摘要:

Cassava is a tropical staple crop which is often intercropped. Its low market value and long growing season relegate it to marginal lands where it is grown by small farmers. Integrated pest management strategies for cassava are directed towards low input conditions and emphasize host plant resistance, biological control, and crop diversification. This paper summarizes recent research on the population dynamics of insect pests and pathogens in cassava intercropping systems, illustrated with a case study in Colombia. Since cassava is most often intercropped for only part of its cycle, it is important to consider the pest dynamics which occur in the period following removal of shorter cycle associated crops. In one case, cassava whitefly abundance remained lower in previously intercropped systems than in monocultures for up to 6 months after intercrop harvest.

ISSN:0143-6147    

DOI:10.1080/09670878909371398

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

In a study of the effects of inter‐cropping and mixed‐cropping of cowpea and sorghum during the kharif, 1982 and 1983, the incidence of leafhoppers and the damage caused by defoliators were most reduced in a row inter‐crop, less in mixed, within row, farming and least in a pure crop of cowpea. Greater green fodder and dry‐matter yields of cowpea were obtained in inter‐crop between rows and in mixed‐crop, within row farming.

ISSN:0143-6147    

DOI:10.1080/09670878909371399

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

The major insect pests: leafhoppers(Empoasca kerri);defoliators (flea‐beetle,Pagria signata;semilooper,Plusia nigrisigna;tobacco caterpillar,Spodoptera litura;and grasshoppers,Colemania sphenarioides, Chrotogonus trachypterusandAtractamor‐pha crenulata crenulata)which damage the cowpea crop and reduce its yield, can be managed by adopting the following practices without the use of insecticides. Growing the least susceptible variety ('IGFRI‐450), using an optimum fertilizer combination of 30 kg N, 100 kg P2O5and 40 kg K2O/ha, with two weedings at the appropriate stages of crop growth, 15 and 30 days old, and sowing the crop at the optimum time, the first week of July. This gave a net profit of Rs.1477 per ha with a cost‐benefit ratio of 1: 1.80.

ISSN:0143-6147    

DOI:10.1080/09670878909371400

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

The granulosis virus (GV) of sugarcane shoot borer,Chilo infuscatellusSnelt., was found to be transmitted vertically when the fourth instar larvae were microfed with the virus at a sublethal dose of 1.1 x 103inclusion bodies/larva. The virus infection was found to alter the sex ratio in pupae in favour of male (1 : 5.70—♀ : ♂) from the normal 1 : 1 ratio. The per cent pupation and adult emergence were also significantly reduced. No adults emerged from abnormal pupae that lacked pigmentation on the ventral surface of the first abdominal segment. The GV was also found to be transmitted from the infected adult to the offspring through eggs and 50% of the larvae that hatched were found to die due to virosis.

ISSN:0143-6147    

DOI:10.1080/09670878909371401

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

In the years 1985–87 a series of surveys for natural enemies of waterhyacinth were conducted in Haryana. A population (1.5 ha) was found heavily affected by a leaf spotting disease at Kurukshetra. Symptoms on the leaves showed lesions of variable size ranging from minute, dark brown lesions to large irregular patches. AnAlternariasp. was isolated from leaf lesions and caused similar disease symptoms when inoculated onto healthy waterhyacinth leaves. On the basis of symptomatology, cultural and morphological characteristics, it was identified asAlternaria alternata(Fr.) Keissler. Waterhyacinth plants when inoculated withAlternaria alternataresponded differently to infection depending upon morphotypic state of development (size) of the plant. Disease incidence and severity showed an increasing trend from small, medium to large waterhyacinth leaves.

ISSN:0143-6147    

DOI:10.1080/09670878909371402

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

The response to infection with potato virus X of tomato cultivars Robin, Jacinto, Tobol, Turquesa and Parana, was studied in a greenhouse trial. Cultivars Robin and Jacinto developed severe mosaic symptoms giving very sensitive and sensitive reactions, respectively and they had a high virus contents as assessed by local lesion assay. Tobol, Turquesa and Parana were moderately sensitive and had low virus contents.

ISSN:0143-6147    

DOI:10.1080/09670878909371403

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Chemical treatment for control ofM. persicaeon pepper showed that soil application for the granular insecticide carbofuran reduced the aphid population below that of the check plots without affecting the prevailing predators. However, pirimicarb also gave good results, in controllingM. persicaeinfestation on sweet pepper. Cypermethrin gave unsatisfactory results and a further outbreak of aphids 3 weeks after the second application was observed. Residues of the used insecticides in fruits and leaves of pepper plants sampled 25 days after the last applications were found to be much lower than the permitted tolerance level. Several species of predators and parasites were collected and observed.

ISSN:0143-6147    

DOI:10.1080/09670878909371404

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Application of electrostatically charged sprays ofBacillus thuringiensisusing MicronRMicro‐ulva chargeable spinning disc sprayer was investigated and its efficiency in improving underleaf surface coverage with charged droplets was determined by comparing the total viable spores counts (VSC) from spores washed off the upper and lower leaf surfaces of sprayed Brussels sprouts. Bioassay experiments were also carried out by comparing mortality of third instar larvae of P.xylostellaconfined to upper and lower leaf surfaces of plants sprayed with charged and uncharged droplets. Higher total viable spore counts (P < 0.001) and a higher mortality of P.xylostella(P = 0.029) indicated improved coverage of the lower surfaces of electrostatically sprayed Brussels sprouts plants.

ISSN:0143-6147    

DOI:10.1080/09670878909371405

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

A field experiment was conducted with three organophos‐phorous insecticidesviz.malathion, methylparathion and quinalphos in paddy in order to recommend their waiting periods for safe consumption of paddy straw and grain under West Bengal agroclimatic condition. The present study revealed that no residue could be detected in harvested paddy straw and grain and half life values as calculated, ranged from 3.46–5.20 days in soil, 1.1–1.7 days in leaves and 1.7–2.5 days in grain irrespective of treatments.

ISSN:0143-6147    

DOI:10.1080/09670878909371406

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Replicated field experiments were conducted during autumn 1982–83 at Jalandhar (Punjab) for evaluating an insecticidal schedule involving soil application of aldicarb (Temik) 10 G and carbofuran (Furadan) 3 G @ 1.0 and 1.5 kg a.i./ha in two different protocolsviz.;(i) single full dose application of granules in furrows at planting and (ii) equal split dose application of granules (half in furrows at planting + remaining half dose near plants base at earthing up), found effective for aphid control, for residues. The findings indicate that aldicarb and carbofuran residues in unprocessed (unwashed, unboiled and unpeeled) potatoes from 1.0 and 1.5 kg a.i./ha doses applied in single full dose in furrows at planting (in the first protocol) persisted above the tolerance limits (0.50 ppm each for aldicarb and carbofuran) up to 70 days. Aldicarb residues in such unprocessed potatoes persisted above the tolerance limit up to 70/49 and 80/59 days respectively, from 1.0 and 1.5 kg a.i./ha doses when applied in two equal split doses at planting/earthing time. However, carbofuran residues in unprocessed potatoes were retained above the tolerance limit up to 70/49 days from both the doses applied in second protocol. At harvest, aldicarb residues in unprocessed potatoes were well within the tolerance limit from both the doses and protocols. On the other hand, carbofuran residues were undetectable from both the doses applied in the first protocol but were retained in traces (0.06 ppm) in unprocessed potatoes even from 1.0 kg a.i./ha dose applied in the second protocol. Residues of both the insecticides in processed (washed, boiled and peeled) potatoes and in water obtained after cooking the potatoes were below the tolerance limits in the beginning from both the doses and protocols which dissipated below the detectability level afterwards.

ISSN:0143-6147    

DOI:10.1080/09670878909371407

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor