InfluentialPoints.comBiology, images, analysis, design...
| Aphids | Find them | How to ID | AphidBlog |
| InfluentialPoints.com Biology, images, analysis, design... |
|
"It has long been an axiom of mine that the little things are infinitely the most important" |
|
|
How to get rid of apple aphidsApple aphids - Control and IdentificationOn this page: Which aphids damage apples How to get rid of apple aphids First check the species! Host resistance Physical removal Biological & integrated control Chemical control Species lists How to identify apple aphids How to identify apple speciesWhich aphids damage apple?About 50 species of aphid feed on apple worldwide, of which 21 are known in Britain. Of these, the rosy apple aphid (Dysaphis plantaginea) is probably the most damaging because it induces crumpled leaf galls at the growing points of the apple as shown in the first picture below. Wingless (=apterous) Dysaphis plantaginea vary in colour from dull pink to purplish grey (see second picture below). They live in large aggregated colonies, often concealed from sight within the galls.
The other most damaging aphid to apple is the woolly apple aphid (Eriosoma lanigerum, see third picture above). Wingless females of woolly apple aphids live in dense colonies on the roots, trunk or branches of apple where it can be a serious pest, often causing deformation and cancer-like swellings of bark. How to get rid of apple aphidsFirst check the species!Trying to kill every potential pest is a waste of money, and is liable to kill-off the insects (and even birds) that normally keep pests in check. If you want to get rid of apple aphids, concentrate on getting rid of rosy apple aphids and woolly apple aphids. Two other aphid species, the green apple aphid (Aphis pomi) and the apple-grass aphid (Rhopalosiphum oxyacanthae) will often be present as well, but they seldom cause significant damage except in nurseries and on young trees. Both of them are coloured green (see pictures below) and are easy to distinguish from the rosy apple aphids in leaf galls and the waxy colonies of woolly apple aphids on the trunk. There are also many other aphid species which occur rarely on apple, but they will not affect your fruit yield. Host resistanceAll commercially grown apples are considered susceptible to rosy apple aphid in Britain (DEFRA/AHDB) but some, such as Bramley, Discovery, Egremont Russet, Golden Delicious and Jonagold, are highly susceptible. Razmjou et al. (2014) evaluated resistance in seven apple cultivars to rosy apple aphid under greenhouse and field conditions in Iran. Among the cultivars tested, the Shaki cultivar was moderately resistant to rosy apple aphid and had the potential to be used in the integrated management of this aphid. Golden Delicious, on the other hand, was highly susceptible. Host plant resistance is considered an essential component of integrated management of this insect pest. Research is also actively underway to investigate the options for breeding varieties that are resistant to the woolly apple aphid. Physical controlIf you are worried about large numbers of green apple aphids on the growing shoots of young apple trees, they can be removed using a well-aimed jet of water from a hand-held sprayer. This damages the aphids, not the things that eat them. For rosy apple aphid, you will need to pick off the crumpled leaf galls containing their colonies since the leaf galls provide them protection against water jets (and insecticides). The number of woolly apple aphids can be greatly reduced by scrubbing the bark with ordinary soapy water, but it will probably take several such scrubbings to eliminate the infestation and, sooner or later, they will probably return... Biological & integrated controlConservation biological control in organic orchards, primarily targeted against Dysaphis plantaginea, has been widely tested with varying degrees of success. Wyss (1995) looked at the effects of weed strips on aphids and aphid-eating predators in an apple orchard in Switzerland. Selected weeds were used to attract predators such as anthocorid bugs. Both Dysaphis plantaginea and Aphis pomi were significantly less abundant in the area with weed strips than in the control area during the period. Brown & Mathews (2007) examined the potential for conservation biological control, in particular the effect of interplanting extrafloral-nectar-bearing peach trees. Kehrli & Wyss (2001) assessed the impact of augmentative releases of indigenous predators (specifically eggs and larvae of the two-spot ladybird beetle (Adalia bipunctata) ) and insecticide applications to control the autumn aphid forms of Dysaphis plantaginea. The picture below shows an adult two-spot ladybird with a colony of another waxy aphid (Rhopalosiphum padi) on bird cherry, that it was rapidly consuming.
The released predators significantly reduced the deposition of overwintering eggs by aphids and consequently reduced the number of hatched fundatrices in spring, 1999. The authors felt prevention of egg deposition of aphids in autumn was a promising control strategy and deserved further exploration for practical use. Note that it is not worthwhile to release adult ladybirds as they are most likely to fly away rather than remain on your apple trees. Solomon et al. (2000) gave a rather pessimistic review of the potential for biological control of Dysaphis plantaginea with predators in northern and central Europe. Several groups of naturally occurring polyphagous predators, such as chrysopids, coccinellids, syrphids and spiders, prey on a Dysaphis plantaginea in orchards, contributing to the reduction in pest populations. However, they are unlikely by-themselves to prevent pest-damage fully and reliably. An exception, due to its abundance in orchards, is the common earwig, Forficula auricularia, although this predator may also cause some fruit injury. For more details on biological control of rosy apple aphid see biological & integrated control of rosy apple aphid. Approaches to biological control of Eriosoma lanigerum have focused on integrated pest management with use of resistant apple varieties, and more specific insecticides that do not kill the natural enemies. There have been several investigations of the use of firethorn (Pyracantha) hedges around orchards to provide a source of parasitoids of woolly apple aphid, most particularly Aphelinus mali. In addition this parasitoid has been widely introduced to countries where it does not occur naturally (=classical biological control) with considerable success. In Australia earwigs (Forficula auricularia) in combination with introduced Aphelinus mali reduced woolly aphid infestations below the action threshold set by commercial growers. Studies in America have given similar results - see video on Can earwigs be beneficial in some orchards? Earwigs can be encouraged by providing simple refuges - such as using a roll of corrugated cardboard in a plastic bottle attached upside down to the trunk of a tree. For more details on biological control of woolly apple aphid see biological & integrated control of woolly aple aphid. Chemical controlDEFRA/AHDB summarise current methods for chemical treatment of orchards for this pest. Pirimicarb used to be the most commonly used insecticide for apple aphid control, but has now been withdrawn. A newer selective insecticide is Flonicamid (Mainman), a pyridincarboxamid that inhibits the feeding behaviour of aphids. It has been shown to provide good control of rosy apple aphid, and is available to gardeners. It has however proved less effective against woolly apple aphid for which the (very new) Batavia (pirotetramat) may be the best option (as far as we know not yet available to gardeners). Two neoneonicotinoids (acetamiprid and thiacloprid) are also effective against rosy apple aphid. Acetamiprid is highly selective and is also effective against mussel scale (Lepidosaphes ulmi). Thiacloprid is active against a wide range of apple pests, but does have adverse effects on earwigs which are important aphid predators, and has been banned as harmful to bees in some European Union countries. Synthetic pyrethroids, especially deltamethrin (e.g. Provanto Ultimate Fruit and Vegetable Bug Killer), should be avoided as their use is harmful to predatory mites and other insects. Rosy apple aphid is normally controlled in commercial apple orchards by an application of an aphicide in the spring. In organic orchards, early season sprays of fatty acids are the preferred treatment but control is often inadequate since fatty acids are only contact acting. Cross et al. (2007) showed that control of the aphid in the autumn with 2-3 sprays of the organically permitted insecticide pyrethrum was moderately effective. The optimum time for spraying was early-mid October, coinciding with the start of migration of males and before mating and egg laying. In most of Europe neem oil is used to control rosy apple aphid in organic orchards, but it is not registered for use in the UK. Species listsBlackman & Eastop list more than 49 species of aphid which feed on apples (Malus domestica, including Malus pumila & Malus sylvestris) worldwide (Show World list). Of those aphid species, Baker (2015) lists 21 as occurring in Britain (Show British list).
They are mostly in 5 genera: Aphis, Dysaphis, Eriosoma, Ovatus and Rhopalosiphum. How to identify Apple AphidsAbout six species are commonly encountered on the orchard apple (Malus domestica) and crab apple (Malus sylvestris) in UK: Aphis pomi, Rhopalosiphum oxyacanthae, Dysaphis plantaginea, Eriosoma lanigerum, Ovatus crataegarius, Dysaphis devecta) - with an additional invasive species, Aphis spiraecola, likely to become commoner in future. These 7 species are listed below in rough order of abundance. Assistance on distinguishing the two species of apple is given below. Aphis pomi (Green apple aphid)Perhaps the most common aphid on apple they seldom cause significant damage, except to young trees. The Aphis pomi aptera (below first) is bright apple green or yellow green and is not wax-powdered. The abdominal dorsum is pale and usually entirely membranous, although rarely a small sclerite or short bar may occur on the spine of tergite 5. The fused last two rostral segments are more than 120 μm in length and marginal tubercles are present on abdominal tergites 2-4 (the latter two characters distinguish Aphis pomi from the very similar invasive Aphis spiraecola). The siphunculi and cauda are conspicuously blackish. The cauda has 10-19 hairs (rarely less than 13). The body length of an adult aptera is 1.2-2.2 mm.
Aphis pomi alates (above second) have a black thorax. The alate abdomen is green, usually with 3 pairs of weakly pigmented black lateral circular spots on the anterior abdominal segments, and a semicircular spot in front of and behind each siphunculus. The green apple aphid does not host alternate. It feeds in dense colonies on the young shoots and undersides of leaves of apple (Malus species) and related plants including pear (Pyrus), hawthorn (Crataegus), Sorbus and Cotoneaster, causing some leaf curl but with little effect on fruit production. Colonies are often attended by ants. Sexual forms occur in autumn, and after mating the females lay sometimes large egg masses on the twigs. It is generally common and is distributed throughout Europe, north Africa, Asia eastwards to India and Pakistan, and North America. Rhopalosiphum oxyacanthae (= insertum) (Apple-grass Aphid)Often found on apple, but only in spring, after which they move to their 'secondary hosts'. Rhopalosiphum oxyacanthae apterae (see first picture below) on apple are small light green to yellow-green aphids that are elongate-oval in shape. They have fairly well-marked dark green stripes down the centre of the back with cross bars and along each side. The 5-segmented antennae are about a third the length of the body. The frontal head tubercles are low, with the median frontal tubercle about the same height as the antennal tubercles. The siphunculi are quite short - about one tenth as long as the body - slightly swollen subapically, and pale with dusky tips. The body length of the adult aptera on the primary host is 2.1-2.6 mm.
Winged Rhopalosiphum oxyacanthae viviparae (see second picture above) have a blackish head, thorax and siphunculi and a green abdomen with some brown plates and pigmentation. The apple-grass aphid aptera on its secondary host - grass roots - (see first picture below) is pale green, yellowish green or bluish green with no clear markings. The antennae are normally 5-segmented and much shorter than half the body length. The siphunculi are brown, 0.11-0.13 times the body length and nearly twice the length of the cauda. The body length of the apterous adult on the secondary host is 1.1-1.9 mm. The apple-grass aphid host alternates between apple and related species (Rosaceae: Cotoneaster, Crataegus, Malus, Pyrus, Sorbus) and the roots of various grasses (Poaceae). It has a sexual stage in its life cycle with eggs laid on apple. The first generation in March induces curling perpendicular to the mid-rib of the young leaves of the primary host. Apple-grass aphids may be attended by ants. Winged forms migrate in late May-June to the underground parts of various grasses, but a few colonies may persist into summer on primary hosts. Because most aphids leave apple after one generation, this species causes minimal damage. Rhopalosiphum oxyacanthae is found in Europe and Japan. Dysaphis plantaginea (Rosy apple aphid)Fairly common on apple, and tends to be the most damaging because of leaf galling. Dysaphis plantaginea is a medium-sized globe-shaped aphid. They induce yellowish crumpled leaf galls on apple in spring (see first picture below). The adult apterae are dull pinkish to slate grey or purplish grey with a greyish-white wax bloom (see second picture below). The antennae of apterae are at least as long as distance from the frons to the base of the siphunculi. The siphunculi of Dysaphis plantaginea are quite long compared to other Dysaphis species, blackish brown and tapered with flanged tips. The cauda is dark, short and triangular. The Dysaphis plantaginea aptera body length is 2.1-2.6 mm.
Alatae from galls (see third picture above) have a reddish-grey abdomen with an extensive dark dorsal patch. The rosy apple aphid host alternates from apple (Malus spp.) where it forms yellowish crumpled leaf galls to plantain (Plantago) where it forms colonies along the veins on the undersides of the leaves. Aphids remain on apple until mid-summer by which time attacked shoots are stunted and twisted. Colonies are often attended by ants. Fruit production may be reduced as fruits from infested shoots are small and malformed. Dysaphis plantaginea occurs in Europe, Africa, much of Asia and North and South America. Eriosoma lanigerum (Woolly apple aphid)Not common, and its colonies grow slowly, but hard to get rid of and can be very damaging in nurseries. Mature and immature wingless females of Eriosoma lanigerum are purple, red or brown and are covered in thick white flocculent wax (see first picture below). This is produced by distinct wax glands on the head and along the thorax and abdomen. The six segmented antennae are 0.17-0.24 times the length of the body. The body length of Eriosoma lanigerum apterae is 1.2-2.6 mm. The fourth instar alatiform nymph of Eriosoma lanigerum (see second picture below) is reddish brown with very small wax glands and consequently much less wax.
Winged viviparous females (shown in the third picture above) have a brown-black head and thorax and a brown abdomen. Their antennae are about 0.4 times the length of the body. The siphunculi are reduced to a pair of rings on the posterior dorsum of the abdomen. Wingless females of woolly apple aphids live in dense colonies (see picture top) on the roots, trunk or branches of the (secondary) host apple (Malus) where it is a serious pest, often causing deformation and cancer-like swellings of bark. Eriosoma lanigerum is also found on related species, such as hawthorn (Crataegus) and Cotoneaster. In most parts of the world, sexual forms have never been found on apple, and overwintering is in fissures on the lower part of the trunk and on the roots. sexuparae producing oviparae and males on apple have been reported in a few countries, with eggs laid on apple, but no resultant fundatrices have been found. In North America aphids of the Eriosoma lanigerum group (which includes several species closely-related to Eriosoma lanigerum, in USA) induce leaf-rosette galls on American elm (Ulmus americana). Some authorities classify such aphids as Eriosoma lanigerum. Others believe that Eriosoma lanigerum (in the strict sense) has lost its primary host and classify the (elm-feeding) host-alternating species as different species within the Eriosoma lanigerum species group. Ovatus crataegarius (Hawthorn - mint aphid)Sometimes found on apple and seldom causes significant damage, but a pest of mint. The aptera of Ovatus crataegarius is yellow-green to apple-green, sometimes mottled with darker green markings (see first two pictures below on primary & secondary host). Their antennae are curved, and about 1.2-1.5 times as long as the body. The antennal terminal process is more than 5 times the length of the base of antennal segment VI. The antennal tubercles are well developed and their inner faces are apically convergent in dorsal view. The pale siphunculi taper gradually from base to flange (cf. Myzus persicae, which has the siphunculi slightly swollen over the distal 0.5-0.7 of length). Their siphunculi are 1.7-2.6 times as long as the tongue-shaped cauda. The body length of adult Ovatus crataegarius apterae ranges from 1.5-2.0 mm.
The Ovatus crataegarius alate (third image above) has a green abdomen with darker green patches. The spring migrant winged forms of Ovatus crataegarius have 22-49 secondary rhinaria on antennal segment III, and 5-20 on antennal segment IV (cf. Ovatus insitus, which have 60-83 secondary rhinaria on antennal segment III, and 36-52 on antennal segment IV). The oviparae of Ovatus crataegarius also have fewer pseudosensoria on their hind tibiae than those of Ovatus insitus. The primary host of the hawthorn - mint aphid is hawthorn (Crataegus) and, less commonly, apple (Malus) or quince (Cydonia). In summer this species host-alternates to mint (Mentha), where it can reach pest status. In warmer climates Ovatus crataegarius may occur as an anholocyclic form on mint, overwintering viviparously near the ground. Ovatus crataegarius has a near worldwide distribution, from Europe and the Middle East to Central Asia, India, Pakistan, parts of Africa, the USA, Canada and Brazil. Dysaphis devecta species group (Rosy leaf-curling apple aphids)These minor, and not very common, apple pests seldom merit control. The Dysaphis devecta species group includes three species: Dysaphis devecta, Dysaphis anthrisci and Dysaphis chaerophylli. All members of the Dysaphis devecta group roll the edges of apple leaves and turn them red to produce a characteristic gall on apple (see first picture below). Late spring colonies of Dysaphis devecta sensu stricto (which do not host alternate) include many apterae or alatiform apterae with sclerotized thorax. Apterae are bluish-grey and wax-powdered (see second picture below). Immature future alatae are dark green to reddish. Late spring colonies of other members of the group (Dysaphis anthrisci & Dysaphis chaerophylli, both of which host alternate) include many immatures and adult alates.
For members of the Dysaphis devecta species complex, the antennae of apterae are shorter than the distance from the frons to the base of the siphunculi, and antennae of alatae are less than the body length (cf. Dysaphis plantaginea which has antennae of apterae at least as long as the distance from the frons to the base of the siphunculi, and those of the alate about as long as the body). The Dysaphis devecta species group includes Dysaphis anthrisci and Dysaphis chaerophylli. Dysaphis devecta remains all year on apple and has no alternate host. Sexual morphs appear before mid-summer, after only three parthenogenetic generations, and overwintering eggs are laid on apple. Dysaphis anthrisci host alternates between apple and cow parsley (Anthriscus sylvestris). Dysaphis chaerophylli host alternates between apple and the leaf bases of various Chaerophyllum species. Members of the Dysaphis devecta species group are found in Europe. Aphis spiraecola (Spirea aphid)A recent UK arrival, and most damaging to citrus. Adult apterae of Aphis spiraecola are bright greenish yellow to apple green. The abdominal dorsum is pale and usually entirely membranous. The fused last two rostral segments are less than 120 μm in length (cf. Aphis pomi which has the fused last two segments more than 130 μm in length). Marginal tubercles are restricted to abdominal tergites 1 & 7, with none present on abdominal tergites 2-4 (cf. Aphis pomi which has marginal tubercles on tergites 2-4 ). The femoral hairs are long and fine, the longest of them being longer than the diameter of the femur at its base. The siphunculi and cauda are black. The cauda usually has less than 12 hairs (7-15) (cf. Aphis pomi on which the cauda usually has more than 13 hairs (10-19)). The body length of an adult Aphis spiraecola aptera is 1.2-2.2 mm.
Alatae (see second picture above) have a dark brown head and thorax, and a yellowish-green abdomen with dusky marginal sclerites. The secondary hosts of Aphis spiraecola are in over 20 plant families, especially shrubs in the Caprifoliaceae, Asteraceae, Rosaceae, Rubiaceae, and Rutaceae. In North America, Brazil and Japan the species also produce sexual forms on primary host - meadowsweets (Spiraea species), or sometimes citrus or apple. Aphis spiraecola is thought to have had its origin in the Far East. In most of the rest of the world it reproduces parthenogenetically on its secondary hosts all year round. Aphis spiraecola is a major pest of citrus fruits, mountain yarrow, apple (North America) and pears (China). It has a worldwide distribution in temperate and tropical regions. Apple species identificationWorldwide, the Malus genus comprises perhaps 30-55 species. The two most common apple species in Britain have pedicels that are shorter than the mature fruit.
First image by Wehha - Own work, CC BY-SA 3.0, Wikimedia commons Stace (2010) lists five other introduced species. These have pedicels at least as long as their mature fruit. Two species are considered naturalized in UK:
The remainder are described as "street trees", and seldom self-seed:
There are undoubtedly other apple species, hybrids and cultivars in UK gardens, parks and streets. Below are mature fruit of an unidentified specimen, possibly a hybrid of Malus floribunda or Malus baccata.
|
