Selection of Endophytic Beauveria bassiana as a Dual Biocontrol Agent of Tomato Pathogens and Pests

Endophytic fungi (EF) can enhance both plant growth and defense barriers against pests and pathogens, contributing to the reduction of chemical pesticides and fertilizers use in agriculture. Beauveria bassiana is an entomopathogenic fungus showing endophytism in several crops, often associated with a good capacity to limit the development of pests and disease agents. However, the diversity of the protective efficacy and plant response to different strains can be remarkable and needs to be carefully assessed for the successful and predictable use of these beneficial microorganisms. This study aims to select B. bassiana strains able to colonize tomato plants as endophytes as well as to control two important disease agents, Botrytis cinerea and Alternaria alternata, and the pest aphid, Macrosiphum euphorbiae. Nine wild-type isolates and one commercial strain were screened for endophytism, then further characterized for plant-growth promotion plus inhibition of disease development and pest infestation. Four isolates proved to have a good control activity against the biotic stressors tested, but only Bb716 was also able to promote plant growth. This work provides a simple workflow for the selection of beneficial EF, paving the way towards more effective use of B. bassiana in Integrate Pest Management (IPM) of tomato.

Mixtures between Beauveria bassiana and potassium silicate to manage thrips in tomato plants for industrial processing

ABSTRACT Thysanoptera species can transmit virus to Solanaceae family vegetables, including tomato plants for industrial processing, causing the disease known as Tomato Spotted Wilt Virus (TSWV). Thrips resistance to insecticides indicate the urgent need of techniques adequate for Integrate Pest Management practices. The objective was to evaluate the control efficiency (CE%) against Frankliniella schultzei (Thysanoptera: Thripidae) of the fungus Beauveria bassiana (Bb), the resistance inducer potassium silicate (KSil) and the chemical insecticide profenophos + cypermethrin (PC) isolated, or in binary mixtures. The treatments were foliar spraying on tomato plants with Bb (T1), KSil (T2) and PC (T3) isolated or in mixtures of Bb+KSil (T4), PC+KSil (T5) and Bb+PC (T6). Thrips were sampled with white plastic trays at 0, 1, 7, 14 and 21 days after application (daa). The CE% of each product (isolated or in mixtures) differed at all time intervals. The Bb+KSil treatment had highest CE% from 24 hours of application, until the end of the experiment, ranging from 95% (1 daa) to 41.5% (21 daa). The CE% decreased in all treatments with a quadratic curve behavior, throughout time. PC insecticide, isolated, showed a decreased CE% through a linear regression. Grouping analyzes indicated the Bb+KSil effect was more dissimilar than the other evaluated treatments. Synergism between Bb and KSil, in mixture, indicate its potential for Integrated Pest Management programs of F. schultzei in tomato plants for industrial processing.

Toxomerus duplicatus Wiedemann, 1830 (Diptera: Syrphidae) preying on Microtheca spp. (Coleoptera: Chrysomelidae) larvae

Microtheca spp. (Coleoptera: Chrysomelidae) are insect pests primarily related to Brassicaceae crops. In the State of Rio Grande do Sul (RS), southern Brazil, they are found on forage turnip, Raphanus sativus L. var. oleiferus Metzg., which is commonly grown during fall/winter seasons. This work reports the predation of Microtheca spp. larvae by Toxomerus duplicatus Wiedemann, 1830 (Diptera: Syrphidae) larvae, on forage turnip crop, in Santa Maria, RS. This register provides new information about Microtheca spp. natural enemies in Brazil, which might be a new option for integrate pest management of these species.

Characterization and selection of Bacillus thuringiensis isolates effective against Sitophilus oryzae

The entomopathogenic bacterium Bacillus thuringiensis is a control agent with toxic and environmental characteristics that allows the control of pest insects according to the Integrate Pest Management (IPM) precepts. In order to find new strains, potentially toxic to Sitophilus oryzae L. 1763 (Coleoptera: Curculinidae), 1.073 strains of B. thuringiensis from parts of Brazil were used. Genetic material was extracted with InstaGene Matrix kit, used for the amplification of sequences in Polymerase chain reaction (PCR), and viewed in 1.5% agarose gel. The gene cry35Ba class was represented by 60 B. thuringiensis isolates (5.6%), which were then subjected to bioassays with S. oryzae larvae. Among the isolates studied, four caused more than 50% mortality in pathogenicity tests, and the isolates 544 and 622 were the most virulent, as determined by CL50 estimates. The four toxic isolates had spherical, bi-pyramidal and cuboid crystals, and a 44-kDa protein was found in sodium dodecyl sulphate - polyacrylamide gel electrophoresis (SDS-PAGE), which coded for the product of cry35Ba genes. These data demonstrate the potential of B. thuringiensis for the management of S. oryzae larvae.

Control of Selected Broadleaf Weeds with Glufosinate as Influenced by Insecticide Coapplication

Coapplication of herbicides and insecticides affords growers an opportunity to control multiple pests with one application, given that efficacy is not compromised. Glufosinate was applied at 470 g ai/ha both alone and in combination with the insecticides acephate, acetamiprid, bifenthrin, cyfluthrin, dicrotophos, emamectin benzoate, imidacloprid, indoxacarb, lambda-cyhalothrin, methoxyfenozide, spinosad, or thiamethoxam to determine coapplication effects on control of some of the more common and/or troublesome broadleaf weeds infesting cotton. Hemp sesbania, pitted morningglory, prickly sida, redroot pigweed, and sicklepod were treated at the three- to four- or the seven- to eight-leaf growth stage. When applied at the earlier application timing, glufosinate applied alone provided complete control at 14 d after treatment, and control was unaffected by coapplication with insecticides. When glufosinate application was delayed to the later application timing, visual weed control was unaffected by insecticide coapplication. Fresh-weight reduction from the herbicide applied to larger weeds was negatively impacted by addition of the insecticides dicrotophos and imidacloprid with respect to redroot pigweed and prickly sida, but only in one of two experiments. In most cases, delaying application of glufosinate to larger weeds resulted in reduced control compared to that from a three- to four-leaf application, with the extent of reduction varying by species. Results indicate that when applied according to the herbicide label (three- to four-leaf stage), glufosinate/ insecticide coapplications offer producers the ability to integrate pest management strategies and to limit application costs without sacrificing control of the broadleaf weeds evaluated.