摘要:

Agroecosystems in the tropics include growing two or more crops in diverse polycultural patterns. In Kenya, cowpeaVigna unguiculata(Walp.) is grown in combination with cereals such as maize and sorghum, perennial legumes such as pigeon peas and root crops such as cassava and sweet potatoes. In the present investigations, field experiments were conducted to study the incidence and damage caused byClavigralla tomentoscollisGerm, andC. shadabiafter flowering, on cowpea intercropped with maize. It was evident from the present studies thatC. tomentoscollisandC. shadabi weremore prevalent on cowpea during the first season rather than during the second season. Both species had a preference for feeding on cowpea intercropped with maize than when it was grown in pure stands. Consequently more pod damage was recorded on cowpea planted with maize. It was therefore concluded that this agricultural system, which is commonly practised by small‐scale farmers in Kenya, is undesirable from the point of view of bug damage.

ISSN:0143-6147    

DOI:10.1080/09670879109371591

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

A preliminary survey was made in the most important maize‐growing regions of Ethiopia to record the species ofCicadulinapresent, their distribution and abundance. Five species ofCicadulinawere found, including two not previously reported from Ethiopia. The maize strain of maize streak geminivirus (MSV) occurred predominantly between 450 and 1800 m above sea level, which coincides with the altitudinal range ofC. mbilaimplicating this species as the principal vector of MSV in Ethiopia. The maize strain isolate was indistinguishable from others from elsewhere in Africa.

ISSN:0143-6147    

DOI:10.1080/09670879109371592

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

The wheat crop suffers badly due to heavy weed infestation.Phalaris minorRetz.,Chenopodium albamL.,Avena fatuaL.,Melilotus albaDeser.,Melilotus indicaAll.,Anagallis arvensisL.,Fumaria parvifloraLam. andConvolvulus arvensisL. are common weeds of wheat in the Indian subcontinent. Besides handhoeing and manual weeding, use of herbicides plays a lårge role in weed management. Minimum tillage has some positive effects on soil. Pre‐emergence application of pendimethalin, terbutryn, methabenzthiazuron, bifenox and oxyfluorfen renders excellent weed control in wheat. Isoproturon, methabenzthiazuron, metoxuron, terbutryn, tralkoxydim and fluroxypyr post‐emergence give effective weed kill. ForAvena fatuaL. control, triallate, difenzoquat and diclofop‐methyl show promising results. Herbicide mixtures give broad‐spectrum weed control. Integrated weed management performs better. Wheat cultivars Sonilika, WH‐147, WH‐2009 and HD‐2329 are tolerant to isoproturon. Moderately susceptible varieties are WH‐157, WH‐291, DWL‐5023 and HD‐2285. All these cultivars show tolerance to pendimethalin. Wheat herbicides now in use do not have residual persistence. In wheat cropping systems, pendimethalin and isoproturon meet the basic requirements

ISSN:0143-6147    

DOI:10.1080/09670879109371593

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Metsulfuron methyl (Ally‐Dupont), a sulphonylurea herbicide, was tested at rates of 0.5–2.0 g a.i./ha for the control ofStriga hermonthica(Del.) Benth. in two cultivars of sorghum in pot experiments. There was good to excellentStrigacontrol 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 ofStrigacontrol. 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 fromStrigainfection 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.

ISSN:0143-6147    

DOI:10.1080/09670879109371594

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

In South Sulawesi rice tungro virus (RTV) disease was found to be endemic in double‐cropped areas, where it was likely to be carried over to the next season in stubbles, ratoons or volunteer plants. The leaf hopper vector,Nephotettix virescenspopulation started to increase 2–3 months after sowing both in wet and dry seasons, and it constituted more than 80% of total green leaf hopper recorded. It was found consistently that incidence of RTV increased with increase of the vector population. Late plantings were more vulnerable to vector infestation and tungro incidence in both wet‐ and dry‐season crops. Tungro epidemics were likely to occur more in the wet season than in dry season due to availability of large vector population.

ISSN:0143-6147    

DOI:10.1080/09670879109371595

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Diseases are major constraints to groundnut production in West Africa. Leaf spots, rust, rosette and seedling diseases are present throughout most of the region and cause substantial losses in yield. Crop growth variability is a major yield‐limiting factor in the Sahel. Aflatoxin contamination is a serious quality problem in the region. Strategies for management of these major diseases are briefly discussed with particular emphasis on the utilization of genetic resistance

ISSN:0143-6147    

DOI:10.1080/09670879109371596

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Five rounds of spray, starting from 30 days after sowing, with 12‐day intervals using carbendazim 0.05% plus mancozeb 0.2% was found to have maximum control over rust and late leaf spot diseases which resulted in 57% increased dry pod yield. However, the reduction of these diseases ultimately contributed to an increase in the 100 kernel weight and shelling percentage. It was also economical to give the fungicidal spray on the maturity stage of the crop.

ISSN:0143-6147    

DOI:10.1080/09670879109371597

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

In a study of the antibiosis effect of 10 cowpea cultivars on the development, fecundity and longevity ofClavigralla tomentosicollisthree, TVu 3198, TVu 3354 and TVu 8525, increased significantly the nymphal developmental period of the bug and caused higher nymphal mortality than the susceptible check. TVu 3372 and TVu 3355 increased the period of nymphal development and TVu 3199 caused higher nymphal mortality than the check. Fecundity of mated females was lowered by TVu 3355, TVu 3354, TVu 8525 and TVu 3364. None of the test cultivars had a significant effect on the longevity of mated females

ISSN:0143-6147    

DOI:10.1080/09670879109371598

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Cultivars of rice are generally much higher tillering than cultivars of other cereals. As a result fields of rice show considerable asynchrony in development. It is not uncommon for tillers in a single hill of rice to be at stages ranging from early booting to anthesis. In order to account for this variation within the population, and to avoid confusion between the development of individual tillers and that of the population, an addition of a third digit to the widely used decimal code for growth stages of cereals (Zadokset al.1974) is proposed. Its application and other changes to the code are discussed.

ISSN:0143-6147    

DOI:10.1080/09670879109371599

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Diseases caused by fungi, bacteria, a possible virus and nematodes have been recorded onLeucaena leucocephalaand at least seven otherLeucaenaspecies throughout the tropics. Most diseases are caused by fungi and include leaf spots, gummosis, pod rots, root and collar rots, stem cankers, anthracnoses, damping‐off, rusts and shoot and twig blights. The most important diseases are considered to beCamptomerisleaf spot (CLS)(Camptomeris leucaenae)gummosis and various root and pod rots. Although not a lethal disease, CLS can cause serious forage dry matter and quality losses. Gummosis is regarded as the most important disease ofL. leucocephalain India and Sri Lanka, but further work is urgently required on its pathology and economic importance. Root rots caused byGanodermaspecies,Fusariumspecies,Pseudolagar‐obasidium leguminicolaandPirex subvinosumkillL. leucocephalatrees throughout Asia and Australia. Pod rots caused byFusariumspecies are of major concern not only because of their direct effects in reducing seed production but also due to their seed‐borne nature. Control strategies based on resistance and cultural management through cutting and grazing are considered the most practical and economic methods. Treatments to control seed‐borne pathogens are essential to reduce establishment problems and for low‐risk germplasm movement. This review is intended to be of use for pasture and forestry researchers as well as quarantine officers in developing countries.

ISSN:0143-6147    

DOI:10.1080/09670879109371600

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor