[MAIPC] end of year SLF research summary

[Richard Gardner]

 I was hoping for a research diapause. Instead, this is a 24/7/365 research project. I thought that with a hard freeze the field season on the Spotted Lanternfly would be over. I could not have been more wrong. When the leaves dropped the wooded areas became more transparent which allowed me to see relationships not possible before leaf drop. Yesterday is a good example in that there was practically a vineyard of wild grape hidden in the leaves on a trail we walk several times a month. A few minutes of walking around showed a strong correlation between wild grape and SLF egg masses on nearby trees. 
 As always, anyone who wants to walk with me is invited to. My wife's eyes and thoughts have proven invaluable. The same would be true of other people.
                                              Richard Gardner                                              Bernville, PA                                              rtgardner3 at yahoo.com                                              410.726.3045



Thoughts on 2018 research on the Spottedlanternfly, Lycorma delicatula, in Berks County PA

Richard Gardner

rtgardner3 at yahoo.com 410.726.3045

Nov. 1,2018, rev. Dec. 12, 2018, Dec. 20, 2018, Dec. 21, 2018, Dec. 31, 2018

 

Observation of habitat

  From field research I have been doing this year the Spotted lanternfly, Lycorma delicatula, is an insect of ecotones. Locally we havefour distinct ecosystems: urban, suburban, rural and forest. Three of theseecosystems are primarily ecotones: urban, suburban and rural.  To this point the three most common foodplants in order of preference appear to be Ailanthusaltissima, Vitis sp. and Celastrus orbiculatus. Acersaccharinum, an ornamental tree common near where I live,appears to be another food source when A. altissima and Vitis sp.are not available.

 

  Urban ecosystems tend to befragmented with few if any forested areas more than 100 yards across. Mostly, theyare a series of vacant lots, small hedgerows between properties, utility right-of-ways and similar disturbed areaswhere plants grow. Additionally, there are domesticated trees planted bymunicipal authorities and landowners. Manmade surfaces abound where SLF eggscan be deposited and vehicles to transport SLF across the landscape. Thedistances between parts of the ecotone appear to be easily traversed by SLFwithout human help since they are often short. Therefore, this appears to themost highly infested of the four local ecosystems.

 

  Suburban ecosystems are lessfragmented than urban areas but have similar characteristics in having vacantlots, disturbed areas between properties and utility right-of-ways with fewdeeper forested areas. Landowners and local government bodies plantdomesticated plants, like urban governments, but on larger tracts of land. Thelargest difference is that there tends to be more space between buildings andlarger patches of land where plants can grow with fewer manmade surfaces andvehicles. Still the distance between parts of this ecotone are relativelyshort.

 

  Rural ecosystems have more openspace and larger blocks of trees, yet with the same patchwork of hedgerows,abandoned tracts of land, utility right-of-ways and similar as urban andsuburban ecosystems. The biggest differences are that the hedgerows can bedeeper/longer, there are small forests scattered across the landscape with manyfewer vehicles and manmade surfaces and the distances between parts of theecotone are further.

 

  Forested ecosystems tend to belarge areas of deep forests with longer and fewer edges even though roads,trails and utility right-of-ways run through them. This is critical becausemost of the plants that the SLF feeds on appear to be ecotone plants, notplants of the deep forest. I seldom find A. altissima, Vitis sp.and C. orbiculatus more than a few yards deep in forests, except wherean ecotone was created by geological features, fallen trees or human disturbance.I have yet to find SLF on any of the forest trees beyond the edges of anecotone. Therefore, this appears to be the least heavily infested of the localecosystems I have investigated.

 

  Each of these ecotones hasdifferent challenges in SLF control. Urban areas have closely spaced ecotonesseparated by roads of varying width and utility acting as minor boundaries forSLF spread and more people which apparently enhance SLF spread. Suburban andrural areas have decreasing numbers of roads with decreasing traffic loads andfewer people making the spread of SLF slower. Forested areas are the slowestfor the spread of SLF because there are fewer people to facilitate itsspreading and food sources tend to be further apart.

 

Hypotheses on foodconsumption 

 To determine which woody plantsare susceptible to SLF predation, analysis of the nutritional content of theirsap needs to be done. Use Ailanthus altissima as a baseline since fromobservation it is the plant with the heaviest infestation and the one it feedson in its original home. First test qualitatively for overall sap components ofA. altissima. Then test quantitively for total sugars, proteins, fats, specificsugars and micronutrients. Compare this data to data from either specificspecies SLF may be using as an energy source or members of their families. Usingsugar content as the primary test of plant desirability it can be assumedplants with the highest sugar content are preferred food.

 

 Another part of this is to runthe same quantitative tests on the waste SLF produces on A. altissima todetermine the amount of sugar and/or other nutrients in the waste, comparing itto the same from other potential food sources. The higher the sugar content inthe waste, potentially the higher the sugar content in the tree becauseapparently the excess sugar will be in the waste produced by the SLF.

 

Supporting concepts onfood consumption 

 A more complex and accuratepredictor of plant preference is the analysis of the utility a plant has for theSLF. Utility is the amount of benefit an organism derives from a specificresource. U = (pU-c)/T. Utility = (potential Utility-cost)/Time. Potentialutility is the maximum utility which can be obtained with no cost. Costs can berelated to the sugar concentration of the sap (either too low or too high touse without additional energy expenditure), a different primary sugar than Ailanthus,sap viscosity and potential toxins in the sap which need to be dealt with,hardness of the bark, thickness of the bark or noxious/toxic chemicals in thebark. Time can either be by life stage from egg to senescence, end of a (the)reproductive cycle or a discrete unit of time such as minutes, hours or days. Environmentalfactors such as air temperature, bark temperature, humidity, amount ofdirect/indirect sunlight on the food source, state of the food source – budbreak, full growth, dormancy and the amount of rain – flood, drought and timefrom most recent rainfall may change the utility values. The higher the qualityof the food and the greater ease of access, the more utility it has. Hence, thehigher the U value, the more energy for growth and reproduction.

 

Observation of genderratio

 This may have a gender componentas it is generally accepted that in most species males have a much lowerreproductive cost than females. Therefore, males may be able to use a resourceof lower quality or less of a high-quality resource than females because of theirlower breeding cost. If this is true, then it helps ensure his progeny and thereproductive viability of the species by reserving either higher qualityresources or more of a higher quality resource for females to maximize their reproductivesuccess.

 

Observation of egglaying strategy

 Egg laying is an aspect which isconfounding me. There appear to be mixed strategies of single females layingeggs and covering them relatively far from other females such as differenttrees/surfaces and group egg laying either contiguous to or near each other.This becomes more complicated because it appears that one SLF female may layeggs close to the eggs of another female with the second female covering bothsets of eggs. Then there are the eggs which are not covered which adds anotherdimension to the puzzle. The large communal egg masses are much less commonthan egg masses randomly scattered on a single tree or across the landscape ona variety of plants and surfaces. So far, I have found eggs on grey birch,black birch, pignut, choke cherry, wild grape, silver maple, box elder, oak sp.and Ailanthus.

 

Supporting concepts onegg laying strategy 

All the egg laying strategies can be reduced to game theory in the sameway determining food sources is. The biggest mistake is to assume that what wesee in this area is not reflective of where the SLF originated. Egg massesscattered around a landscape may ensure lower egg predation in the home habitat.Whereas, egg masses on a food source ensures that hatching nymphs have areadily available food source. Large masses of eggs in a small area may ensurethat if egg predation occurs, some of the eggs will survive. The problem withassigning values to variables such as predation and proximity to food is thatwe do not know what the conditions are in the original habitat. When the SLFbecame established here the variables changed. What was a good strategy inAsia, may be a neutral or negative strategy here. Or, the strategy is good herefor different reasons than in Asia. The scattering of the eggs across thelandscape in Asia may have avoided predation, but here allows for the efficientmovement of multiple generations of SLF across our landscape. The one constantis that the egg laying and other survival strategies are rapidly evolving tomeet the new challenges offered by our ecology as it is different than the homeecology of the SLF.

 

Dec.12

Observation of egg massesand location

 What I have been learning in the last week orso is that the apparent chaotic egg laying and the coating on top of the eggmasses, with subsequent color changing and cracks developing may in part be theSLF camouflaging the egg masses from the egg predators which it experienced inAsia. When I looked at the local trees and the egg masses, there are a lot ofsimilarities between the egg masses, lichen, cankers and similar on the bark oftrees. However, this is not Asia, so I cannot say exactly what the Asianvegetation looks like.

 An issue I came across today was that gypsy mothhabitat and SLF habitat overlap and their eggs may be laid on the same trees.The only difference I see is that SLF is confined to the edge of forests,hedgerows and other ecotone areas since this is where its primary foods arelocated. The gypsy moth lays eggs on trees wherever it finds them, includingthe deep forest, the edge of forests, hedgerows and trees in cities. Gypsy mothegg masses are light brown foam while SLF egg masses are smooth, sometimes goingfrom dirty white to light tan after laying. I am not sure if there is anoverlap or the extent of the possible overlap of food plant species that Gypsymoths and SLF feed on. The timing of the egg laying is different. Gypsy mothstend to lay eggs mid to late summer. SLF egg laying appears to be late summerto a killer freeze. 

 

Supporting concepts onegg laying location

Thetiming may be based on the preferred foods of each. Gypsy moth larvae feedmostly on the leaves of deciduous hardwoods, which come into leaf late winterto mid-spring. This is much earlier in the year than Ailanthus, whichcomes into leaf in the late spring, one of the last trees to do so. Emergenceof the immature stage for both may also be related to their food sources andfeeding method. Gypsy moth larvae feed by chewing and digesting leaves. This isvery different than the SLF nymphs and adults drilling into a plant and suckingthe sap. I am not sure how much ahead of bud break and leafing out sap runs in Ailanthusor how much after leaf drop it continues. This will affect the timing of SLFegg hatching since Ailanthus still appears to be the primary food ofSLF.

 

Observation of egglaying location

 One last observation I made today is that Ifound SLF eggs only on grey birch trees in and surrounding the stand of Ailanthustrees. No egg masses were found on Ailanthus trees where I had seen SLFearlier in the fall. Reviewing the photos from earlier today, there weregenerally one to three egg masses on each grey birch where the eggs masses werefound. As usual there was no apparent order in the scattering of the egg masseswithin the grey birch stand. This needs more time walking to see if this isgenerally true in other areas.

 A general ongoing observation is that I haveseldom seen SLF egg masses much higher than 4 or 5 feet off the ground. The oneobvious exception is on domesticated silver maple.

 

Supporting conceptson genetic traits

 Ailanthus has been isolated fromthe SLF since the mid-1700’s when seeds were brought from China to Paris. Nextthe tree went to London before coming to Philadelphia after the end of the AmericanRevolutionary War in 1784. As often happens, when a defense is no longer neededit will either cease to exist or exist at a very low level. It will be excitingto watch the changes in Ailanthus over time with the reintroduction ofthis threat to it and the possibility that the tree by itself will control theSLF by bringing back or reinventing defense mechanisms to this specific threat.*

 

 A final point is that the SLF wasintroduced in this country only a few generations ago, perhaps fourgenerations, but most probably several more. What will happen in the nextseveral years is hard enough to guess. What may happen beyond that is beyondour ability to comprehend at the present time. That the SLF we are seeing arederived from one to a few females is important. The fewer parents the morelimited the gene pool. This means that the SLF does not have the full genetictoolbox of where it came from to deal with multiple new challenges such aspredators, disease and foods (which may be toxic) in its new home. There laysour greatest hope – that the SLF will encounter a challenge which will eithercontrol it or hopefully eradicate it.

 

Dec. 20

Supporting conceptson travel

  If my observations aboutgrasshoppers are correct, in general hoppers, especially big ones, need longopen areas to move in because they do not have the ability to control theirflight the way flyers such as moths and black flies do. This is what edge habitats/ecotonesare usually like, wooded areas next to open fields.

 

  To make the jumps betweenfeeding and egg deposition areas may mean long straight leaps along the edge ofa forest, across a field or down a hedgerow. Shorter jumps in the edges ofwooded areas of 2 to 10 feet from one food source to another or to an egglaying site are not a problem in a wooded area. However, the longer travelling jumps during the apparent explosion ofadults across the landscape during the fall are only possible in open areas andalong the outside edges of hedgerows and wooded areas. This further reinforcesthe idea that SLF is not a forest pest, but can be one of rural, suburban andurban areas which are composed of a mixture of hedgerows, small forests andlarge open areas. This is one area I intend to research this fall.

 

 Dec. 21 

Observationof habitat as compared to gypsy moth

 The gypsy moth, Lymantria dispar, is a far more destructive pest of forests than theSLF. A few years ago, I saw hardwood trees completely stripped of their leaves andcovered with Gypsy moth egg masses in the forest just east of Port Clinton. Inareas of similar size, I may see perhaps a dozen SLF egg masses compared tohundreds of gypsy moth egg masses. SLF primarily feeds on Ailanthus. Gypsy moths feed on most hardwood and coniferous trees.The difference is that SLF lives where we do, in the cities and suburbs. To seethe gypsy moth requires going to a forest. Hence, SLF is much more visible thanthe more destructive gypsy moth. 

 

Dec. 31

  An important observation in the comparativedamage between Gypsy moth and SLF is that the range of the SLF is a subset ofthe range of the Gypsy moth in the same way the SLF foods are at best a subsetof Gypsy moth. (I am not sure if Gypsy moths feed on the same foods as SLF, butSLF does not feed on the same range of foods as Gypsy moths.) Throughout mylife I have seen Gypsy moth egg masses in urban, rural and forested areas. Ihave yet to see SLF egg masses more than 50 feet into a forest with the eggmasses deposited in reference to nearby Ailanthustrees or wild grape.

 

Hypotheses on genderratio

  One of the odd consequences of the SpottedLanternfly is that it may move diseases between Ailanthus trees.If so, this will be at the point where the nymph stage becomes adults andexplosively move across the ecology. Once the adults settle on an Ailanthus tree,I doubt they move except females to lay eggs on non-Ailanthus. I’m not sure, but doubtful, thatfemales move afterwards to a different Ailanthus tree in astand to feed until dying or to feed until producing a second brood.  My observation is that there is anunexpectedly large skewed gender ratio in favor of males on Ailanthus trees instead of the expectedone-to-one correspondence between the genders.  Either I am unable to tell sexually immaturefemales from males or more probably females die soon after egg deposition whilemales continue living until a hard freeze kills them. 

 

Observation of egglaying 

  On Dec. 24, we walked from the gate at thelower parking area in SGL110-10 to the top of the ridge on a dirt road built bythe PA Game Commission. Very clearly, SLF hitched rides on vehicles fromdifferent parts of Berks County and dropped off on the way up the mountain tolay eggs no more than 30 feet from the dirt road. Also, once at the top wefound many dead SLF still stuck to Ailanthustrees, but not one egg mass on any of the 30+ to Ailanthus trees.

 

Hypotheses on fertilityafter feeding on wild grape, silver maple and Ailanthus

  If close association of SLF egg masses withwild grape vines (Vitis sp.) is avalid indicator of fertility, then feeding on Ailanthus is not required for egg production. To this point I havefound this association weakly along the Appalachian Trail at Ft. Franklin Road,Lehigh County and strongly along the Appalachian Trail at Rt. 183, Betheltownship, Berks County. At both locations I found SLF feeding on wild grapeearlier in the fall without any Ailanthustrees nearby. Along Sterner Hill Road, Blue Marsh and SGL110-10 on the serviceroad to the top of the ridge, headed towards the Auburn Overlook, there is a strongassociation between SLF egg masses and Vitissp. without nearby Ailanthustrees. I will continue looking for similar associations to strengthen theargument and checking these egg masses for hatched SLF nymphs in the spring. Forme the only definitive proof of viable reproduction is an F2 generation,grandchildren. The F1 generation, children, can be sterile, which means thateven though the parents produced viable eggs they were still not successful inreproducing their parental line and the species.

 

  I will be also bechecking domesticated silver maples (Acersaccharinum) in a friend’s yard to look at the egg masses for hatching inthe spring.

 

  From observation atmultiple sites such as the end of Peacock Road, Blue Marsh, SGL110 near theAuburn Overlook, Sterner Hill Road towards the lake, Blue Marsh and elsewhere,feeding on Ailanthus trees does notguarantee egg laying. This may be due to a chemical produced by Ailanthus either preventing SLF sexualmaturation or a similar cause which in effect sterilizes SLF.

 

Concluding thought

  My biggest concernis that “researchers” are biasing their data and results by being intent on“solving” this apparent problem instead of observing and knowing SLF and itseffects. It is vital at this point that scientists spend most of their timewalking and observing instead of participating in the nonsensical and naïvepanic which is infecting everyone from homeowners to farmers and politicians.The proposed strategy which I heard about of trying to remove all the Ailanthus trees from the infested areais one without practical application. It would require walking every squaremeter of land to locate possibly 10,000,000 Ailanthustrees. Then when it is discovered that SLF can reproduce after feeding on Vitis sp. will there also be attempts toremove that from the ecology? And, and, and?

 

WALK MORE AND TINKER LESS

 

 

 

*Thewild (European) parsnip Pastinaca sativa L. apparently decreased its defenses when introduced to theEuropean North American colonies in the early 1600’s due to the lack of aprincipal herbivore - the parsnip webworm, Depressaria pastinacella. Defenses built back up with theaccidental reintroduction of D. pastinacella in the late 1800’s. (Increasein toxicity of an invasive weed after reassociation with its coevolvedherbivore, Arthur R. Zangerl and MayR. Berenbaum, PNAS October 25, 2005 102 (43) 15529-15532.

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.maipc.org/pipermail/maipc-maipc.org/attachments/20181231/1eafcc48/attachment-0001.html>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: Thoughts on 2018 research on the Spotted lanternfly,rev. Dec. 31, 2018b.docx
Type: application/vnd.openxmlformats-officedocument.wordprocessingml.document
Size: 32858 bytes
Desc: not available
URL: <http://lists.maipc.org/pipermail/maipc-maipc.org/attachments/20181231/1eafcc48/attachment-0001.docx>