Bionomics, behaviour and control of the codling moth, Cydia pomonella (L.) (Lepidoptera: Tortricidae), in pome fruit orchards in South Africa

Dissertation (PhD(Agric))--Stellenbosch University, 2003.

ENGLISH ABSTRACT: The codling moth, Cydia pomonella (L.) has been a major pest of pome fruits since before the turn of the last century. However, despite its high economic profile little is known about the bionomics and . behaviour of this pest in apple orchards in South Africa, information required for the development of a sustainable integrated management programme. In field trials there was contingency between the time of year and the upper and lower half of the tree. First generation moths laid significantly more eggs in the bottom half of the tree while second and third generation moths laid significantly more eggs in the top half of the tree. The preferred oviposition sites on Granny Smith (GS) and Golden Delicious (GD) cultivars, in order of preference, were leaves, fruit and wood. More eggs were laid on the fruit ofGS spurs (35.6 %) than on those ofGD spurs (10.7 %). On fruit spurs there was a significant increase in the number of eggs on GD leaves and GS fruit over the season, whereas the number of eggs on GS leaves and GD fruit remained constant. On branches there was an increase in the number of eggs on GD and GS leaves, but not on the fruit or wood. The preferred oviposition site on the fruit was the fovea of the stalk insertion and the rounded cheek area surrounding the fovea. The distribution within different fruit bearing classes (1 - 4 fruit per spur) was random only for one fruit per spur, while on the other spur classes clustering occurred. In laboratory studies of the embryonic and immature stages there was a linear relationship between rate of development and constant temperatures of 15, 17,20,25 and 30·C ± l·C. The lower threshold temperatures for embryonic, larval and pupal development were 11.1, 7.9, 9.9°C respectively. The degree-days required to complete embryonic, larval and pupal development were 80.5, 345, and 279 respectively. The response of the different stages to constant temperatures was similar to that under fluctuating temperatures. At temperatures below 16°C or abouve 27°C moths did not mate and few eggs were laid. Moth longevity decreased with increasing temperature. There was seasonal variation in longevity and oviposition at constant and fluctuating temperatures. Summer adults produced significantly more eggs than spring adults at constant temperatures. At a constant temperature of2S·C and fluctuating temperatures there were five distinct larval instars. The similarity between the mean head capsule width and ranges for each instar reared on fruit of different stages of development at fluctuating temperatures indicates that fruit development and temperature have little influence on mean head capsule width. From sleeve-cage studies in the orchard there was no significant difference in the fecundity of spring and summer moths. In the beginning of October spring moths produced significantly fewer eggs than in November. Egg mortality increased from 8.2 %in spring to 21.2 %in summer. Failure of 1st instar larvae to penetrate the fruit ranged from 4.9 % to 19.5 %, while mortality oflarvae from egg hatch to emergence from the fruit ranged from 29.7 % to 42.9 %. Mortality of 5th instar larvae after emerging from the apples ranged from 0 % to 8.7 % and pupal mortality from 0 % to 3.5 %. On large 27-year old trees more overwintering larvaewere found on Golden Delicious (13.9) than on Granny Smith trees (5.7), with over 70 % oflarvae being found in pruning wounds on both cultivars. On small 7-year old Golden Delicious and Granny Smith trees the mean number oflarvae was 0.5 and 2.0 per tree. A combined mating disruption and insecticide control programme reduced codling moth resistant populations to levels requiring a minimum to no insecticide intervention for several seasons. The efficacy of a pheromone based strategy, number of pheromone treatments, number of dispenserslha and level of insecticide intervention required are strongly influenced by prevailing weather conditions. Fruit infestation in orchards under a mating disruption programme and under an insecticide programme were greater along the borders compared to the interior. The presence of horticultural mineral oil on the leaves and branches did not have a detrimental effect on oviposition nor was there any significant ovicidal effect. A significant ovicidal effect was obtained when applied after oviposition. In field trials, insecticides with lower levels of efficacy than the primary insecticide, azinphos-methyl, provided acceptable control when successfully incorporated into a spray programme which followed a policy of alternation of insecticides across generations. The least variation in the number of degree-days between biofix and first egg hatch of the spring flight was when the second trap catch (Biofix 2) was used as the biofix. A biofix based on the first evening when the temperature reached or exceeded 1TC at 18:00 after first trap catch also showed less variation than when the biofix was based on first trap catch. The mean number of degree-days accumulated between Biofix 2 and first egg hatch was found to be 139.1 ° D. The number of degreedays between the first and second flight biofixes varied between 531.2 and 488.87°D with a mean of 508.1°D.

AFRIKAANSE OPSOMMING: Kodlingmot (Cydia pomonella) is reeds sedert die vorige eeu 'n sleutelplaag van kemvrugte. Ten spyte van die hoë ekonomiese profiel, is daar min kennis betreffende die bionomie en gedrag van hierdie plaag in appelboorde in Suid-Afrika. Hierdie inligting is noodsaaklik vir die ontwikkeling van 'n volhoubare geïntegreerde bestuursprogram. Tydens veldproewe is 'n korrelasie tussen die tyd van die jaar en eierlegging in die boonste of onderste helfte van bome gevind. Eerste-generasie motte het betekenisvol meer eiers in die onderste helfte van die bome gelê, terwyl tweede- en derde-generasie motte meer eiers in die boonste helfte van die bome gelê het. In toenemende volgorde was die voorkeur eierleggingsposisies op Granny Smith (GS) en Golden Delicious (GD) appels die blare, vrugte en hout. Meer eiers is op vrugte van GS spore (35.6%) as op dié van GD spore (10.7%) gelê. Op vrugspore was daar 'n betekenisvolle toename in aantal eiers op GD blare en GS vrugte deur die seisoen, terwyl die getal eiers op GS blare en GD vrugte konstant gebly het. Op takke was daar 'n toename in aantal eiers op GD en GS blare, maar nie op vrugte of hout nie. Die voorkeur eierleggingsposisie op vrugte was die fovea van die steelaanhegting en die wang rondom die fovea. Die verspreiding tussen verskillende vrugdraende klasse (1 - 4 vrugte per spoor) was slegs in die een-Vrug-per-spoorklas ewekansig, terwyl daar in die ander spoorklasse groepering voorgekom het. In laboratoriumstudies van embrioniese en onvolwasse stadia is 'n lineêre verband tussen ontwikkelingskoers en konstante temperature van 15, 17,20,25 en 30°C±I°C gevind. Die onderste drempel-temperature vir embrioniese, larwale en papie-ontwikkeling was onderskeidelik II. 1°C, 7.f?C en 9.9°C. Graaddae benodig vir voltooiing van embrioniese, larwale en papie-ontwikkeling was onderskeidelik 80.5,345 en 279. Die respons van verskillende stadia by konstante temperature het ooreengestem met hul respons onder wisselende temperature. Motte het nie gepaar nie en min eiers is gelê by temperature onder 16°C of bo 27°C. Die lewensverwagting van motte het afgeneem met toename in temperatuur. Seisoenale variasie in . lewensverwagting en eierlegging het voorgekom by konstante sowel as wisselende temperature. By konstante temperature het somer-volwassenes betekenisvol meer eiers as lente-volwassenes geproduseer. By 'n konstante temperatuur van 25°C, sowel as by wisselende temperature, het vyf duidelik onderskeibare larwale instars voorgekom. Die ooreenkoms tussen die gemiddelde kopkapsulewydte en wydte-reeks vir elke instar wat op vrugte van verskillende stadiums van ontwikkeling by wisselende temperature geteel is, dui daarop dat vrugontwikkeling en temperatuur weinig invloed op gemiddelde kopkapsule-wydte het. Tydens mou-hok studies in die boord is geen betekenisvolle verskil in die fekunditeit van lente- en somer-motte waargeneem nie. Vroeg in Oktober het lente-motte betekenisvol meer eiers as in November geproduseer. Eiermortaliteit het van 8.2% in die lente tot 21.2% in die somer toegeneem. Faling van 1ste instar larwes om vrugte te penetreer het van 4.9% tot 19.5% gewissel, terwyl mortaliteit van larwes vanaf uitbroei tot uitkoms uit die vrug van 29.7% tot 42.9% gewissel het. Mortaliteit van Sde instar larwes na uitkoms uit die vrug het van 0% tot 8.7% gewissel, en papie-mortaliteit van 0% tot 3.5%. Op groot, 27-jaar oue bome is meer oorwinterende larwes op Golden Delicious (13.9) as op Granny Smith (5.7) gevind, en meer as 70% van die larwes op beide kultivars is op snoeiwonde gevind. Op klein, 7-jaar oue bome was die gemiddelde aantallarwes op Golden Delicious en Granny Smithbome 0.5 en 2.0 onderskeidelik. 'n Gekombineerde paringsontwrigting- en insekdoder beheerprogram het weerstandbiedende kodlingmot-populasies verminder tot 'n vlak waar minimum tot geen insekdoder-toedienings vir verskeie seisoene gemaak is. Die effektiwiteit van 'n feromoon-gebaseerde strategie, aantal feromoonbehandelings, aantal vrystellers/ha en vlak van insekdoder-toediening word sterk deur heersende weersomstandighede beïnvloed. Die rande het hoër vruginfestasie as die middel getoon in boorde onder paringsontwrigting sowel as boorde onder insekdoder-programme. Die teenwoordigheid van minerale olie op blare en takke het geen nadelige effek op eierlegging gehad nie en dit het geen betekenisvolle eierdodende effek gehad nie. Indien die olie ná eierlegging toegedien is, is daar wel 'n betekenisvolle eierdodende effek waargeneem. Tydens veldproewe het insekdoders met laer effektiwiteit as die primêre insekdoder, azinfos-metiel, aanvaarbare beheer verskaf indien dit suksesvol geïnkorporeer is in 'n spuitprogram deur 'n beleid van afwisseling van insekdoders oor generasies. Die kleinste variasie tussen die aantal graaddae tussen biofix en eerste uitbroei van eiers is gevind indien die tweede lokvalvangs as biofix gebruik is. 'n Biofix gebaseer op die eerste aand na die eerste lokval vangste wat die temperatuur 17°Cofhoër was teen 18:00, het ook 'n kleiner variasie getoon as die eerste lokvalvangs. Die aantal graaddae tussen die tweede en derde vlug biofix het tussen 531.2 en 488.87°D gewissel, met 'n gemiddelde van 508.1°D.

Doctoral