Biotypes B and Q of Bemisia tabaci (Gennadius), collected from the islands of Tenerife and Majorca respectively, were exposed to competition conditions on tomato cv. Marmande in the laboratory. Both biotypes were established in single and mixed cultures at different densities. Increased mortality of biotype Q females and immature instars was observed together with a lower rate of fecundity and progeny size compared to biotype B, when reared in single or mixed cultures. The female:male sex ratio of F1 individuals of biotype Q was higher in single than in mixed cultures. However, the sex ratio of F1 individuals of biotype B was the same in single and mixed cultures, suggesting reproductive interference. Whitefly density did not affect interspecific interactions. It had a moderate effect on developmental rate of both biotypes, and on mortality of immature instars and progeny size of biotype B only. The results indicate that under laboratory conditions the studied biotype B should displace biotype Q.

The particle film technology based on processed kaolin sprays has been recently introduced for the control of the olive fruit fly Bactrocera oleae (Rossi), the key pest of olive groves. A 3-year field experiment was conducted from 2005 to 2007 at Villarejo de Salvanés, Spain to assess the efficacy of a kaolin-based product (Surround WP) for controlling B. oleae and two other olive insect pests: the olive black scale Saissetia oleae (Olivier) and the olive psyllid Euphyllura olivina (Costa). The effects of Surround WP on the arthropod community of olive trees and on natural enemies were also evaluated. In a high olive fruit fly pressure year (2007), Surround WP sprays significantly reduced the incidence of B. oleae and that of S. oleae. However, Surround WP treatments did not have any effect on E. olivina populations. Both the abundance and the diversity of arthropods were reduced by Surround WP treatment. The principal response curve (PRC) analysis revealed a significant deleterious effect of Surround WP on the natural enemy arthropod community of the olive grove. The most affected taxa were the following: the coccinellids Scymnus mediterraneus IablokoffKhnzorian, Stethorus punctillum Weise and Hyperaspis reppensis (Hbst.); the mirid Brachynotocoris ferreri n. sp. Baena (in litteris); different species of Orius and the families of Philodromidae, Scelionidae, Pteromalidae, Chrysopidae and Aphelinidae. Processed kaolin is proposed as an alternative to chemical control of the olive fruit fly. However, the effect of processed kaolin treatments on natural enemies should be taken into account in a rational pest control programme.

Penicillium oxalicum, a biocontrol agent for Fusarium oxysporum f.sp. lycopersici, was tested for its ability to induce resistance against tomato wilt. P. oxalicum and F. oxysporum f.sp. lycopersici were placed at separate sites on tomato plants or in soil, avoiding a direct interaction between the fungi. P. oxalicum induced resistance as expressed by a reduction in disease severity, area under disease progress curve and stunting induced by the pathogen. P. oxalicum colonized the tomato rhizosphere during the experiments but it was not detected inside stems, demonstrating that P. oxalicum and Fusarium oxysporum f.sp. lycopersici remained spatially separated. Biological control was observed both in sensitive and ‘resistant’ cultivars, indicating the role of a general resistance mechanism. In both cultivars P. oxalicum treatment alone did not produce disease symptoms. Therefore P. oxalicum could be a suitable biocontrol agent in cases of cultivar resistance failure. These results suggest that P. oxalicum can trigger defence mechanisms in the plant.

Laboratory studies were carried out on aspects affecting competition between biotypes B and Q of whitefly [Bemisia tabaci (Gennadius)]: mating behaviour, egg viability and pyriproxyfen resistance. Pairs of biotype B females and males spent more time as courting couples than pairs with Q males, regardless of female biotype. Mixed pairs of biotype Q females and biotype B males spent more time as courting couples than biotype Q pairs. Egg viability from the different crosses and from single females was similar. Pyriproxyfen application to a mixture of whiteflies with a biotype ratio B/Q of one gave a reduction in the ratio because of higher resistance of the Q biotype to the insecticide. The data agrees with the observed displacement of biotype Q by biotype B whiteflies under laboratory conditions, and vice versa in the field.

Plant resistance to the B and Q biotypes of sweetpotato whitefly, Bemisa tabaci (Gennadius), induced by benzo [1,2,3] thiadiazole-7-carbothioic acid-S-methyl ester (BTH or acibenzolar-S-methyl) in tomato 'Marmande' plants was evaluated in free-choice and no-choice assays under different conditions. BTH is the active ingredient of the Syngenta plant activator Bion. BTH treatment affected host preference of B. tabaci (B and Q biotypes) adults on plants sprayed with Bion at 0.2 and 0.4 g/liter during the earlier days of free-choice assays. As a consequence, a decrease in the total number of eggs (although female fecundity was not affected) and in the final number of pupae and empty pupal cases was observed. The effect produced by BTH applied at 0.1 g/liter Bion was not significant. In no-choice assays, a reduction of the numbers of first-stage larvae and total individuals and a delay in insect development were observed when local treatment was restricted to one leaflet per plant, 5 d before B. tabaci (biotype B) infestation. This acquired resistance induced by BTH seemed to be locally expressed because of the differences between treated and nontreated leaflets in the same plants, whereas no differences in nontreated leaflets were observed between BTH-treated and control plants.