Cassava Storage Root Yield Losses from Root-Knot Nematode (Me10idogyne incognita and M. javanica) Parasitism SUMMARY

Transcription

1 Cassava Strage Rt Yield Lsses frm Rt-Knt Nematde (Me10idgyne incgnita and M. javanica) Parasitism Authr: Fields E. Caveness, Internatinal Institute f Trpical Agriculture, Ibadan, Nigeria. SUMMARY The rt-knt nematdes, Me10idgyne incgnita race 2 and M. javanica, significantly (P = 0.05) reduced stalk height, stalk weight and strage rt ("tuber") weight f tw cassava (Maniht escu1enta) cu1tivars, TMe and TMe 30572, after a 15.5-mnth grwing perid in the trpical rainfrest zne f suthern Nigeria. A slight reductin in mean plant height in cnjunctin with a severe reductin in stalk weight wuld prvide an inferir and less rbust planting stake fr the next crp.' Nematde galls were nt bserved n strage rts but nly n fine feeder rts. At harvest the feeder rts generally remain unseen in the sil and any yield reductin may be attributed t ther causes r the prblem may pass unnticed. Cassava (Maniht escu 1enta) supplies abut 60% f the daily fd calries fr the majrity f peple living in the wrld's trpic zne. Glbal imprtance f cassava has greatly increased with the rise in ppulatin, its use as a surce f animal feedstuffs, and as raw material fr industry. Cassava raw rt prductin annually exceeds 100 millin tns and in cnjunctin with the vegetable use f the leaves as a valued prtein surce, the crp assumes cnsiderable imprtance in the ttal wrld utput f fdstuffs. Cassava is als f cnsiderable scial, ecnmic and plitical imprtance as it is almst whlly a prduct f develping natins. The study f nematdes as pests f cassava has received little attentin cnsidering that the crp is ne f mankind's majr surces f carbhydrate and is a majr factr in the ecnmies f sme cuntries. Hwever, the fact that nematde infectin f cassava is widespread has lng been dcumented (1, 5, 6, 7, 9, 10, 11, 12, 13, 14, , 18, 20). Sasser (17) estimates that abut 6% f the wrld prductin is lst t nematde attack. A lss f 6 millin tns f carbhydrate is highly significant in a fd-shrt wrld. This paper reprts n parasitism f tw rt-knt nematde species n tw cu1tivars f cassava. Materials and Methds Tw cu1tivars f cassava, TMe and TMe 30572, were planted in micrp10ts at IITA in the rainfrest zne f Nigeria. The micrp10ts were frmed f cncrete pipe and had a surface area f 0.26 m 2 with a sil depth f 1 m. One mnth prir t planting, each micrplt was fumigated with an verdse f D-D Mixture at 381

2 600 l/ha t eradicate all nematdes. During fumigatin, the sil surface was sealed with black plastic sheeting. Three weeks after planting cassava stakes and when rts had develped, each micrplt was inculated with abut 10,000 eggs f Melidgyne incgnita race 2 r M. javanica. Nninculated cntrl plts were included. The trial was a cmpletely randmized design with 20 replicatins. The rt-knt nematde cultures had been reared n tmat in the greenhuse. Eggs were harvested using the sdium hypchlrite methd f Hussey and Barker (8). The cassava stakes were planted at the beginning f the rains and were nt irrigated thrugh the 4-mnth dry seasn which began 8 mnths later. The cassava was harvested at 15.5 mnths and 3.5 mnths int the rainy seasn f the secnd year. Sil ppulatins f the rt-knt nematde juveniles were determined by taking three 100 cm j cres frm each micrplt with a sil sampling tube 2.5x20 cm. Nematdes were islated frm the sil using the mdified Baermann funnel methd (21) and cncentrated by the settling-siphn methd (2). The rts were subjectively rated fr the degree f gall develpment. Results and Discussin Sil sampling shwed a wide variatin in rt-knt nematde juvenile ppulatin levels and ppulatins were gruped accrding t density fr analysis (Table 1). Rt-knt index means shw greater feeder rt-gall expressin by M. incgnita n bth cassava cultivars than by M. j avanica. Rt-gall expressin was abut the same n bth cassava cultivars fr the tw nematde species (Table 2). N gall frmatin was bserved n strage rts. Based n egg cunts, M. incgnita reprductin was nt significantly different n the tw cultivars while M. ]avanica shwed a greater rate n TMe (Table 3). M. javanica juvenile ppulatins ranged frm lw t very high n bth cassava cultivars, while M. incgnita had juvenile ppulatins up t medium n TMe and high n TMe M. incgnita juvenile ppulatins did nt reach high densities n either cassava cultivar. Table 1. Categries f sil ppulatins f rt-knt nematde juveniles after 15.5 mnths f parasitism n cassava by Melidgyne incgnita race 2 and M. javanica. Rt-knt nematde ppulatin density Nne Very lw Lw Medium High Very high Mean number juveniles per liter f sil ,150 5, ,300 2,500 7,500 Range ,800 2,800 The grand means f bth nematdes n the tw cassava cultivars were significantly different (p = 0.05) fr each ppulatin level fr stalk height, stalk weight and strage rt weight (Figure 1). The phenmenn f increased plant grwth under light nematde parasitism (Figure 1, Table 4) has been reprted previusly (3, 4, 19). 382

3 Table 2. Rt-knt index means n cassava feeder rts after 15.5 mnths f parasitism by Melidgyne incgnita race 2 and M. javanica. Rt-knt index scale f 0 = n galling; 4 = maximum galling. Means f 20 replicatins. Rt-knt index Nematde TMe TMe Mean M. incsnita M. javanica Mean Table 3. Mean numbers f rt-knt nematdes eggs/g f cassava feeder rt tissue after 15.5 mnths f parasitism by Melidgyne incsnita race 2 and M. javanica. Means f 20 replicatins. Number f e8ss Nematde TMe TMe Mean M. incsnita M. javanica 1, Mean As seen in Figure 1, the slight reductin in mean plant height cupled with the severe reductin in stalk weight wuld prvide an inferir and less rbust planting stake fr the fllwing crp. The graph shws that a strage rt yield reductin f abut 17% t 50% can ccur withut a nticeable decline in plant height. As the rt galls are n the fine feeder rts and generally remain unnticed in the sil, a yield smaller than expected may be attributed t ther causes r the prblem may pass unnticed. Table 4. The grand summary f relative strage rt weights f cassava after 15.5 mnths f parasitism by the rt-knt nematdes, Melidsyne incgnita race 2 and M. javanica. Rt-knt nematde ppulatin density Nne Very lw Lw Medium High Very high Relative strage rt weight %

4 Height (mm) Weight (kg) 2r ~ L Stalk height -.-.~ _... / Stalk weight... "." L_~~~...::~::-::_:::-:::_::-':::~~!!... ~ , 50,, Strage rt weight,,, '" '" "",, e ~ c: u... +" e Q) 0> '" 'ō ~ (J) O~-----~-----~------~-----~ ~ ,000 2,000 5,000 Ppulatin density Rt-knt nematde n cassava. 50 Cf Figure 1. The grand summary f stalk height, stalk weight and strage rt weight f tw cassava cultivars, TMe and TMe 30572, after 15.5 mnths grwing perid in assciatin with Melidgyne incgnita race 2 r M. javanica. 384

5 References Caveness, F.E End f tur prgress reprt n the nematlgy prject. USAID, Lags, Nigeria (revised). Caveness, F.E A simple siphn methd fr separating nematdes frm excess water. Nematrpica 5: Caveness, F.E Rt-knt nematdes n selected fd crps in Nigeria, pp In Prc. f the Secnd IMP Res. Planning Cnf. n Rt-knt Nematdes, Melidgyne spp. February 20-24, Abidjan, Ivry Cast. 93 pp. Caveness, F.E Cwpea, lima bean, cassava, yams and Melidgyne spp. in Nigeria, pp In Rt-knt Nematdes (Melidgyne Species) Systematics, Bilgy and Cntrl, eds. F. Lamberti and C.E. Taylr. Academic Press, Lndn. 477 pp. Deslandes, I.A Diseases f cassava in the nrtheast (Brazil). Bletim d Ministeri da Agricultura 30: Dicksn, D.W Nematde prblems n cassava. Prc Cassava Prductin Wrkshp, Centr Internacinal de Agricultura Trpical, Cali, Clmbia. Series CE-14: Hgger, C.H Plant-parasitic nematdes assciated with cassava. Trpical Rt and Tuber Crps Newsletter 5:4-9. Hussey, R.S. and K.R. Barker A cmparisn f methds f cllecting incula f Melidgyne spp., including a new technique. Plant Dis. Reprter 57: Luc, M. and G. de Guiran Les nematdes asscies aux plantes de l'uest African. Liste preliminaire. Agrnmie Trpical. Ngent-sur-Marne 15: Martin, G.C Plant species attacked by rt-knt nematdes (Melidgyne spp.) in the Federatin f Rhdesia and Nyasaland. Nematlgica 4: Neal, J.C The rt-knt disease f the peach, range and ther plants in Flrida due t the wrk f Anguillula. U.S. Dept. Agr. Div. Entml. Bull. 20: 3l. Niemann, E., M. Lare, J. Tchinde, and 1. Zakari Cntributin t the knwledge regarding diseases and pests f cultivated plants in Tg. Zeitschrift fur Pflanzenkrankheiten und Pflanzenschutz 7: Nirula, K.K. and R. Kumar Cllateral hst plants f rt-knt nematdes. Current Science 32: Parris, G.K A check list f fungi, bacteria, nematdes and viruses ccurring in Hawaii and their hsts. Plant. Dis. Reprter Supple pp. Peachy, J.E. and L. Edmnstn-Lw Plant nematde threats t inter-african phytsanitary barriers. Cmmnwealth Bur. f Helminthlgy, St. Albans, Herts., England, Misc. Pub. 1/1967. Rahm, G Alguns nematdes e semiparasitas das plantas c~lturaes d Brazil. Arq. Inst. BiI. Sa Paul 1: Sasser, J.N Ecnmic imprtance f Melidgyne in trpical cuntries, pp In Rt-knt Nematdes (Melidgyne Species) Systematics, Bilgy and Cntrl, eds. F. Lamberti and C.E. Taylr. Academic Press, Lndn 477 pp. Steiner, G. and E.M. Buhrer A list f plants attacked by Tylenchus dipsaci, the bulb r stem nematde. Plant Dis. Reprter 16: Wallace, H.R Nematde eclgy and plant diseases. Edward Arnld, Lndn. 128 pp. West Indies University. Augustine, Trinidad. Whitehead, A.G. and J.R. methds f extracting 55: pp. Reprt f the Faculty f Hemming A cmparisn f small vermifrm nematdes frm sil. 385 Agriculture. St. sme quantitative Ann. Appl. BiI.

6