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Honeydew For Dinner
Notes From The Field
Honeydew For Dinner
Honeydew For Dinner
February 24, 2016
The honeydew to which I refer is not the edible melon, but aphid scat. To the untrained ear, this may sound like the hip name for an indie rock band. Allow me to clarify. Aphids are animals. They comprise a family of insects with nearly 4,500 species identified to science! Yes some are pests. Well, many. This is not an article on agribusiness or the human-wildlife conflicts therein. Rather, it’s a piece on a hidden relationship of the natural realm.
There are different types of symbiotic relationships that occur in nature. Mutualism is a type of symbiotic relationship when both parties benefit from each other. A not so intuitive example is the human-plant connection. We need the oxygen that plants respire, as they need our exhaled carbon dioxide. See, we’re part of the fabric of nature. Score! Other examples of symbiosis would take us down a dark path of parasitoids, hosts, and death. Let’s focus on a more friendly, yet unintended symbiotic relationship. A fungus growing in a woods near you is benefiting from the excretions of aphids. The aphids are unaware that their,
poo, is a nutritious food source for a sooty mold fungus.
Colonies of beech woolly aphid (Grylloprociphilus imbricator) supply nutrition from their drip-collected scat to a sooty mold fungus (Scorias spongiosa). The tree pictured here is American beech (Fagus grandifolia) and is the species that supports this hidden relationship.
The sooty mold fungus species
is part of the largest division of the Fungus Kingdom called the Ascomycete fungi. In nature, plants have to make their own food, animals have to find it, while fungi have a varied approach. Fungi cannot walk, swim, or fly to their source of nutrition. They cannot make their own food, as they lack the plant-unique ability to photosynthesize sugar from sunlight. Hmm… And still, as a group of living organisms, fungi survive. In fact, they thrive! Some fungi can have a mutualistic relationship with plant roots in which nutrients are exchanged. Other fungi can parasitically obtain energy by solely living off another organism, to the host’s detriment. Still some others obtain their food by breaking down dead organic material. Where does our sooty mold fungus fit?
Science is a moving target. Often, the answers that science provides beg further inquiry. The sooty mold fungus does not fit perfectly into any of the nutrient-gathering categories mentioned above. The beech wooly aphid scat, or honeydew, provides a growing medium for the fungus. The American beech is the only tree to host the beech wooly aphid. The sooty mold fungus highlighted in this article exclusively grows on the honeydew. Therefore, if you stumble upon the black and sometimes resinous material stacked upon a branch over the next few weeks, you’re undoubtedly standing upon an American beech. There are easier ways to identify a tree!
You can find the mystery mold anytime from late summer onward, because this is when the aphids will begin to colonize and create honeydew. The growing fungus will at first appear unpigmented, like a bleached sponge. Overtime, the sooty mold will mature into a dark fungus, sure to confuse the next passerby. The biology of sooty mold fungi, including their interactions with the surrounding environment, is still an incomplete puzzle. What other hidden relationships do we unknowingly stand among in the natural realm?
Nature Speaks Eloquently
Maintaining Our Cool
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