N. W. Heather

Fifty Years of Radiation Biology in Entomology: Lessons Learned from IDIDAS

Abstract The purpose of the International Database on Insect Disinfestation and Sterilization (IDIDAS: http://www-ididas.iaea.org/ididas/) website is to collect and share information about radiation doses for disinfestation and reproductive sterilization of arthropods and to perform a comparative analysis and quality assurance check on existing data. IDIDAS was developed based on a literature review and analysis of >2,750 references, published during the past five decades. In total, 309 species of arthropods, mostly of economic importance, from 196 genera, 84 families, 9 insect orders, and 2 arachnid orders, have been subjected to irradiation studies for purposes of (1) research, such as sperm precedence determination and parasitoid-host interaction studies, (2) disinfestation for quarantine or phytosanitary purposes or (3) different pest control applications, including the sterile insect technique (SIT) and biological control programs. Sensitivity to radiation among families, and in particular orders, varies sometimes over two orders of magnitude, with Arctiidae and Pyralidae (Lepidoptera) being the most radioresistant, requiring the highest sterilizing doses (100–300 Gy), and Acrididae (Orthoptera) and Blaberidae (Dictyoptera) the lowest (<5 Gy). Within Diptera, Coleoptera and Hemiptera radiation doses vary widely among families and range from 20 to 200 Gy. Soft Acari species belonging to Ixodidae are more sensitive than hard species of Argasidae and Tetranychidae mites. In general, most insect, mite, and tick families require a sterilizing dose of <200 Gy. Analysis of data shows that, with few exceptions, generic doses of radiation apply to species within the same genus, and thus, there is generally no need to develop radiation biology data for all species. Although the objective of this database is to present the optimum dose for research, disinfestation, or sterilization at the species level, there is some inconsistency in the recorded doses resulting from variation in many factors affecting sensitivity to radiation. Thus, this review highlights the need for further efforts to standardize experimental dosimetry and irradiation procedures for arthropods and provides a suitable platform for guiding future research in this area.

Cold disinfestation of Australian mandarins against Queensland fruit fly (Diptera: Tephritidae)

Abstract Three cultivars of mandarins, ‘Imperial’, ‘Ellendale’ and ‘Murcott’ and one tangelo, ‘Minneola’, were shown to be disinfested of Queensland fruit fly, Bactrocera tryoni (Froggatt) by cold treatment at 1 °C for 16 days. From a total of 3885 treated fruit of all cultivars, estimated to contain 176,715 first instars — judged to be the most tolerant in-fruit stage of the pest — there were no survivors. This treatment efficacy meets all known international market requirements.

A heated air quarantine disinfestation treatment against Queensland fruit fly (Diptera: Tephritidae) for tomatoes

A circulated heated-air treatment at 92% RH to achieve and maintain a minimum fruit core temperature of 44°C for 2 h is shown to disinfest tomatoes against Queensland fruit fly, Bactrocera tryoni (Froggatt) for market access quarantine purposes. The efficacy of the treatment exceeded 99.99%, tested at the 95% confidence level. An estimated 78 439 eggs were used for large-scale trials, as the stage of the pest most tolerant of heat at the treatment temperature.

Efficacy of Leptospermum petersonii Oil, on Plutella xylostella, and Its Parasitoid, Trichogramma pretiosum

ABSTRACT The efficacy of lemon-scented tea tree oil (LSO), Leptospermum petersonii (FM. Bailey), was evaluated against the diamondback moth, Plutella xylostella (L.) under laboratory conditions. Feeding activity and development of larval stages were significantly reduced on broccoli leaves that had been dipped in LSO. Oviposition deterrence was also found when an adult stage was exposed to treated leaves. Fecundity dropped by >50% at concentrations >0.5%. The LC50 value for third instar larvae was estimated to be 2.93% 7 d after treatment. Experiments were also conducted under greenhouse conditions to assess the efficacy of LSO against the diamondback moth. Our results suggest that LSO has modest potential for development as a botanical insecticide. The oil was also tested at concentrations from 0.5 to 6% for oviposition deterrence of an egg parasitoid of the diamondback moth, Trichogramma pretiosum (Riley). LSO deterred parasitization in choice tests but not in no-choice tests. LSO did not cause mortality of T. pretiosum during 24 h in a contact toxicity test. We conclude that LSO had no significant effects on the parasitoid, and therefore LSO is compatible with this biocontrol agent for integrated management of the diamondback moth.

Mechanism and effectiveness of safflower oil against female Queensland fruit fly Bactrocera tryoni

Queensland fruit fly, Bactrocera tryoni (Froggatt) (Diptera: Tephritidae), infests many horticultural fruit crops in the eastern part of Australia. Farmers usually apply synthetic insecticides to control this pest. Little is known on the use of plant products especially vegetable oils for fruit fly control although they are considered to be safer than synthetic insecticides. In this study, safflower oil was investigated for its mechanism and effectiveness against female B. tryoni. In a laboratory test, safflower oil treatments (2.5 and 5.0 ml l−1) reduced the number of fly punctures on treated artificial fruits, no matter whether pre‐punctures were present or absent. Safflower oil treatments also reduced the number of fly landings and eggs laid, but only when the treated artificial fruits were without pre‐punctures. These results confirmed that safflower oil is active against female B. tryoni mainly by preventing this fruit fly from making oviposition punctures, not by discouraging them from depositing eggs or by repelling them. The slippery nature of safflower oil is considered to be responsible for a reduction in the susceptibility of artificial fruit to fruit fly punctures. Further investigation using fruit‐bearing tomato plants (a no‐choice test) in a glasshouse situation revealed that safflower oil application at concentrations of 10 and 15 ml l−1 reduced the number of oviposition punctures but failed to reduce the number of eggs laid. To increase efficacy of safflower oil under field conditions, multiple tools may be needed to reduce fruit fly populations and oviposition behaviour, such as the addition of trap‐crops, provision of artificial oviposition sites, or mixing the insecticides with the oil.