Thesis (MScAgric)--University of Stellenbosch, 2003. / ENGLISH ABSTRACT: Various aspects of the biology and ecology of woolly apple aphid, Eriosoma
lanigerum, were investigated, including initial galling damage caused by E. lanigerum to
the roots of apple trees, the possible relationship between E. lanigerum and Xiphinema and
Pratylenchus nematodes and the effectiveness of Biostart 2000® and Furfural® as possible
control agents of E. lanigerum in the orchard.
Preliminary root damage by first instar E. lanigerum feeding was characterized by
the mechanical injury of endodermis and parenchyma tissues. Damage by second, third and
fourth instar E. lanigerum was similar, but the symptoms were more pronounced. Damage
caused by adults included a pronounced swelling at infected areas of the root. Cell walls
hardened until the root was radially strengthened with sclerenchyma tissue and nonconducting
xylem vessels while the cuticle expanded greatly through the growth of corklike
cambium tissue.
There was no direct relationship between the population dynamics of E.
lanigerum and those of Xiphinema and Pratylenchus nematodes. The occurrence of E.
lanigerum appeared to be seasonal while P. penetrans and Xiphinema numbers fluctuated
erratically. Undamaged root nitrogen levels seemed to correspond with the normal root
growth cycle. Nitrogen levels from galled roots were significantly lower than those of
undamaged roots, probably due to E. lanigerum feeding. Soils rich in fine sand and clay
sustained higher populations of E. lanigerum and Xiphinema than sandy soils. The number
of E. lanigerum found in soil samples correlated well with the damage index allocated to
the samples. The numbers of Xiphinema found in soil samples also correlated well with the
damage index allocated to the samples according to suspected Xiphinema damage
symptoms.
Both Biostart 2000® and Furfural® were effective as control agents of woolly apple
aphid. Furfural'Ï, a chemical waste product of the sugarcane industry, was however not as
effective as Biostart 2000®, a product that includes an activator and three bacterial species,
Bacillus laterosporus, B. chitinosporus and B. licheniformis. The bacteria in the Biostart
2000® treated pots could replicate themselves under suitable conditions while Furfural®
dilutes with each watering. Biostart 2000® is also easier to prepare than Furfural® since the
components of Biostart 2000® readily mix to form a paste easily thinned by water, whereas
Furfural® is an oily substance that does not easily disperse in water.
Root damage was initiated soon after E. lanigerum started feeding, however there
was no apparent relationship between E. lanigerum and the nematode species. The most
promising, environmentally friendly control measure was Biostart 2000®. / AFRIKAANSE OPSOMMING: Verskeie aspekte van biologie en die ekologie van die appel bloedluis, Eriosoma
lanigerum, was ondersoek insluitende aanvanklike galvorming veroorsaak deur E.
lanigerum op wortels van appelbome, die moontlike verwantskap tussen E. lanigerum en
Xiphinema en Pratylenchus nematodes en die effektiwiteit van Biostart 2000® en Furfural®
as moontlike beheeragente van E. lanigerum in die boord.
Aanvanklike wortelskade deur eerste ins tar E. lanigerum voeding was gekenmerk
deur die meganiese beskadiging van endodermale en parenchiem weefsel. Skade
veroorsaak deur tweede, derde en vierde instar E. lanigerum was soortgelyk alhoewel die
simptome meer beklemtoond was. Skade deur volwassenes het 'n meer duidelike swelsel
by geïnfekteerde wortelareas ingesluit. Selwande het verhard totdat die wortel
radiaalsgewys versterk was met skierenchiem weefsel en nie-geleidende xileemvate terwyl
die kutikula grootliks toegeneem het deur die groei van kurkagtige kambiumweefsel.
Daar was geen direkte verwantskap tussen die bevolkingsdinamika van E.
lanigerum en dié van Xiphinema en Pratylenchus nematodes nie. Die voorkoms van E.
lanigerum was seisoenaal terwyl P. penetrans en Xiphinema se getalle onvoorspelbaar
gefluktueer het. Onbeskadigde wortel stikstofvlakke het ooreengestem met die normale
wortel groeisiklus. Stikstof vlakke van galwortels was noemenswaardig laer as dié van
onbeskadigde wortels, heel waarskynlik as gevolg van voeding deur E. lanigerum. Grond
ryk aan fyn sand en klei het groter bevolkings van E. lanigerum en Xiphinema onderhou as
sanderige gronde. Die aantal E. lanigerum in grondmonsters het goed ooreengestem met
die skade indeks wat aan die monsters toegeken was. Die aantal Xiphinema in
grondmonsters het ook goed ooreengestem met die beskadigingsindeks wat aan die
monsters toegeken is weens vermoedelike Xiphinema skade simptome.
Beide Biostart 2000® en Furfural® was effektief as beheeragente van die
appelbloedluis. Furfural'", 'n afvalproduk van die suikerriet industrie, was egter minder
effektief as Biostart 2000®, 'n produk bestaande uit 'n aktiveerder en drie bakterie spesies,
Bacillus laterosporus, B. chitinosporus en B. licheniformis. Die bakterië in die Biostart
2000® behandelde potte kon vermeerder onder gunstige toestande terwyl Furfural® na elke
besproeiing verdun het. Biostart 2000® is ook makliker om aan te maak as Furfural®
aangesien die bestanddele van Biostart 2000® geredelik meng tot 'n wateroplosbare pasta,
terwyl Furfural® 'n olierige vloeistofis wat moeilik 'n waterige suspensie vorm.
Wortelskade het plaasgevind kort nadat E. lanigerum begin voed het, alhoewel daar
geen duidelike verwantskap tussen E. lanigerum en nematode spesies voorgekom het nie.
Die mees belowende omgewingsvriendelike beheermaatreël was Biostart 2000®.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/53551 |
| Date | 12 1900 |
| Creators | Van Jaarsveld, Alwyn Jacobus |
| Contributors | Pringle, K. L., Geertsema, H., Stellenbosch University. Faculty of AgriSciences. Dept. of Conservation Ecology and Entomology. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | Unknown |
| Type | Thesis |
| Format | 75 p. : ill. |
| Rights | Stellenbosch University |
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