Comparative Effects of Some Botanical Extracts and Chemicals in Controlling the Red Spider Mite Tetranychus evansi Baker & Pritchard on Solanaceous Crops

The tomato red spider mite, Tetranychus evansi, is an invasive pest reported on solanaceous crops in Benin around 2008, causing heavy economic damage. The control of this mite by farmers is mainly done through intensive applications of chemical pesticides that are not always effective. In the present study, we evaluated in a laboratory, at IITA-Benin, the effects of two botanical insecticides: the Cashew Nut Shell Liquid (CNSL) and Neem oil. This is together with Acarius 18 EC, a chemical acaricide generally used by growers on eggs and adult females T. evansi. The half recommended dose (0.5 l/ha), the recommended dose (1 l/ha), and the double recommended dose (2 l/ha) of Acarius and Neem oil as well as solutions at 1%, 2 %, 3%, 4% and 5% of CNSL were tested. Mean egg hatching rates varied significantly among treatments, ranging from 0.00 ± 0.00% (Neem oil and CNSL) (respectively at half recommended dose and 4%) to 100% (Control). Mortality of adult female T. evansi also differed significantly among treatments (P < 0.0001), ranging from 22.00 ± 4.20% to 100%. The highest mortality rates were recorded with Neem oil at any doses and with CNSL at 4%, whereas the lowest rate was recorded with the control treatment. Fecundity of pesticide-treated females T. evansi and proportion of eggs that hatched revealed significant differences among all doses of products (P < 0.0001). It appears from this study that even the half recommended dose of Neem oil and the CNSL at 4% were very effective on suppressing T. evansi populations and should, therefore, be subject to further studies to test their compatibility with natural enemies, and to determine strategies for their efficient applications in greenhouse and under field conditions.   &nbsp

Investigation of amaranth production constraints and pest infestation reduction by basil intercropping

Open Access JournalAmaranth (Amaranthus cruentus L.) is the most consumed leaf vegetable in Benin. A study carried out in south Benin have shown that the production of this vegetable is severely limited by insect pest pressure. The present study aimed to identify the major constraint limiting amaranth production in Ségbana municipality, located in the north of Benin and proposed sustainable agroecological solutions to farmers. Thus, a survey was conducted among 150 farmers in three villages of Ségbana (Lougou, Sokotindji and Piami) through well-structured questionnaires to know the major constraint limiting amaranth production. Agroecological methods for managing pests of this vegetable were offered to farmers through an experimental trial consisting of a Fisher block with four treatments and five replications conducted in Sokoundji village. The control treatment (To) consisted of amaranth in pure culture; the treatment (T1), amaranth plants surrounded by basil plants; (T2) rows of amaranth alternated with basil rows and (T3), amaranth plants alternated with basil plants in all directions. Every 5 days, 5 plants were randomly selected per treatment and the numbers of S. recurvalis and P. basalis were counted. Pest damage and yield per treatment were also assessed. Almost all farmers surveyed (100%) reported pest attacks as the major constraint limiting amaranth production. The results obtained on the abundance and the herbivory rate showed powerful negative effects (Df = 3; P < 0.0001) of the different treatments. Moreover, the treatment T2 (amaranth plants alternated with basil rows) gave the highest yield (1.25 t/ha of fresh leaves) and differed significantly from the other treatments (Df = 3; p = 0.039). The association basil – amaranth reduced the abundance of P. basalis and S. recurvalis and also improved the amaranth productivity with LER = 1.16. The association basil – amaranth is more beneficial than pure cultures because it hosts less of the insect pests studied, provides higher yields and makes rational use of the growing space

Susceptibility of ten tomato cultivars to attack by Tetranychus evansi Baker & Pritchard (Acari: Tetranychidae) under laboratory conditions

Published online: 28 Jul 2020We evaluated, in a laboratory experiment, the susceptibility of 10 tomato cultivars to the attack by the tomato red spider mite Tetranychus evansi, an invasive pest of this crop in Benin. Among the 10 cultivars tested, six were imported (i.e. Roma VF, Tima, Rio Grande, Buffalo, Petomech, and TLCV15) and four local (i.e. Akikon, Tounvi, TomL4, and Kèkèfo). Leaf disks (2.5 cm diameter) excised from leaves of tested cultivars, and placed upper side down on top of water-soaked cotton wool laying in 9.5 cm diameter Petri dishes (6 leaf disks per Petri dish), served both as experimental units and feeding source for the mites. Mites were individually placed on leaf disks of each cultivar and several biological parameters – development, reproductive parameters and longevity – were assessed. The experiments were performed at 27 ± 1 °C, 65–70% RH, and 12:12 h (L: D) photoperiod. Our results revealed significant effects of tomato cultivars on several biological parameters of T. evansi, especially the developmental time of the egg stage (P ˂ 0.0001), and the larval stage (P = 0.0113), as well as female oviposition period (P = 0.0002). Likewise, female longevity (P = 0.0095) and fecundity (i.e. egg/♀, P = 0.0055) were significantly affected. The sex-ratio of the progeny was generally similar for all the cultivars except for Buffalo and Tounvi on which most juveniles did not develop beyond the larval stage. These two cultivars appeared as potential tomato cultivars for implementation of IPM strategies for the control of T. evansi

Farmers control practices against the invasive red spider mite, Tetranychus evansi Baker & Pritchard in Benin

n 2008, the invasive tomato red spider mite Tetranychus evansi (Acari: Tetranychidae), a pest of sola- naceous crops, was identi fi ed for the fi rst time as the cause of serious damage on tomato ( Solanum lycopersicum L.; Solanaceae) crops in Benin. Since then, frequent outbreaks have been observed on Solanaceae and other leafy vegetables such as purple amaranth ( Amaranthus cruentus L.; Amaranthaceae) and bitter leaf ( Vernonia amygdalina D.; Asteraceae) in all growing areas in southern Benin. The objective of this study was to evaluate the intensity of damage by this invasive pest and the impact of farmers' control practices on purple amaranth, African eggplant (Solanum macrocarpon L. ; Solanaceae) and tomato crops. A survey was carried out in January 2013 among 150 farmers in the three major growing areas in southern Benin: S em e-Kpodji, Grand-Popo and Pahou. Tetranychus evansi was the only mite observed, causing production losses estimated at 65% for African eggplant, 56% for tomato and 25% for purple amaranth. Previously encountered species such as Tetranychus urticae Koch, Tetranychus ludeni Zacher (Acari: Tetranychidae) and Polyphagotarsonemus latus Banks (Acari: Tarsonemidae) were not observed in any of the 45 samples. To protect the infested crops, growers sprayed various synthetic pesticides at high frequencies according to crop phenology 3, 6 and 12 times per month, respectively, on purple amaranth, African eggplant and on tomato, on average. The most frequently used pesticides were pyrethroids and organophosphate compounds. Farmers reported that these compounds were largely ineffective against T. evansi . The risks posed to human and environmental health, as well as existing alternatives to chemical pesticide use, are discussedn 2008, the invasive tomato red spider mite Tetranychus evansi (Acari: Tetranychidae), a pest of sola- naceous crops, was identi fi ed for the fi rst time as the cause of serious damage on tomato ( Solanum lycopersicum L.; Solanaceae) crops in Benin. Since then, frequent outbreaks have been observed on Solanaceae and other leafy vegetables such as purple amaranth ( Amaranthus cruentus L.; Amaranthaceae) and bitter leaf ( Vernonia amygdalina D.; Asteraceae) in all growing areas in southern Benin. The objective of this study was to evaluate the intensity of damage by this invasive pest and the impact of farmers' control practices on purple amaranth, African eggplant (Solanum macrocarpon L. ; Solanaceae) and tomato crops. A survey was carried out in January 2013 among 150 farmers in the three major growing areas in southern Benin: S em e-Kpodji, Grand-Popo and Pahou. Tetranychus evansi was the only mite observed, causing production losses estimated at 65% for African eggplant, 56% for tomato and 25% for purple amaranth. Previously encountered species such as Tetranychus urticae Koch, Tetranychus ludeni Zacher (Acari: Tetranychidae) and Polyphagotarsonemus latus Banks (Acari: Tarsonemidae) were not observed in any of the 45 samples. To protect the infested crops, growers sprayed various synthetic pesticides at high frequencies according to crop phenology 3, 6 and 12 times per month, respectively, on purple amaranth, African eggplant and on tomato, on average. The most frequently used pesticides were pyrethroids and organophosphate compounds. Farmers reported that these compounds were largely ineffective against T. evansi . The risks posed to human and environmental health, as well as existing alternatives to chemical pesticide use, are discusse