Gypsy Moth Dispatch 2018

Winter in July at Seaside Cemetery--
defoliated oak trees make a morbid landscape

We're experiencing a gypsy moth outbreak such as hasn't struck our area since the early 1980s. Back then we feared massive deforestation or at least the elimination of vulnerable tree species. The threat abated after a few years, possibly due to the importation from Japan of Entomophaga maimaiga, a fungus lethal to the gypsy moths' insatiable larvae. Few other solutions have effect. There are too many of the critters, and we've come to understand the folly of counter-attacking broadly with chemical pesticides.

Caterpillars skeletonizing an oak leaf

The past couple of years have brought widespread destruction by gypsy moth larvae during the spring months. Uncountable numbers of the caterpillars are suddenly, voraciously present. Eating and growing through several molts they have gained the attention of anyone outdoors, crawling over every surface and suspended by silk threads that carry them wind-blown to adjacent trees. Their resurgence may be due to relatively dry conditions in recent spring seasons that impeded the dispersal of Entomophaga maimaiga spores.

A male gypsy moth on the wing this week

Last month the caterpillars pupated, meaning they secreted themselves within cocoons to accomplish the metamorphosis into winged adults. The moths won't eat again in their brief maturity, having the singular goal of procreation. The males hatch first and fly ceaselessly in search of a mate. Myriad numbers of them are filling the air just now building up tension for that primal imperative. The flightless females will soon emerge with an alluring fragrance.

A motion of mid-summer reverie

In my back yard I sit in the thin shade of leafless oaks. Begonias beside me are scalded by the unaccustomed penetration of sunlight through the tree canopy. Male moths flutter inquisitively over every surface sometimes brushing against me with fairy kisses. They diffuse through the garden as though trying to maintain equidistance from each other, searching obsessively but without conflict. To innocent eyes they make a delicate if prolific ballet with no apparent appetites.

Defoliated apple tree, Halibut Point State Park

The damage came earlier at the ravenous jaws of the wormy stage. Besides oaks they are fond of apple trees. The trees lost their sugar-producing leaves at an early stage of development of the fruit. They will probably put forth new leaves at a considerable energy cost. We'll have to see if that comes at the expense of maturing the fruit. 


Defoliated oak tree, Halibut Point State Park

  An adjacent Scarlet Oak tree suffered similar damage.

A branch of the same oak tree re-foliating

New leaves are beginning to form on the oak tree giving hope for its survival if not for a crop of acorns to sustain squirrels and turkeys.

Gypsy moth caterpillars at work

The caterpillars' bristly armature and perhaps its foul taste protect them from many foraging birds, although white-footed mice relish them on the ground.

A Black-billed Cuckoo in the oak tree prior to defoliation

Personally I hope that the gypsy moth outbreak supports an influx of one ardent predator, the furtive black-billed cuckoo that I haven't yet managed to photograph clearly.

A male gypsy moth approaching a female

Meanwhile the prospective parents of proliferation begin their courtship.

Females laying egg masses on an oak tree trunk, next to their cocoon shells. That distance from their cocoons spans their life journey.

The impact of gypsy moths on our oak trees exacerbates the damage caused earlier in the year by winter moths whose populations have reached historic proportions locally. Weakened trees become more susceptible to other pests and pathogens. The shifts and imbalances may be related to weather patterns associated with climate change.

The ecological consequences of gypsy moth defoliation are not necessarily catastrophic in the view of Cape Ann naturalist Chris Leahy who has observed the species enrichment and diversification following fires that preserve meadow lands or create open spaces in forests. Flooding caused by beaver dams can have a similar localized effect.

Entomologists have high hopes that the Entomophaga maimaiga fungus will regain control of gypsy moth populations under propitious rainfall patterns in coming years. They believe they understand the mechanisms but acknowledge these operate within uncontrollable complexities.

Property owners concerned to safeguard individual plants can explore various options with an experienced arborist.