Effects of augmentative releases of eggs and larvae of the ladybird beetle, Adalia bipunctata, on the abundance of the rosy apple aphid, Dysaphis plantaginea, in organic apple orchards

The impact of augmentative releases of larvae and eggs of the indigenous ladybird beetle Adalia bipunctata (L.) (Coleoptera: Coccinellidae) against the rosy apple aphid Dysaphis plantaginea Pass. (Homoptera: Aphididae), a major pest insect on apple trees, was assessed in field experiments in Switzerland, during 1997. In a first experiment, eggs and larvae were released on 3-year old apple trees infested with five aphids at four different predator-prey ratios (0:5, 1:5, 1:1, 5:1). In a second experiment, eggs and larvae were released at a predator-prey ratio of 5:1 on branches of apple trees naturally infested with aphids. In both experiments, the interaction with ants was taken into account and the releases were done at two different times in spring. The results showed that an augmentative release of larvae significantly prevented the build-up of colonies of D. plantaginea. Significant reductions in aphid numbers were recorded at the two highest predator-prey ratios, 1:1 and 5:1. Larvae were efficient just before flowering of apple trees at a time when growers normally have to spray their trees. On trees where ants were present the larvae of A. bipunctata were significantly less efficient. Effects of eggs of A. bipunctata, however, were less reliable. At the first date of release (5 April), they did not hatch, probably as a consequence of bad weather conditions.     

Isolation of microsatellite markers from the rosy apple aphid Dysaphis plantaginea

We report the development of five polymorphic microsatellite loci from the aphid Dysaphis plantaginea, a serious pest on apple. Using a multimotif enrichment protocol, we have isolated loci that are proving to be valuable tools for studying aphid movement at both between‐county and within‐orchard scales.     

Colonization of apple orchards by predators of <Emphasis Type="Italic">Dysaphis plantaginea</Emphasis>: sequential arrival,response to prey abundance and consequences for biological control

Episyrphus balteatus (DeGeer) (Diptera: Syrphidae), Adalia bipunctata (L.) (Coleoptera: Coccinellidae) and Aphidoletes aphidimyza (Rondani) (Diptera: Cecidomyiidae) are the three most abundant natural enemies of Dysaphis plantaginea Passerini (Homoptera: Aphididae) in Asturian (NW Spain) apple orchards. They attack this aphid in sequence: E. balteatus arrived first, followed by A. bipunctata and then by A. aphidimyza. The cecidomyiids arrived too late to have a regulating effect. The syrphids laid an average of 2.3 ± 1.7 eggs per aphid colony and the coccinellids 18.4 ± 9.9 regardless of the degree of the infestation rates of the apple shoots. This value corresponds to the size of an egg batch laid by one female. Therefore, these aphid predators did not respond numerically to the abundance of the pest. The results of this study indicate that natural populations of syrphids and ladybird beetles are unable to control D. plantaginea, and therefore a more complex strategy than waiting for natural enemies is required.     

Effects of augmentative releases of the coccinellid, Adalia bipunctata, and of insecticide treatments in autumn on the spring population of aphids of the genus Dysaphis in apple orchards

The impact of augmentative releases of indigenous predators and insecticide applications to control the autumn aphid forms of the genus Dysaphis (Homoptera: Aphididae), major pest insects on apple trees, was assessed in one-year field experiments in Switzerland. Eggs and larvae of the two-spot ladybird beetle Adalia bipunctata (L.) (Coleoptera: Coccinellidae) were released on 4-year old apple trees in various numbers at five different dates in autumn 1998 when sexuales of the aphids were present. Additionally, Pyrethrum HP was sprayed at the same five dates to compare the effectiveness of these augmentative releases to a commonly applied insecticide. Augmentative releases of larvae before mid-October significantly prevented the deposition of overwintering eggs by aphids of the genus Dysaphis and consequently reduced the number of hatched fundatrices in spring, 1999. There was a significant negative functional response among the number of released coccinellid larvae in autumn 1998 and the number of observed fundatrices on apple trees in spring 1999. Applications of Pyrethrum HP before mid-October were more effective than augmentative releases of larvae of A. bipunctata. The release of coccinellid eggs had no impact on the number of fundatrices of the genus Dysaphis in the next spring because they did not hatch due to bad weather conditions. The weather conditions in autumn seemed to have an impact on the autumn migration of the winged aphids back to their primary host. The prevention of egg deposition of aphids in autumn is a promising control strategy and deserves further exploration for practical use.     

Effects of autumn kaolin treatments on the rosy apple aphid, Dysaphis plantaginea (Pass.) and possible modes of action

Abstract:  Autumn applications of the repellent processed-kaolin particle film (Surround® WP) might be an alternative to the insecticides commonly used in spring to control the rosy apple aphid, Dysaphis plantaginea (Pass.) (Hom., Aphididae). To assess the mode of action and the impact of kaolin on autumn forms of D. plantaginea , trials were conducted in field cages and in open-fields in autumn 2003. Choice and no-choice experiments in field cages showed that winged aphids landed in significantly lower numbers and gave birth to significantly fewer females on kaolin-treated branches compared with the untreated control. In a first open-field trial, single applications at 10 different dates and with two different concentrations of kaolin were conducted after harvest to assess the influence of the kaolin concentration on the autumn forms of D. plantaginea . No differences were found between the different concentrations and spraying dates. In a second open-field trial, single and multiple applications of kaolin were tested at different dates after harvest. Repeated applications of kaolin significantly reduced females in autumn and fundatrices in spring, whereas single kaolin treatments had no significant effect on D. plantaginea . None of the kaolin treatments reduced aphids below the economic threshold. In conclusion, kaolin showed promising results to control autumn forms of D. plantaginea. However, with a more detailed forecasting model for the autumnal flight of this aphid, treatments could be conducted more precisely and more effectively, especially in years with exceptional climatic conditions, such as in 2003.     

DL‐β‐Aminobutyric acid application negatively affects reproduction and larval development of the rosy apple aphid,Dysaphis plantaginea,on apple

The rosy apple aphid, Dysaphis plantaginea (Passerini) (Hemiptera: Aphididae), is one of the major pests of European apple orchards, commonly controlled by the use of synthetic insecticides. In the present work, the non‐protein amino acid DL‐β‐aminobutyric acid (BABA), known to induce plant resistance against a wide range of abiotic and biotic stresses, has been tested for its protective effect against this pest on apple. We first verified the lack of any contact effect of BABA on the insect itself. Next we applied BABA as a soil drench to apple and monitored its effect on the population development of aphids after artificial infestation. We demonstrated that BABA strongly reduced the population growth and that this compound severely affected various life‐history characteristics of the aphid such as female longevity and fecundity, nymph mortality, and larval development.     

Intraguild responses of aphid predators on apple to the invasion of an exotic species, Harmonia axyridis

The effects of the invasion ofan exotic predator, Harmonia axyridis(Pallas) (Coleoptera: Coccinellidae), wereinvestigated using three experiments on theecology of aphid predators on apple. Oneexperiment, 1992, was collected prior to theH. axyridis invasion, and two others,1996 to 1997 and 1999 to 2000, were collectedafter the invasion. Except for one year, 1999,H. axyridis was the dominant coccinellid,replacing the formerly dominant Coccinellaseptempunctata L. (Coleoptera: Coccinellidae),another exotic species. The dominance of H. axyridis was greater among larvae thanamong adults. There was no apparent effect ofthe H. axyridis invasion on abundance ofthe predator, Aphidoletes aphidimyza(Rondani) (Diptera: Cecidomyiidae) and apossible positive effect on the abundance ofchrysopids (Neuroptera: Chrysopidae). Principal component analysis indicated thatalthough individual species were affected, theoverall effect of H. axyridis invasion onthe predator guild as a whole was negligible. The data indicate that the interaction betweenthe two exotic species, H. axyridis andC. septempunctata, may be allowing nativecoccinellids to become more abundant on applethan when C. septempunctata was thedominant coccinellid.