This study was conducted in 3 different counties (Tepic, Xalisco and San Blas) of the avocado growing area of Nayarit. For identification of species, thrips collections were conducted during 2008 using knockdown and net sweeping techniques. A total of 72 species were captured, 10 of which were phytophagous of which the most prevalent was Heliothrips haemorrhoidalis (Bouché) (13.42%); 16 were predaceous of which the most prevalent was Franklinothrips vespiformis (D. L. Crawford) (8.26%) and 46 species (26.83%) were considered occasional visitors. Species registered for the first time in Mexico were as follows: Heterothrips xolismae Hood 1936; H. pubescens Hood 1934; Frankliniella ramirezi Mound & Marullo 1996; F. sandovalensis Retana 1998 and Macrophthalmothrips heinzei Mound 1972.
México is the main producer of avocado worldwide, with an annual production of 1,124, 565 tons harvested from 114,471 ha (FAOSTAT 2008) in 26 states. Nayarit is the second largest producer within a production area of 2,703 ha (SIAP 2009). The counties of Nayarit with the largest avocado acreage planted are Tepic, Xalisco and San Blas. The crop presents a large diversity of thrips species (Cambero et al. 2010), which are considered important pests because they cause lesions on leaves, flowers and fruits (González et al. 2000). Studies performed on avocado in Nayarit by Cambero et al. (2010) showed the presence of 40 species associated with the avocado crop just in Xalisco. This study was performed with the following objectives: a) to determine thrips species associated with avocado in the counties of Tepic, Xalisco and San Blas, Nayarit, and b) to learn their importance as avocado pests, and their predaceous habits.
MATERIALS AND METHODS
Captured thrips were monitored weekly by sampling from Jan to Dec 2008 in 5 commercial avocado orchards located in Tepic, Xalisco and San Blas, Nayarit. In Tepic, collections were conducted in 2 orchards planted to the ‘Hass’ cultivar, the first at the Ejido Camichin de Jauja named ‘Tintilagua’ (21°29 × 18.5″N, 104°46 × 18.4″W, 1,117 masl), and the second at ‘El Fortin’ at Ejido Venustiano Carranza (21°31 × 00.5″N, 104°58 × 57.8″W, 1,099 masl). In Xalisco 2 orchards of the cultivar Hass were sampled, i.e., ‘La Chapula’ at Ejido Xalisco (21°25 × 09.4″N, 104°54 × 53.9″W 1,035, masl), and ‘La Carbonera’ at Ejido El Cuarenteño (21°27 × 34.1″N, 105°00 × 19.1″W 1,787, masl). In San Blas samples were taken in the orchard ‘El Cedro’ at Ejido Mecatan (21°32 × 47.4″N, 105°08 × 23.1″W, 384 masl), which was planted to the “Choquette’ and ‘Hall’ cultivars.
PHYTOPHAGOUS THRIPS SPECIES COLLECTED IN AVOCADO GROVES IN XALISCO, TEPIC AND SAN BLAS, COUNTIES OF NAYARIT.
PREDACEOUS SPECIES OF THRIPS COLLECTED IN AVOCADO GROVES IN XALISCO, TEPIC AND SAN BLAS, COUNTIES OF NAYARIT.
Knockdown sampling and sweep netting were used (Cambero et al. 2010) to collect thrips from trees as well as from weeds within the orchards. The insects collected were placed in 5 cc transparent plastic vials containing 70% ethyl alcohol, and taken to the Entomology Laboratory of the Universidad Autónoma Agraria Antonio Narro, where thrips were mounted and identified according to Johansen & Mojica (1997).
RESULTS AND DISCUSSION
A grand total of 9,428 thrips of different stages were collected during this research. A total of 775 thrips adults in good condition were identified, which represented 8.22% of the grand total of captured specimens. The 775 thrips adults belong to 72 species. Ten species (273 specimens) were phytophagous (Table 1), 16 predaceous (Table 2) and 46 occasional visitors (Table 3).
The phytophagous species are those that feed on avocado trees and are commonly established on them. Johansen et al. (2007) reported 33 species in Mexico that can cause injury to avocado trees. In this research 10 species were found with such injurious habits (Table 1). Heliothrips haemorrhoidalis (Bouché) was the most abundant phytophagous species (13.42% of the total). Mound & Marullo (1996) observed that males of this species are very rare, and very few specimens are available in insect collections. In this work 24 H. haemorrhoidalis adult males were found. Scirtothrips perseae Nakahara is the most important pest of avocados of Mexico (Johansen et al. 2007). However, in this research it was not detected.
Sixteen predaceous species were detected (Table 2). Johansen et al. (2007) recognized 10 predaceous thrips species related to avocado agroeco-systems. In this study the most representative were Franklinothrips vespiformis (D. L. Crawford) (8.26%), followed by Leptothrips primigenus Johansen (8.13%) and Franklinothrips orizabensis Johansen (7.22%). The rest of the species ranged from 0.13% to 5.5% of the total of 775 collected (Table 2). Several members of Franklinothrips are considered as successful biological control agents against thrips plant pests (Loomans & Vierbergen 1999). Hoddle et al. (2008) reported that Scolothrips sexmaculatus (Pergande) is found particularly in fruit trees and considered to be a significant mite predator comparable to various Leptothrips species.
Forty six visitor species were identified (Table 3). They are considered to be visitors because of their only occasional presence on avocado trees. Johansen et al. (2007) listed 40 visitor species that are phytophagous and that live on weeds within and around the orchards, or are transported by the wind as aerial biological material and dispersed into orchards. The mycophagous species within vegetable debris are also occasional visitors, and they include species in the Allothrips, Elaphrothrips, Macrophthalmothrips and Terthrothrips genera.
Frankliniella was the genus with the largest number of species (18), followed by Elaphrothrips (3). Within the genera Heterothrips, Caliothrips, Humbolthrips, Microcephalothrips, Neohydatothrips and Macrophthalmothrips 2 species of each. It is important to point out the presence of 19 new species (sp. nov.) and 2 genera new to science (Gen. nov.); all are now in the process of description.
The authors express their gratitude to Consejo Nacional de Ciencia y Tecnología (CONACyT) project number MOD-ORD-11-11-PCI-1103-06-11 and to avocado orchards owners for their valuable support.