InfluentialPoints.comBiology, images, analysis, design...
| Aphids | Find them | How to ID | ID by host |
| InfluentialPoints.com Biology, images, analysis, design... |
|
"It has long been an axiom of mine that the little things are infinitely the most important" |
|
|
Rhopalosiphum nymphaeaeWater lily aphid, Reddish-brown plum aphidOn this page: Identification & Distribution Biology & Ecology Life cycle Natural enemies Other aphids on the same host Damage, control & beneficial effectsIdentification & DistributionApterae of Rhopalosiphum nymphaeae on the primary host (Prunus spp., see first picture below) are brownish. Apterae on a secondary host (e.g. water lily, see second picture below) are more or less shiny reddish-brown to dark olive. The dorsal cuticle has reticulation formed by regularly-shaped roundish bead-like spinules. The antennae are about 0.6 times the body length, with the terminal process 2.3-3.9 times the base of antennal segment VI. On the primary host the apical rostral segment (RIV+V) is 1.0-1.1 times longer than the second hind tarsal segment (HTII). On the secondary host RIV+V is 1.15-1.45 times longer than HTII. The siphunculi are more than twice the length of the cauda and are distinctly swollen on the distal half. The cauda is elongate and slender. The Rhopalosiphum nymphaeae aptera body length is 1.6-2.6 mm.
Rhopalosiphum nymphaeae alatae (see first picture below) are shining brown. Secondary rhinaria are distributed 14-24 on antennal segment III, 0-8 on segment IV and 0 on V. The abdomen has marginal and postsiphuncular sclerites. The immatures (see second picture below), and sometimes the adults, may be dusted with a light grey wax on the head, thorax and legs, and/or transverse white wax bands on abdominal tergite I.
The specimens in isopropyl alcohol below are Rhopalosiphum nymphaeae apterae, dorsal & ventral.
The clarified slide mounts below are of adult viviparous female Rhopalosiphum nymphaeae : aptera & alate from secondary hosts.
First image courtesy PaDIL, copyright Simon Hinkley & Ken Walker (Museum Victoria) under Commons Attribution license; In spring the water lily aphid feeds on various Prunus species (such as Prunus spinosa) where it feeds on leaf petioles and fruit stalks curling the leaves. In early summer Rhopalosiphum nymphaeae alatae migrate to the secondary hosts comprising a large variety of water plants, including Nymphaea (water lilies), Potamogeton (pondweeds), and Sparganium (arrowheads). Recorded from at least 45 plant families it is considered quite polyphagous. Its distribution is almost cosmopolitan - in Britain it is found from the south of England to the north of Scotland. Biology & EcologyLife cycleRhopalosiphum nymphaeae overwinter in the egg stage on a variety of Prunus species including domestic plum (Prunus domestica) and blackthorn (Prunus spinosa). In spring the eggs hatch, and feeding by the nymphs induces curling of the leaves, which provides a degree of protection to the developing nymphs. They are often not the only aphid species developing on Prunus in spring. A common associate is the mealy plum aphid (Hyalopterus pruni, see green aphids in the picture below), which can be present in large numbers.
In late spring winged alatae (see picture below) develop which migrate to their secondary hosts, mainly a variety of aquatic and semiaquatic plants, and other nonaquatics such as tulips under glass.
The picture below shows an adult aptera and first instar nymph on water lily. Note the residual whitish grey wax bordering the prothorax.
Large colonies may develop on water lilies, the aphids congregating along the leaf veins and invading the flowers. The rate of development, natality and survivorship rates of Rhopalosiphum nymphaeae has been studied in relation to its potential for virus transmission both to crops and aquatic weeds (Ballou et al., 1986). The optimal temperatures for Rhopalosiphum nymphaeae were 21 to 27 °C. Hance et al. (1994) established the life and fertility table on Azolla, an agronomically important aquatic fern used as green manure and fodder. They computed the intrinsic rate of increase which indicated a theoretical doubling in population size every 2.2 days. The various different nymphal instars are shown in the picture below.
Images copyright Sally Luker, all rights reserved Storey (2007) looked at host preference by Rhopalosiphum nymphaeae among different related secondary hosts. They tended to prefer the host plant they were reared on, suggesting that familiarity played a role in shaping host preference. Stroyan (1984) reported that the aphids have some ability to survive underwater by retaining an air film, perhaps by means of the cuticular spinules. Similar behaviour has recently been reported by Simon Leather in his blog, but Bennet & Buckingham (2000) only found them on parts of water plants either at the water surface or rising above the surface of the water.
Image copyright Sally Luker, all rights reserved. In autumn they migrate back to Prunus, the primary host. Sexual forms develop, namely winged males and apterous female oviparae. The fertilized females then lay the overwintering eggs on the primary host. Natural enemiesAli et al. (2009) found that the syrphid Ischidon scutellaris was an especially efficient predator on the water lily aphid. There are also several reports of predation by coccinellids. Saraswati et al. (1990) reported that Meochilus sexmaculatus, Coccinella septempunctata, Micraspis discolor, Brumoides suturalis and Scymnus species 'controlled' populations of Rhopalosiphum nymphaeae in Jan-March on Euyale ferox, a major cash crop in India. Later in the year, winged forms develop
The picture above shows part of a dense colony that developed on water plants in a glasshouse - note the preponderance of fourth instar alatiform nymphs. Other aphids on same host:Primary hostsRhopalosiphum nymphaeae has been recorded from 27 Prunus species. Blackman & Eastop list 25 species of aphid as feeding on plum (Prunus domestica) worldwide, and provide formal identification keys (Show World list). Of those aphid species, Baker (2015) lists 16 as occurring in Britain on one or more of the primary hosts (Show British list).
Secondary hostsRhopalosiphum nymphaeae has been recorded from 10 Nymphaea species. Blackman & Eastop list 4 species of aphid as feeding on water lilies (Nymphaea species) worldwide, and provide formal identification keys (Show World list). Of those aphid species, Baker (2015) lists all 4 as occurring in Britain (Show British list).
Damage, control & beneficial effectsOn fruit trees dense colonies may develop in spring on young shoots causing noticeable distortion of the foliage. Such colonies usually die out by June, and control is seldom required. Control on water lily is by forcibly spraying with water to dislodge and drown aphids. Insecticides should not be used as they are toxic to fish and pond life.
Image copyright Sally Luker, all rights reserved. Regarding beneficial effects, Rhopalosiphum nymphaeae has been used for biological control of duckweed (Heteranthera limosa) which is a pest of rice in California. Field experiments showed that the aphids reduced total weed biomass by 58% and 87% in two years (Oraze & Grigarick, 1992). Tomanovic et al. (2012) notes that in Europe the water lily aphid is an important non-crop reservoir for five economically important parasitoids of crop pest aphids, namely Aphidius colemani, Aphidius matricariae, Aphidius rhopalosophi, Lysiphlebus fabarum and Trioxys auctus.
|
