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Simple Summary The popularity of brassicaceous leafy greens has grown in recent years due to health benefits and the local food movement. However, for many producers and especially organic producers, flea beetles represent a major challenge to production because they chew small holes in the leaves reducing quality and appearance. The goal of our project was to assess the efficacy of row covers and essential oils in controlling flea beetles as an alternative to organic and conventional insecticides. We grew Arugula and Mizuna mustard greens in replicated experimental plots in the spring and fall of 2019. We found that in most cases, plants within the Agribon and ProtekNet row cover treatments had the least amount of flea beetle damage and the highest yields, while plants within the essential oil treatments and organic insecticides did not differ from unsprayed, uncovered control plots. Conventional insecticides had an intermediate level of control against flea beetles, but did not perform as consistently as row cover treatments. We believe that row covers could provide a strong management method for all growers of brassicaceous leafy greens, especially where quality standards are high. Abstract Brassicaceous leafy greens are an important crop for small growers but are difficult to produce due to damage by flea beetles. Flea beetles are problematic for growers as they chew many small holes through leaves rendering produce unmarketable. We tested the efficacy of several essential oils, the woven-mesh row cover ProtekNet, and the spunbonded row cover Agribon, compared to organic and conventional insecticides and no spray controls in the spring and fall of 2019. We found that the two row cover treatments (Agribon and ProtekNet) provided the best control of flea beetles and associated damage. Thyme oil was highly phytotoxic and killed the crop entirely and rosemary and neem essential oils caused mild phytotoxic burns. Organic insecticides rarely performed better than the no spray control. While conventional insecticides controlled most flea beetles, the crop was often still too highly damaged to sell. The results of our study suggest row covers offer producers an effective method of flea beetle control that reduces their dependence on insecticides for conventional and organic production.

Describes two species of flea beetles, Phyllotreta cruciferae, and P. striolata, their life cycles, distribution, and damage to crop plants such as cabbage, collards, broccoli, radish, mustard and turnip. Also notes chemical and non-chemical control methods.

The flea beetles Phyllotreta cruciferae (Goeze) and Phyllotreta striolata (F.) (Coleoptera: Chrysomelidae) are serious pests infesting canola (Brassica napus L.; Brassicales: Brassicaceae) in the Northern Great Plains of the United States. In Montana, P. cruciferae is the only flea beetle species that attacks canola during the crop growing stage. Management of P. cruciferae is usually focused on treating adults feeding on canola seedlings, which is the stage most vulnerable to flea beetle damage. In the Golden Triangle area in Montana, canola growers traditionally use seed treatments or calendar based spraying to control P. cruciferae. Here, we compared calendar-based spraying with seed treatment and threshold-based treatment. The experiment treatments included threshold levels (15e20, 25, 45% of leaf area damaged), calendar based sprays (15, 30 and 45 day intervals after plant emergence), seed treatments (imidacloprid), and untreated controls. The trials were done at two locations (Conrad and Western Triangle Agricultural Research Center). We found that calendar-based spraying at a 15-day interval did not differ significantly in yields from threshold-based treatment at 15e20% leaf damage. Also, the seed treatment did not give significantly higher yields compared to calendar-based sprays. A negative correlation was detected between leaf damage and yield in each treatment. Overall, calendar-based and threshold-based treatments were most effective in improving yields. However, treatment made at the threshold of 15e20% leaf area damage is recommended in order to reduce the number of chemical applications and also to reduce the possibility of selecting for resistance in flea beetles. © 2014 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/3.0/).

This thesis is an investigation into the understanding of flea beetle (Phyllotreta spp.) resistance in spring-type and winter-type canola quality Brassica napus L.. Canola is one of the world’s most widely grown oilseed crops and an economically important crop in Western Canada. Genetic resistance to this common pest would add to the available tactics for integrated pest management of flea beetles in canola. The purpose of this research was to better understand the interactions of the flea beetle with canola at key feeding times in the life cycle of the flea beetle and identify genetic components related to flea beetle herbivory on canola seedlings. The objectives were to: 1) investigate seasonal effects of flea beetle herbivory on both spring-type and winter-type canola; and 2) identify quantitative trait loci (QTL) for flea beetle herbivory in two winter-type doubled haploid (DH) populations using simple sequence repeat (SSR) markers and single nucleotide polymorphic (SNP) markers. Year and seasonal effects were noted but overall trends amongst entries were similar concluding that flea beetle feeding patterns did not change throughout its life cycle. Spring-type and winter-type germplasm reacted similarly under flea beetle feeding. As such, there does not appear to be any novel resistance mechanisms that evolved as a result of divergent growth habit types in canola. Seven QTL were identified over the iii two DH populations studied. Linkage group (LG) N13 had multiple QTL identified. The remaining QTL were located on LG N04, N06, N15 and N17. It is unknown as to what mechanisms these QTL are associated with. The results of this thesis provide insight into flea beetle-canola plant interactions and identify some genetic areas of interest related to flea beetle herbivory in canola. DuPont Pioneer

A bioassay arena and a laboratory screening protocol were developed for assessing lines of Arabidopsis thaliana L. (Heynh.) for feeding damage by the adult crucifer flea beetle, Phyllotreta cruciferae (Goeze). The arena consists of a 96-well microtitre plate with a modified top to contain flea beetles and allow ventilation. Eight lines of A. thaliana, arranged in an 8 × 8 Latin square design, were screened simultaneously in each arena using 50 starved flea beetles. Two cotyledons and the first pair of true leaves per plant were rated visually under a dissecting microscope using a visual damage rating scale. The protocol was used to screen 29 wild ecotypes, eight mutant lines and a single transgenic line of A. thaliana. Discrimination between both cotyledon and leaf tissue was apparent for young beetles that were both non-reproductive or reproductive, but not for old reproductive beetles. Differences were observed between Asian and European ecotypes of A. thaliana, suggesting that geographic origin may play a role in susceptibility of Arabidopsis ecotypes to flea beetle feeding. The transparent testa regulatory gene mutants (lines 82, 111, 164) were most susceptible to flea beetle feeding, possibly indicating a role for anthocyanins and/or flavonoids in governing flea beetle susceptibility. Significant variation in damage levels indicates that expression of flea beetle resistance in the A rabidopsis genome is plastic, and that potential exists to use the wide array of publicly available Arabidopsis germplasm as tools in the transfer of resistance to agronomically important host plants. Key words: Seedling bioassay, Arabidopsis thaliana, wild ecotypes and mutants, crucifer flea beetle, Phyllotreta cruciferae, host plant resistance

This research investigated the phenology of the striped flea beetle (Phyllotreta striolata (Fabricius) (SFB) and crucifer flea beetle (Phyllotreta cruciferae (Goeze)) (CFB), and examined the efficacy and the persistence of biological activity of the reduced-risk insecticides cyantraniliprole, clothianidin, and thiamethoxam applied as seed treatments to spring canola. Yellow sticky cards were placed around field perimeters in order to assess if CFB and SFB have synchronous phenology. It was found that CFB and SFB have largely asynchronous populations in southern Ontario. In laboratory bioassays, while flea beetle control with cyantraniliprole was comparable to that provided by thiamethoxam or clothianidin at the cotyledon stage, control did not persist through the 1st and 2nd leaf stages. Thiamethoxam and clothianidin both provided moderate control of flea beetles in both 1st and 2nd leaves. Field studies suggested that cyantraniliprole may offer control of flea beetles comparable to that provided by thiamethoxam and clothianidin. E.I. DuPont Canada Co.

Crop brassicas with waxy leaves (> 1000 mg kg−1) were fed upon by flea beetles, Phyllotreta cruciferae (Goeze) (Coleoptera: Chrysomelidae), at a low rate, and feeding occurred predominantly at the edges of leaves. Species with non-waxy leaves (−1) were fed upon at a high rate, and feeding occurred randomly throughout the leaf. The regression of feeding rate upon amount of epicuticular wax had an R2 = 0.64, indicating that 64% of the feeding variation of flea beetles on diverse species and cultivars of Brassicaceae was explained by a single factor regression. Feeding studies on low-wax (eceriferum, cer) Brassica mutants confirmed that leaf epicuticular wax is an important antixenotic factor that affects the rate and pattern of feeding of flea beetles. The CC genome of B. oleraceae was identified as the source of the waxy-leaf character that gives rise to the low feeding rate and edge-feeding pattern of flea beetles. The digenomic amphidiploid B. napus (AACC genome), derived from the monogenomic diploids B. oleraceae (CC genome) and B. rapa (AA genome), and the digenomic amphidiploid B. carinata (BBCC genome), derived from monogenomic diploids B. oleraceae and B. nigra (BB genome), had waxy leaves and an edge-feeding pattern and rate similar to members of the B. oleraceae group. All other monogenomic diploids (AA, BB, DD, SS, RR) and digenomic amphidiploids (AABB) not possessing the CC genome had non-waxy leaves, a high rate of feeding and a random feeding pattern by flea beetles.Key words: Brassica, epicuticular wax, feeding, resistance, Phyllotreta cruciferae

Two distinctive leaf feeding patterns, termed "edge" and "random", by flea beetles, Phyllotreta cruciferae (Goeze) were identified in 38 Brassicaceae belonging to nine groups of known genomic composition. Edge feeding occurred in the monogenomic diploid Brassica oleracea group (cc genome) and the digenomic amphidiploid B. napus group (aacc genome). All other genomic groups were fed upon randomly. Experimental manipulation of the plant (by leaf edge removal and new edge creation) and the insect (by antennectomy) and paired feeding tests with plants selected for type of feeding pattern revealed some of the salient features of pattern feeding by P. cruciferae. Leaf edge feeding was correlated with a feeding rate one-tenth of that observed for random feeding, suggesting that edge feeding may be determined by physical and/or chemical factors that render the leaf unpalatable or difficult to feed upon or both.Key words: Insecta, Phyllotreta cruciferae, Brassicaceae, feeding pattern, feeding rate

Antixenosis (nonpreference) and tolerance were identified as two mechanisms of resistance in seedlings of mustard, Sinapis alba 'Ochre', that likely account for the high level of resistance that this plant shows to flea beetles, Phyllotreta cruciferae Goeze, in the field. Sinapis alba showed antixenosis in no-choice and choice feeding tests with a susceptible species, Brassica napus 'Westar'. The beetles consumed about twice as much of the B. napus foliage as compared with S. alba. The highest level of antixenosis occurred in younger seedlings, indicating that S. alba puts forth an optimum defense when it is most vulnerable to flea beetle herbivory. Seedlings of S. alba were tolerant of low levels of flea beetle feeding damage to their cotyledons and continued to grow at almost the same rate as undamaged seedlings, whereas the growth of B. napus declined continuously with the level of feeding damage. The level of tolerance shown by S. alba combined with antixenosis probably accounts for the resistance reported for this crop in the field. In comparison with S. alba, B. napus seedlings, which show no tolerance and are preferred hosts, succumb rapidly to flea beetle attack unless protected with an insecticide. Key words: Insect resistance, mechanism, flea beetle, seedling, mustard, Sinapis alba

In field tests in Hungary, Slovenia and Bulgaria, in allyl isothiocyanate-baited traps significantly more beetles of Phyllotreta cruciferae, Ph. vittula, Ph. undulata, Ph. nigripes, Ph. nodicornis, Ph. balcanica, Ph. atra, Ph. procera, Ph. ochripes, Ph. diademata and Psylliodes chrysocephalus (Coleoptera, Chrysomelidae, Halticinae) were captured than in unbaited control traps. With the exception of Ph. cruciferae, this is the first report on significant field attraction by allyl isothiocyanate for these species. The species spectrum captured included six important agricultural pests. At all sites a great portion of the catch (ranging from ca 30 to 98%) was Ph. cruciferae, irrespective of the plant culture. The second most abundant species present at most sites was Ph. vittula. The present results are very promising from the point of view of applicability of allyl isothiocyanate in Europe as a bait in cabbage flea beetle traps for detection and monitoring.

A 5-yr field study to develop a method for assessing the susceptibility of crucifer seedlings to damage by the flea beetles Phyllotreta cruciferae (Goeze) and Phyllotreta striolata (F.) is described. The recommended method consisted of five replicate 5-m rows per cultivar in a randomized complete-block design. Each test was sown three times at weekly intervals, to assure that at least one test received an appropriate level of flea beetle damage. Each test was assessed 4–5 wk after seeding by counting the number of surviving seedlings in each row and by weighing the dried aboveground portion of 10 randomly selected seedlings, although the latter discriminated fewer lines. The damage caused by flea beetles varied spatially, but this source of variation was minor and did not compromise the tests. This method proved adequate for discriminating among crucifer species and agronomically similar cultivars, some of which showed consistent, significant differences in their responses to flea beettle damage.Key words: Crucifer, rapeseed, flea beetle, pest resistance