José Adalberto De Alencar

Nível de dano, plantas invasoras hospedeiras, inimigos naturais e controle do psilídeo da goiabeira (Triozoida sp.) no submédio São Francisco

This study was conducted to increment the integrated management of Triozoida sp. (Hemiptera, Psylliidae) in guava plants at the Sao Francisco River Valley. The damage level, weed hosts, selectivity and effect of the thiamethoxam 10GR and 250WG in the control of psylliidae were evaluated. The experiment was carried out in an irrigated area, at Petrolina, Pernambuco, in a randomized block design with four replications. Treatments consisted of: 1) thiamethoxam 10GR applied on soil; 2) thiamethoxam 250WG sprayed weekly; 3) thiamethoxam 10GR applied on soil + thiamethoxam 250WG sprayed weekly; 4; 5; 6) thiamethoxam 250WG sprayed when 10, 20 and 30% of infested branches were reached, respectively; 7; 8; 9) thiamethoxam 10GR applied on soil + thiamethoxam 250WG sprayed when 10, 20 and 30% of infested branches were reached, respectively; and 10) control (no insecticide). The percentage of infested branches in the control treatment differed significantly from the treatments 2 (2.8%), 3 (4.3%), 4 (19.7%), 7 (13.4%), 8 (14.5%) and 9 (15.0%). When thiamethoxam was used, the population reduction of natural enemies ranged from 12.5 to 39.6%, corresponding, in the selective scale, to grades (1 = non offensive (< 25%), 2 = not very toxic (25-50%). Number and weight of fruits were similar in all the treatments. Fifty one weed species and no host of Triozoida sp. were found.

Evaluation of onion accessions for resistance to thrips in Brazilian semi-arid regions

ABSTRACT This study aimed to evaluate onion accessions regarding their resistance to Thrips tabaci Lindeman, in order to enable the development of cultivars that are resistant to this pest. The experiments were carried out without chemical control, in a randomized block design with three replications, in Petrolina, PE and Juazeiro, BA. Six evaluations of thrips populations were carried out starting 15 days after transplanting, each one after 7 days. Simple correlations were estimated among all variables. Statistical differences were observed for the number of adults in different evaluations, while the number of nymphs showed no statistical differences. The largest average yields of commercial bulbs were observed for ‘Vale Ouro IPA 11ʹ, ‘BRS Alfa São Francisco’, ‘Franciscana IPA 10ʹ and ‘Sirius F1ʹ while ‘Red Creole’, ‘Creole Mercosul’ and ‘Conquista’ had the lowest yield. The bulb commercial yield had simple negative correlations with nymph degree of infestation (DI) in the four evaluation phases and adult DIs at 22 days. Negative correlations between commercial bulb yield and central angle of the plant were observed, indicating that plants with higher bulb yield have a lower angle of the central leaves. The results of the study suggest that the resistance mechanism is due mainly to tolerance to the pest.

EFEITO DO CONTROLE CULTURAL E QUÍMICO SOBRE O ÁCARO DA NECROSE DO COQUEIRO, EM COCO-ANÃO IRRIGADO

One of the most harmful pests of coconut tree crop is the mite Aceria guerreronis. This pest damage the coconut fruits in the first development stage, causing partial or total losses in fruit production. The objective of this work was to evaluate the effect of chemical products and crop management in the control of A. guerreronis, aiming to use them in a management program for this pest. The research was carried out in Petrolina-PE from August to December, 1999. A complete randomized block design, with four treatments and four replications, was used. Each replication consisted of two plants of green dwarf coconut tree variety. Treatments were: A ¾ Cleaned plants without chemical control; B ¾ Cleaned plants with chemical control; C ¾ Plants not cleaned and with chemical control; D ¾ Plants not cleaned and without chemical control. All fruits damaged by mite were taken out from plants in the treatments with cleaned plants for three times. Fenpyroxymate, tetradifon and adhesive, at the levels 200ml, 300ml and 15ml for 100 l water, respectively, were mixed and applied for three times. Results showed that the individual uses of chemical products and crop management had efficiency of 26-87% and 64-89%, respectively, on mite control. However, the association of these two control managements showed a synergic effect on mite control with efficiency of 87-96%.