INTRODUCTION
The subflexus straw moth, scientifically named Chloridea (Heliothis) subflexa (Guenée) (Lepidoptera: Noctuidae: Heliothinae), is native to North America (Baker et al., 2004; Pogue, 2013). It occurs in tropical and subtropical regions of the American continents in the following countries: United States, Canada, Mexico, Jamaica, Puerto Rico, Cuba, Nicaragua, Costa Rica, Panama, Trinidad and Tobago, Colombia, Ecuador, Venezuela, Peru, Argentina, Bolivia and Brazil (Heath et al., 1990; Poole et al., 1993; Bado et al., 2005; Groot et al., 2007; Groot et al., 2009; Pogue, 2013; De Souza et al., 2015). The areas of occurrence in Brazil include the Amazon, Northeastern region (Pernambuco, Paraíba), Southeastern (Rio de Janeiro) and Midwestern regions (Mato Grosso do Sul; Goiás) (Poole et al., 1993; De Souza et al., 2015).
Chloridea subflexa is a frugivorous and monophagous species with plant hosts in the genus Physalis (Oppenheim and Gould, 2002a; Benda et al., 2011). Until now, the principal interest in this species consisted of studies on hybridization under laboratory conditions using C. virescens, naturally reducing population sizes of this pest-insect by inducing sterility of the males (Mitchell and Heath, 1987). However, in the last few years, the subflexus straw moth became the main pest-insect in tomatillo crops (Physalis ixocarpa Brotero) in Mexico (Groot et al., 2007; Pogue, 2013; Bautista-Martínez et al., 2015) and cape gooseberry (Physalis peruviana L.) crops in Argentina (Bado et al., 2005).
Therefore, the objective was to provide the first record of damage from C. subflexa on P. peruviana in Brazil.
MATERIAL AND METHODS
The observations were made on an organic cape gooseberry plantation in Hidrolândia (16º57’51.79” S and 49º11’02.09” W; 865 m altitude) - west central region of Brazil, from 2014 to 2015. Damaged fruit with the presence of larvae in different instars was observed in 100 plants each year (Fig. 1).
The specimens were collected in the larval stage and kept on a natural diet until reaching the adult stage (Fig. 2). Species identification was carried out based on morphological criteria (head, thorax, forewing, male and female genitalia) (Poole et al., 1993). The identification was performed by the entomologist Vitor Osmar Becker (Serra Bonita Reserve). The adult individuals were stored at the Insectarium of the School of Agronomy of the Federal University of Goiás, Brazil.
RESULTS AND DISCUSSION
The fruits were not harvested in the two years of cape gooseberry cultivation because of the attack from C. subflexa. The plants flourished in a period similar to that reported in the Southeastern region (Rodrigues et al., 2013) and earlier than the Southern region (Betemps et al., 2014). Flowering took place 35 days after transplanting in 2014 (01/07/2014), and, earlier, 25 days after transplanting in 2015 (25/05/2015).
The moths have a shiny body and green-olive spots in the abdomen and wings (Pogue, 2013). There are medial lines preceded by light brown (cream color), specifically in the wings where the basal region has a lighter color than the medial region (Poole et al., 1993). The key traits in distinguishing C. subflexa from C. virescens are related to the prothoracic tibia and palps (Poole et al., 1993).
Oviposition is more frequent in vegetative (stem and leaves) than in reproductive structures (bud, flowers, fruit) (Benda et al., 2011). The vegetative areas are preferred because of the higher surface area. It is noteworthy that oviposition may also occur in non-host plants from different genera, such as: Digitaria, Cyperus, Gossipium and Tagetes (Benda et al., 2011).
Newly emerged larvae infiltrate the calyx, where Physalis berries may be found, and begin feeding. The larvae feed on the mesocarp of the fruit. This damage may occur superficially or the larvae may consume the entire mesocarp, leaving only the epicarp of the fruit. The aforementioned damage pattern is common to larvae in more advanced instars. In addition, damage is more common in green fruit than in ripe ones (characterized by the yellowish or orange color of the epicarp).
Feeding is usually restricted to fruit of the same plant, where at least three berries are necessary for the larvae become pupae (Benda et al., 2009). The damage hinders in natura consumption and industrial use of Physalis fruit.
The calyx provides an enclosure for the larvae, creating a structural refuge that reduces its detection by parasitoids and predators (Baumann and Meier, 1993; Sisterson and Gould, 1999; Oppenheim and Gould, 2002a). This structure acts as a mechanical barrier and has withanolides and glycosides that are feed deterrents (Baumann and Meier, 1993; Dinan et al., 1997) for other phytophagous insects.
The only parasitoid associated with C. subflexa in the United States is Cardiochiles nigreceps Vierick (Hymenoptera: Braconidae). The rates of parasitism are very low (1 to 4%) (Sisterson and Gould, 1999; Oppenheim and Gould, 2002a; Oppenheim and Gould, 2002b) and are not only related to the presence of the calyx.
De Moraes and Mescher (2004) reported that regurgitations of C. subflexa do not have volicitin. Volicitin is a key substance in inducing the responses of the plant to herbivory (via volatile compounds) and its absence is associated with the lack of linoleic acid in Physalis fruit. Linoleic acid is key for normal development and insect metamorphosis, especially for the order Hymenoptera (e.g., C. nigreceps) (De Moraes and Mescher, 2004). Thus, C. subflexa has the ability to grow in fruit that are not nutritionally suitable for other insects and, as a consequence, it is an improper host for natural enemies (De Moraes and Mescher, 2004).
Some Physalis species have defense mechanisms against attacks from C. subflexa. These can be related to mechanical damage such as fruit abscission in P. angulata and P. pubescens (Petzold et al., 2009) or egg desiccation in P. angulata as a consequence of the release of chemical substances (Petzold et al., 2009; Petzold-Maxwell et al., 2011).
This high degree of specialization of C. subflexa for Physalis plants (Barthel et al., 2016) hinders the implementation of management strategies in commercial areas, especially in the case of tomatillo and cape gooseberry. Groot et al. (2007) suggested that monitoring with traps using pheromones is a key strategy for integrated C. subflexa management programs. It is noteworthy that chemical management must be focused on the adult insect once the caterpillars are protected by the calyx in the larval stage. In organic systems, the removal of other Physalis species is recommended, such as the angular winter cherry (P. angulata), along with cultivation in a protected environment in areas of high infestation.
We reiterate that cape gooseberry cultivation is expanding in Brazil, especially in the southern (Lima et al., 2009; Muniz et al., 2011; Betemps et al., 2014) and southeastern regions (Rodrigues et al., 2012). Brazilian production does not meet domestic demand, so importation from Colombia, the largest world producer, becomes necessary (Muniz et al., 2014). The fruits are eaten raw or processed (via juices, jellies, dehydrated) (Puente et al., 2011). The berries stand out because of their exotic taste and high mineral content, antioxidants, and medicinal and bioactive substances (Puente et al., 2011; Ramadan, 2012; Rop et al., 2012; Rutz et al., 2012; Namiesnik et al., 2013; Bravo et al., 2014; Fischer et al., 2014; Moneim et al., 2014; Al-Olayan et al., 2014; Ahmed, 2014).
CONCLUSION
The occurrence of Chloridea (Heliothis) subflexa in Physalis peruviana production areas can derail organic production because of the damage that is caused. Therefore, studies related to the biology and ecology of this insect, its host and the natural control agent are needed to support strategies for integrated management under the Brazilian conditions.