Relation between plant density and arthropod density in cabbage fields

Abstract

The relationship between plant density and the abundance of arthropods was examined by planting cabbages in four densities (0.25, 1, 4, or 8 plants per square meter). Four herbivorous species were examined: the small white butterfly Pieris rapae crucivora Boisduval, the diamondback moth Plutella xylostella (Linnaeus), the beet semi-looper Autographa nigrisigna (Walker), and the green peach aphid Myzus persicae (Sulzer). The number of spiders and the number of eggs of syrphid flies were also examined. The number of individuals per unit ground area increased curvilinearly with increasing plant density for most arthropods. To clarify the mechanism causing such a curvilinear increase, the oviposition behavior of Pieris rapae crucivora was examined. The oviposition process of a female was divided into three components: (1) entering the field, (2) alighting on a plant to bend her abdomen, and (3) attaching an egg on the leaf. The first and the second components curvilinearly increased with increasing plant density, while the third component was not influenced by the plant density. The analysis of the flight path of P. rapae crucivora indicated that the curvilinear increase in the frequency of abdominal bending behaviors occurs since a female flies at least about 1.3 m between successive abdominal bending behaviors, irrespective of the plant density, when the plant density is sufficiently high.

Biodiversity and stability of herbivore populations: influences of the spatial sparseness of food plants

“…However, most of the experimental results examining the effect of plant density contradict the resource concentration hypothesis if the size of the experimental plots is kept constant. The density of herbivores per plant decreased with increasing density of host plants in most cases (Luginbill and McNeal 1958;Pimentel 1961;Way and Heathcote 1966;A'Brook 1968;Farrell 1976;Solomon 1981;Latheef and Ortiz 1983;Root and Kareiva 1984;Power 1987; Segarra-Carmona and Barbosa 1990; Thompson and Quisenberry 1995;Yamamura 1999). Only a few experiments supported the resource concentration hypothesis (Ralph 1977;Turchin 1988) and several experiments did not detect consistent results (Mayse 1978;Bach 1980;Boiteau 1984;Power 1989;Coll and Bottrell 1994).…”

Flutuação populacional e distribuição vertical de Brevicoryne brassicae (L.) (Hemiptera: Aphididae) em couve

“…A densidade das plantas de couve, maior no campo 1, pode ter interferido no tamanho da população de B. brassicae, pois, segundo vários autores (FARREL, 1976;UVAH e COAKER, 1984;LAL et al, 1989;HONEK e MARTINKOVA, 1999;KARUNGI et al, 2000), o aumento da densidade de plantas hospedeiras pode provocar uma redução no número de pulgões, embora esta redução não seja freqüente (YAMAMURA, 1999).…”

Biological Control of Insect Pests in Agroecosystems

“…However, despite the confirmation of this hypothesis in many cases (Andow, 1991), several recent studies have invalidated this prediction (see Yamamura, 1999, for a review), providing support for a Resource Dilution Hypothesis (Otway et al, 2005;Rhainds and English-Loeb, 2003) associated with different patterns of responses. For example, Valantin-Morison et al (2007) found a negative correlation between plant density and oilseed rape damage due to root maggot, cabbage stem flea beetle, and pollen beetle.…”