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.

https://bioone.org/journals/journal-of-economic-entomology/volume-96/issue-6/0022-0493-96.6.1724/Radiation-Biology-and-Inherited-Sterility-in-False-Codling-Moth-Lepidoptera/10.1603/0022-0493-96.6.1724.pdf

Radiation Biology and Inherited Sterility in False Codling Moth (Lepidoptera: Tortricidae)

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.

The development and evaluation of Cryptophlebia Leucotreta granulovirus (CrleGV) as a biological control agent for the management of false codling moth, Cryptophlebia Leucotreta, on citrus

The gene Cry1Ab derived from the entomopathogenic bacterium Bacillus thuringiensis is currently deployed commercially for control of Pyralid stem borers of maize in the USA. In this study various events of the Bt-gene were evaluated in maize inbred lines and hybrids for leaf feeding resistance to the local stem borers Busseola fusca and Chilo partellus, using artificially infested plants under greenhouse and field conditions. The event MON810 proved superior to all other events tested. C. partellus was more susceptible than B. fusca to the same events. Significant maternal effects were observed. Efficacy was not negatively affected by variations in the time of infestation. Hybrids did not respond equally to transformation with the same event, which was attributed to differences in adaptation to adverse environmental conditions.

Evaluation of Bt.-Transgenic maize for resistance to the stem borers Busseola fusca (Fuller) and Chilo partellus (Swinhoe) in South Africa

The comparative influence of Busseola fusca (Fuller) and Chilo partellus (Swinhoe), both as separate and mixed populations, on growth and yield of grain sorghum was investigated in a field experiment, using an artificial infestation in cages. C. partellus was more injurious than B. fusca as indicated by whorl damage, stalk injury and yield loss. In the case of mixed populations, dispersion of larvae and damage were independent of B. fusca numbers. A regression equation, Logit Y = 0.24 + 2.06 logit x, relating visible plant damage to yield loss was determined. Control strategies in the case of mixed stem borer populations should be directed against C. partellus.

Comparative injuriousness of Busseola fusca (Lepidoptera: Noctuidae) and Chilo partellus (Lepidoptera: Pyralidae) on grain sorghum

During the 1998/99 season considerable stem damage was caused by B. fusca in commercial plantings of Bt-maize, without leaf feeding damage during the vegetative stages of plant development. This indicated that larvae may survive on some less toxic plant part subsequent to the vegetative stages. In this study a laboratory bioassay was conducted, using forced feeding of larvae on various parts of Bt-maize. In a field trial larval survival and plant damage were recorded following artificial infestation of Bt- plants one week before, and one and three weeks after tasseling. It appears that there is a window of approximately 14 days immediately preceding tasseling, in which relatively late infestations may result in increased larval survival, due to the availability of silks as a primary food source to neonate larvae. The Bt-protein concentration in silks appears to be low enough to allow survival of some larvae until completion of the first two instars, after which the ear tips and husk leaves serve as import...

Larval mortality and injury patterns of the African stalk borer, Busseola fusca (Fuller) on various plant parts of Bt-transgenic maize

Maize plants were artificially infested with egg batches of Busseola fusca at different times after crop emergence. Regression equations of yield loss on percentage plants with eggs varied over different seasons, which was attributed to hybrid differences and variation in climate.

Giliomee

Papers

Response of maize to levels and times of infestation by Busseola fusca (Fuller) (Lepidoptera: Noctuidae)

Field evaluation of synthetic sex attractants of the false codling moth, Cryptophlebia leucotreta (Lepridoptera: Tonricidae)