Biology, images, analysis, design...
|"It has long been an axiom of mine that the little things are infinitely the most important" |
Black peach aphidIdentification & Distribution Biology & Ecology Damage & Control
Identification & Distribution:Adult apterae of Brachycaudus persicae (see dark individuals in pictures below) have a shiny sclerotized dark brown or black dorsum. The black flanged siphunculi are more than 0.1 times the body length, clearly more than twice the length of the cauda and longer than the hind tarsi (distinguishes from Brachycaudus schwartzi which has markedly shorter siphunculi). The cauda is dark, short and broad. Immature stages of Brachycaudus persicae are yellowish to dark brown. The body length is 1.5-2.2 mm.
The fused apical rostral segments of the aptera are shorter than 0.175 mm in length. Winged spring migrants have similar coloration to the apterae, and have 23-51 secondary rhinaria on the third antennal segment, 9-21on the fourth, and 1-6 on the fifth. Brachycaudus persicae nymphs are yellowish-brown to dark brown.
Brachycaudus persicae is most commonly found in large spring colonies on young stems of peach (Prunus persica) or almond (Prunus armeniaca), often persisting into the summer on root suckers. In Europe there is some evidence of host alternation from Prunus to Orobanchaceae, but Brachycaudus persicae may remain all year on Prunus. Aphids apparently of this species are also widely distributed on peach outside Europe, including the Middle East, southern Africa, Australia, New Zealand, and North and South America.
Biology & Ecology:
We have only found Brachycaudus persicae on one occasion - on peach, nectarine and apricot in glasshouses at Hadlow College - where these pictures were taken.
There seems to be little published information on the ecology of Brachycaudus persicae either on its primary or secondary hosts. Secondary hosts are known to include Euphrasia, Melampyrum, and Rhinanthus where they live on the above-ground parts (Heie 1992).
Several types of natural enemy were present on the aphid colonies. A bright orange Entomopthora fungal pathogen (see above) was especially prevalent.
The dense aphid colonies produced abundant honeydew which attracted varous insects to feed on it such as the Chrysopa carnea adult shown below.
Damage and control
Heavy infestations of Brachycaudus persicae can be very damaging to host trees, especially in greenhouses. Shoots are distorted, growth is retarded, and young plants may be killed.
Shearer & Frecon (2002) investigated whether preplant root dips or postplant sprays or drenches could be used to control the black peach aphid on young peach trees. In greenhouse trials, Brachycaudus persicae died after being placed on peach trees that had their roots dipped in the insecticide imidacloprid before planting. All rates tested controlled this aphid. Approximately 50% of untreated trees died from Brachycaudus persicae infestations in greenhouse studies. Results from a field experiment show that peach trees root-dipped in imidacloprid before planting or drenched with imidacloprid after planting eliminate aphid infestations and prevent root colonization for at least a year.
Fos & Massonié (1993) showed in laboratory experiments that apterous and alate adults transmitted plum pox virus to seedlings of two peach cultivars. It was thought that the aphid might participate in the natural spread of plum pox diseases because it colonizes peach, apricot and plum orchards throughout the year.