Comparative demography of the spider mite Tetranychus ludeni on two host plants in West Africa.

It is well recognized that the quality of host plants affects the development and survival of plant-feeding arthropods. The effects of two leafy vegetable crops, amaranth, Amaranthus cruentus L. (Caryophyllales: Amaranthaceae) and nightshade, Solanum macrocarpon L. (Solanales: Solanaceae) were examined on the development and demographic parameters of the spider mite, Tetranychus ludeni Zacher (Acari: Tetranychidae). This mite was recently identified as a pest of the two leafy vegetables which are widely used in West Africa. The experiments were conducted at the International Institute of Tropical Agriculture, Benin, West Africa, in a growth chamber at 27°C, 70% ±10% RH and 12: 12 (L:D). Immature development of T. ludeni was shorter on A. cruentus than on S. macrocarpon, whereas female longevity was the same on the two vegetable crops. Total fecundity per female was higher on A. cruentus than on S. macrocarpon, largely due to longer survival of adult female T. ludeni on the former; however, no differences were observed in the daily fecundity of T. ludeni on the two plant species. The comparison of intrinsic rates of natural increase (rm), the net reproductive rates (Ro) and the survival rates of adult stage of T. ludeni on the two vegetable crops suggests that T. ludeni performs better on S. macrocarpon than on A. cruentus. Reasons for the lower rate of population growth observed on amaranth should be studied in more details as this could be used in IPM strategies such as intercropping to reduce pest density and in developing biopesticides for use against T. ludeni in vegetable farms in Africa

Mite pests of major importance on indigenous leafy vegetables in Benin: the search for appropriate control strategies

Mite fauna associated with Amaranthus cruentus L. and Solanum macrocarpon L., two major indigenous leafy vegetables produced in Benin, was monitored in July-October 2004, on IITA-Benin Station where no pesticides were applied and on a farmer-managed vegetable farm near Abomey-Calavi with pesticide applications on nearby plots. The major phytophagous mites Tetranychus urticae Koch and T. ludeni Zacher (Tetranychidae), were present on both vegetables with relatively higher abundance on S. macrocarpon than on A. cruentus. Polyphagotarsonemus latus Banks (Tarsonemidae) present only on S. macrocarpon. P. latus was the most dominant mite pest with remarkably higher impact in the environment where broad spectrum pesticides are used. Predatory mites found belonged to the family Phytoseiidae. Contrary to P. latus, predators were more abundant in the environment without pesticide and this certainly explains the lower mite pest abundance at IITA than on the farmer-managed farm, thereby pointing at the potential of indigenous phytoseiid species in controlling P. latus. Additionally, we investigated the effects of the two plants on the development and demographic parameters of T. ludeni, a less studied mite pest. The experiments were conducted at IITA-Benin in a growth chamber at 27°C, 70% ± 10% RH and 12:12 (L:D). Comparison of demographic parameters of T. ludeni on the two plants suggests that T. ludeni performs better on S. macrocarpon than on A. cruentus, explaining its lower abundance on the later. Future studies should focus on the reasons for the lower population growth on amaranth as this finding could be used in IPM strategies (e.g. intercropping), to reduce pest density, and in developing biopesticides against major vegetable mite pests in Africa. Testing cultivars resistance and the efficiency of indigenous predator species together with searching for efficient exotic predators for introduction against vegetable mite pests in Africa should be encouraged

Inventaire de la faune des acariens sur Amaranthus cruentus L. (Amaranthaceae); Solanum macrocarpon L. et Solanum aethiopicum L. (Solanaceae) dans le SudBenin

A survey of the mite fauna associated with Amaranthus cruentus L. (amaranth), Solanum macrocarpon L. (Gboma) and S. aethiopicum L. (African eggplant), three major indigenous vegetables produced in Benin, was carried out from August to October 2004 both at IITA-Benin station and on a vegetable farm at Togba in Abomey-Calavi area. Thirty-three mite species belonging to 12 families were found on the three vegetables. These species included phytophagous mites, predatory mites of the family Phytoseiidae, and another group whose feeding habits were not clear. The following phytophagous mites were found: Tetranychus urticae Koch and T. ludeni Zacher, in the family Tetranychidae; Polyphagotarsonemus latus (Banks) and another unidentified mite species, in the family Tarsonemidae. The two Tetranychus species were present on all three vegetables whereas tarsonemids were found only on the two solanaceous plants. Polyphagotarsonemus latus was the most dominant pest during the course of the experiments. It is the major mite pest on solanaceous plants, especially on Gboma in vegetable farms, where broad-spectrum pesticides harmful to natural enemies are used. The phytoseiids group was the most diversified with 16 species out of the 33 identified and more predominant in IITA plots where no pesticides were applied, compared to Togba plots where pesticides were regularly applied on nearby plots. They seem to better control P. latus on Gboma than on African eggplant. Other mites identified on the three vegetables belong to the following families: Acaridae, Tydeidae, Erythraeidae, Cunaxidae, Anystidae, Ascidae, Bdellidae, Uropodidae and Oribatidae.Un inventaire de la faune des acariens associes a Amaral1.thus cruentus L. (amarante), Solanum macrocarpon L. (Gboma), et SoLanum aethiopicwn L. (aubergin fricaine), h•ois principaux legumes indigenes cultives au Benin, a ete entrepris d'aout a octobre 2004 sur la Station de IITA Benin et sur Ie perimetre maraicher de Togba, deux sites situes aux environs d' Abomey-Calavi. Sur l'ensemble des deux sites, et sur les trois legumes, 33 especes d'acariens appartenant a 12 familles ont ete recensees. On y distingue des ravageurs, des predateurs de la famille Phytoseiidae, et un groupe compose d'acariens dont Ie mode d'alimentation reste a elucider. Les acariens ravageurs comprennent Tetranychus urticae Koch et T ludeni Zacher (Tetranychidae) et Polyphagotarsonemus latus (Banks) (Tarsonemidae) et un autre tarsoneme non identifie. Les deux especes de Tetral1ychus etaient presentes sur tous les legumes tandis que les tarsonemes etaient rencontres uniquement sur les solanacees. Polyphagotarsonemus latus etait l'acarien ravageur Ie plus dominant au cours de l'etude; et il infligeait plus de degats aux solanacees, specialement sur les parcelles de Cboma traitees avec des pesticides a large spectre en champs de fermiers. Les phytoseiides etaient les plus diversifies en especes (16), et plus abondants a IITA -lm site sans pesticide -qu'a Togba oll des pesticides etaient regulierement appliques dans Ie voisinage des parcelles experimentales. Ces acariens semblent contrOler P. latus mieux sur Cboma que sur l'aubergine africaine. Les autres acariens recenses appartiennent aux families des Acaridae, Tydeidae, Erythraeidae, Cunaxidae, Anystidae, Ascidae, Bdellidae, Uropodidae et Oribatidae

Visual, vibratory, and olfactory cues affect interactions between the red spider mite Tetranychus evansi and its predator Phytoseiulus longipes

Phytoseiulus longipes Evans (Mesostigmata: Phytoseiidae) is an exotic predator widely used in biological control programs for the red spider mite Tetranychus evansi Baker & Pritchard (Acari: Tetranychidae) in East Africa. However, little is known about the cues mediating this prey/predator interaction. Here, we performed behavioral assays to test the involvement of visual, vibratory, and olfactory cues using a combination of dead/living insects enclosed in either perforated or non-perforated transparent/opaque capsules. We monitored insect responses with a video tracking system and analyzed the data with Ethovision software. Our results showed avoidance behavior of T. evansi in the presence of live P. longipes through visual, vibratory, and olfactory cues. P. longipes was attracted by vibratory and olfactory cues emitted by T. evansi. The composition of volatiles from T. evansi was identified by GC/MS as methyl salicylate (MeSA), linalool, beta-caryophyllene, octanoic acid, decanoic acid, dodecanoic acid, tetradecanoic acid, hexadecanoic acid, and octadecanoic acid. Our behavioral assays with predatory mites in a Y-tube olfactometer revealed that among the identified volatiles, only MeSA, linalool, and MeSA + linalool attracted P. longipes. The implications of these findings for the control of T. evansi are discussed