摘要:

Eight viruses are reported from cowpeas in Africa. Three are beetle‐transmitted (cowpea yellow mosaic comovirus, cowpea mottle virus (carmovirus?), and southern bean mosaic sobemovirus), two are aphid‐borne (cowpea aphid‐borne mosaic potyvirus and cucumber mosaic cucumovirus), two are whiteflytransmitted (cowpea golden mosaic virus (geminivirus?) and cowpea mild mottle carlavirus), and the vector of the eighth (sunn‐hemp mosaic tobamovirus) is still unknown. Cowpea viruses are described from lowland, humid and sub‐humid West Africa, as well as from mid‐altitude ecological zones mainly found in eastern and southern Africa. Wherever facilities are limited and detailed characterization is not possible, a simple procedure using a combination of serology (agar‐gel diffusion test), inoculation to test plants, and vector transmission studies, is proposed for the identification of the cowpea viruses reported so far from Africa. The possibilities of controlling these viruses are briefly discussed.

ISSN:0143-6147    

DOI:10.1080/09670879209371724

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Development of resistance inDrechslera oryzaeBreda de Haan (Subram. and Jain) was observed under field conditions by continuous treatment of edifenphos. Before the application of fungicide, 96% of the isolates showed a sensitive level, but within 5 years the level of sensitivity dropped and the proportion of resistant populations increased to 52% in 1988. Cross‐resistance studies indicate that edifenphos resistance can be counteracted by spraying mancozeb as an alternative fungicide.

ISSN:0143-6147    

DOI:10.1080/09670879209371725

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Investigations were conducted in Rondonia State, Brazil, for two years to evaluate the effectiveness of integrated control involving phytosanitation and fungicide sprays in reducing pod losses due to witches’ broom disease of cocoa(Theobroma cacaoL.) caused byCrinipellis perniciosa(Stahel) Singer. The fungicides tested were cuprous oxide, tebuconazole and tank mixtures of cuprous oxide with tebuconazole or chlorothalonil. All fungicide treatments significantly reduced the incidence of pod disease in both years. However, use of integrated measures clearly exerted more disease control than fungicide use alone. None of the formulations tested protected the vegetative shoots from infection. Cuprous oxide was seen as the fungicide most likely to be adopted for commercial use. The results are discussed with suggestions for further investigations on chemical control of witches’ broom disease.

ISSN:0143-6147    

DOI:10.1080/09670879209371726

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Banana, an increasingly important crop in Kenya, is now threatened by the presence there of black leaf streak disease, caused byMycosphaerella fijiensis.Following an epidemic of leaf disease in 1989, a survey was carried out in the major bananagrowing areas of Kenya. Black leaf streak was recorded for the first time in Kenya but was absent from western Kenya.

ISSN:0143-6147    

DOI:10.1080/09670879209371727

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

A wilt of purple passion fruit(Passiflora edulisf.edulisSims) is widespread in Zimbabwe.Fusarium solani wasconsistently isolated from discoloured vascular tissue of plants obtained from several farms. All isolates of the fungus were pathogenic. The possible role ofPhytophthora nicotianaevar.parasiticain the wilt disease was investigated because it was frequently isolated from the stem base of plants affected by passion fruit wilt and from dying seedlings. Plants inoculated withF. solanislowly succumbed to the wilt, whereas those infected with a mixture ofF. solaniandP. nicotianaev.parasiticaorP. nicotianaev.parasiticaalone died rapidly. Planting stock is grown from seed ofP. eduliswhich is very susceptible to both pathogens. Red passion fruit(Passiflora caerulea)is resistant to both pathogens and should be considered as an alternative rootstock.

ISSN:0143-6147    

DOI:10.1080/09670879209371728

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Rice blast caused byPyricularia oryzaeoccurs on wheat under natural field conditions in Brazil. Isolates ofP. oryzaecollected from rice, wheat and grass weedsDigitaria sanguinalis, Rhynchelytrum roseum, Pennisetum setosumandEleusine indicawere tested for virulence to 30 rice, five wheat and one barley cultivars. All isolates from rice, wheat and grass weeds were pathogenic to the wheat cultivars and barley. However, none of the 10 wheat and seven grass isolates infected any of the 30 rice cultivars.

ISSN:0143-6147    

DOI:10.1080/09670879209371729

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

‘Chickpea wilt complex’, an important disease of chickpea, was effectively controlled by a biological agentTrichoderma harzianumand its integration with fungicides. Evaluation of wheat bran sawdust medium forT. harzianumshowed high potentiality. Soil application with different doses ofT. harzianumgave 53–50–85.70% disease control in the glasshouse, increasing with the amount ofT. harzianumapplied. In the field integration ofT.harzianumwith different fungicides significantly reduced the incidence of ‘chickpea wilt complex’ and increased crop yield. Seeds treated with Vitavax‐200 and Ziram resulted in 29.9% disease control, which was further increased to 63.3% when integrated with soil application ofT. harzianum.

ISSN:0143-6147    

DOI:10.1080/09670879209371730

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Six organic amendments and one soil sterilant (Basamid) were screened at different rates to a given amount of soil, for their efficiency to enhance the population ofTrichodermaspp. Coffee pulp significantly (P= 0.01) enhanced the population ofTrichodermaspp. in the soil compared to other amendments. The enhancement was rate‐dependent with 16 and 22 g carbon giving the optimum population. TheTrichodermaspecies enhanced includedT. koningii, T. harzianumandT. longibrachiatum.The implications of these results in relation to biological control of soil‐borne plant pathogens are discussed.

ISSN:0143-6147    

DOI:10.1080/09670879209371731

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Five field trials at Moshi examined control of white grubCochliotis melolonthoidesfor 3 years given by a single treatment of controlled‐release granules containing 140 g chlorpyrifos a.i./kg. In the first 2 years CR‐chlorpyrifos (2.94, 5.88 and 7.84 kg a.i./ha) and preplant and pre‐first ratoon ethylene dibromide (118.8 kg a.i./ha) treatments effectively reduced white grub densities compared to the untreated. Yields at harvest of the plant and first ratoon crops showed that treatments of CR‐chlorpyrifos at 5.88 and 7.84 kg a.i./ha, yielded significantly higher than EDB, except CR‐chlorpyrifos at 5.88 kg a.i./ha in plant cane in trials 1 and 3, and at the highest rate in plant cane in trial 3. There were no significant differences between the two higher rates of CR‐chlorpyrifos. In the third year EDB was not reapplied, and EDB and the untreated plots were totally damaged by white grubs. The two higher rates of CR‐chlorpyrifos reduced white grub densities in the second ratoon crop to a greater extent than the 2.94 kg a.i./ha rate in four of the five trials. In the second ratoon crop there were no significant differences between cane yields given by the three CR‐chlorpyrifos rates in two trials, but in the other three trials both the higher rates resulted in greater yields: in these three trials there were no significant (P< 0.05) differences in the yields given by CR‐chlorpyrifos at 5.88 and 7.84 kg a.i./ha.

ISSN:0143-6147    

DOI:10.1080/09670879209371732

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

The encyrtidsAenasius advenaComp. andBlepyrus insularis(Cam.) are the key parasitoids of the striped mealybugFerrisia virgata(Ckll.) in many countries. Adult parasitoids were exposed to the guava leaves treated with 13 insecticides and 18 acaricides/fungicides. Diazion (0.05%) was found to be non‐toxic toA. advenaand least toxic toB. insularis.The other chemicals such as endosulfan (0.07%), phosalone (0.07%) and dichlorvos (0.20%) showed lesser toxic residual activity while chlorpyriphos (0.05%), carbaryl (0.10%) and fenthion (0.10%) had shown significantly higher residual activity to both the parasitoids. The fungicides, except triademifon, proved harmless toA. advenaand B.insularis.It is hoped that the results would help to plan the pest management programme in crops whereF. virgatais problematic.

ISSN:0143-6147    

DOI:10.1080/09670879209371733

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor