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The pest status and chemical control of whitegrubs and cutworms in forestry in the Natal Midlands.

The limited availability of land to forestry and the ensuing emphasis on intensive silviculture,



developed a renewed interest in soil pests in the establishment of plantations. Ten field trials



were planted over three seasons to determine the mortality factors influencing the



establishment of commercial eucalypt and black wattle plantations in the Natal Midlands, and



simultaneously, to investigate the chemical control of the soil pest component. A complex



of indigenous soil pests contribute to an average 22,9 % failure of Acacia mearnsii and



Eucalyptus grandis seedlings from reaching full establishment. This pest complex, which



includes termites, whitegrubs, cutworms, tipulid larvae, wireworms, millipedes and



nematodes, was responsible for an average 12,3 % of the failure of the plantings to establish.



In the absence of termites, in shallow humic soils, whitegrubs followed by cutworms were



the most frequent and economically important pests. Eucalypts are more susceptible than



wattle seedlings to whitegrub damage when planted in marginal sites. Seedlings in the



summer rainfall region were most susceptible to whitegrub damage from December to April;



and to cutworm damage during the first two months after planting. An average of 398



hectares was annually damaged by whitegrubs and cutworms. The total annual loss in



planting costs and the additional costs of blanking over the three year study period were 1,22



and 2,65 million rands respectively.



Existing non-chemical control applicable to woodlot forestry is reported. Chemical control



as one of the options in the management of whitegrubs and cutworms was evaluated. The



controlled release formulations of carbosulfan 10% and chlorpyrifos 10% at 1,0 g active



ingredient/tree (a.i./tree), gamma BRC 0,6% dust at 0,06 g a.i./tree and the synthetic



pyrethroid deltamethrin 5 % SC at 0,025 g a.i./tree were persistent and effective in



controlling whitegrubs, even when applied early in the planting season. Deltamethrin 5 % SC



at 0,025 g a.i./tree was also successful in controlling cutworms. / Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 1995.

Identiferoai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:ukzn/oai:http://researchspace.ukzn.ac.za:10413/10908
Date12 June 2014
CreatorsGovender, Pramanathan.
ContributorsMiller, Ray M.
Source SetsSouth African National ETD Portal
Languageen_ZA
Detected LanguageEnglish
TypeThesis

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