Factors affecting infestation by larvae of Phyllophaga spp. (Coleoptera: Scarabaeidae) in Costa Rica

Abstract

Observations were made on the behaviour of some Costa Rican species of Phyllophaga. Studies of oviposition and early larval survival under controlled conditions indicated that P. menetriesii (Blanchard) laid most eggs under a ground cover containing grasses and that the presence of living roots in the soil was important to the survival of the young larvae of the two most common species, P. menetriesii and P. vicina (Moser). At Turrialba, Costa Rica, the destruction of young maize plants by larvae of these two species and the consequent reduction in yield were significantly greater in land which was weedy or in close association with stands of old cassava plants, than where weeds had been effectively controlled and cassava was absent. Both plant loss and yields of maize were significantly correlated with larval densities. The best correlations were with numbers of second- and third-instar larvae sampled in July and with the total numbers of third-instar larvae sampled. Regression analyses established that 4·45 seedlings, or approximately 170 kg dry grain/ha, were lost per larva per square metre sampled during the seedling stage in July. An expression to calculate the economic threshold was determined. Significantly more larvae of P. vicina were found in maize growing on ridged than on unridged land, and where applications of lime and phosphate fertilizer had been made to an acid soil. The significance of weed control on infestation is discussed.

Lime application can help protect pastures against black beetle

“…Nor did lime have any impact on sugar cane whitegrub numbers in the Midlands area of South Africa (McArthur 2005). King (1985) found improving soil fertility of an acid soil through applications of lime and phosphate fertilisers increased larval populations of the scarab Phyllophaga vicina in maize in Costa Rica. Therefore, published literature provides little assistance as to possible direct or indirect mechanisms of lime.…”

Especies del complejo de jobotos (Phyllophaga spp., Anomala spp y Cyclocephala spp.) asociadas a cultivos, en el Valle Central y Pacífico seco de Costa Rica.

“…Seguidamente, fueron colocados en etanol al 70% v/v, para su posterior identificación. El raster y las estructuras taxonómicas observadas en el estadio L3 de las larvas y propuestas por King (1985) y Morón (1986,1988) fueron la base para la identificación a nivel de género y especie.…”

Grub Density of Lepidiota mansueta (Coleoptera: Scarabaeidae) in Different Habitats of the Majuli River Island of Assam, India

“…Females of various species of white grubs preferred grass and weeds, as young larvae need plant roots to survive. Moreover, ovipositing females can sense the presence actively growing plants (King, 1985). In case of white grubs, larvae are quite limited in movement, therefore the female must place her eggs in an environment that most suited to young grubs (Litsinger et al, 2002).…”