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Black peach aphid, Brown peach aphid, Peach trunk aphid, Giant black bark aphidOn this page: Identification & Distribution Biology & Ecology Life cycle & Development rates Laboratory studies Natural enemies Other aphids on the same host Damage Biological Control
Identification & Distribution
Adult apterae of Pterochloroides persicae are oval in shape with a double row of large pigmented spinal tubercles on the dorsum (see pictures below). The body colour is grey with transverse rows of dark spots with brown centres. The antennae and legs are barred with red-brown and black bands. The siphunculi are as large pores on broad dark hairy cones. Pterochloroides persicae are large aphids, with body length of the adult apterae between 2.7 and 4.2 mm.
First image above, by permission, copyright Karim Mimoun, all rights reserved.
Pterochloroides persicae form dense colonies preferably in the shaded part of the tree. They produce copious amounts of honeydew and are usually attended by ants. They probably originated from East-Central Asia and dispersed westwards along traditional trade routes in past centuries along with their host trees. In recent decades Pterochloroides persicae has spread westwards and southwards into Europe and the Middle East where it has become an important pest of peach and almond trees.
Biology & Ecology
Life cycle & Development rates
1). Field observations
Talhouk (1972) carried out field investigations on Pterochloroides persicae and Brachycaudus helichrysi, two common aphids of the almond tree in Lebanon. In the Lebanon, almond trees are grown on both sides of the Lebanon range with the same species aphids found on both sides. On the warmer western side Pterochloroides persicae reproduces parthenogenetically on the bark of almond throughout the year. In the east, which is dryer and cooler, with freezing temperatures in winter, sexual females and males appear in October-November. Winter eggs are laid from late October to mid-January and hatch between mid-January and mid-March. Adult fundatrices are present from mid-April, fundatrigeniae until early May, and alates develop in June-July. These latter migrate to other almond trees or to peach, and colonies at this time are small with individuals widely scattered. Pterochloroides persicae does not depend on attendance by ants for survival as it can eject its honeydew efficiently, but ants are often present collecting existing honeydew deposits. It has few predators and apparently no parasites in the Lebanon.
Darwish et al. (1989) studied the biology and ecology of Pterochloroides persicae, under field conditions on peach trees in Shebin El Kom, Egypt. The aphid is anholocyclic in Egypt, developing through 18 overlapping parthenogenetic generations throughout the whole year. There were two annual peaks in the proportion of alatae viviparae in the population, the major one at the end of April and May, and another one at the end of October. These alatae spread the infestation.
Mahendiran, G. et al. (2018) reported Pterochloroides persicae for the first time from the Kashmir Valley, India. The aphid overwintered as eggs - these began to hatch from the first week of March. The first noticeable build up of the species was observed during the second week of May, with alatae first observed about the same time. The population density peaks in May and then declines in June and July. The second population build-up starts towards the end of July, with many alates in late August, and the population peaking in September-October. Eggs are laid from late October.
2). Laboratory studies
Khan et al. (1998) evaluated different hosts and developmental biology and reproductive potential of Pterochloroides persicae under laboratory conditions. Branches from peach, plum, apricot and pear trees were used to find a suitable host for mass-rearing of the species under laboratory conditions. Peach was the most suitable host, followed by plums, apricots and pears. During the experimental period of 21 days the aphid population on peach peaked 20 days after the release of third instars. On plum branches, the aphid density peaked after 16 days, and on apricot branches after 17 days. Aphids did not settle on pear branches and died by the 5th day after release. A total of 17-55 nymphs/female were raised in the entire reproductive life with an estimated reproductive rate of 4.51 nymphs/female per day.
Mdellel et al (2011) studied the population behaviour and distribution of brown peach aphid (Pterochloroides persicae) on different host trees. Five host plants were identified (peach, almond, plum, apricot and apple). Population dynamics studies showed that aphids first appeared on roots and then moved up to cover the collar and the trunks, where populations behaved differently. The effects of host and temperature on biotic potential were studied under controlled field conditions. Adults were reared individually at different temperatures (15, 20 and 25°C) on peach, almond, plum and apricot tree branches. 20°C is the best temperature for the reproductive potential of Pterochloroides persicae and peach was the best host for the species in terms of mass rearing.
Mdellel (2012) identified two mitochondrial haplotypes in Pterochloroides persicae that differed in a single nucleotide associated with different feeding sites. The nuclear gene analyzed, however, failed to reveal any variability in this species. The variability found at the mitochondrial locus was related to the season of aphid sampling and with the site of feeding, with haplotype I mostly detected in samples collected in spring and summer on trunks and branches and haplotype II only detected in aphids collected in autumn on roots. The observed pattern of molecular variation suggests the presence of two clonal races of Pterochloroides persicae coexisting in the studied area differentially adapted to conditions prevalent in the alternative seasons and/or to different feeding sites.
Mdellel et al.(2015) described the morphological variation of Pterochloroides persicae individuals originating from three host-plants, peach, almond and plum, from two localities in Tunisia which have similar climatic conditions. 13 morphological characters were investigated in 90 wingless aphids collected from plants of the three host species. A significant difference was observed in length of antennal segment I, IV and V, in length of body and in length of siphunculi. Results indicate that host plant species can affect the morphology of Pterochloroides persicae.
Rakhshani et al (2005) carried out a survey on the distribution and seasonal occurrence of Pauesia antennata in some provinces of Iran. Pauesia antennata was the only specific parasitoid of Pterochloroides persicae that occurred in all of the sampling areas where the aphid was active. Activity of the parasitoid in spring was severely reduced by chemical treatments. Because of the host specificity, distribution and synchronization with its host, Pauesia antennata can be an effective biological control agent. Five species of hyperparasitoids, the megaspilid Dendrocerus carpenteri , the encyrtid Syrphophagus aphidivorus, the pteromalids Pachyneuron aphidis and Euneura lachni, and an eulophid Tetrastichus species were active in the studied area.
Mdellel et al (2015) noted that Pauesia antennata is considered to be the most effective biological control agent of Pterochloroides persicae. He therefore determined selected biological parameters of the parasitoid. The longevity of the mature parasitoid was 3.90 ± 0.22 days, the developmental time was 14.48 ± 1.05 days and the life span was 19.46 ± 0.68 days. The maximum flight activity and oviposition were observed at the second and third days of the parasitoid lifespan. The parasitism, emergence rates and the sex ratio were affected by the variations in the number of Pterochloroides persicae relative to each population of the parasitoid.
Mdellel & Ben Halima (2015) carried out a study from 2010 to 2014 to identify natural enemies associated with colonies of Pterochloroides persicae in cultivated Prunus sp at different sites in Tunisia. The predators recorded were principally the coccinellid Coccinella algerica, two syrphid, Episyrphus balteatus and Metasyrphus corollae, and one lacewing Chrysoperla carnea. Coccinella algerica was observed from February to June and the highest number of adults and larva was registered on April in the three studied sites. Nevertheless, good numbers of syrphid flies and lacewing were observed from April to June respectively in Chott Mariem and Jammel.
Other aphids on same host:
Pterochloroides persicae has not yet been recorded in Britain.
Damage and control
Dense colonies of Pterochloroides persicae on peach trees will cause direct feeding damage, causing desiccation of the affected branch, and defoliating the tree. Sooty mould may grow due to the presence of honeydew, can reduce the tree's photosynthetic capacity, decrease the harvest and reduce its quality. Control of this pest can be chemical or biological. If the attack was intense the previous year, preventive treatment can be made before flowering with a pyrethroid such as Deltamethrin (Moya, 2014). Through the spring and summer, it should only be treated when the aphid is present - or if honeydew appears on the leaves or at the trunk base. Appropriate insecticides include Imidacloprid (maximum one application in spring) or Lambda-cyhalothrin (maximum two treatments per year). However, chemical treatment of fruit trees carries important health and environmental risks - and may reduce aphid control by predators and parasitoids - hence should be avoided whenever possible.
By the 1990s Pterochloroides persicae had assumed pest status on peach and almond in several countries in southern Europe, the eastern Mediterranean, North Africa and in the Arabian peninsular. In Yemen it was reported to be causing severe damage. Distribution records suggest that it is gradually increasing its range westwards and southwards from a focus in the eastern Mediterranean and Central Asia. Kairo & Poswal (1995) reviewed the taxonomy, worldwide distribution, pest status, biology and ecology of Pterochloroides persicae and options for integrated pest management, with particular attention given to the prospects for biological control. Several braconid parasitoids, including Pauesia antennata and an Aphidius species, were identified as promising biological control agents.
In the late 1990s there was a successful biological control programme carried out against Pterochloroides persicae on peach in Yemen, which was reviewed by Cock et al. (2015). By the mid-1990s the aphid had spread through Yemen and was inflicting severe losses on the country's 70,000 farmers who grew fruit tree crops for sale and home consumption. Yields and fruit quality were affected, and in some areas the aphids were causing tree decline. Chemical control meant spraying every 2 weeks, which was costly and had environmental and health implications. An internationally funded emergency response project was set up with the Department of Plant Protection (GDPP) in Yemen. Literature searches indicated that an aphidiine parasitoid, Pauesia antennata was the most commonly recorded and predominant natural enemy of Pterochloroides persicae in Central Asia. Extensive surveys in Pakistan indicated that it was the only parasitoid of late instars/adults there and it was prioritized for further study. Extensive studies of both the aphid and the parasitoid led to a biological control proposal, and clearance for introduction of the parasitoid was received in December 1996.
Studies by Abdul-Hak (1997) in Yemen indicated that before Pauesia antennata was released, Pterochloroides persicae was present throughout the year, reproducing parthenogenetically at all surveyed sites. Populations increased from mid-September through to the end of July with peak populations recorded from the beginning of May to mid-July. Female alates produced at the end of April/beginning of May dispersed to other orchards. Abdul-Hak's studies also indicated that indigenous natural enemies were limited to generalist predators which were clearly not keeping the exotic aphid in check. Breeding colonies of Pauesia antennata were established and by July the GDPP had reared more than 65,000 parasitoids, and over 50,000 of these were released in the field. At the peak of production 1000 parasitoids a day were being released. Releases were concentrated at three main sites around Sana'a and within 2 months the aphid populations in these areas, and beyond, had completely collapsed as a result of parasitoid attack. Within 2 months, Abdul-Hak was finding parasitism rates of approximately 40-90% in orchards within 25 km of Sana'a. After two months the parasitoid was found at farms more than 50 km away from release sites, and after four months up to 120 km away from release sites. The release programme was extended to the south and south-east to increase dispersal, and successful country-wide control was achieved as the parasitoid spread and established in Yemen. Just under 350,000 parasitoids were released in all.
Abdul-Hak's data also indicated that after parasitoids were released, the only orchards where Pterochloroides persicae populations did not decrease dramatically was in those where farmers continued to use chemicals. He also cited a fall in pesticide use in stone- and pome-fruit orchards country-wide from 22 tonnes in 1995 at the height of the outbreak, to 2.5 tonnes in 1998, by which time Pauesia antennata had controlled the pest; the cost of pest control fell nine-fold in the same period. He did report a potential hyperparasitoid problem: two pteromalid species newly recorded for Yemen were identified from the parasitoid. Although hyperparasitism was less than 30% in 1997 and caused no problems in that year, in 1998, it exceeded 75% and even 80% in places and thus became a problem. The approach was to treat trees in affected areas with pesticide and release fewer Pauesia antennata. Hyperparasitism subsequently fell back to around 30%.
There seems little room for doubt that the introduction of Pauesia antennata led to the successful biological control of brown peach aphid. The classical biological control programme was proclaimed a success in Yemen. The front page of the Yemen Times for 6-12 October 1997 carried the headline, "Over 7.6 million trees saved: a biological enemy for the peach stem aphid introduced in Yemen". Although the benefits have not been quantified, they are evident from the qualitative information available. Livelihoods and incomes were preserved, avoiding the use of substantial amounts of insecticides, for the 70,000 farmers who grew fruit tree crops for sale and home consumption. If we accept the figure of 7.6 million fruit trees saved (that is a little over 100 trees per farmer) the loss of which would have been significant.
Rihem et al. (2017) made preliminary observations on releases of Pauesia antennata to control Pterochloroides persicae. Adult developmental time, rate of mummification, rate of emergence and sex ratio of Pauesia antennata were determined in a greenhouse for 2 generations. In the field, 6 couples of the parasitoid were introduced to 3000 host individuals and then the presence of mummies of Pterochloroides persicae on almond trees proved the host's acceptance with a 35% rate of mummification.