José Janduí Soares

Influência de tricomas do algodoeiro sobre os aspectos biológicos e capacidade predatória de Chrysoperla externa (Hagen) alimentada com Aphis gossypii Glover

Cotton trichomes, acting as a resistance factor to Aphis gossypii Glover, can also affect its natural enemies, reducing the efficacy of the control agents and increasing prey searching time. The effects of different trichome densities, observed in three cotton cultivars (Antares - low pilosity; CNPA 7H - hirsute and Deltapine Acala 90 - high pilose), on biological aspects and predatory ability of Chrysoperla externa (Hagen), fed on A. gossypii reared on IAC-22 cotton seedlings, were evaluated. Developmental period and viability of C. externa larva were not significantly affected by trichome densities. However, C. externa oviposition period was longer when larva were fed on A. gossypii reared on Antares leaves. Also, daily and total egg numbers laid by C. externa were not influenced by any cotton cultivars on which it was maintained during the larval phase. Highest longevity of C. externa females was observed when they were fed, during the larval phase, on leaves of the lowest pilosity cultivar (Antares). During larval period, C. externa consumed, respectively, 540.0; 494.3 and 454.8 aphids, when it was maintained on CNPA 7H, Antares and Detapine Acala 90 cultivars leaves. Cotton cultivars showed good compatibilities with the predator species; the results clearly indicate the feasibility of A. gossypii aphid control through the use of C. externa on cotton cultivars with proper trichome densities.

Influência da posição do fruto na planta sobre a produção do algodoeiro

Estudou-se a distribuicao da producao, a qualidade da semente e o peso de frutos em relacao as diferentes posicoes do fruto na planta de algodao. Os dados foram oriundos do mapeamento de 360 plantas da cultivar CNPA 7H, em area irrigada no municipio de Bom Sucesso, PB. Mais de 80% da producao da cultivar e proveniente do baixeiro e terco medio e da primeira e segunda posicao frutifera da planta. A qualidade das sementes e afetada a medida que os frutos se afastam da primeira posicao para as demais.

Tipos de resistência a Alabama argillacea (Huebner) (Lepidoptera: Noctuidae) envolvidos em genótipos de algodoeiro: I - não-preferência

The mechanism of resistance (nonpreference) of cotton genotypes (Gossypium hirsutum L.) to the cotton leafworm, Alabama argillacea (Huebner, 1818) was studied. Oviposition nonpreference in field (15 genotypes) and cages (six genotypes) were evaluated in free choice and no choice tests. The eggs present in the upper third of the plants were counted. Feeding nonpreference was evaluated with leaf disks, under laboratory conditions, using the genotypes CNPA 9211-21, CNPA 9211-31, JPM 157, STO 285 N, T 953-13-4-2 and T 1122-13-1, and first and third instar larvae, with twenty replications. Nonpreference was measured through dry weight consumption. No oviposition preference was found among the studied genotypes. The CNPA 9211-31 genotype was less consumed by small larvae, thus indicating that the feeding nonpreference mechanism of resistance to A. argillacea is present in this genotype.

Fitorreguladores e remoção da gema apical no desenvolvimento do algodoeiro

The objective of this paper was to verify the effect of growth regulators in the development of cotton. Two experiments were carried out in 1992/93 and 1993/94, one in Itaju, SP, and another in Jaboticabal, SP, Brazil. The Itaju experiment consisted of nine treatments and four replications, and that of Jaboticabal, six treatments and five replications, all using a completely randomized block design. The results indicate a favorable use of regulators to promote the development of cotton.