The nematode fauna of an estuarine mangrove Avicennia marina mudflat in Southeastern Australia has been intensively studied. About 85% of the nematodes occur in the top cm of soft mud, but 5-7 species inhabit the deeper anoxic mud down to 10 cm, both at low and high tide. One square metre was intensively sampled from four zones with different nematode faunas. At the low tide zone 58% of the nematodes were epistrate feeders, including many diatom-feeders, but in the mangrove zone selective microbial feeders made up over 60 y0 of the population, while between high water neap and high water spring, above the mangrove zone, omnivore/predators and plant root feeding nematodes increased in relative importance. Random replicate cores reliably sampled species occurrence, but gave a high variance in density estimates. Replicate aliquots from homogenised mud gave lower density variance. Nematode densities (maximum 5 x lo6 m-') were not as high as have been reported from non-mangrove estuaries in other countries, but were within the range found in mangroves elsewhere in Australia. Margalef Species Richness values ranged from 1.7 to 3.89, which is similar to values found in other mangroves mudflats in Australia. Nematode biomass ranged from 888 mg dry weight m* (383 mg C m -') at the low tide zone to 19 mg dry weight m -2 (8 mg C m -') at the upper tide level.

The fecundity of four important coleopteran stored‐grain pests, Rhyzopertha dominica (Fab.), Sitophilus oryzae (L.), Oryzaephilus surinamensis (L.) and Tribolium castaneum (Herbst.) was assessed after exposure to wheat treated with five benzoylphenyl ureas (BPUs), members of the chitin‐synthesis inhibitor group of insect growth regulators (IGRs). Chlorfluazuron was found to control all four species more effectively than triflumuron, teflubenzuron, flufenoxuron or diflubenzuron. Two weeks of exposure of parents to 0.5 mg kg −1 of all the BPUs, except diflubenzuron, inhibited almost all F1 production and all the F2 production of each species. The fecundities of T. castaneum and O. surinamensis recovered almost to their untreated levels after two weeks of exposure to 1 mg kg −1 of BPUs followed by two weeks on untreated wheat, but the effect of the exposure persisted for at least two weeks on untreated wheat in adult S. oryzae and to a lesser extent in R. dominica. The mean F1 response of the four species after two weeks of exposure to four doses showed clearly that the four newer BPUs were all similar in their overall effectiveness and significantly more effective than diflubenzuron, although diflubenzuron was equally effective against S. oryzae. At 0.1 mg kg −1 triflumuron was less effective against O. surinamensis, while teflubenzuron and flufenoxuron were not very effective against the rice weevil, S. oryzae. Chlorfluazuron provided the most effective control of all four stored‐product pest species, including the weevil, S. oryzae. The BPUs show particular potential for use in the stored‐product industry because low dosages will effectively control the rice weevil in addition to the other major pest species.

The native Eucalyptus leaf beetle Chrysophtharta bimaculata (Olivier) (Coleoptera: Chrysomelidae) has become a pest of the introduced, plantation species, Eucalyptus nitens Maiden in Tasmania, Australia. However, in the field it prefers to oviposit on the Tasmanian native species, E. regnans F. Muell. This laboratory study found that the performance of C. bimaculata larvae was superior on foliage of E. nitens compared with E. regnans. Larval development was 4 days shorter on E. nitens than on E. regnans foliage. Total food consumption per larva and relative consumption rates were about 30% lower while relative growth rates and weight of emergent adults were more than 25% higher on E. nitens than E. regnans. Efficiency of conversion (ECI) of fresh food into larval wet weight was 0.26 on E. nitens compared with 0.14 on E. regnans. Mortality of larvae feeding on E. nitens (23%) was only one third of that on E. regnans (69%), a result of high first instar mortality on E. regnans. Although the amount of foliage consumed per larva was lower on E. nitens (0.23 g vs 0.32 g), the differential mortality meant that the amount of E. nitens consumed per egg batch was 60% more than that of E. regnans. If these results occurred in the field, then the same monitored population of C. bimaculata eggs may result in heavier defoliation of plantation E. nitens than of E. regnans. These data show that the reported oviposition preference of C. bimaculata for E. regnans in the field cannot be explained by selection of host factors related to superior larval performance.

Development times, body size and oviposition rates of Chrysophtharta agricola (Chapuis) were assessed at day/night temperature regimens of 17.3/12.5°C and 24.2/17.2°C. Development times of egg, larval, prepupal and pupal stages were 8.4, 20.0, 7.1 and 12.1 days, respectively, at the higher regimen and 7.0, 14.2, 4.0 and 8.2 days, respectively, at the lower regimen. Signi®cantly larger adults were produced at the lower temperature regimen. Field adults were signi®cantly larger than adults reared in the laboratory at both temperatures but were closer in size to those reared at the lower temperature. The total number of eggs laid by females during their lifetime (13±69 days) in the laboratory ranged from 139 to 915 eggs (mean477), averaging 12 eggs per female per day. Chrysophtharta agricola had a similar life-history and development rates to the congeneric pest Chrysophtharta bimaculata Olivier and could become a serious pest of Eucalyptus nitens.

1 In Australia, eucalypt plantations require management to prevent economic damage by native chrysomelid leaf beetles, generally by aerially spraying a broad-spectrum insecticide. These beetles also pose a serious threat to plantations in other countries. 2 Various alternatives, both 'landscape' and 'control' options, for managing leaf beetles were reviewed and evaluated by a panel of experts. Options were scored on effectiveness, feasibility for use, impact on the environment, perceived social acceptability (including by certification bodies) and perceived cost. 3 None of the options were scored as well as broad-spectrum insecticide for effectiveness, feasibility and perceived cost, although virtually all of the other options scored better for environmental and social outcomes. 4 The highest ranked options were the 'landscape' option of tree improvement to reduce susceptibility to insect attack, and the 'control' option of attract-and-kill traps. The next three ranks were two 'landscape' options aimed at enhancing the effectiveness of natural enemy populations by conserving their overwintering sites and their alternative food and hosts, and then silvicultural management. 5 The best strategy for an Integrated Pest Management programme would be a combination of 'landscape' options to reduce the frequency of pest outbreaks and, if outbreaks occur, spraying with biological insecticides until attract-and-kill traps become available, possibly in combination with repellent sprays in a push-pull strategy. If control measures fail to prevent damaging defoliation, plantations could be fertilized to encourage recovery. 6 Because most of the alternative options are not yet available, many research directions were identified, with the highest priorities being to develop plantation stock that is less susceptible to defoliation and to develop attractants for leaf beetles.

No abstract

A group of insect growth regulators, the chitin synthesis inhibitors (CSIs), are being more widely used as many insects have become resistant to broad-spectrum insecticides. This study investigated the mode of action of one CSI, particularly looking at the delayed effect of treating adult insects on the survival and development of their progeny. The study describes the responses of adult stored grain beetles Sitophilus oryzae (L.) (Curculionidae) and Rhyzopertha dominica (F.) (Bostrichidae) to wheat treated with chlorfluazuron. For both species, wheat treated with chlorfluazuron reduced progeny survival at a constant rate from 1 day to 8 weeks after it had been treated. There was a direct, negative concentration-time relationship between the treatment of the adults with chlorfluazurontreated wheat and the survival and developmental rate of their progeny. Adults that were pre-exposed for one or more weeks before oviposition to wheat treated with chlorfluazuron had significantly lower progeny survival than adults that were not pre-exposed. The EC 95 values were 16-fold higher for R. dominica and 40-fold higher for S. oryzae from assays without pre-exposure, than with pre-exposure. Pre-exposure of R. dominica with 0.1 mg kg −1 and of S. oryzae with 0.4 mg kg −1 of chlorfluazuron reduced progeny survival by 95%. Higher concentrations of chlorfluazuron produced a reduction in mean population developmental time of several days. These findings have important implications for bioassays of CSIs, since pre-exposure of the adults can significantly reduce the numbers of F1 progeny. Therefore standard bioassays may seriously underestimate the efficacy of the CSI being assayed.

Chitin synthesis inhibitors, like many other insect growth regulating insecticides, do not kill adult insects but cause mortality of the immature stages. Pre‐exposure of adult stored grain Coleoptera, Rhyzopertha dominica (F.) (Bostrichidae) and Sitophilus oryzae (L.) (Curculionidae) and development of their progeny in grain treated with the chitin synthesis inhibitor, chlorfluazuron, influenced the mortality and development rate of the progeny. Hatch rate of eggs from R. dominica adults that had both developed and laid on wheat treated with 0.75 mg kg−1 chlorfluazuron was reduced by almost 50% compared with untreated eggs, with an LC50 of 0.84 mg kg−1. Eggs laid on treated wheat by R. dominica adults that had been exposed only to treated wheat for 2 weeks before oviposition showed greater reduction in hatch: 75% reduction of normal hatch rate at 0.25 mg kg−1 and almost 100% reduction at 2 mg kg−1 chlorfluazuron, with an LC50 of 0.19 mg kg−1 chlorfluazuron. X‐rays were used to monitor the development and mortality of the immature stages of S. oryzae that developed within the wheat grains. Numbers of eggs laid were not affected by chlorfluazuron treatment. The combination of pre‐exposure of adults and chlorfluazuron concentration had an additive effect on mortality of immature S. oryzae. Pre‐exposure of adults caused most mortality in the first three weeks of development (eggs and larvae), whereas development in treated wheat caused mortality from weeks 3 to 8 (pupae and adults); higher concentrations of chlorfluazuron caused higher mortality. Development in wheat treated with 1 mg kg−1 chlorfluazuron caused 12% corrected overall mortality of progeny while pre‐exposure to the same concentration and development in untreated wheat caused 29% corrected mortality. Pre‐exposure combined with development in wheat treated with 1 mg kg−1 caused 30% corrected mortality. Thus, pre‐exposure of adults appears to have a greater effect on mortality of S. oryzae progeny than development of immature stages in treated grain. Development on treated grain had no effect on development rate. Pre‐exposure of adults did not appear to affect the rate of immature development, as assessed by X‐rays, but did slow the emergence of adults, lengthening development time by about 2 days. This significant, additive effect of pre‐exposure of adults on the mortality of their progeny will enhance the toxicity of chitin synthesis inhibitors such as chlorfluazuron, since most adults receive treatment when the immature stages are treated in crops either before they are harvested or in storage. Assessing the proportion of eggs that hatch from pre‐exposed adults would be a simpler bioassay for CSIs.