The influence of synthetic pyrethroids on phytophagous mites and their natural enemies in apple orchards

Heunis, J. M. (Juanita Maria) (1992-03)

Thesis (MSc)--Stellenbosch University, 1992.

One copy microfiche.

Thesis

ENGLISH ABSTRACT: The effects of synthetic pyrethroids on the spider mite, Tetranychus urticae Koch, and its natural enemies was investigated. The pyrethroid cyfluthrin, sprayed for the control of fruit weevil Phlyctinus callosus, did not cause mite outbreaks and was not harmful to the predators when sprayed before they appeared on the apple trees. This spray also gave good control of thrips, bollworm (Heliothis armigera) and fruit weevil (P. callosus). A late season spray of deltamethrin against codling moth, caused an increase in the phytophagous mite population. This was assosiated with a temporary reduction in the population level of the predatory beetle, Oligota fageli. The plants found on the orchard floor were examined. The plant diversity was low and plants that acted as hosts of phytophagous mites during the winter were scarce. However, Solanum nigum carried high mite populations and infected the adjacent apple trees. The plants were too few to have an effect on the whole orchard. Eight synthetic pyrethroids were tested for repellency in a leafdisk dip and spray bioassay using T. urticae. Deltamethrin and fenvalerate caused no walk-off. Cyfluthrin and fluvalinate caused moderate walk-off and bifenthrin, cyhalothrin and lambda-cyhalothrin caused high walk-off.

AFRIKAANSE OPSOMMING: Die invloed van sintetiese piretroIedes op die rooispinmyt, Tetranychus urticae Koch en hul natuurlike vyande is ondersoek. Die piretroIed, cyfluthrin, gespuit vir die beheer van snuitkewer, P4ctinus callosus, het the mytuitbrake veroorsaak the en was ook the skadelik vir predatore nadat dit vroeg in die seisoen, voordat myte in die appelbome verskyn het, gespuit is the. Die bespuiting het ook goeie beheer van blaaspootjies, bolwurm (Heliothis amdgera) en P. callosus gegee. Deltametrien wat later in die seisoen toegedien is vir die beheer van kodlingmot, Cydia pomonella, het 'n mytuitbraak veroorsaak. Dit word geassossieer met die tydelike onderdrukking van die populasievlak van die predatoriese kewer, Oligota fageli. Die plante in die dekgewas is ondersoek. Die plant-verskeidenheid was laag en plante wat kon dien as oorwinterings gashere vir fitofage myte kon dien was skaars. Solanum nigrum het egter groot bevolkings myte gedra wat die appelbome naaste aan hulle eerste besmet het. Daar was egter te min van hierdie plante om 'n invloed op die hele boord te he. Agt piretroIedes is vir afwering van T. urticae in 'n blaarskyf doop en spuit bioessal getoets. Deltamethrin en fenvalerate het geen afwering getoon the. Cyfluthrin en fluvalinate het 'n redelike afwering, terwyl bifenthrin, cyhalothrin en lamda-cyhalothrin het 'n hod mate van afwering getoon

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