False codling moth

Abstract: False codling moth, Cryptophlebia leucotreta (Meyrick), male and female mature pupae and newly emerged adults were treated with increasing doses of gamma radiation and either inbred or out-crossed with fertile counterparts. For newly emerged adults, there was no significant relationship between dose of radiation and insect fecundity when untreated females were mated to treated males (N♀ by T♂). However, fecundity of treated females mated to either untreated (T♀ by N♂) or treated males (T♀ by T♂) declined as the dose of radiation increased. A similar trend was observed when mature pupae were treated. The dose at which 100% sterility was achieved in treated females mated to untreated males (T♀ by N♂) for both adults and pupae was 200 Gy. In contrast, newly emerged adult males treated with 350 Gy still had a residual fertility of 5.2% when mated to untreated females, and newly emerged adult males that were treated as pupae had a residual fertility of 3.3%. Inherited effects resulting from irradiation of parental (P1) males with selected doses of radiation were recorded for the F1 generation. Decreased F1 fecundity and fertility, increased F1 mortality during development, and a significant shift in the F1 sex ratio in favor of males was observed when increasing doses of radiation were applied to the P1 males.

Abstract: A granulovirus isolated from Cryptophlebia leucotreta larvae was shown through restriction endonuclease analysis to be a novel strain (CrleGV-SA). No more than one isolate could be identified from a laboratory culture of C. leucotreta. However, a preliminary examination of restricted DNA profiles of isolates from different geographical regions indicated some minor differences. In surface dose bioassays on artificial diet, LC50 and LC90 values with neonate larvae were estimated to be 4.095 x 10 OBs/ml and 1.185 x 10 OBs/ml respectively. LT50 and LT90 values with neonate larvae were estimated to be 4 days 22 h and 7 days 8 h, respectively. Detached fruit (navel orange) bioassays with neonate larvae indicated that virus concentrations that are likely to be effective in the field range from 1.08 x 10 to 3.819 x 10 OBs/ml. In surface dose bioassays with fifth instar larvae LC50 and LC90 values were estimated to be 2.678 x 10 OBs/ml and 9.118 x 10 OBs/ml respectively. LT50 and LT90 values were estimated to be 7 days 17 h and 9 days 8 h, respectively. A new artificial diet for mass rearing the host was developed. Microbial contamination of diet was significantly reduced by adding nipagin and sorbic acid to the diet and by surface sterilising C. leucotreta eggs with Sporekill. Almost 20 % more eggs were produced from moths reared on the new diet compared to moths reared on the old diet. A further 9 % improvement in egg production and a reduction in the labour required to produce eggs, was made with the development of a new oviposition cage attached to the moth eclosion box. Virus was mass produced in fifth instar C. leucotreta larvae by surface inoculating diet with the LC90. When 300 individuals were placed onto inoculated diet, 56 % of them were recovered six to 11 days later as infected larvae. Mean larval equivalents was 1.158 x 10 OBs/larva. When larvae and diet were harvested together, highest yields of virus were achieved at eight days after inoculation. Microbial contamination in semi-purified preparations of CrleGV ranged from 176211 to 433594 (OB:CFU ratio). Half-life of CrleGV in the field was estimated to be less than 1 day on the northern aspect of trees and between 3 6 days on the southern aspect. Original activity remaining (OAR) of the virus dropped below 50 % after 5 days on the northern aspect of trees and was still at 69 % on the southern aspect of trees after 3 weeks. In field trials, CrleGV reduced C. leucotreta infestation of navel oranges by up to 60 % for a period of 39 days. CrleGV in combination with augmentation of the C. leucotreta egg parasitoid, Trichogrammatoidea cryptophlebiae, reduced infestation by 70 %. The integration of CrleGV into an integrated pest management (IPM) system for the management of C. leucotreta on citrus is proposed.

Abstract: The false codling moth Thaumatotibia leucotreta (Meyrick) is a key pest of citrus, stone fruit, and other crops in many countries throughout continental Africa, including South Africa. There is a growing awareness that this damaging pest could soon be introduced into other countries including the USA as a direct result of increased international trade and daily direct flights fromAfrican countries. South Africa currently employs a combination of cultural, chemical, microbial and augmentative biological control to suppress false codling moth. Augmentative biological control makes use of the egg parasitoid Trichogrammatoidea cryptophlebiae Nagaraja. However, this integrated programme is not adequate for effective false codling moth control. The sterile insect technique (SIT) is now being developed as an additional method for false codling moth suppression in South Africa, but also as a tactic that could be rapidly integrated in an area-wide integrated pest management strategy if false codling moth were to be introduced or become established as an exotic invasive pest in other countries such as the USA. The SIT is regarded as a host-specific and environment-friendly pest control tactic that is compatible with the application of augmentative biological control. However, fully successful integration of the SIT and parasitoid releases into an effective pest management approach can occur only if the parasitoids do not negatively impact irradiated insects and their progeny more severely than they affect the wild pest population, and if the release of irradiated insects does not negatively impact the efficacy of the parasitoids. Therefore, knowledge of the compatibility of T. cryptophlebiae and the release of irradiated false codling moth is crucial to the evaluation of the combined use of these tactics. The development and combination of these offshore integrated pest management strategies in South Africa will develop and/or enhance scientific expertise and infrastructure in that country, reduce wild populations of false codling moth and lower the risk of its introduction into countries currently free of this pest. In addition, the development of these control tactics and the improved infrastructure (e.g. rearing/irradiation facilities in South Africa) will provide resources, technology, and strategies for eradicating invasive populations of the false codling moth should this pest be introduced into new geographical areas.