Patrick Greany

Changes in haemolymph proteins of the fall armyworm, Spodoptera frugiperda (J. E. Smith), associated with parasitism by the braconid parasitoid Cotesia marginiventris (Cresson)

Abstract Changes in haemolymph proteins of the fall armyworm, Spodoptera frugiperda , associated with parasitism by the parasitoid Cotesia (= Apanteles) marginiventris were monitored by sodium dodecyl sulphate polyacrylamide gel electrophoresis. As early as hour 4 after parasitization treatment, several electrophoretically slow-migrating, high-molecular-weight proteins were detected in the hosts haemolymph. These proteins were detected earlier in haemolymph from parasitized larvae than in haemolymph from control larvae, and their concentrations were higher in heavily parasitized host larvae (≥ 3 eggs/host) than in lightly parasitized larvae (1 egg/host). Additionally, unique proteins that migrated electrophoretically with bovine serum albumin appeared in the haemolymph of parasitized larvae at hour 8 after parasitization treatment and were evident in haemolymph collected through to hour 64.

Vitellin and vitellogenin in the soldier bug, Podisus maculiventris: Identification with monoclonal antibodies and reproductive response to diet†

A 171,000 M(r )polypeptide of Podisus maculiventris (Say) (Heteroptera: Pentatomidae) that constituted 16% of the protein in eggs also constituted up to 25% of the protein in hemolymph of fed females. It was identified as the major or sole apoprotein of vitellogenin. Eggs contained major polypeptides of 171, 106, and 51 kDa. The hemolymph polypeptide was identified with a polypeptide (vitellin) in egg extracts by comparing molecular weights, specificity of occurrence in fed females, and immunological reactivities. Females, starved for 5 days after eclosion to assure complete previtellogenic development, produced vitellogenin within a day after feeding on larval Galleria mellonella, and within 4 days after feeding on an artificial diet. Appearance of vitellogenin preceded ovarian growth by 2-3 days. Two monoclonal antibodies raised against egg proteins of P. maculiventris were selected for their strong reaction against egg extract and female hemolymph and null reaction against male hemolymph. Only one 170-kDa band in egg and hemolymph reacted with the antibodies on denaturing Western blots. These monoclonal antibodies are being used to develop an enzyme-linked immunosorbent assay (ELISA) to quantitate reproductive response of females to diets of differing quality.

Improving the cost-effectiveness, trade and safety of biological control for agricultural insect pests using nuclear techniques

Abstract If appropriately applied, biological control offers one of the most promising, environmentally sound, and sustainable control tactics for arthropod pests and weeds for application as part of an integrated pest management (IPM) approach. Public support for biological control as one of the preferred methods of managing non-indigenous and indigenous pests is increasing in many countries. An FAO/IAEA Coordinated Research Project (CRP) addressed constraints related to costly production systems for biological control agents, and the presence of accompanying pest organisms during their shipment. These constraints can be alleviated using nuclear techniques such as ionizing radiation or X-rays to reduce production and handling costs (e.g., by expanding the period of host suitability, increasing shelf life, avoiding unnecessary sorting steps before shipment, etc.), and to eliminate the risk of shipping fertile host or prey pest individuals or other hitchhiking pests. These nuclear techniques can also help to reduce the risks associated with the introduction of exotic biological control agents, which can become pests of non-target organisms if not carefully screened under semi-natural or natural conditions. Radiation is also a very useful tool to study host-parasitoid physiological interactions, such as host immune responses, by suppressing defensive reactions of natural or factitious hosts. Applied at a very low-dose, radiation may be used to stimulate reproduction of some entomophagous insects. Additionally, radiation can be applied to semi- or completely sterilize hosts or prey for deployment in the field to increase the initial survival and build-up of natural or released biological control agents in advance of seasonal pest population build-up. Finally, the work carried out under this CRP has demonstrated the feasibility of integrating augmentative and sterile insect releases in area-wide IPM programmes, and to utilise by-products from insect mass-rearing facilities in augmentative biological control programmes. This special issue provides an overview of the research results of the CRP.

Changes in limonin and naringin levels in grapefruit albedo with maturity and the effects of gibberellic acid on these changes

Abstract Variability in the two major bitter components, naringin and limonin, in grapefruit peel albedo was determined over four seasons in Marsh grapefruit. The effects of the growth regulator gibberellic acid (GA) on seasonal content of these two bitter components in albedo was also determined. Limonin and naringin content decreased with maturity and were affected by some treatments with (GA). In Marsh grapefruit albedo, naringin was the major flavanone glycoside, representing more than 80% of the total flavanones. In a non-bitter grapefruit hybrid, only traces of naringin were present in the albedo, and the non-bitter isomer naringenin 7β-rutinoside was the major flavonoid present.

Ecdysteroid levels/profiles of the parasitoid wasp, Diapetimorpha introita, reared on its host, Spodoptera frugiperda and on an artificial diet.

Diapetimorpha introita is an ichneumonid ectoparasitoid of the fall armyworm, Spodoptera frugiperda. Since it has been reported that D. introita wasps reared on an artificial diet exhibit a significantly lower percentage of adult eclosion and fecundity than host-reared wasps, this study was undertaken to elucidate the factors responsible for the reduced viability observed in diet-reared wasps. A system of markers has been devised to track the development (from the initiation of cocooning through adult eclosion) of D. introita. Although wasps reared on artificial diet developed more slowly than did those reared on host pupae, both diet- and host-reared wasps passed through the same stages of development - the eyes enlarged and moved backward, the gut was purged and upon ecdysis the exarate pupa emerged. The thorax was the first to darken, followed by the head and then the abdomen. Pharate pupal formation occurred before gut purge. Two peaks of hemolymph ecdysteroids were observed, one in wasps in which gut purge was almost complete and the second in day-2 exarate pupae. Ecdysone and 20-hydroxyecdysone were the major ecdysteroids present in hemolymph sampled at these times. Small quantities of 20,26-dihydroxyecdysone, polar ecdysteroids and/or possibly 26-hydroxyecdysone were also present. In six stages of development, hemolymph ecdysteroid titers were significantly higher in host-reared than in diet-reared wasps (Eye 1, Eye 2, Gut Purge 2, Pharate Pupa, Head/Thorax Dark, and Abdomen Dark). Relatively high percentages of mortality were observed in diet-reared wasps in four of these stages and in two others which occurred in close proximity to one of the stages, the Abdomen Dark stage. Thus, insufficient ecdysteroid in the hemolymph may be responsible, in part, for the relatively high percentage of mortality that occurred in wasps reared on an artificial diet.

Interplay between foraging behaviour, adult density and fruit ripeness determines the effectiveness of gibberellic acid and host-marking pheromone in reducing susceptibility of grapefruit to infestation by the Mexican fruit-fly, Anastrepha ludens

The potential of gibberellic acid (GA3) and host-marking pheromone as management tools for control of Mexican fruit-fly (Anastrepha ludens) was evaluated in the field. Varying numbers of GA3-treated and untreated “Ruby Red” grapefruit were hung in branches of field-caged citrus trees and exposed to four different densities of gravid A. ludens females (1, 5, 15 and 30 individuals per cage) over the entire harvest season (October to February). Infestation was not lowered by GA3-treatment when fly density was set at 0.06, 0.19 and 0.38 females per fruit. Results depended mainly on fruit ripeness and female density. A reduction in infestation (almost eight-fold) was recorded at a fly density of one female per 200 fruit (0.0005 female/fruit rate), when fruit was treated with 15 ppm of GA3 (applied once) and exposed to flies early in the harvest season (November). At a higher GA3 concentration (20 ppm applied twice) and a fly density of 30 females per 100 fruit (0.3 female/fruit rate), no statistically significant reduction in damage was recorded. Late in the season, when untreated fruit were overripe (i.e. were of poor quality), there was a tendency for females to preferentially oviposit into GA3-treated (and therefore superior quality) fruit. We also tested the combined effect of GA3 and host-marking pheromone and pheromone-treated fruit on the oviposition behaviour of A. ludens and found that the presence of pheromone, with or without GA3, reduced infestation to nearly zero. Wediscuss our findings in the context of the interplay between oviposition behaviour, fly density and fruit ripeness (i.e. the season) and the complexities involved in the design of biorational fruit-fly management schemes.