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depression: the mcan yield was 7.1% of that in Slerilizccj soil. The yield of Lotus pedunculatus was also scvcrely depressed. whereas red clover, subterranean clovcr and lucerne were less affected. Nematodc counis showed ihai all clover species were hosis for M. hopla bul only wbite and red clover for // trifolii.

*3191 Noel. G. R-; LownsberY. B. F. Effects of temperaturę on the pathogenicity of Tylenchorhynchus clarus to alfalfa and observations on feeding. Journal of Ncmatology. (1978) 10 (2) 195*198 [En] Div. of Nematol, Univ. of Calif., Davis. CA 95616. USA.

The addiiion of a suspension of surface-axenized Tylenchorhynchus clarus reduced top and root growlh of pot-grown lucerne. Reproduction of T. clarus was greater at 24 and 27 than ai 21 C. The interaclion of nematodes ujth temperaturę did not produce significant elTects on lucerne growth in the 4.5 month experimental period. T. clarus fed endo- and ectoparasitically.

#0192 Norton, D. C; Tollefson. J.; Hinz. P.; Thomas. 5. H.    Corn yield inereases relative to nonfumigant

Chemical control of nematodes. Journal of Nematołogy. (1978) 10 (2) 160-166 [En] Iowa Agric. and Home Economics Exp. Sta., Ames, Iowa. 50011, USA.

The average maximum yield inerease of Zea mays in Iowa in 1973 was 2195- Rreater in nematicide-treated plots than in untreated płots. Yields were negatively correlated with nematodc numbers or biomass in almost every test. Correlation coefficients for nematode numbers in the soil and yield were -0.56 for Helicotylenchus pseudorobustus, -0.45 for Hoplolaimus galeatus. —0.51 for Pratylenchus spp.. -0.64 for A'iphinema americanum and for numbers in the roots and yield were -0.63 for PratyeJnchus spp. and -0.56 for Hoplolaimus galeatus. CoefTicients for yield and total nematode numbers averagcd -0.65 in roots and -0.55 in soil. Negative correlations were greater for comparison of yield with total parasitic nematode biomass than with numbers of individual nematodes of a species or total numbers of parasitic nematodes.

019 3 Zinov'ev, V. G.    IA study of the mechanisms of

growth formation in plants infected with Aleloidogyne.) In Problemy parazitologn. Materiały VIII nauchnoi konferentsii parazitologov UkSSR.    Chast' I. Kiev,    USSR;    Izdatel’stvo

“Naukova Dumka”. (1975) 188-190 [Ru]

Galls were formed in freshly isolated roots of tomato or lucerne (but not of    wheat or rye)    infected    with one

Mcloidogyne incognito tarva_;    10 days later gali

growth stopped. to be resumed only if thc root was sub-cultured and supplied with plant host extracts. In roots grown in culturc for 14 years galls formed only if given plant extracts or growth-inducing substances. Larger amounts of nucleic acids were found in infected than in uninfected, isolated roots. Growth stopped if the larva was killed by immersion of the gali in water at 51C for 10 minutes but resumed if the root    was placed in    nutrient    containing

exudates of maturę female M. incognita, cven if thc exudate was previousJy autodaved or filtered. Used on their owi), nematode exudates did not stimulate gali growth; plant extracts stimulated growth in the presence of livc larvae. thc efTect being enhanced    by the addition    of adult    nematode

exudate. Growth of isolated gali tissue (1 to 2 mm*) was stimulated by aqueous extracts of young galls only during the First passage (7 to 10 days).

#0 194 Elgin, J. H., Jr.; Evans. D. W.; Faulkner. L R.

Response of resistant and susceptible alfalfa cultivars to regional isolates of stem nematodes. Crop Science (1977) 17 (6) 957-959 [En] Field Crops Lab., Plant Gcnetics & Germplasm Inst., ARS. USDA. Agric. Res. Centre (West). Beltsville. MD 20705, USA.

Ninę isolates of Ditylenchus dipsaci were collected from difTercnt regions of USA and Canada and tested for variations in pathogenicity at 15. 20 and 25 C on lucerne cvs Ranger and Moapa (susceptible) and Lahontan and Calivcrdc

65 (resistant) to determine if variations in plant responses should be considered when breeding for resistance to stem nematode. Ali isolates were generally capabłe of parasitiziug lucerne but difTerences in virulcnce were detectcd. No interaclion with temperaturę or with lucerne cultivar was obserscd. The authors conclude that a resistant lucerne developed in a breeding programme using one pathogenic isolate of D. dipsaci would probably be resistant to isolates from other regions.

#0195 VraIN, T. C.; BaRKER, K. R.; HOLTZMaN, G. I. Influence of Iow temperaturo on ratę of deve!opment of Meloiodgyne incognita and A/, hopla larvae. Journal of Nematology. (1978) 10 (2) 166-171 [En] North Carolina Agric. Exp Sta., Raleigh. N-C. 27606. USA.

Development of Meloidogyne incognita and M. hopla larvae in clover roots (Melilotus alba) was studied at 20. 16. 12 and 8 C in growth chambers and in the field from Ociobcr to April in North Carolina. USA. Larvae of both species invaded roots and developed at 20. 16 and 12 C, but not at 8 C. The time necessary to completc the larval stages at euch temperaturę was determined. The minimal temperaturę for de\clopment of M. incognita Jarvae was 10.08 C and 8.8 C for M. hapla larvae. In the field, soil temperaturę at 10 cm deep was fuvorablc for development of lanae until the end of November, and agam from February on. All stages of the nematodes survived freezing temperatures in the roots. Reproduction of both species was evident in March or April after inoculalion and accumulation of 8.500 to 11.250 deęrce-hours.

.0196 ALL, J. N.; Jellum, M. D. Efficacy of insecticide-nematocides on Sphenophorus callosus and phytophagous nematodes in field corn. Journal of the Georgia EntomologicaJ Society (1977) 12 (4) 291-297 [En] Dep. of Entomology, Univ. of Georgia, Athens, USA.

Applications of 8 nematicides at rates of 0.1 (CGA 12223) or 0.2 (fensulphothion, ethoprop, oxamyl. aldicarb. carbofuran, oftanol, parathion) kg a.i./l.OOO m row at sowjng of Zea mays resulted in reduced numbers of Meloidogyne. Helicotylenchus. Criconemoides and Belonolaimus in the soil 40 days later. At harvest, 75 days after sowing. no control was evidcnt, exccpt for carbofuran and oftanol on Criconemoides, and no vield difTerences were found-

#0197 Bergeson, G. B. Control of the lesion nematode {Pratylenchus spp.) in corn with carbofuran. Plant Disease Reporter (1978) 62 (4) 295-297 [En] Dep. of Botany & Plant Path.. Purduc Univ., West Lafayette, Indiana 47907, USA.

Carbofuran at 2.25 and 4.5 kg a.i./ha had no efTect on the incidence of stalk rot of corn [Zea mays) in smali replicated field plots in Indiana, USA. but significantly reduced numbers of Pratylenchus and inereased yiełds in 3 out of 4 years. Yield inereases from 10 plots (0.5 ha or larger) in 1974 and 6 plots in 1975 treated with 2.25 kg a.i./ ha averaged 12.6 and 14.4%, respectively. Reduction of Pratylenchus in roots for 1974 and 1975 averaged 84.5 and 98.3%, respectively.

6 198 RhOades. H. L. Indigofera hirsuta as a summer cover crop for controlling Belonolaimus longicaudatus and Meloidogyne incognita in Florida, U.S.A. [Abstract]. In International Congress of Plant Pathology (3rd). Munchen. GFR. 16 23 August. 1978. Absrracts of papers. Berlin and Hamburg; Paul Parey. (1978) 375 [En] Agric. Res. and Education Center, Sanford. Florida. USA.

The effects of summer crops on populations of Belonolaimus longicaudatus and Meloidogyne incognita and yields of subsequent vegeiable crops were studied during 1973 to 1977. High populations of Belonolaimus longicaudatus developed on Sorghum vulgare. Sesbania macrocarpa and a natura! population of weeds but declined to Iow !evełs on Indigofera hirsuta. Root-knot nematode populations in generał were high on sesbania. moderatc to Iow on sorghum and Iow on hairy indigo and weeds. Yields of cabbage. cucumber and snap beans were significantly hicher following 112 hairy indigo than following sesbania. sorghum or weeds. Soil