Search

Biology of the leaf gall inducer Neotrioza tavaresi Crawford, 1925 (Hemiptera, Psyllidae) on strawberry guava tree (Psidium cattleianum). A field study was conducted in Curitiba region, State of Paraná, southern Brazil, to describe the life cycle of Neotrioza tavaresi Crawford, 1925, a leaf galling insect in strawberry guava trees (Psidium cattleianum). Three cycles were observed (1997, 1998, 1999) during regular field trips and the insects were observed in Piraquara municipality, where 15 samples with 50 infested leaves were sampled in the 1997-98 cycle. Galls were dissected for detailed studies. Neotrioza tavaresi has a univoltine cycle in which adult individuals were found inside the galls from August onwards. The sexually mature insects with sex ratio 1, emerged from the galls after their dehiscence caused by feeding of the adult insects on the gall walls. Adult emergence started in early October and ended by early December, with its peak in November. Copulation took place as soon as adults exit the gall and egg laying started the next day. Females had more than 100 ovarioles containing 218.7±44.7 (n=50) fully formed eggs. This indicated the short sexual adult life-span (aprox. 5-7 days) of the species, also characterized by a concentrated oviposition. Adult individuals fed and laid their eggs on younger shoots of the plant. The bottoms of the yellowish eggs were inserted into the leaf tissue, mainly on its adaxial edge (78.1%). The nymphs hatched and, as they fed on the adaxial side of expanding leaves, modified the cell growth pattern and the round-shape galls developed on the adaxial side with one insect inside. The gall wall showed distinct layers, with the inner one suppliyng the food to the insects, and the outer layer supplying gall protection. Nymphs went through five instars and the exuviae remained stuck on a ball of wax inside the gall. All parasitoids found were Hymenoptera belonging to Chalcidoidea: Eulophidae (1 sp), Pteromalidae (2 spp) and Encyrtidae (3 spp). The findings suggest that leaf gall inducer and parasitoids insects and plant life cycles are closely connected and both leaf sprouting and gall opening seem to be triggered by the same environmental and plant conditions. The high abundance of shoots may favor insect performance as adult individuals can easily find an ideal place for feeding, copulating and laying eggs.

Uma espécie do gênero Eurytoma (Hymenoptera, Eurytomidae) causa a galha-do-ramo do araçazeiro - Psidium cattleianum Sabine, 1821 (Myrtaceae). O inseto não foi identificado a nível de espécie, mas seus aspectos bioecológicos foram estudados em laboratório e em campo. É um possível agente para o controle biológico do araçazeiro que é planta daninha invasora em vários países. As coletas foram realizadas no primeiro planalto do Paraná. Estudou-se vários parâmetros de Eurytoma sp.: forma, cor, número de segmentos do corpo, largura da cabeça, comprimento do corpo, mortalidade e ciclo de desenvolvimento na fase larval; duração, tamanho, comprimento na fase pupal; cópula, proporção sexual, longevidade de machos e fêmeas, comportamento no acasalamento e alimentação na fase adulta. A galha é um dos fatores limitantes do araçazeiro, sendo a atividade larval a principal causa de danos na planta. Durante o ano seguinte à emergência do adulto, a galha seca, todas as folhas caem e o ramo morre, estabilizando o crescimento do araçazeiro. Eurytoma sp. - agent promising for biological control of strawberry guava in Hawaii Abstract A species from Eurytoma (Hymenoptera, Eurytomidae) genus causes a gall in the stems of strawberry guava - Psidium cattleianum Sabine, 1821 (Myrtaceae). The insect was not identified in the specie level, but its biecological aspects were studied in laboratory and fields conditions, seeking the possible use as specific natural enemy of the strawberry guava. Sample collection was done in the first plateau of Paraná State, natural occurrence area of the plant. It was determined the following parameters for Eurytoma sp.: shape, color, number of segments of the body, width of the head, length of the body, mortality, development in larval phase, duration, size, development and length in pupa phase, and copulation, sexual rate, longevity of males and females, copulation behavior and feeding in the adult phase. The gall is one of the limiting factors of strawberry guava, being the larval activity of Eurytoma sp. the main cause of the damages. After the first year of adult emergence, the gall dries out and in the next year the stem dies, stabilizing the strawberry guava growth.