New record of Microtechnites bractatus (Say) (Hemiptera: Miridae) infesting Crotalaria spp. and injuries of Miridae in cultivated plants in the State of Paraná, Brazil

T This study reports for the first time the plant bug Microtechnites bractatus (Say) in Crotalaria juncea and Crotalaria spectabilis, in the state of Paraná, Brazil. We characterized the injuries caused by M. bractatus and Collaria scenica Stal in cultivated plants and in Crotalaria spp. Considering that M. bractatus damage has been incorrectly attributed to C. scenica, we present here a contribution to the correct characterization of these insect pests and their damage over some agricultural

Miridae is the most numerous family among Heteroptera, with 11,139 species described (Schuh, 2013), from which about 1,087 occur in Brazil . Amongst these plant bugs, there are also described phytophagous, fungivorous, saprophagous and predators species (Henry and Wheeler 1988;Wheeler, 2001;Nogueira et al., 2019a). Therefore, this group is particularly important to agriculture, acting as insect-pests to cultivated plants (Carvalho and Afonso, 1977) or as biological control agent in crops (Nogueira et al., 2019a). Some species are described as phytopathogenic bacteria transmissor, besides of other Cimicomorpha (Mitchell, 2004). Some phytophagous of this family registered in Brazil of Collaria spp. and Microtechnites spp. are also associated with numerous plant families (Nogueira et al., 2019b) and causing chlorosis in the plants (Wheeler, 2001;Jung and Lee, 2012).
On the other hand, Collaria is currently composed of 14 species distributed among the Afrotropical, Nearctic and Neotropical regions and C. scenica is found in Uruguay, Argentina, Brazil and Colombia (Morales et al., 2016;Barreto-Triana et al., 2018). These species are generally associated with Poaceae, such as wheat (Triticum aestivum), oats (Avena sp.), ryegrass (Lolium multiflorum), corn (Zea mays) among others (Barboza et al., 2011;Barreto-Triana et al., 2018). The damage caused by C. scenica is characterized by whitish streaks along the leaf blade, caused by the insertion of the buccal apparatus in the longitudinal direction of the leaf veins and feeding from the cellular content (Martinez and Barreto, 1998).
While C. scenica is registered in several regions in Brazil and the world, the only reports of the occurrence of M. bractatus in Brazil are from Santa Catarina, São Paulo and Minas Gerais (Carvalho and Afonso, 1977;Carvalho, 1989;Nogueira et al., 2019b). However, it is also possible that their occurrence and geographic distribution probably is underreported. In pastures areas of the South-Central region of Paraná State, for example, the damage caused by these insects are being attributed to others mirids (i.e. Collaria scenica) or to other arthropods, leading negligence and under notification of M. bractatus occurrence in the field.
In the present study, the objective was to report the occurrence of M. bractatus in plants of Crotalaria juncea and Crotalaria spectabilis grown in the Center-South region of Paraná-Brazil, and to make a comparative analysis of the intensity of the symptoms caused by M. bractatus and C. scenic in some Fabaceae and Poaceae plants.
The occurrence of M. bractatus was characterized in C. spectabilis and C. juncea crops maintained in Guarapuava, Paraná, Brazil (25°23"03.33"S, 51°29'39.24"W and with an average altitude of 1100 meters). For insect species confirmation, some samples were sent to the PhD. Paulo Sérgio Fiuza Ferreira, professor and taxonomy specialist of Miridae at Federal University of Viçosa, in Viçosa, Minas Gerais, Brazil.
The presence of insects and the identification of the damage caused to the plants of Crotalaria sp., were evaluated delimiting ten points of 0.50 m 2 in a total area of 396 m 2 of each specie of plant. At each of these points, the number of insects present, sex ratio, and location were quantified in three plants. Moreover, three plants per point (30 plants per treatment) were randomly selected to access the number of eggs deposited.
In order to characterize the feeding of M. bractatus and C. scenica in different host plants, nymphs of both species were obtained from laboratory colonies and used to proceed the bioassays. Sections of leaves were offered to two newly emerged couple of the insects, which received bean (P. vulgaris) and black oats (Avena strigosa) during nymphal period, respectively. The treatments were in the plants where the insects have being recorded in the field: (i) black oats, (ii) ryegrass (L. multiflorum), (iii) beans, (iv) white clover (T. repens), (v) Tifton (Cynodon spp.), (vi) fescue (Festuca sp.), (vii) corn (Z. mays) and (viii) crotalaria (C. juncea). For the feeding bioassays, the plants and insects were kept in an airconditioned room with controlled conditions of temperature (18 ± 2 ºC) and photoperiod (12h Light:12h Dark).
The insects were placed in a petri dish (9 cm x 1 cm) lined with paraffin and filter paper moistened with distilled water, containing a leaf or a leaf section of treatments plants. Photographic records were taken to measure the damage upon the experiment was set up and four days later. For each plant tested, four replications were set up. The presence and intensity of chlorosis in each of the treatments were characterized with a score evaluation from 1.0 to 4.0 points, according to the modified methodology of Calderón et al. (1982). The score 1.0 was used for the absence of damage characterized as a normal leaf color, without discoloration or stains. The score 2.0 was assumed for slight damage, discolored leaf and with stains, not beyond than 1/3 of the leaf. The score 3.0 was used for moderate damage, yellowish or white spots covering between 1/3 and 2/3 of the leaf and beginning of yellowing. Finally, the score 4.0 was used for severe damage, almost or total yellowing of the leaf and necrosis. Four evaluators blinded as the allocation of the treatments, attributed a score to each replication, which were submitted to the Mann-Whitney test (p <0.05), using the median value to perform the classification according to the damage scale.
Microtechnites bractatus occurred in seedlings (15 to 25 days after emergence) of C. juncea and C. spectabilis. The injury resulting from the feeding of these insects consisted of whitish spots, causing chlorotic spots, initially sparse on the leaves, which evolved to continuous spots ( Fig. 1A-E). The largest number of insects were quantified in C. juncea, with an average of 3.9 (from 1 to 9) insects per sampled point, whereas in C. spectabilis the average was 2.5 (from 1 to 5). In both crops, males were found in greater numbers, with a sex ratio of 0.3: 1 (11 females and 37 males) in C. juncea and 0.5: 1 in C. spectabilis (11 females and 23 males).
From the 30 plants per treatment that were used for evaluating oviposition, it was found that the laying was performed on the leaves (87.5%) and also on the petiole (12.5%) (Fig. 1F). In seedlings that served for oviposition, the average number of eggs found per seedling was 0.63 (from 0 to 9) in C. juncea and 0.17 (from 0 to 2) in C. spectabilis.
In the plants evaluated here, the symptoms caused by feeding of M. bractatus and C. scenica were different in intensity, which possibly depends on the insect's adaptation to plant species. The symptoms are due to the characteristic feed behavior of Miridae, which are categorized as destructive lacerate-and-flush feeders (Mitchell, 2004). In the laboratory bioassays, both species of plant bugs fed on Poaceae (A. strigosa, L. multiflorum, Festuca sp. and Z. mays), confirmed that M. bractatus also occurs in grasses, causing severe symptoms (Fig. 2). On the other hand, C. scenica did not feed on Fabaceae, attesting that the association of this species with crops of legumes have been occurred erroneously (Luana K. Ribeiro, unpublished data).
Regarding to the damage level, M. bractatus caused severe damage in L. multiflorum (4.0), moderate damage in T. repens, P. vulgaris and C. juncea (3.0) and mild damage in Z. mays and Festuca sp. (2.0) ( Table 1). Among the evaluated Poacea, only Cynodon spp. did not serve as food for M. bractatus, what could indicate some defense traits in this plant. In turn, C. scenica caused severe damage in A. strigosa and L. multiflorum (4.0), moderate damage in Z. mays and Festuca sp.
In Poaceae, M. bractatus is actually associated with Avena sp., Hordeum sp., Sorghum bicolor, Triticum sp., Z. mays (Henry, 1983,   Maes and Carvalho, 1989;Nogueira et al., 2019b), although these records were not related to the south of Brazil. Also in this region, the damage and reduced yield in Poaceae are only associated with C. scenica (Barboza et al., 2011), which is also registered in other regions of the world (Martinez and Barreto, 1998). Hence, in this research, we confirm the presence of M. bractatus and C. scenica in these plant hosts in South Center of Paraná, Brazil.
Thus, this study collaborates with the notification of the occurrence of M. bractatus in the region, which can assist in the stages of monitoring and diagnosing the occurrence in agricultural crops. From this, it will be possible to characterize its occurrence and estimate the real extent of the damage caused by these insects. In the Center-South region of Paraná, where the growing of grasses (Triticum sp., H. vulgare, Avena sp. and Z. mays), legumes (G. max and P. vulgaris) and pastures (Trifolium spp., L. multiflorum, F. arundinaceae and Cynodon spp.) is the basis of agriculture, these stages may be decisive, since the reports of damage caused by mirids have been increasingly frequent.
In this research, the first record of M. bractatus in the state of Paraná is reported, as well as the first record in the crop of Crotalaria spp. This way, it not only expands the geographical distribution of these species, with the inclusion of the state of Paraná, but also contributes with information on host crops of these Miridae.  p<0,05). **Damage score and levels according Calderón et al., (1982).