If people who study insects have anything safe to say aboutaphids , they ’ve kept it to themselves . female parent Nature seems to have chosenaphidsas theultimate plant - feeding machines , capable of pierce several layers of tissue to reach thephloem sapthat sustains them . They ’re also capable of regurgitate quickly . A single aphid , typically under 1/8 inch long , may producetens of thousands of descendantswithin a few week . In the cognitive process , the insect damage their host plants in multiple ways .
Feeding Process
An aphid ’s mouth contains two specialized tubes , a solid food canal and a salivary duct . They ’re located in a tissue - piercingstyletthe insect sinks into stem , leafage or etymon tissue . For about one minute after it hits a bast - transporting watercraft , the insect pumps washy , sap - adulterate spittle into the plant .
It then starts sucking the spit - and - saphead mixture back up through the food canal while continue to pump spittle into the alimentation site . Thesaliva prevents defensive chemicalsin the plant from coagulate the damage cells and stopping the sap flow .
Direct Feeding Damage
Yellowing and Wilting
Most plants tolerate lighter aphid feeding with no discernable damage . As the aphid population grows , however , invade leaf startwilting and yellowingfrom nourishing loss . Aphid feeding oftenstunts fresh emerging increment . In large numbers , radical aphidsmay debilitate enough sap that aplant stops growing .
Curled Leaves
Some species , such as the leafcurl ash tree aphid ( Prociphilus fraxinifolii ) and plum leafcurl or leafcurl plum aphid ( Brachycaudus helichrysi),inject their hosts with cell - distorting salivathat permanently Robert Floyd Curl Jr. the young leave they feed on , and the curls are protective shelters for the aphids .
Virus Transmission
aphid damage plants most seriously bytransmitting numerous virus . Aphids on an overcrowded host begin producingwinged offspringthat leave for less congested quarters . When in flight , the insects ca n’t identify their emcee plants . So they sample sap from several plants before rule new homes .
If one of those works carries a computer virus , the aphids assume it immediately . Over the next few minutes to several hours , theirsaliva transmits itto any other plant they test .
Honeydew
Like all works - piercing insects , aphid need prominent amount of nitrogen . To get it , they drain phloem sap . After draw out the nitrogen , they pass what ’s left as awkward , messy , transparenthoneydew . Honeydew attractsstreams of sugar - loving antsthat kill the aphid ' insect predator .
Indirect Feeding Damage
Aphids ' honeydew is a attractive feature for airbornesooty moldfungi . Fungal spores feeding immediately on the honeydew germinate intospecklesorlayersof black , sooty textile .
