Biology, images, analysis, design...
|"It has long been an axiom of mine that the little things are infinitely the most important" |
Spotted poplar aphidOn this page: Identification & Distribution Biology & Ecology Other aphids on the same host Damage & Control
Identification & Distribution
Adult apterae of Aphis maculatae are brownish black, with black siphunculi and cauda, and a paler head, legs and antennae. The body is marked with conspicuous patches of white wax powder on the lateral areas and along broken dorsal bands. The antennal tubercles are undeveloped. The antennae have numerous conspicuous setae as long as, or longer than, the width of the segments of the antennae, and antennal segment III has 15-22 secondary rhinaria over the distal 0.8 of its length. The tibiae have numerous long, fine hairs. Their siphunculi and cauda are black (cf. Aulacorthum solani & Macrosiphum euphorbiae, which also occur on the primary host, Cornus, but have pale siphunculi and cauda). The body length of adult Aphis maculatae apterae is 1.7-1.8 mm. Immatures (see second picture below) are light rusty brown, mostly covered with white wax powder patches with only the mid-dorsum of abdominal tergites II and III, and around the bases of the siphunculi, wax-free.
Both images above by permission, copyright Claude Pilon, all rights reserved.
The alate Aphis maculatae (see pictures below of immature and mature alatae) has a black head and thorax, and the abdomen is blackish brown. There are powdered wax spots on the lateral areas anterior to the siphunculi, and dorsal pairs on abdominal tergites I, IV, VII and VII. Their antennae are dusky throughout.
Images above by permission, copyright Claude Pilon, all rights reserved.
Image of Aphis maculatae aptera copyright CBG Photography Group under a Creative Commons - Attribution Non-Commercial Share-Alike License.
Aphis maculatae overwinter in the egg stage on red-osier dogwood (Cornus sericea =Cornus stolonifera). Their eggs hatch in spring, and populations develop on the Cornus. In late spring to early summer alatae develop which host alternate to various poplar species (Populus spp.), where they sometimes form large colonies on twigs and leaves. Foottit & Maw (1997) note that it may persist (possibly asexually) on the latter. The distribution of Aphis maculatae is transcontinental in Canada and northern United States, north to Yellowknife, south in mountains to Colorado and Pennsylvania.
Other aphids on the same host
Aphis maculatae has been recorded from 1 species of Cornus (Cornus sericea =Cornus stolonifera) - plus, possibly, Cornus paniculata.
Aphis maculatae occurs on 5 species of Populus (Populus acuminata, Populus angustifolia, Populus balsamifera, Populus nigra, Populus tremuloides).
Damage and control
The spotted poplar aphid has long been an occasional pest of young poplar stands in northern North America. Spring migrants move from dogwood to poplar during the summer and form very large colonies. Nymphs and adults feed on the apical meristem and the newly emerging leaves, and large colonies may completely cover several centimeters of the growing tips. Aphids move upward with the advancing growth and leave behind tiers of distorted or puckered leaves.
Wilson & Moore (1986) determined host preference by the aphid for various poplar clones in a nursery. Additionally they measured growth impact of feeding by large colonies of aphids and assessed the efficacy of two insecticidal soaps for control of the aphid. Susceptibility ranking of more than 50 clones of hybrid Populus whips showed a wide range of attack ranging from none to very heavy. Clones with Populus x jackii parentage were the most susceptible, whereas Carolina poplar was unscathed. However growth loss differed little between very heavily aphid-attacked whips and unattacked whips.
These results differed from those of Osgood (1962). He found that, when infested for 2 months with a large aphid colony, quaking aspen suckers grew very little during the entire first growing season and took on a bushy appearance. When he compared growth between infested and uninfested aspen suckers he found by the end of the season the infested ones were about 30% shorter. These, however, caught up in height by mid-August of the second year. Also, he noted that the lateral buds burst on these suckers and caused much branching, a trait reserved mostly for 2-year growth.
In the two insecticidal soap tests carried out by Wilson & Moore (1986), both formulations and dosages controlled the aphids about equally (80-90% reduction) on the three clones. Control was slightly less on another. They saw no reinfestation of the test whips, although Osgood reported that reinfestation can occur after a colony vacates or is removed from aspen suckers. Wilson & Moore concluded that the insecticidal soaps gave sufficient control to disrupt the aphids for the remainder of the season.