Annual Report 2011 Biological control of field bindweed,

Convolvulus arvensis G. Cortat, G. Grosskopf-Lachat, H. L. Hinz, A. Thuis and A. Tateno

May 2012

CABI Ref: VM10065 Issued May 2012

Biological control of field bindweed, Convolvulus arvensis

Annual Report 2011

G. Cortat, G. Grosskopf-Lachat, H. L. Hinz, A. Thuis and A. Tateno

CABI Rue des Grillons 1, CH-2800 Delémont, Switzerland Tel: ++ 41 32 421 4870 Fax: ++ 41 32 421 4871 Email: Europe-CH@cabi.org Sponsored by: USDA-APHIS-CPHST

This report is the Copyright of CAB International, on behalf of the sponsors of this work where appropriate. It presents unpublished research findings, which should not be used or quoted without written agreement from CAB International. Unless specifically agreed otherwise in writing, all information herein should be treated as confidential.

Table of Contents Summary .................................................................................................................... 1

1. Introduction ....................................................................................................... 3

2. Work Programme for Period under Report ..................................................... 3

3. Shipments of Test Plants ................................................................................. 4

4. Melanagromyza albocilia HENDEL (Dipt.: Agromyzidae) ................................ 5

4.1. Background ................................................................................................. 5

4.2. Field collections and emergence ............................................................... 5

4.3. Feeding, mating and oviposition tests ...................................................... 6

4.3.1. Behavioural observation trials ................................................................... 6

4.3.2. Sequential no-choice feeding and oviposition tests .................................. 7

4.3.3. Single-choice feeding and oviposition tests .............................................. 8

4.3.4. Oviposition and development trials on potted plants ................................. 8

4.4. Conclusions and outlook ........................................................................... 9

5. Longitarsus pellucidus FOUDRAS and L. rubiginosus FOUDRAS (Col.: Chrysomelidae) ......................................................................................................... 9

5.1. Background ................................................................................................. 9

5.2. Field collections, overwintering and rearing ............................................ 9

5.3. Host-range investigations ........................................................................ 10

5.3.1. No-choice larval transfer tests with Longitarsus pellucidus in 2011 ........ 10

5.3.2. No-choice larval transfer tests with Longitarsus pellucidus in 2010 ........ 11

5.3.3. Multiple-choice field cage tests with Longitarsus pellucidus in 2011 ....... 11

5.3.4. Open-field test with Longitarsus pellucidus and L. rubiginosus in 2011 .. 12

5.4. Conclusions and outlook ......................................................................... 13

6. Proposed Work Programme for 2012 ............................................................ 13

7. Acknowledgements ........................................................................................ 14

8. References ...................................................................................................... 14

Annex ....................................................................................................................... 16

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Summary

1. Field bindweed, Convolvulus arvensis, is a perennial vine of Eurasian origin that has been introduced into North America and Australia. The plant has an extensive root system, can form dense tangled mats and harbour plant diseases, and is toxic to horses. In the 1970s, the US Department of Agriculture (USDA) initiated a programme for the biological control of field bindweed. Two biological control agents were released, the gall mite Aceria malherbae and the bindweed moth Tyta luctuosa. The gall mite became established but impact under field conditions varies, while establishment of the bindweed moth has never been confirmed. Therefore, the project is being revisited and investigations on three additional potential biological control agents started in 2009, i.e. the stem-mining agromyzid fly Melanagromyza albocilia and the root-mining flea beetles Longitarsus pellucidus and L. rubiginosus. 2. Melanagromyza albocilia has two generations per year. Its larvae mine in the stems and roots of field bindweed. In 2011, flies of the first generation emerged between mid-May and mid-June, and flies of the second generation emerged in September. Attack rates of plants collected in Germany in September and October 2011 ranged between 18% and 27%, but only 11.5% of the plants contained viable pupae or larvae. From the pupae, only about 10% of flies emerged in 2011 and the mean parasitism rate at emergence, for the period 2009–11 was 67%. The relatively low attack rates in the field, combined with low adult emergence rates and high parasitism, demands sustained efforts in mass collection. 3. To better understand requirements for mating, feeding and oviposition of M. albocilia, several different methods were tried in 2011. Greater fly activity was observed in containers where flies were offered more space (cylinders and gauze bags vs vials and petri dishes). The addition of honey as a food source appears to trigger mating and oviposition. Preliminary no-choice and single-choice feeding and oviposition tests were conducted, which yielded valid results. In addition, we found pupae and larvae in potted plants that were exposed in the lab, which is an encouraging first step towards establishing a rearing colony and conducting development tests in 2012. In summary, we made considerable progress in 2011 in the development of valid methods for the testing and future rearing of M. albocilia. In 2012, we are planning to further refine methods developed in 2011 and to continue host-specificity tests and efforts to establish a rearing colony at CABI. 4. Longitarsus pellucidus has one generation per year, but adults of the F1 generation appear to be able to overwinter and lay eggs a second time the following spring. The adults feed on the leaves of Convolvulus arvensis, whereas the larvae feed on the roots. No-choice larval transfer tests were set up with 16 test plant species, ten native to North America. Adults emerged from the three populations of Convolvulus arvensis exposed and the three native North American (NA) species Convolvulus equitans, Calystegia malacophylla and Calystegia subacualis. Three multiple-choice cage tests were set up with the target and native NA plants that were attacked under no-choice conditions: Convolvulus equitans, Calystegia macrostegia, Calystegia malacophylla, Calystegia purpurata and Calystegia sepium (hedge bindweed). Adults emerged from all species exposed. An open-field test was conducted with the same plant species to determine if this result was a consequence of the design. A site was chosen where both L. pellucidus and L. rubiginosus (see below) occur. Final results will be available in 2012 and will indicate if we can still consider these two insects as potential agents for field bindweed.

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5. Longitarsus rubiginosus also has one generation per year. The adults feed on the leaves of Convolvulus arvensis and Calystegia sepium. As adults emerged from the native NA species Convolvulus equitans and Calystegia purpurata in no-choice larval transfer tests conducted in 2010, we included this agent in the open-field test established with L. pellucidus (see above).

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1. Introduction

Field bindweed, Convolvulus arvensis, is a perennial vine that can form dense tangled mats, thereby outcompeting native forbs and grasses (Hegi, 1966). Heavy infestations in cereal crops can reduce yields by 30–40% or more (Westra et al., 1992; DiTomaso and Healy, 2006). Plants can harbour the viruses that cause potato virus X disease, tomato spotted wilt and vaccinium false bottom (DiTomaso and Healy, 2006). In addition, the foliage of field bindweed contains alkaloids that can cause intestinal problems in horses grazing on heavily infested pastures (Todd et al., 1995). Field bindweed is native to Eurasia, but was introduced into North America during the 18th century (Phillips, 1978) and into Australia in the early 1800s (Parsons and Cuthbertson, 2001) and is now considered one of the most noxious weeds of agricultural fields throughout temperate regions of the world (DiTomaso and Healy, 2006). Field bindweed occurs throughout North America except in the extreme North (USDA, NRCS, 2011). The plant is difficult to control with conventional methods owing to its extensive root system and seed longevity (Hegi, 1966). In the 1970s, the US Department of Agriculture (USDA) initiated a programme for the biological control of field bindweed. Two biological control agents have been released in North America so far. The gall mite Aceria malherbae (Nuzzaci) (Acari: Eriophyidae) was released in Texas in 1989 and has been redistributed since in several US states and in Canada (Boldt and Sobhian, 1993; McClay et al., 1999). In heavily infested plants, the shoots are distorted and growth is severely stunted. However, establishment and impact under field conditions are variable and appear to depend on moisture levels. In addition, effective control of field bindweed with A. malherbae requires additional management such as regular mowing and redistribution of mites. The bindweed moth Tyta luctuosa (Denis & Schiffermüller) (Lepidoptera: Noctuidae) was released in 1987 in Arizona, Iowa, Missouri, Oklahoma and Texas, but establishment had not been confirmed as of 2002 (Littlefield, 2004; Jacobs, 2007). Through an initiative of Dr Richard Hansen (USDA-APHIS-CPHST [Animal and Plant Health Inspection Service – Center for Plant Health Science and Technology], Fort Collins, Colorado, USA), the project was revisited and CABI in Switzerland provided with start-up funding to investigate additional potential agents. Three insects were selected for screening, i.e. the agromyzid fly Melanagromyza albocilia (Hendel) (Diptera: Agromyzidae) and the flea beetles Longitarsus pellucidus (Foudras) (Coleoptera: Chrysomelidae) and Longitarsus rubiginosus (Foudras). Larvae of M. albocilia mine in bindweed stems and root crowns, and can kill infested shoots. Adult L. pellucidus and L. rubiginosus feed on leaves of field bindweed, while larvae mine in the roots and are reported to be highly specialized on Convolvulus arvensis in the native range. The test plant list used for the screening of the mite and the moth is being revised to cover mainly native North American (NA) species, ornamentals and crop plants in the family Convolvulaceae.

2. Work Programme for Period under Report

Melanagromyza albocilia (Dipt.: Agromyzidae) • Develop methods for host-range testing;

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• Provided a method can be developed, conduct no-choice and single-choice feeding and oviposition tests with critical NA test plants;

• Mass-collect puparia in southern Germany in July and September for additional work at CABI.

Longitarsus pellucidus (Col.: Chrysomelidae) • Continue to study biology and phenology; • Maintain rearing colony and collect adults in the field in summer; • Set up no-choice larval development tests in spring 2011 with critical test

plants not exposed in 2010; • Set up multiple-choice field cages and/or an open-field test with species that

supported larval development in 2010.

Longitarsus rubiginosus (Col.: Chrysomelidae) • Set up multiple-choice field cages and/or an open-field test with species that

supported larval development in 2010.

Test plant list • Revise list according to comments from North American partners; • Submit list to the Technical Advisory Group (TAG) in the USA; • Obtain seeds or plants of missing test plant species.

3. Shipments of Test Plants

Table 1. Seeds of test plants and Convolvulus arvensis obtained in 2011.

Received Sourcea Plant species Quantity 12 September 2011 CDFA, California Dichondra argentea 50 seeds

Calystegia occidentalis ssp. fulcrata

30 seeds

20 September 2011 USDA-ARS, California

Calystegia longipes 14 seeds

Calystegia malacophylla ssp. pedicillata

>100 seeds

Calystegia sepium 60 seeds Calystegia soldanella 100 seeds Calystegia stebbinsii 40 seeds

7 October 2011 USDA-ARS-NPARL, Montana

Convolvulus arvensis from various NA and EUR origins

Not counted

Calystegia longipes Not counted Calystegia soldanella Not counted Cressa truxillensis a CDFA: California Department of Agriculture; USDA-ARS: US Department of Agriculture – Agricultural Research Service; NPARL: Northern Plains Agricultural Research Laboratory; NA: North American; EUR: European.

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During 2011, we received seeds of seven native NA test species as well as the target weed, Convolvulus arvense, and Calystegia sepium from Drs Mike Pitcairn and Dale Woods (California Department of Food and Agriculture), Dr Lincoln Smith USDA-ARS (Agricultural Research Service), California, and Dr John Gaskin USDA-ARS-NPARL (Northern Plains Agricultural Research Laboratory) (Table 1).

4. Melanagromyza albocilia HENDEL (Dipt.: Agromyzidae)

4.1. Background Melanagromyza albocilia is a small, metallic-green agromyzid which has two generations per year (Spencer, 1976). Females of M. albocilia insert their eggs under the epidermis of field bindweed leaves. Freshly hatched larvae feed first on the leaf tissue, and then tunnel through the midrib of the leaves downwards to the base of the stem or into the root (Tóth et al., 2005). Mature larvae gnaw a hole in the stem or the root crown before pupation, through which the adults emerge. Tóth et al. (2005) observed that stems started to weaken and dry out after pupation of the fly. The fly overwinters in the pupal stage.

4.2. Field collections and emergence Between 16 May and 10 June 2011, 11 males and 11 females emerged from the 206 pupae collected in September 2010 in southern Germany in the Upper Rhine Valley, with a parasitism rate of 73.5%. Due to this low emergence rate, regular field trips were conducted to the Rhine Valley to collect more infested plants. Plants collected at the beginning of June showed no sign of attack, while during July, 93 pupae and 29 larvae were extracted from field-collected plants. From these, only six females and four males emerged in September, with a 50% parasitism rate. Between August and October 2011, four mass collections of Convolvulus arvensis were conducted and over 3000 plants were dissected. We distinguished live and dead (parasitized, deformed or damaged) pupae and larvae, as well as empty pupae or mines (Table 2). The state of pupae was visually assessed and while parasitoids were sometimes visible through the case, we recorded a pupa as dead when it was evident that the fly was deformed or when the pupa was dry and flattened. No larvae were visibly parasitized. A total of 11.5% of the plants collected in September and October contained viable pupae or larvae. Only 9.6% flies emerged in September from viable pupae collected in July 2011, while 10.7% emerged from pupae collected in fall 2010. This number is very low and although we evaluated fitness of pupae at dissection in 2011, damage and parasitism are not always visible at such an early stage. Moreover, pupae can become mouldy and die during the overwintering period. In the past, most plants were dissected on site during collection and pupae were kept inside the shoots until adult emergence. The reasons for a low success rate were not assessed. In contrast, pupae collected in fall 2011 were placed in Petri dishes lined with filter paper or into ELISA cells. They are being checked regularly and mouldy pupae are removed. A total of 435 pupae are currently being overwintered in an outdoor shelter under ambient temperatures for adult emergence in 2012. During the mass collection on 5 October, 105 plants of Calystegia sepium were collected at the same site at which infested Convolvulus arvensis plants were collected, and dissected in the lab. No

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pupae, larvae or any sign of attack by M. albocilia were found in Calystegia sepium, indicating M. albocilia’s narrow host range under field conditions. Table 2. Dissection of Convolvulus arvensis plants collected in southern Germany in 2011.

Date of collection 21 Jul 02 Aug 29 Sep 05 Oct 18 Oct No. plants dissected –a – 146 1807 967 Total no. pupae 177 25 27 222 180

% Live 52.5 44.0 70.4 77.9 72.8 % Deadb 20.3 16.0 22.2 16.2 16.1 % Empty 27.1 40.0 7.4 5.9 11.1

Total no. larvae 44 13 6 18 5 % Live 65.9 100 16.7 66.7 0 % Deadb 34.1 0 83.3 33.3 100

Empty mines – – 14 100 57 a –, data not available. b Dead pupae and larvae, assessed visually, comprise parasitized, deformed or damaged individuals.

4.3. Feeding, mating and oviposition tests Because no attack by the fly could be obtained under confined conditions in 2010 (Grosskopf-Lachat et al., 2011), emphasis in 2011 was on conducting observational trials to determine suitable conditions for feeding and oviposition. All exposed plant material was checked under a dissecting microscope for signs of feeding or oviposition. Plants suspected to have eggs were kept fresh as long as possible and checked regularly to record any development. Sequential no-choice and single-choice tests were conducted with flies that had mated.

4.3.1. Behavioural observation trials

METHODS Nine paired freshly emerged flies were placed in a small plastic tube or a Petri dish (diameter 9 cm). Seven pairs were offered a cut shoot of Convolvulus arvensis inserted in moist florist foam and two pairs in tubes were given no plant material. The flies were observed for a single period of ten to 30 minutes. Seven no-choice behavioural observation tests were conducted in transparent plastic containers (cylinders) with cut shoots of Convolvulus arvensis or Calystegia sepium inserted in florist foam. The first four pairs were also offered flowers from diverse wild plants available in the garden. Behaviour (feeding, mating, oviposition) was recorded during observational sessions of five minutes each, every hour for one to two days. One pair was released in a mating cage, comprising a gauze bag with one corner attached to a stick, to provide more space for the flies. The cage was placed outside in full sunlight and the flies were offered honey, smeared onto one corner of the gauze bag. RESULTS From our experience with other agromyzid flies, we were hoping to observe mating shortly after the flies were paired, but the flies did not seem to be interested in their partners. In the small containers, flies were observed drinking

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water from the florist foam and grooming, but were not very active. In the cylinders, the flies were much more active, walking on the container walls or on the plant. Several flies were observed drinking water from the foam, one feeding on a leaf of Convolvulus arvensis and one on a flower. In the latter case, mating occurred after a little more than two days, but only feeding was found on the exposed leaves (Plate 1). A ‘mating dance’ was observed, whereby the male approached the female from the side and walked in circles, then stopped to observe the female’s reaction. The pair released in the gauze bag was observed feeding on the honey. The following day, mating could be observed, which lasted four hours. The female was then moved to a cylinder with a cut shoot of Convolvulus arvensis inserted in moist florist foam and the female laid an egg soon after (Plate 1).

Plate 1. Above: female Melanagromyza albocilia (left), feeding marks on Convolvulus arvensis (centre), and an egg embedded in the leaf tissue (right). Below: larva in a Convolvulus arvensis stem (left), and pupae (right).

4.3.2. Sequential no-choice feeding and oviposition tests

Based on our experiences during the behavioural observation trials, we established some preliminary no-choice feeding and oviposition tests. METHODS In September 2011, 19 sequential no-choice tests were conducted with three pairs of flies in cylinders. Shoots inserted in florist foam were offered to the flies, alternating test plants (Convolvulus equitans and Calystegia sepium), and Convolvulus arvensis as the control, during a period of one to three days. The flies

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were also offered yeast, milk powder, sugar and honey. Five-minute observations were made at irregular intervals. When no feeding and/or oviposition occurred on the control that was exposed after a test plant without attack, the test was considered not valid. RESULTS The flies were observed feeding on all the additional sources of food (sugar, yeast, milk and honey). Two matings were observed in cylinders with control plant shoots. The first one lasted over 3.5 hours and oviposition occurred within two days. The duration for the second is not known and no eggs could be found. Feeding occurred on seven of 12 controls, three of four Calystegia sepium and one of three Convolvulus equitans. Oviposition occurred on five controls, two Calystegia sepium and one Convolvulus equitans.

4.3.3. Single-choice feeding and oviposition tests

METHODS Single-choice tests were conducted in cylinders simultaneously exposing one cut shoot of Convolvulus arvensis as a control and one of Convolvulus equitans, Calystegia sepium, Calystegia malacophylla or Calystegia purpurata inserted in florist foam to pairs of flies. All but two pairs were also offered yeast, milk powder, sugar and honey. Tests that had no attack (feeding and/or oviposition) on either the test plant or the control were considered not valid. RESULTS Feeding occurred on all the seven valid control plants and oviposition on two. Feeding marks and eggs were found on Calystegia sepium and Calystegia purpurata (Table 3), but in the second case the control plant was wilting, thus this replicate was not valid as a choice test. Table 3. Results of preliminary single-choice feeding and oviposition tests with Melanagromyza albocilia in 2011.

Plant species No. plants exposed

No. valid replicates

No. plants with feeding

No. plants with eggs

Convolvulus arvensis 12 7 7 2 Convolvulus equitans* 1 1 0 0 Calystegia sepium 4 1 1 1 Calystegia malacophylla* 3 2 0 0 Calystegia purpurata* 3 3 3 1

* Plant species native to North America.

4.3.4. Oviposition and development trials on potted plants METHODS Four pairs of flies were offered potted Convolvulus arvensis in wooden screen cages. All were offered milk powder, yeast and sugar, and three pairs also had honey and two flowers in florist foam. The cages were kept in the lab and behaviour was recorded during five-minute observations at irregular intervals over a period of 3 to 7 days. Three females and two males that were alive at the end of the experiments in October were released onto two potted Convolvulus arvensis covered with gauze bags and placed in a greenhouse to overwinter for potential adult emergence in 2012. RESULTS Mating and oviposition behaviour were only observed when honey was present. Heavy aphid attack caused all shoots to die prematurely and they were dissected. Two dead, dried out pupae were found in the shoots of one plant; one

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dead larva was found in another plant; two more plants had possible mines; and nothing was found in the two remaining plants.

4.4. Conclusions and outlook In contrast to last year, we made considerable progress in 2011 in developing valid methods for the testing and future rearing of M. albocilia. In most of the tests conducted in September, the flies were offered milk powder, yeast, sugar and honey in addition to plant material. As observed in several experiments, honey seems to trigger mating and oviposition. In 2012, we therefore hope to have better success with oviposition, by offering honey to all freshly emerged flies. Depending on the number of flies available, we might also conduct additional observational trials in Petri dishes and no-choice and single-choice feeding and oviposition tests in cylinders. Finding pupae and larvae in the potted plants that were exposed in the lab is an encouraging first step towards establishing a rearing colony and conducting development tests in 2012. However, the relatively low attack rates in the field combined with low adult emergence and the high parasitism rate still demands a sustained effort in mass collections to obtain a sufficient number of adults.

5. Longitarsus pellucidus FOUDRAS and L. rubiginosus FOUDRAS (Col.: Chrysomelidae)

5.1. Background According to the literature, three Longitarsus species are associated with field bindweed, Convolvulus arvensis, and hedge bindweed, Calystegia sepium, in central Europe, i.e. Longitarsus longipennis Kutschera, L. pellucidus and L. rubiginosus (Lohse and Lucht, 1994; Koch, 1992). During field studies carried out in Slovakia in 1998, L. pellucidus and L. longipennis were the only Longitarsus species associated with field bindweed and L. rubiginosus was not present in any of the field samples (Tóth et al., 2004). In contrast, we did not record any adults of L. longipennis in field samples collected from Convolvulus arvensis and Calystegia sepium in the area around Delémont.

5.2. Field collections, overwintering and rearing Between 5 May and 12 July 2011, four field sites in the Swiss Jura were visited and adults collected (Table 4). At three of the sites, both field bindweed (Convolvulus arvensis) and hedge bindweed (Calystegia sepium) were present, but only the former was sweep-netted. At the fourth site (Courroux), only Calystegia sepium was present. Both L. pellucidus and L. rubiginosus were found on all the sites, but in different proportions. Longitarsus pellucidus was already present at the beginning of May while Longitarsus rubiginosus was found from mid-June onwards. The overall number of L. pellucidus collected was far more important than L. rubiginosus at two of the sites, while at the other two sites, L. rubiginosus was more common and L. pellucidus in low abundance (Table 4). All flea beetles were determined under a dissecting stereo microscope. All flea beetles collected were used in host-range tests (see below).

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Table 4. Numbers of Longitarsus pellucidus and L. rubiginosus collected at different field sites in 2011.

Sites Plant species present L. pellucidus L. rubiginosus Delémont 1 Co. arvensis and Ca. sepiuma 66 1 Delémont 2 Co. arvensis and Ca. sepiuma 2 9 Courroux Ca. sepium 1 16 Bassecourt Co. arvensis and Ca. sepiuma 56 8

a Only Convolvulus arvensis plants were sweep-netted.

In October 2010, 142 adult L. pellucidus were placed onto potted plants covered with gauze bags for overwintering in the garden at CABI. Between 14 March and 15 April 2011, 101 adults were retrieved (i.e. 71% survival) and placed in cylinders with cut shoots of Convolvulus arvensis inserted in moist florist foam. During 2010, 1687 eggs were collected and overwintered under semi-natural conditions in Petri dishes, lined with moist filter paper. A fraction of these (293 eggs) came from a rearing colony of L. pellucidus contaminated with L. rubiginosus, due to a misidentification of the adults. The 180 larvae hatching from these eggs were used for rearing purposes only. Some of the L. pellucidus adults collected at field sites (see above) were placed in transparent cylinders and offered cut shoots of Convolvulus arvensis inserted in moist florist foam. Between 11 April and 2 May 2011, 3356 eggs of L. pellucidus were collected from the cylinders for larval transfer tests. From mid-April until the beginning of June, a total of 435 larvae (180 from the contaminated rearing colony and 255 L. pellucidus) were transferred onto 23 potted Convolvulus arvensis plants for rearing. The rest of eggs collected in 2010 and 2011 (all L. pellucidus) were used for larval transfer tests (see below). In May, most of the adult L. pellucidus were used in multiple-choice tests (see section 5.3.3). A few were kept in cylinders and continued to lay eggs until mid-July, when the last adults were released in the open-field test (see section 5.3.4).

5.3. Host-range investigations 5.3.1. No-choice larval transfer tests with Longitarsus pellucidus in 2011

METHODS From mid-April until mid-June 2011, 2141 larvae were transferred onto a total of 85 plants: 35 Convolvulus arvensis plants of three different origins (California and Colorado, USA, and Europe) and 1–5 plants of 16 test species, ten native to North America. Depending on plant size, batches of 10–30 first instar larvae were transferred with a fine paintbrush onto the base of potted plants. All plants were covered with gauze bags and kept in an unheated greenhouse. Plants were checked for adult emergence once or twice a week from the beginning of June onwards. Emerging adults were visually identified and then deep-frozen for later confirmation of identification by dissecting males to compare the shape of the genitalia. RESULTS The number of target plants exposed in 2011 that supported adult emergence was higher than the previous year (31.4 vs.15.4). Adults of L. pellucidus emerged from the three populations of Convolvulus arvensis (Table 5). The flea beetles were able to develop on the three natives Calystegia malacophylla, Calystegia subacualis and Convolvulus equitans. None of the test species outside the genera Convolvulus and Calystegia was attacked (Table 5).

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Table 5. No-choice larval transfer tests with Longitarsus pellucidus in 2011.

Plant speciesa No. replicates Mean no. adults

emerged ± SEb Success rate (%)c

exposed with emergence Convolvulus arvensis (CA) 13 3 3.0 ± 1.5 3.1 Convolvulus arvensis (CO) 11 5 5.0 ± 1.9 9.8 Convolvulus arvensis EUR 11 3 1.0 1.3 Convolvulus equitans* 1 1 6.0 20 Calystegia macrostegia* 1 0 0.0 0.0 Calystegia malacophylla* 1 1 2.0 6.7 Calystegia soldanella* 4 0 0.0 0.0 Calystegia subacaulis* 2 1 2.0 3.3 Ipomea batata 5 0 0.0 0.0 Ipomea hederifolia* 5 0 0.0 0.0 Ipomea lacunosa* 5 0 0.0 0.0 Ipomea leptophylla* 4 0 0.0 0.0 Ipomea nil* 5 0 0.0 0.0 Ipomea purpurea 5 0 0.0 0.0 Ipomea tricolor 5 0 0.0 0.0 Jacquemontia tamnifolia* 1 0 0.0 0.0 Operculina aequisepala 1 0 0.0 0.0 Solanum tuberosum 5 0 0.0 0.0

a CA: California, USA; CO: Colorado, USA; EUR: Europe; * plant species indigenous to North America. b For replicates that supported development. c Percentage adults emerged of the total number of larvae transferred.

5.3.2. No-choice larval transfer tests with Longitarsus pellucidus in 2010

In 2010, 71 plants were exposed in larval transfer tests. Due to misidentification of adults, the larvae were from a rearing colony containing both L. pellucidus and L. rubiginosus. In 2010 adults of both flea beetle species emerged from 38.5% of the Convolvulus arvensis exposed, with only 2.7% of the larvae transferred successfully developing into adults (mean number of adults per plant: 1.5 L. pellucidus and 2.3 L. rubiginosus). It is possible that not all flea beetles had emerged by the end of the first season and we therefore kept the plants for potential further emergence in 2011. In 2011, only four additional L. rubiginosus and one L. pellucidus emerged, one of which developed on Dichondra donnelliana, and one on Calystegia sepium, both NA natives (see Annex 1 for final results).

5.3.3. Multiple-choice field cage tests with Longitarsus pellucidus in 2011

METHODS At the end of April, three field cages (2 × 2 × 1.6 m) were set up with 19 potted plants of the following species in each: six controls of different origins (California, Colorado and Europe) and sizes to match the test plants, and 1–3 plants each of five test species, four native to NA. The plants were grouped into three pots of the same species (except for Calystegia malacophylla) to recreate a natural patchy distribution and embedded in sawdust (Plate 2). Between 2 and 10 May, 20 females and ten males of L. pellucidus were released in each cage. The adults were

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removed mid-June, and all the plants were individually sleeved. Plants were checked for adult emergence once or twice a week. RESULTS Adults emerged between the end of June and the beginning of August from all species exposed (Table 6). From some test species, more adults emerged than from the controls (Plate 2).

Table 6. Multiple-choice tests with Longitarsus pellucidus in 2011.

Plant species No. plants exposed

% plants with adult emergence

Mean no. adults emerged ± SEa

Convolvulus arvensis 18 66. 7 1.9 ± 0.6

Convolvulus equitans* 9 77. 8 6.0 ± 3.6

Calystegia macrostegia* 9 77.8 1.4 ± 0.2

Calystegia malacophylla* 3 33. 3 1.3

Calystegia purpurata* 9 77. 8 4.0 ± 1.1

Calystegia sepium* 9 77. 8 4.2 ± 2.6

* Plant species indigenous to North America. a Each cage was treated as one replicate.

Plate 2. Longitarsus pellucidus (left), and patchy distribution of the plants in the multiple-choice cage test (right).

5.3.4. Open-field test with Longitarsus pellucidus and L. rubiginosus in 2011

An open-field test was established to verify that the result of the multiple-choice field cage test (see above) was not a consequence of the design. METHODS On 5 July 2011, an open-field test was set up at a site in Delémont, where both L. pellucidus and L. rubiginosus occur. The same species as for the multiple-choice cage test were exposed and 38 potted plants were randomly distributed in a square and embedded in the soil at a distance of about 30–40 cm apart. To make sure that there were enough adults present to attack the plants, 53

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females and 37 males of L. pellucidus and 14 females and 14 males of L. rubiginosus were released on the square between 12 and 19 July. On 7 September, the plants were brought back to CABI, individually sleeved and placed in an unheated greenhouse for overwintering. Plants will be regularly checked for emerging adults in summer 2012.

5.4. Conclusions and outlook Results in 2011 confirmed that both Longitarsus species have a relatively large physiological host range as indicated by the results of no-choice larval transfers, and L. pellucidus also proved to be quite oligophagous under multiple-choice field cage conditions. Successful larval development was even higher on some test species than on Convolvulus arvensis. Although the results might be an artefact of experimental design and/or size of control plants, test results so far do not support the hypothesis of high host specificity in these Longitarsus species. The results of the open-field cage test are expected to determine whether it is worth continuing investigations with these two species or not. Although successful larval development was low again in 2011, we decided not to keep the test plants exposed in 2011 for emergence in 2012, since additional emergence occurring during the second summer for the plants exposed in 2010 proved not to be worth the effort.

6. Proposed Work Programme for 2012

Melanagromyza albocilia (Dipt.: Agromyzidae) • Continue improving methods for rearing and host-range testing; • Conduct no-choice and single-choice feeding, oviposition and development

tests with critical NA test plants; • Mass-collect puparia in southern Germany.

Longitarsus pellucidus and L. rubiginosus (Col.: Chrysomelidae) • Provided that the results of the open-field test are satisfactory, continue

screening these two species with critical test plants not exposed yet; • Collect adults in the field and maintain rearing colonies.

Emmelia trabealis (Lep.: Noctuidae) and Hypocassida subferruginea (Col.: Chrysomelidae)

• Depending on the level of funding available, conduct preliminary open-field tests with Emelia trabealis (Scopoli) and Hypocassida subferruginea (Schrank) and critical test species in the Slovak Republic, in collaboration with Peter Tóth (Slovak Agricultural University, Nitra).

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7. Acknowledgements

We greatly acknowledge Mike Pitcairn and Dave Woods (California Department of Food and Agriculture, USA), Lincoln Smith (USDA-ARS, California, USA) and John Gaskin (USDA-ARS, Northern Plains Agricultural Research Laboratory, Montana, USA) for providing test plant material. We also thank Christian Leschenne, Florence Willemin and Jeanne Steullet (all CABI) for the propagation of our plants. Dr Patrick Häfliger (CABI) ensured that the layout of the report was correct for printing. In 2011, this project was funded by USDA-APHIS-CPHST.

8. References

Boldt, P.E. and Sobhian, R. (1993) Release and establishment of Aceria malherbae (Acari: Eriophyidae) for control of field bindweed in Texas. Environmental Entomology 22, 234–237.

DiTomaso, J.M. and Healy, E.A. (2006) Weeds of California and Other Western States. Volume 1. Aizoaceae – Fabaceae. University of California Department of Agriculture and Natural Resources, 1760 pp.

Grosskopf-Lachat, G., Hinz, H.L. and Tataru, A. (2011) Biological control of field bindweed, Convolvulus arvensis. Unpublished Annual Report 2010, CABI Europe – Switzerland, Delémont, Switzerland, 18 pp.

Hegi, G. (1966) Dicotyledones. V. Band, 3. Teil Pirolaceae – Verbenaceae. Carl Hanser, München, Germany, 515 pp.

Jacobs, J. (2007) Ecology and management of field bindweed (Convolvulus arvensis L.). Invasive Species Technical Note No. MT-9. USDA-NRCS, Montana.

Koch, K. (1992) Die Käfer Mitteleuropas. Ökologie. Band 3. Goecke & Evers, Krefeld, Germany, 389 pp.

Littlefield, J.L. (2004) Tyta luctuosa. In: Coombs, E.M., Clark, J.K., Piper, G.L. and Cofrancesco, A.F. Jr (eds) Biological Control of Invasive Plants in the United States. Oregon State University Press, Corvallis, Oregon, pp. 155–156.

Lohse, G.A. and Lucht, W.H. (1994) Die Käfer Mitteleuropas. 3. Supplementband mit Katalogteil. Goecke & Evers, Krefeld, Germany, 403 pp.

McClay, A.S., Littlefield, J.L. and Kashefi, J. (1999) Establishment of Aceria malherbae (Acari: Eriophyidae) as a biological control agent for field bindweed (Convolvulaceae) in the Northern Great Plains. The Canadian Entomologist 131, 541–547.

Parsons, W.T. and Cuthberston, E.G. (2001) Noxious Weeds of Australia, 2nd edn. CSIRO Publishing, Victoria, Australia.

Phillips, W.M. (1978) Field bindweed: the weed and the problem. In: Proceedings of the North Central Weed Control Conference, pp. 140–141.

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Spencer, K.A. (1976) The Agromyzidae (Diptera) of Fennoscandia and Denmark. Fauna Entomologica Scandinavica. Volume 5. Scandinavian Science Press Ltd., Klampenbourg, Denmark, 606 pp.

Todd, F.G., Stermitz, F.R., Schultheis, P., Knight, A.P. and Traub-Dargatz, J. (1995) Tropane alkaloids and toxicity of Convolvulus arvensis. Phytochemistry 39, 301–303.

Tóth, P., Tóthová, M. and Cagáň, Ĺ. (2004) Flea beetles (Chrysomelidae: Alticinae) associated with field bindweed (Convolvulus arvensis L.) in Slovakia. Acta Fytotechnica et Zootechnica 4, 99–103.

Tóth, P., Cristofaro, M. and Cagáň, Ĺ. (2005) Seasonal biology of Melanagromyza albocilia (Diptera: Agromyzidae) and seasonal patterns of field bindweed infestation, under field conditions in Slovakia. Entomologica Fennica 16, 254–262.

USDA, NRCS (2011) The PLANTS Database. National Plant Data Center, Baton Rouge, Louisiana. http://plants.usda.gov (accessed May 2011).

Westra, P., Chapman, P., Stahlmann, P.W., Miller, S.D. and Fay, P.K. (1992) Field bindweed (Convolvulus arvensis) control with various herbicide combinations. Weed Technology 6, 949–955.

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Annex

No-choice larval transfer and development test with Longitarsus pellucidus and L. rubiginosus 2010, final results.

Plant species

No. plants exposed

Total no.

larvae

Success rate (%)a

% with adult em.

L. rubiginosus L. pellucidus

No. replicates with emergence

Mean no. adults emerged ± SEb

No. replicates with emergence

Mean no. adults emerged ± SEb

Convolvulus arvensis Europe 25 750 3.2 44.0 8 2.5 ± 0.5 4 1 Convolvulus arvensis USA 14 420 2.6 35.7 3 2.0 ± 0.3 2 2.5 ± 0.3 Convolvulus equitans* 6 180 0.6 16.7 0 0 1 1 Calystegia longipes* 1 30 0 0 0 0 0 0 Calystegia macrostegia* 5 150 2.0 40.0 1 1.0 2 1 Calystegia malacophylla* 1 30 10.0 100.0 0 0 1 3 Calystegia purpurata* 4 120 16.7 100.0 3 1.3 ± 0.3 4 5.3 ± 1.3 Calystegia sepium* 4 120 14.4 50.0 1 1.0 1 12.0 Dichondra donnelliana* 9 270 0 0 0 0 0 0 Ipomoea lacunosa* 1 30 0 0 0 0 0 0 Ipomoea lindheimerii* 1 30 0 0 0 0 0 0

* Plant species indigenous to North America. a Percentage of adults emerged of total number of larvae transferred. b For replicates that supported development.

Distribution list John Baker Ron Beenen Rob Bourchier Ludovit Cagáň Rosemarie DeClerck-Floate Rochelle Eisen John Gaskin Richard Hansen Jeff Littlefield Jerry Marks Alec McClay Andrew Norton Mike Pitcairn Mark Schwarzländer Lincoln Smith Jane Sooby Peter Tóth Susan Turner CABI library (2)

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