The authors are grateful to the Forest Service of Canton Ticino and the Federal Office for the Environment FOEN for partially funding this study.

1. Tree Selection and Assessment Design
<ol>
	<li>If possible, identify the epidemic stage of the study area by determining the arrival years of Dryocosmus kuriphilus and Torymus sinensis and the T. sinensis parasitization rate by using reliable sources (e.g., scientific publications, forest services, chestnut grove managers&#39; knowledge).
	<ol>
		<li>If no reliable sources are available, identify the four main epidemic stages (Early, Peak, Recovery, Biocontrol) by computing the <e...

<ol>
	<li>Stone, G. N., Sch&#246;nrogge, K., Rachel, J., Bellido, D., Pujade-villar, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+population+biology+of+oak+gall+wasps+(Hymenoptera:+Cynipidae).">The population biology of oak gall wasps (Hymenoptera: Cynipidae).</a> Annual Review of Entomology. (47), 633-668 (2002).</li><li>Abe, Y., Melika, G., Stone, G. N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+diversity+and+phylogeography+of+cynipid+gallwasps+(Hymenoptera:+Cynipidae)+of+the+Oriental+and+eastern+Palearctic+regions,+and+their+associated+communities.">The diversity and phylogeography of cynipid gallwasps (Hymenoptera: Cynipidae) of the Oriental and eastern Palearctic regions, and their associated communities.</a> Oriental Insects. 41 (1), 169-212 (2007).</li><li>Aebi, A., Schoenenberger, N., Bigler, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Evaluating+the+use+of+Torymus+sinensis+against+the+chestnut+gall+wasp+Dryocosmus+kuriphilus+in+the+Canton+Ticino,+Switzerland.">Evaluating the use of Torymus sinensis against the chestnut gall wasp Dryocosmus kuriphilus in the Canton Ticino, Switzerland.</a> Agroscope Reckenholz-T&#228;nikon Report. , (2011).</li><li>Maltoni, A., Mariotti, B., Tani, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Case+study+of+a+new+method+for+the+classification+and+analysis+of+Dryocosmus+kuriphilus+Yasumatsu+damage+to+young+chestnut+sprouts.">Case study of a new method for the classification and analysis of Dryocosmus kuriphilus Yasumatsu damage to young chestnut sprouts.</a> IForest. 5 (1), 50-59 (2012).</li><li>Gehring, E., Bellosi, B., Quacchia, A., Conedera, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Assessing+the+impact+of+Dryocosmus+kuriphilius+on+the+chestnut+tree+branch+architecture+matters.">Assessing the impact of Dryocosmus kuriphilius on the chestnut tree branch architecture matters.</a> Journal of Pest Science. 91 (1), 189-202 (2018).</li><li>Kato, K., Hijii, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effects+of+gall+formation+by+Dryocosmus+kuriphilus+Yasumatsu+(Hym+.,+Cynipidae+)+on+the+growth+of+chestnut+trees.">Effects of gall formation by Dryocosmus kuriphilus Yasumatsu (Hym ., Cynipidae ) on the growth of chestnut trees.</a> Journal of Applied Entomology. 121 (1-5), 9-15 (1997).</li><li>Meyer, J. B., Gallien, L., Prospero, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Interaction+between+two+invasive+organisms+on+the+European+chestnut:+Does+the+chestnut+blight+fungus+benefit+from+the+presence+of+the+gall+wasp?.">Interaction between two invasive organisms on the European chestnut: Does the chestnut blight fungus benefit from the presence of the gall wasp?.</a> FEMS Microbiology Ecology. 91 (11), 1-10 (2015).</li><li>Turchetti, T., Addario, E., Maresi, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Interactions+between+chestnut+gall+wasp+and+blight:+a+new+criticality+for+chestnut.">Interactions between chestnut gall wasp and blight: a new criticality for chestnut.</a> Forest@ - Rivista di Selvicoltura ed Ecologia Forestale. 7 (1), 252-258 (2010).</li><li>Moriya, S., Shiga, M., Adachi, I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Classical+biological+control+of+the+chestnut+gall+wasp+in+Japan.">Classical biological control of the chestnut gall wasp in Japan.</a> , 407-415 (2003).</li><li>Quacchia, A., Moriya, S., Bosio, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effectiveness+of+Torymus+sinensis+in+the+Biological+Control+of+Dryocosmus+kuriphilus+in+Italy.">Effectiveness of Torymus sinensis in the Biological Control of Dryocosmus kuriphilus in Italy.</a> Acta Horticulturae. 1043, 199-204 (2014).</li><li>Kotobuki, K., Mori, K., Sato, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=2+methods+to+estimate+the+tree+damage+by+chestnut+gall+wasp+Dryocosmus-kuriphilus.">2 methods to estimate the tree damage by chestnut gall wasp Dryocosmus-kuriphilus.</a> Bulletin of the fruit tree research station A (Yatabe). 2 (12), 29-36 (1985).</li><li>Sartor, C., Dini, F., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Impact+of+the+Asian+wasp+Dryocosmus+kuriphilus+(Yasumatsu)+on+cultivated+chestnut:+Yield+loss+and+cultivar+susceptibility.">Impact of the Asian wasp Dryocosmus kuriphilus (Yasumatsu) on cultivated chestnut: Yield loss and cultivar susceptibility.</a> Scientia Horticulturae. 1997, 454-460 (2015).</li><li>Johnstone, D., Moore, G., Tausz, M., Nicolas, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+measurement+of+plant+vitality+in+landscape+trees.">The measurement of plant vitality in landscape trees.</a> Arboricultural Journal: The International Journal of Urban Forestry. 35 (1), 18-27 (2013).</li><li>Guyot, V., Castagneyrol, B., Deconchat, M., Selvi, F., Bussotti, F., Jactel, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Tree+diversity+limits+the+impact+of+an+invasive+forest+pest.">Tree diversity limits the impact of an invasive forest pest.</a> Plos One. , (2015).</li><li>Gehring, E., Bosio, G., Quacchia, A., Conedera, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Adapting+sampling+effort+to+assess+the+population+establishment+of+Torymus+sinensis,+the+biocontrol+agent+of+the+chestnut+gallwasp.">Adapting sampling effort to assess the population establishment of Torymus sinensis, the biocontrol agent of the chestnut gallwasp.</a> International Journal of Pest Management. , (2017).</li><li>Hall&#233;, F., Oldeman, R. A. A., Tomlinson, P. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> The Formation of Trees and Forests. An architectural analysis. , (1978).</li><li>Gyoutoku, Y., Uemura, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ecology+and+biological+control+of+the+chestnut+gall+wasp,+Dryocosmus+kuriphilus+Yasumatsu+(Hymenoptera:+Cynipidae).+1.+Damage+and+parasitization+in+Kumamoto+Prefecture.">Ecology and biological control of the chestnut gall wasp, Dryocosmus kuriphilus Yasumatsu (Hymenoptera: Cynipidae). 1. Damage and parasitization in Kumamoto Prefecture.</a> Proceedings of the Association for Plant Protection of Kyushu (Japan). 31, 213-215 (1985).</li><li>M&#252;ller, E., Stierlin, H. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Sanasilva+Kronenbilder+mit+Nadel-+und+Blattverlustprozenten.">Sanasilva Kronenbilder mit Nadel- und Blattverlustprozenten.</a> Eidgeno&#776;ssische Forschungsanstalt fu&#776;r Wald, Schnee und Landschaft: Birmensdorf. , (1990).</li></ol>

The authors have nothing to disclose.

Dryocosmus kuriphilus lay eggs in chestnut tree buds, inducing the formation of galls in spring. Repeated and uncontrolled D. kuriphilus attacks cause, in addition to gall formation, general branch corruption, including the death of many shoots and a significant loss in green photosynthetic leaf area5. Trees usually react by attempting to produce substitutive shoots via the activation of dormant buds. For this reason, especially during the epidemic peak and the recovery stage, cl...

The chestnut gallwasp Dryocosmus kuriphilus Yasumatsu (Hymenoptera: Cynipidae) is the most significant global insect pest of the genus Castanea1,2,3. Through its repeated galling activity, it prevents and inhibits normal shoot development4,5, causing a progressive reduction of leaf area and a consequent loss of tree green biomass and vigour5,6, dormant bud reactivation5 and an increase in gallwasp post-emergence branch mortality7,8.
The European experience of the gallwasp epidemic shows that uncontrolled and repeated gallwasp attacks may induce a high level of crown corruption in Sweet chestnut (Castanea sativa Mill.). This can result in crown leaf area losses of up to 70% that are neither compensated for by substitutive foliage produced by the activation of dormant buds nor by building second flushes during the same vegetation period5.
The only successful method to reduce the pest population and allow chestnut trees to recover is biological control through its natural antagonist the parasitoid Torymus sinensis Kamijo (Hymenoptera: Torymidae)9,10. Once biological control through its natural enemy is achieved, the chestnut trees start to produce new healthy sprouts. If tree damage level is very high, this may occur starting from the terminal bud only, due to the fact that it is usually infestation-free because of its formation after gallwasp oviposition activity4. This implies a long recovery process before the whole tree crown is re-established5.
In order to check the positive reaction of chestnut trees after biological control by Torymus sinensis is reached, and to verify the need for sylvicultural (pruning, thinning) intervention, forest managers and chestnut growers need a method for quick and reliable assessment of damage level and related branch architecture and leaf area evolution throughout the gallwasp epidemic from the initial infestation phase by the pest to recovery after biological control by its antagonist. Several methods for assessing gallwasp infestation degree (MAID) have been developed and used worldwide to date, such as measuring the proportion of attacked buds11 or the average number of galls per bud12. MAID do not directly measure green biomass (e.g., leaf area), reserve structures such as dormant buds, reaction structures (e.g., reactivated dormant buds and second flushes), or previous year damage (e.g., dead shoots) as major proxies of current tree vitality and vigour6,13,14. Moreover, most MAID are only based on the number of galls found on tree branches and underestimate real branch damage, especially during the peak of the pest epidemic (Figure 1).
In this paper, we describe the damage composite index (DCI) approach proposed by Gehring et al.&#160;20185 that considers proxies of green biomass, reserves such as dormant bud, and tree reactions (dormant bud reactivation and second flushes), enabling a realistic, reliable, and reasonably rapid assessment of damage through all stages of an epidemic, especially when combined with the assessment effort optimization proposed by Gehring et al.&#160;201715.
In particular, the objectives of this paper are 1) to give a detailed description of the field protocol, including the relevant branch features to be assessed, 2) to present the damage composite index formula, and 3) to propose an improved severity scale conversion for the DCI.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Name of Material/ Equipment</td>
			<td>Company</td>
			<td>Catalog Number</td>
			<td>Comments</td>
		</tr>
		<tr>
			<td>Clipboard</td>
			<td>Any brand</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Camping chair 
			(Foldable and lightweight chair)</td>
			<td>Any brand</td>
			<td></td>
			<td>Companies: Kelty, Campz, Half-Ton.</td>
		</tr>
		<tr>
			<td>Felco 9 secateurs 
			(One-hand pruning shear)</td>
			<td>Felco</td>
			<td></td>
			<td>Other companies: Bahco.</td>
		</tr>
		<tr>
			<td>AP-5M-Aluminium Pole 
			(Telescopic tree pruner pole)</td>
			<td>Bahco</td>
			<td>8152079</td>
			<td rowspan="2">Other companies: Spear &#38; Jackson, Kingfisher, Hortex, Fiskars.</td>
		</tr>
		<tr>
			<td>P34-37 top pruner 
			(Telescopic tree pruner head)</td>
			<td>Bahco</td>
			<td>8002787</td>
		</tr>
		<tr>
			<td>100 ft Fiberglass Long Tape 
			(30 m measuring tape)</td>
			<td>Stanley</td>
			<td>34-790</td>
			<td>Other companies: Tjima, Freemans, Astor, Lux.</td>
		</tr>
		<tr>
			<td>Parallel 10.5mm 
			(Low stretch kernmantel rope, flexible and lightweight for rope access)</td>
			<td>Petzl</td>
			<td>R077AA03</td>
			<td rowspan="10">Basic equipment for tree climbing&#160; (if necessary). Many other equipment configurations can be used for tree climbing, depending on the situation and on single operator preferences. We used Pezl equipment but many other companies offer similar products (e.g. Edelrid, Notch, Climbing technologies, DMM, ...). For a complete overview of equipment and companies we recommend a search in google&#160; &#34;tree climbing gear&#34; as search keyword. PLEASE NOTE: tree climbing activities should be done only by professionals and are submitted to specific regulatory prescriptions according to the country.</td>
		</tr>
		<tr>
			<td>Avao Sit 
			(Harness for work positioning and suspension)</td>
			<td>Petzl</td>
			<td>C69AFA 2</td>
		</tr>
		<tr>
			<td>Rig 
			(Compact self-braking descender)</td>
			<td>Petzl</td>
			<td>D21A</td>
		</tr>
		<tr>
			<td>Ascension 
			(Handled rope clamp for rope ascents)</td>
			<td>Petzl</td>
			<td>B17ALA</td>
		</tr>
		<tr>
			<td>Eclipse 
			(Storage for throw-line)</td>
			<td>Petzl</td>
			<td>S03Y</td>
		</tr>
		<tr>
			<td>Airline 
			(Throw-line)</td>
			<td>Petzl</td>
			<td>R02Y 060</td>
		</tr>
		<tr>
			<td>Jet 
			(Throw-bag)</td>
			<td>Petzl</td>
			<td>S02Y 300</td>
		</tr>
		<tr>
			<td>Vertex best 
			(Comfortable helmet for work at height and rescue)</td>
			<td>Petzl</td>
			<td>A10BYA</td>
		</tr>
		<tr>
			<td>Zillon 
			(Adjustable work positioning lanyard for tree care)</td>
			<td>Petzl</td>
			<td>L22A 040</td>
		</tr>
		<tr>
			<td>Ok 
			(Lightweight oval carabiner)</td>
			<td>Petzl</td>
			<td>M33A SL</td>
		</tr>
	</tbody>
</table>

evaluating dryocosmus kuriphilus-induced damage on castanea sativa

Dryocosmus kuriphilus Yasumatsu has become a major pest for Castaneasativa since its arrival in Europe. Its galling activity results in the formation of different gall types and prevents the development of normal shoots. Repeated and uncontrolled attacks cause, besides the production of galls and the attendant gall-related reduction in leaf area, progressive corruption of the branch architecture, including the death of branch parts, and an increase in dormant bud activation. Thus far, there have been few attempts to quantify branch architecture damage. Further, the different methods for assessing infestation degree (MAID) that have been developed focus only on the galls' presence and abundance.
Using the leaf area to sapwood area relationship as a green biomass indicator, we developed in a previous study a damage composite index (DCI) that takes into account the most important branch architectural features, allowing for realistic damage assessment during the entire epidemic process. 
The aim of this study is to present this novel method and highlight differences in the damage description with respect to other broadly used indices. Results show how the DCI depicts branch damage better, especially during the epidemic peak, compared to MAID, which tend to underestimate it. We conclude by suggesting how to properly evaluate the overall impact of the pest by means of our composite damage index, the infestation degree using classic methods, and crown transparency evaluations.

A total of 25 localities in Ticino, Switzerland were visited between 2013 and 2016 in order to create a temporal gradient covering all gall wasp epidemic stages. In total, we collected and analyzed 94 branches in 5 sites at an early epidemic stage (arrival of the pest and beginning of tree damage), 200 branches in 5 sites at the epidemic peak (medium to severe damage due to high level of D. kuriphilus attack), 200 branches in 5 sites at the recovery stage (biocontrol by T. si...

Watch this Scientific Journal Video about Evaluating Dryocosmus Kuriphilus-induced Damage on Castanea Sativa at JoVE.com

Evaluating Dryocosmus Kuriphilus-induced Damage on Castanea Sativa

It is common practice to assess the damage caused by Dryocosmus kuriphilus by considering the abundance of galls alone rather than by also taking related branch corruption into consideration. We propose a composite damage index that takes into account the most important branch features, thus enabling more realistic damage assessment.

Evaluating Dryocosmus Kuriphilus-induced Damage on Castanea Sativa

Dryocosmus kuriphilus Yasumatsu has become a major pest for Castaneasativa since its arrival in Europe. Its galling activity results in the formation of ...

This method was developed by relating leaf area loss due to the gall wasp attack to the main branch feature such as dormant buds, galls, and dead shoots involved. Considering and combining these feature in a composite damage index allow a realistic evaluation of the tree state during the entire epidemic process, including the recovery phase. The main advantage is that it reveals the real branch alteration even during the recovery phase when the presence of galls becomes poor.We first had the idea for this method when we realized that Dryocosmus kuriphilus attack also causes corruption of the branch architecture beside gall-related reduction in leaf area. Though this method is species specific, the methodology used to create it can be adapted and implemented to any other tree species and related pest. In order to collect the data, arrange for a clipboard, a camping chair, secateurs, a telescopic tree pruner, and a 30-meter measuring tape.Get tree climbing equipment for analysis if the top crown is above eight meters. While collecting, gather three types of branches which represent damaged, healthiest, and an intermediate one to constitute the entire branch diversity. Then, attach the start of the measuring tape near the blade of the telescopic tree pruner.Then use the telescopic pruner to cut the branch. Once the branch is cut, record its cutting height, aspect, and whether the branch type is architectural or reiteration. Next, to gather general information about the branch, assign a unique ID and record the age and the maximum length of the branch from the first branching point to the apex.First look for a sprout, which is a freshly formed structure that has grown during the current vegetative season from a developed bud on a shoot. Next gather an alive shoot, which is a sprout that has developed from the previous vegetative season with respect to the sampling date, then a dead shoot which has died either due to D.kuriphilus attack or naturally. Then collect the reactivated dormant buds which are freshly formed sprouts that have grown during the present vegetative season from a dormant bud on a multi-layer branch part that is older than the shoot.Finally look for a gall on the shoot which usually develops on the base or along the axis of a sprout. Then count and record all the live and dead shoots, reactivated dormant buds, and all the galls on the shoots respectively. To calculate the damage composite index, select the section corresponding to the dead shoot, then calculate the proportion of the dead shoot.Next calculate the proportion of the reactivated dormant bud. After measuring the reactivated dormant bud population, calculate the number of galls on the shoots. Then measure the damage composite index considering the population of dead shoot, reactivated dormant bud, and the number of galls.Next measure the damage severity on the basis of the damage composite index scale. This plot represents early stages of infestation comparing between the DCI and the two MAIDs within the branches. In the plot the Y-axis represents a standardized severity scale where both DCI and the two MAIDs are very low, thereby indicating minimum damage in the early stages.This plot compares the DCI and the two MAIDs during the peak stages of the infestation. The DCI represents a very high damage level when compared to both the MAIDs showing intermediate damage. Interestingly, in the peak and the recovery stages, a heterogeneous branch pattern is observed based on the damage incurred on the basis of the corruption level of the branch.In the case of high corruption level, MAIDs tend to underestimate the real damage because they are only based on the presence of galls. The next two plots represent the DCI and the MAIDs in the recovery and the recovered stages of the infestation. During the recovery stage, the plot shows smaller yet significant differences between the DCI and the two MAIDs.However there isn't any difference between the indices in the recovered stage, with the DCI and the two MAIDs showing somewhat similar values. The damage composite index allows to evaluate the real damage caused by Dryocosmus kuriphilus on the branch architecture. Combining this procedure with other methods, like the Sanasilva crown transparency approach and the traditional method for assessing the infestation degree, ensure a thorough pest assessment.Specifically use this procedure to evaluate the branch architecture damage. Use the traditional method for assessing the infestation degrees such as the proportion of attacked bark to evaluate the pest population and use the Sanasilva crown transparency index for a general crown assessment. After watching this video, you should have a good understanding of how to apply the damage composite index to properly evaluate the impact of Dryocosmus kuriphilus on the branch architecture of the chestnut tree.

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7.1K Views.  WSL Swiss Federal Research Institute. This method was developed by relating leaf area loss due to the gall wasp attack to the main branch feature such as dormant buds, galls, and dead shoots involved. Considering and combining these feature in a composite damage index allow a realistic evaluation of the tree state during the entire epidemic process, including the recovery phase. The main advantage is that it reveals the real branch alteration even during the recovery phase when the presence of galls becomes poor.We first h...