Natural Parasitism of Diaphorina citri (Hemiptera: Psyllidae) Collected From Two Host Plants in the Apatzingán Valley, Mexico, by Tamarixia radiata (Hymenoptera: Eulophidae).

Tamarixia radiata (Waterson) (Hymenoptera: Eulophidae) is an idiobiont ectoparasitoid of the Asian citrus psyllid, Diaphorina citri Kuwayama (Hemiptera: Psyllidae). This study evaluated natural parasitism of the different nymphal instars of D. citri by T. radiata on three different dates in 2015 at four sites with Mexican lemon (Citrus aurantifolia Swingle) groves and at one site with orange jasmine (Murraya paniculata [L.] Jacq.) plants in the Apatzingán Valley, Michoacán state. Different patterns of parasitism by T. radiata were observed among the different nymphal instars of D. citri, sites, and collection dates. No parasitism of first and second instars was observed, and it only reached up to 5.0% in third instars. In fourth and fifth instars, parasitism was highly variable (2-69 and 1-38%, respectively). In terms of the accumulated parasitism across host instars, the highest percentages were observed in the collections conducted in May in Crucero de Parácuaro (86%) and Antúnez (91%), and they were approximately 45% in the collections conducted on 23 March in Antúnez and on 10 April in Nueva Italia-2. In the remaining collections, parasitism was between 2 and 15%. Our results suggest that T. radiata is an important mortality factor for populations of D. citri; this could have potentially important implications for the biological control of D. citri and for the management of huanglongbing, a disease transmitted by D. citri, in citrus groves.

Behavior of Tamarixia triozae Females (Hymenoptera: Eulophidae) Attacking Bactericera cockerelli (Hemiptera: Triozidae) and Effects of Three Pesticides on This Parasitoid.

The parasitism and host feeding behavior of Tamarixia triozae (Burks) (Hymenoptera: Eulophidae) females on Bactericera cockerelli (Sulc) (Hemiptera: Triozidae) fourth instars that have infested tomato (Lycopersicon esculentum Miller) leaflets are described and quantified. Females took approximately 31.14 ± 4.39 min to search for their first suitable host. The recognition and handling times for oviposition were 2.66 ± 0.18 and 4.26 ± 0.39 min, respectively. T. triozae parasitized 4.66 ± 0.61 nymphs in a period of 6 h. The parasitoid explored and probed its host by walking along the margins of its body while antennating and repeatedly introducing the ovipositor beneath the nymph. The handling times before and during host feeding were 8.42 ± 0.67 and 8.29 ± 0.60 min, respectively. T. triozae females consumed 1.00 ± 0.00 B. cockerelli nymph after parasitizing 3.3 ± 0.48 nymphs. EPA-a refined soybean oil-imidacloprid, and abamectin caused between ~70 and 100% T. triozae adult mortality after a 48-h contact treatment with fresh pesticide residue and a 47-91% decrease (abamectin > imidacloprid > EPA) in adult emergence when parasitized B. cockerelli fourth instars were directly sprayed. These data suggest that the use of these insecticides in combination with T. triozae in integrated pest management programs should be carefully evaluated.

Foliar persistence and residual activity of methoxyfenozide against beet armyworm (Lepidoptera: Noctuidae).

A greenhouse study was conducted to investigate the persistence of methoxyfenozide in pepper (Capsicum annuum L.) foliage. An aqueous suspension of methoxyfenozide was sprayed on pepper plants at concentrations of 72 and 144 mg of active ingredient (a.i.)/L. Foliage was collected at different intervals of time (0, 3, 5, 10, 20, 30, 40, and 50 days) after the treatment, and the methoxyfenozide residue was measured by high-performance liquid chromatography. The foliage was also used in bioassays to determine the residual toxicity on and the consumption rate of the third-instar larvae of the beet armyworm, Spodoptera exigua (Hübner) (Lepidoptera: Noctuidae). The methoxyfenozide concentrations observed after 50 days had decreased to 19 and 69 µg/g per sample, corresponding to a loss of 61% and 28% from the application concentrations of 72 and 144 mg a.i./L, respectively. When fitting a first-order kinetics degradation model, the half-life (DT50 ) of this compound was 76 days. Both application concentrations of methoxyfenozide caused a high mortality rate (≥97%) when the larvae were fed the pepper foliage collected at all of the time intervals. Lastly, at all of the time points, the consumption rate by the larvae was reduced to between 57% and 92% for both concentrations that were bioassayed. Our results indicate that, under the present greenhouse conditions, the degradation of methoxyfenozide was slower than that reported by other authors and that its residues were highly toxic to S. exigua larvae. The implications of these results for the management programs of this pest are discussed.