must result in a substantial delay in the need for refumigation. The costefficiency of respraying, for the protection of bagged milled rice, was investigated in six stores in East Java, Indonesia. All six stores were sprayed immediately after fumigation and then four were resprayed, at monthly intervals, with fenitrothion e.c. or w.p. Store reinfestation was monitored using bait‐bag traps and spear sampling, and the performance of the treatments assessed in the light of the calculated minimum delay to refumigation required for costeffective pest control. The major pest in all stores wasT.castaneumalthough other insects were present, especially Psocoptera. No substantial slowing of insect reinfestation was observed in the resprayed stores; the possible reasons for this are discussed. Thus neither of the respray treatments could be regarded as cost effective. Abandoning respraying of bagged milled rice stores might, at worst, result in a small increase in the frequency of fumigation but reliance on fumigation together with a single non‐residual spray treatment is likely to be a cheaper and more efficient option.

ISSN:0143-6147    

DOI:10.1080/09670879209371734

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Chickpea suffers severe competition due toChenopodium albumL. infestation. Two to three hoeings are generally given to checkC. albumbut increasing labour costs and scarcity of farm labour make the manual weeding difficult. Usage of herbicides appears to be a logical solution. Pre‐emergence applications of pendimethalin or ametryn alone at 1.5 kg ai ha−1or one handweeding at 35–40 days after seeding following either 1 kg ai ha−1of pendimethalin, ametryn or fluchloralin or metribuzin at 0.3 kg ai ha−1applied pre‐emergence gave effective control ofC. albumand seed yields similar to clean‐weeded chickpeas. There was an 84% reduction in seed yield of chickpea without weeding.

ISSN:0143-6147    

DOI:10.1080/09670879209371735

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Pot and field studies were conducted to determine the effect of the duration ofRottboellia cochinchinensis[Lour.] W. D. Clayton presence or absence on the growth, development and yield ofZ. maysL., and to establish the length of the critical period of weed interference. The crop was maintained weed‐free or weedinfested throughout the growth season or for periods of 0, 2, 4, 6, 8 and 10 weeks after emergence (w.a.e.), respectively. The crop and weed densities used were 55 000 plants/ha, and 55 plants/m2, respectively. Regression models were fitted to the growth data and comparison of the relevant regression lines made. The results indicated that the presence or absence of the weed for the varying periods had no effect on the crop plant height, leaf area ratio (LAR), relative growth rate (RGR), net assimilation rate (NAR), and crop growth rate (CGR), but there was consistent trend of reduced LAI and shoot dry weight in the weed‐infested treatments. Increasing the periods of weed‐free treatments increased yields exponentially, while increasing the periods of the weed infestation decreased yields exponentially. The study demonstrated a critical period ofR. cochinchinensisinterference onZ. maysgrowth and development, and yield from 0 to 63 d.a.e., and suggests that the reduction in crop yield may be through non‐competitive interference by the weed on the crop.

ISSN:0143-6147    

DOI:10.1080/09670879209371736

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Two field experiments on chemical weed control in Faro 41 upland rice(Oryza sativaL.) 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 includedCynodon dactylon, Commelina benghalensis, Dlgitaria horizontalis, Eleusine indica, Panicum maximumandPennisetum purpureumas grass weeds. The broadleaf weeds wereEmilia sonchifolia, Ageratum conyzoides, Portulaca oleraceae, Richardia brasiliensisandIpomoea Involuncrata.The sedgesMariscus alternifoliusandCyperus esculentuswere 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.

ISSN:0143-6147    

DOI:10.1080/09670879209371737

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Field experiments were done during winter seasons of 1988–89 and 1989–90 at Haryana Agricultural University, Hisar, India. Wild oat (Avena ludoviciana)was effectively controlled at 20 and 30 d.a.s. with 0.25 to 0.35 kg/ha tralkoxydim. The average reduction of wild oat population by 0.30 and 0.35 kg/ha tralkoxydim was 73.5 and 85.4%. Significantly better efficacy of tralkoxydim was obtained with spraying than broadcasting it with urea or sand at both the stages of application. An increase in the concentration of tralkoxydim enhanced control of wild oat. On an average of application times and methods, tralkoxydim at 0.25 kg/ha gave poor wheat yields. Tralkoxydim application at 30 d.a.s. produced significantly better crop yields than its earlier application.

ISSN:0143-6147    

DOI:10.1080/09670879209371738

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

The influence of four transplanting dates and three plant densities (30, 36 and 42 plants/12.8 m2) on the incidence of jassid,Amrasca biquttula biquttulaIshida, per cent fruit infestation (weight basis) by shoot and fruit borer,Leucinodes orbonalisGuen. and marketable yield of egg‐plant(Solanum melongena)was investigated under sprayed and unsprayed conditions. Early transplanted (17th July) crops resulted in increased incidence of both pests. Plant density per unit area inversely affected the jassid population. However, maximumL. orbonalisinfestation was observed with highest plant density of 42 plants/12.8 m2plot. Spraying of demetonmethyl (0.025%) significantly reduced the jassid population. Similarly, use of endosulfan (0.07%) reduced the per cent fruit infestation by borer from 25.1 (unsprayed) to 15.8 (sprayed) per cent. Greater marketable fruit yield was obtained in early and recommended transplanted crops, than in delayed transplantings. Spraying the crop with insecticides gave increased marketable fruit yields over the unsprayed crop of up to 25%.

ISSN:0143-6147    

DOI:10.1080/09670879209371739

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

A study to evaluate control strategies for insect pests in cowpea with emphasis on flower thrips,Megalurothrips sjostedtiTrybom, was carried out on farms in Dzwafu and Minjibirr villages in Nigeria. Two insecticides, Sherpa Plus and Cymbush Super ED, applied at different cowpea growth stages, were tested. Insect numbers were higher and yields lower in Dzwafu than Minjibirr. Both insecticides were effective and profitable, giving increased yields and marginal returns. Sherpa Plus gave slightly better insect pest control. Applying the insecticides at flowering gave better thrip control and grain yields than application at flower bud formation. Grain yields and profit margins increased when insecticides were applied at both growth stages. However, insecticidal application decreased haulm yields. Spraying at flowering caused the greatest reduction. insect pest control for cowpea grain production thus is antagonistic to haulm production for fodder, which may be the primary requirement in some areas. Therefore, techniques for managing cowpea pests should take farmers’ requirements into account.

ISSN:0143-6147    

DOI:10.1080/09670879209371740

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Caged experiments were carried out for two seasons (1987–88 and 1988–89) to investigate the potentialities of indigenous Coccinellidae in regulating aphid populations in wheat fields of Central Saudi Arabia. The results indicated that the use ofCoccinella undecimpunctataL., the predominant predator in Gassim, alone or in combination withAdonia variegataGoeze andC. novemnotataHbrst. at similar ratios as found in the fields, can satisfactorily control wheat aphids in a confined environment. Yields obtained from such coccinellid‐treated wheat are not significantly different from those obtained from an uninfested control. Untreated aphid‐infested wheat resulted in lower yields in both seasons (an average of 30.9% less than the aphid‐free control for the two seasons). Head length and grain number per head were substantially lower in aphid‐infested untreated control than in the coccinellid and the aphid‐free treatments. Use ofC. undecimpunctataalone or in combination with others resulted in increased yields by 35.6% and 39.7% in 1987/88, and by 38.5% and 27.9% in 1988/89. The aphids were kept significantly lower in the coccinellid treatments than in the infested untreated control, after the 3rd week of coccinellid introduction.

ISSN:0143-6147    

DOI:10.1080/09670879209371741

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Local flora was screened for pesticidal activity against insect pests of field crops,Aesculus indica(flower and leaf) extract was found effective (up to 75% mortality) against sugarcane mealybug(Saccharicoccus sacchari). Schinus molli(leaf), andAesculus Indica(leaf and flower) extract caused significant (60–70%) mortality in yellow rice stem borer(Schirpophaga incertulas)larvae.Azadirachta indicaleaf powder fed to chickpea pod borer(Heliothis armigera)caused failure in pupation and adult emergence. Addition ofAzadirachta IndicaandBroussentia papyriferato artificial diet restricted the adult emergence inHeliothis armigera.Similarly, prolonged larval period (21 days compared to 14 in control), delayed pupation and deformed adult formation resulted after treatment withAzadirachta indica(leaf) andMelia azedarech(fruit) powder. Significant mortality (60–90%) was observed in sugarcane pyrilla(Pyrilla perpusilla)adults treated withAzadirachta indica, Dryopteris ramosaandSchinus molte(leaf) extract.

ISSN:0143-6147    

DOI:10.1080/09670879209371742

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

A key to 36 species of Tingidae commonly found on economically important plants from around the world is presented. The primary external characters used in the identification of tingids are discussed and illustrated, and habitus illustrations are provided for 29 of the 36 included species. The key also presents information on the host plants and geographic distribution of each species.

ISSN:0143-6147    

DOI:10.1080/09670879209371743

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor