Fundam. appl. NemalOl., 1997,20 (6), 593-599

Damage potential of zeae to Zea mays as affected by edaphic factors (1)

Lorin R. KRU5BERC*, Sandra SARDANELU* and Arvydas P. GRYBAUSKAS**

*Deparlmenl ofPlan1 Biology and *''1Jeparlmenl ofNatural Resource Sciences and Landscape ATChileclure, University of Mm)'land, Coltege Park, MD 20742, USA. Accepted for publication 21 February 1997.

Summary - During 1986-1990, the effects of the corn cyst , HelR.rodera zeae, on growth and grain yield of , Zea mays, were studied in field microplots. These experimenrs were conducred in microplots conraining a coarse-rextured or a fine-rextured soil, with and without added minerai fertilizer, and with and without H. zeae. Maize growth (dry weight) and yield were suppressed by 13 ro 73 % in 4 of the 5 years in the presence of H. zeae. These plant responses to H. zeae were greater in coarse-texrured than in fine-textured soil. Fertilizer amendments did not alleviate suppression of plant growth by H. zeae. The nematode caused more damage to maize plants in hot, dry rather than cool, wet seasons.

Résumé - Effets defacumrs édaphiques sur le potentiel de dégats causés par Heterodera zeae au lnaïs - On a étudié les effets du nématode à kyste du maïs, Heterodera zeae, sur la croissance et la récolte en grain du maïs, Zea mays, en micropar­ celles pendant les années 1986-1990. Ces expériences ont été conduites en microparcelles contenant du sol à texture fine ou grossiére, avec ou sans engrais minéraux, et avec ou sans H. zeae. La croissance du maïs (poids sec) et la récolte de grain ont décru de 13 à 73 % pendant 4 ans sur 5, en présence de H. zeae. L'effet de H. zeae sur les planres a été plus important dans le sol de texNre grossière que dans le sol à texrure fine. Les engrais n'onr pas diminué les effets de H. zeae sur la croissance des plantes. Le nématode a plus endommagé les plants de maïs pendant les périodes chaudes et sèches que pendant les périodes fraîches et humides. Key-words : cyst , Heterodera, maize, microplots, pathogenicity, soil type, weather.

The corn cyst nematode, Heterodem zeae, was first population densities of the corn cyst nematode based detected in the Western hemisphere in Kent County, on soil analysis, but no increases in yield of maize Maryland in 1981 (Sardanelli et al., 1981). In Octo­ were observed compared to unfumigated soil. Hence, ber 1992, an infestation of H. zeae associated with ir was decided ra determine the ability of the corn cyst poorly growing maize was found in centràl Virginia nemarode to suppress yield of maize in Maryland about 200 miles (320 km) southwest of the Maryland using field microplots where treatments could be bet­ infestarion (Eisenback el al., 1993). Many species of ter conrrolled than in large field plots. A preliminary cysr nemarodes are widely recognized as destructive to report on the results of these microplor srudies has many economically important hosr plants, including, been published (Krusberg & Sardanelli, 1991). Heterodem glycines on , H. schachtii on sugar The objectives of this study were to determine over beer and crucifers, and Globodera roslOchiensis and G. several years the influence ofH. zeae on yield ofmaize pallida on poraro (Miller, 1986). Because maize (Zea grown in a coarse or a fine-textured soil, with and mays) is a major crop in the United Srares, discovery without the application of fertilizer. of the corn cyst nemarode was cause for concern. H. zeae was placed under a joint federal and state quaranrine in 1986 (Cawley, 1986). Materials and methods Surveys for H. zeae and experiments using nemari­ This srudy was conducted in an isolated field in cides were conducred in narurally infested fields in Prince George's Counry, Maryland outside the quar­ Maryland in the early 1980s. During 1982 to 1984, anrine area with the approval of the Maryland Depart­ several granular nematicides and one fumigant were ment of Agriculture. The srudy area was firsr cul­ applied in experimental field plots where soil popula­ rivated to remove al! planrs. Microplots were located tion densities of cysts ranged from 50 to 300/250 cm3 on a 3 x 3 m grid with a 3 m border kept devoid of soil in Kenr and Harford counries, Maryland (Krus­ plants around the outermost microplors. The soil berg el al., unpubl.). Fumigation greatly lowered soil around the microplors was kept fallow by rototilling

(1) Partial support for this project was provided by the Maryland Agricultural Experiment Station.

Fundam. appl. NemalOl. 1164-5571/97/06/ © Gauthier- Villars - ORSTOM 593 L. R. Krusberg et al. when maize was growing in the microplots, and by and the cysts and females counted using the filter applications of glyphosate during other times of the paper/Büchner funnel technique (Krusberg el al., year. 1994). The residue from the 45 !-lm sieve was placed Cylindrical microplot collars were constructed from in a modified Baermann funnel for recovery of vermi­ sheet fiberglass, and were 45 cm in diameter by 60 cm form nematades. long. These coIlars were inserted into holes dug with a Ali treatments were arranged in a randomized com­ tractor-mounted auger ta a depth of 45 cm. Methyl plete block design with ten replications. Plant dry bromide-fumigated silt loam field soil (Matapeake silt weight and grain yield data were analyzed as a rand­ loam, Typic Hapludult, fine-silty, mixed, mesic soil omized complete block three-factar factorial com­ consisting of 14 % sand, 62 % silt, 24 % clay and 1.8 bined over years (McIntosh, 1983). The main % organic matter) or loamy sand field soil (Norfolk treatment effects were soil type, fertilizer and H. zeae loamy sand, Typic Paleudult, fine-loamy, siliceous, inoculation. The initial and final nematode popula­ thermic soil consisting of 90 % sand, 5 % silt, 5 % tion density data that were collected from the infested clay and 0.5 % organic matter) was used to fiIl the plots were analyzed as a randomized complete block microplot coIlars. two-factor factorial combined over years. The main A population of H. zeae from Kent County was treatment effects were soil type and fertilizer. Soil propagated on Zea mays Pioneer brand 3184 dent processed from uninfested plots revealed no cross­ corn growing in 17-liter plastic pots fiIled with washed contamination and therefore had no nematode popu­ builder's sand. The POts were placed on plant propa­ lations to respond to treatments. Uninfested plots gation mats on benches in the greenhouse ta maintain were thus not included in the analysis of nematade the sand at about 30 oc. The sand was coIlected from population levels. 10-week-old cultures, mixed in a cement mixer to dis­ tribute the nematades evenly, and was then thor­ Table 1. ANOVA for plant dry weighl and grain weighl. oughly mixed into the soil by shovel in designated microplots at the rate of 13 1 of sand inoculum per microplot. Samples coIlected from the microplots Source df P* 10 days after infestation contained an average of 110 cysts full of eggs, ca. 209 eggs/cyst (HutzeIl & Plant Grain Krusberg, 19901, plus 1900 second-stage juveniles Weight Weight 02) per 250 cm soil. Microplot soil was infested with Year 4 <.01 <.01 H. zeae a single time, on 6 May 1986. Block 9 <.01 <.0] AI! microplots were planted with Pioneer brand Soil Type 1 <.01 <.01 3184 dent corn with five seeds per microplot. When the seedlings were about 20 cm taIl, they were thinned Year x Soil 4 .02 .02 to the two most vigorous plants per microplot. Desig­ CCN Inoculation ] <.01 <.01 nated microplots received fertilizer at levels optimum Year x CCN 4 <.01 .05 for maize production, based on soil analyses. Fertilizer Soil x CCN 1 <.01 <.0] was applied when plants were 30 ta 60 cm tall. Dur­ Year x Soil x CCN 4 <.01 <.01 ing dry periods microplots were irrigated weekly at a rate of 20 mmlha. Fertilizer 1 <.01 <.01 Planting and harvesting dates were as foIlows: 1986: Year x Fertilizer 4 <.01 <.01 planted on May 16 and harvested on September 9; Soil x Fertilizer 1 <.01 .02 1987: planted on May 22 and harvested on Septem­ Year x Soil x Fertilizer 4 .20 .13 ber 14; 1988: planted on May 31 and harvested on CCN x Fertilizer 1 .42 .92 September 12; 1989: planted on June 5 and harvested Year x CCN x Fertilizer 4 .68 on September 18; 1990: planted on May 23 and har­ .98 vested on September 20. Soil x CCN x Fertilizer 1 .58 .67 Soil samples were coIlected from microplots for Year x Soil x CCN x Fertilizer 4 .83 .89 assay of H. zeae population densities within 2 weeks error 350 before planting (Pl) and within 1 month after harvest 3 *Probability (0-1) that differences between source means (Pf). Soil samples of 250 cm , a composite ofsix cores are due ta chance, based on F-Test. per microplot, taken from each microplot were pro­ cessed by washing and decanting. The suspension was passed through a 250-)lm pore sieve (to retain the Data were collected on microplot soil temperature cysts) and over a 45-)lm pore sieve (ta retain the J2). at 15 cm depth at 8:00-9:00 a.m. and on rainfaIl once The residue from the 250 )lm sieve was processed, per week throughout each growing season.

594 Fundam. appl. NemalOl. Hererodera zeae affeccing Zea mays

1200 • Sand + CCN 0 Sand • CCN /il Sill + CCN I!'l Silt - CCN

1015 LSD (0.05) = 86 1000

Cl 800

~ Cl ë.::: 600 ë., D. 400

200

0 1986 1987 1988 1989 1990 Fig. 1. Effec/s ofsoil /ex/Ure and presence or absence ofHererodera zeae on the dry weight ofZea mays plants grown in field rnicroplots during 1986-1990.

• Sand + ceN o Sand· eeN ~Silt + eeN IlISilt . eeN 500 48' LSD 55

~ 400 ~ .t:- .~ 300 ::Cl c: '§ 200 C)

100

0 1986 1987 1988 1989 1990 Fig. 2. Effec/s of soil tex/ure and presence or absence of Hererodera zeae on the yie/d of grain from Zea mays plants grown in field rnicroplots during 1986-1990.

Results (Fig. 2). In 1989 the nemarade faiJed ra suppress plant biomass or grain yield in either sandy or silry Maize biomass (Fig. 1) and grain yield (Fig. 2) were soil. Surprisingly, application of fertilizer had no effect suppressed by H. zeae in 4 of the 5 years of this study. on the suppression by H. zeae of plant biomass or Biomass was suppressed less than grain yield in those grain yield (Table 1). 4 years. Average plant dry weight in the presence of Both soil type (Fig. 3) and application of fenilizer H. zeae in sandy soil was decreased by 13 % in 1986, (Fig. 4) affected the numbers of H. zeae cYStS full of 20 % in 1987, 66 % in 1988, and 16 % in 1990. eggs extracted from soil samples during the 5 years of Grain weights were decreased by 22 % in 1986,31 % this srudy. In general, larger numbers of cystS were in 1987, 73 % in 1988, and 21 % in 1990. In silty soil detected in sandy soil than silry soil (Fig. 3) and in soil H. zeae suppressed maize biomass only in 1987, plant from microplots receiving fenilizer annually, as com­ dry weight by 12 % (Fig. 1) and grain yield by 15 % pared ra unferrilized microplot sail (Fig. 4). During

Vol. 20, nO 6 - 1997 595 L. R. Krusberg et al.

450 40. _InitiaI No. In Sand LSD (0.05) 49 400 o Initiai No. In Silt I!I Final No. In Sand 0 LSD (0.05) 56 o 350 r.l Final No. in Silt 0 on '"_ 3 0 0 en êii Û 250

~ 200 1 .0 ë :;; 150 .a E :J 100 Z

50

0 1986 1987 1988 1989 1990

Fig. J. Initial (Pi) and final (Pt) annual sail popularion densùies of Heterodera zeae GYSIS full of eggs in sandy or silly field microplol sail plamed wùh Zea mays during J986- J990 (per 250 cm3 sail).

400 _Inilial Fertllizer 36 '358 No. + Initiai LSD (0.05) 56 350 o Initiai Ferlillzer 0 No. 0 ~ 300 III Final No. + Fertliizer Final LSD (0.05) 49 '" III Final No. Ferlilizer 2 2 5 0 ,.,en U _ 200 :J 16 IL ë 150 <; .a 100 E :J Z 50

0 1986 1987 1988 1989 1990

Fig. 4. Inùial (Pi) andfinal (Pt) annual sail poptJalion demùies of Heterodera zeae CYSLS full of eggs in soil from field microplols wùh 3 and WÙhOUl added fenilizer and plant.ed 10 Zea mays du ring J986- J990 (pa 250 cm 50il) .

the first growing season, 1986, average numbers of for cysts full of eggs, but at 2- to 10-foid greater num­ cysts increased in ail microplots 3- to 4-fold from the bers (data not shown). time of infestation of microplot soil on 6 May 1986 Data on soil temperature and rainfall in the micro­ until after-harvest soil samples were collected in late plots for the years 1986-1990 are given in Fig. 5. In September 1986. In the following years, the numbers every year except 1989 morning soil temperatures of cysts obtained from microplot soil decreased con­ reached 25 oC or above at sorne time during July and/ tinuously during each growing season and from 1 year or August. Rainfall was rather low d uring the 1986, ta the next; in fall 1990 soil from infested microplots 1987, and 1988 growing seasons, being close to a 3 contained 15-40 cysts full of eggs/250 cm . Numbers total of 38 cm for each year. Rainfall was abundant of total cysts extracted from soil samples during the and rather evenly distributed during the 1989 growing 5 years of this study followed a pattern simiJar to that season with a total of 80 cm, and the highest morning

596 Fundam. app!. Nemawl. Hererodera zeae affecting Zea mays

12 30r-=------,• Soli Temperature 1986 25 ~-~~~~~------10

20 8

15 6

10 4

5 2

0

25 10

20 8

1 5 6

1 0 4

5 2

1988 G 25 , 0

20 B

1 5 6 ?:l ~. 1 0 4 ::l

5 2 g ,.-.. -·Ô () CI) '-"El 25 1 0

20 8

1 5 6

1 0 4

5 2

25 10

20 8

15 6

10 4

5 2 o -J--_ o May 1 June 1 July 1 Aug 1 Sep 1 Oct 1 May 15 Jun 15 July15 . Aug15 Sep 15

Fig. 5. Mean morning (810 9 a.m.) soillemperaLUre in microplOIS and LOLal rainfall al 2-week imervals dunng lhe growing seasons of 1986-1990.

Vol. 20, n° 6 - 1997 597 L. R. Knlsberg et al. soil temperature reached was 24 oc. The 1990 season Table 2. Population densities per 250 cn/ soil of Hererodera experienced both high soil temperatures at 8 to 9 AM, zeae in IWO adjacerllfields in Ken! Coumy, Marylandfrom 1985 above 25 oC in July-September, and ample rainfall, Ihrough 1994. 620 mm total for the season. Dare sail Field 1 Field 2 colJecred Discussion Total cysts J2 * Total cysts J2 Suppression of grain yield in the presence of H. zeae 9/13/85 3 79 1 51 was demonstrated in the field microplot studies, but 9/25/86 5 257 5 761 not in nematicide evaluations previously conducted in 9/24/87 8 166 3 533 naturally infested field plots. Several factors may have contributed to the differences in test results. Soils for 10/17/88 50 1485 28 2,805 the microplots were fumigated with the biocide, 11115/89 13 16 48 501 methyl bromide, and then added to the collars. Tests 10/11190 3 23 8 170 in natural field infestations would have less altered soil 10/24/91 58 503 53 413 microbial populations and therefore would be more likely to contain antagonists and competitive organ­ 1112/94 25 198 23 403 isms (Freckman & Ettema, 1993). However, exami­ * Second-srage juveniles. nation of numerous cysts extracted from soil samples did not reveal the presence of fungal mycelium, dis­ coloration or deterioration in either study. Microplot With the exception of an increase after the initial soils were artificially infested at calibrated nematode infestation in 1986, cyst numbers declined each suc­ densities within a limited rooting area. In a naturally ceeding year in the field microplots to final low !evels infested field, nematode distribution as to presence in 1989 and 1990. Cyst nematode population decline and density is clustered. This distribution contributes 10 microplots has been previous!y documented to variability in population determinations resulting (Kerry, 1975; Hartwig, 1981). The decline is gener­ from soil sampling in a field with moderate to low ally attributed to changes in the soil microbial popula­ nematode densities (Noe & Campbell, 1985). AIso, tion that eventually can include pathogens, anta­ the field plot tests were ail conducted in silty soil. In gonists and competitors to the cyst nematode popula­ the microplot tests, H. zeae suppressed maize yields to tion. Most of the infested fields detected in surveys in a greater degree and more consistantly in sandy soil Maryland contained very low populations of this than in silty soil. Microplots were spaced on 3 m cent­ nematode (Krusberg & Sardanelli, 1989). The popu­ ers and seedlings were thinned to the two most vigor­ lation density of H. zeae was followed in two adjacent ous. This spatial arrangement allowed for much naturally infested fields on a farm in Kent County, greater exposure of microplot soil to the warming Maryland from 1985 to 1991 and in 1994 (Table 2). effects of sunlight than in a field soil planted with pro­ Four soil samples were collected from each field. Each duction equipmenr. Soil temperatures were not meas­ sampie was a composite of 50 soil cores collected ured in the field plot trials, but shading effects on the along ca. 100 m of row. Sampling was done at the soil surface due to close plant spacing may have same location in each field between mid-September resulted in cooler temperatures. Previous studies and mid-November each year. These fields were demonstrated this nematode to be favored by high soil planted continuously to maize during this observa­ temperatures. Ir completes its life cycle most rapidly, tion, the on!y exception being a planting of Field 1 in in 15-18 days, at 33 oC, requires 42 days at 25 oC, 1989 with . The soil was the same silty loam and will develop completely but eggs will not hatch at o as used in the microplots. A natural ri se and fall in the 20· C (Hutzell & Krusberg, 1990). Reproduction of populations was observed but the population remains H. zeae on maize plants growing in soil is most rapid relatively low. at 36 oC and the greatest juvenile emergence from cysts was at 30 oC (Hasluni el al., 1993). Studies on H. zeae can cause serious losses in maize yields, an Indian population of H. zeae also found 30 oC as especially under conditions meeting its high optimum the most favorable temperature for emergence of juve­ temperature requirements. We believe that H. zeae niles from cysts (Srivastava & Sethi, 1984). Thus soil reduced maize biomass and grain yield in microplots texture and temperature as weil as inoculum distribu­ but not in previous field trials because conditions were tion within the root rhizosphere appear to have been more conducive in the microplots. However, it more conducive for CCN infestation and pathogenic­ appears unlikely for H. zeae to reduce yields in pro­ ity in the microplot studies than in the previously con­ duction fields of maize in Maryland except perhaps in ducted field trials. very sandy fields with a low plant population under an

598 Fundam. appl. NemalOl. Heterodera zeae affecting Zea mays extended period of high ambienr temperatures. It HUTZELL, P. A. & KRUSBERG, L. R. (1990). Temperature would be more likely ta find production conditions and the life cycle of Helerodera zeae.]. NernalOl., 22: 414­ conducive to the development of yield losses from the 417. corn cyst nemarode in the southeastern D.S. rather KERRY, B. R. (1975). Fungi and the decrease of cereal cyst­ than the Mid-Atlantic or Corn belt regions. nematode populations in cereal monoculture. EPPO Bull., 5:353-361. Acknow1edgments KRUSBERG, L. R. & SARDANELLl, S. (1989). Survival of We thank L. Michael Goff (Maryland Department of Heœrodera zeae in soil in the field and in the laboratory. Agriculture) for his cooperation and assistance with this ]. NemalOl., 21: 347-355. study. This research was partially supported by the Mary­ KRUSBERG, L. R. & SARDANELLI, S. (1991). Pathogenicity land Department of Agriculture. of Helerodera zeae to Zea rnays in field microplots.]. Nema­ 101.,23:536-537 [Abstr.]. References KRUSBERG, L. R., SARDANELU, S., MEYER, S. L. F. & CRO\XfLEY, P. (1994). A method for recovery and count­ CAWLEY, W. A. (1986). Quaramine order number 86-/. ing of nemarode cysts.]. Nemawl., 26:599. Annapolis, MD, USA, Maryland Dept. Agric., 2 p. McINTOSH, M. S. (1983). Analysis of combined experi­ EISENBACK, J. D., REAVER, D. M. & STRO,VlBERG, E. L. ments. Agron.]., 75: 153-155. (1993). First report of corn cyst nemarode (Heœrodera MILLER, L. 1. (1986). Economic importance of cyst nema­ zeae) in Virginia. PI. Dis., 77: 647. todes in North America. In: Lamberti, F. & Taylor, C.E. (Eds). CYSl nemalOdes. New York, USA, Plenum Press: FRECKMAN, D. w., & ETTENtA, C. H. (1993) Assessing nemarade communities in agroecosysrems of varying 373-385. human intervention. Agric., ECOSYSl., Envir., 45:239-261. NOE, l P. & CAi\·tpBELL, C. L. (1985). Spatial pattern ana­ lysis of plant-parasitic nematodes.]. NemalOl.) 17:86-93. HARTWIG, E. E. (1981). Breeding productive soybean culti­ SARDANELLI, S., KRUSBERG, L. R. & GOLDEN, A. M. vars resistant ra the soybean cYSt nematode for the south­ (1981). Corn cyst nemarode, Hererodem zeae, in the ern United States. PI. Dis., 65:303-307. United States. PI. Dis., 65:622. HASHMI, S., KRUSBERG, L. R. & SARDANELU, S. (1993). SRIVASTAVA, A. N. & SETHI, C. L. (1984). Relationship of Reproduction of Heœrodera zeae and its suppression of initial populations of Heœrodera zeae \Vith plant growth of corn plant growth as affected by remperature.]. NemalOl., maize and nematode reproduction. Indian]. NernalOl., 14: 25:55-58. 110-114.

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