The Influence of Cover Crop Cultivation on Populations of Injurious Insects and Mites in Florida Citrus Groves

Abstract

JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.. Florida Entomological Society is collaborating with JSTOR to digitize, preserve and extend access to The Florida Entomologist.Cultural practices involving the natural ground cover or cover crop vary considerably from area to area and grove to grove in Florida. This variation is, in some instances, governed by the level of the water table or the type of soil involved. More frequently, however, cultivation is modified by the opinions of the grower. Some growers maintain weed-free groves by frequent disking, harrowing or chopping. Others permit cover crop development during the summer months but practice clean cultivation in the fall, winter and spring. Still others allow weeds and wild grasses to grow unhampered from one picking season to the next. Horticultural and agronomic reasons cited for such variations in practices include moisture conservation, soil conservation, fire protection, soil protection, tree stimulation and efficient grove management. Furthermore, many growers believe that such practices cause increases or decreases in insect and mite abundance. To date only two studies have been conducted on the influence of cover crop cultivation on insect and mite infestations. The first was an investigation by Osburn and Mathis (1944) concerning the citrus rust mite, Phyllocoptruta oleivora (Ashmead). These workers concluded that there was no difference between rust mite infestations on trees in clean cultivated plots and on trees grown in plots having a cover crop. They did, however, record stimulation of the trees in the clean cultivation plots. Two years later the same workers (Osburn and Mathis, 1946) reported markedly greater infestations of Florida red scale, Chrysomphalus aonidum (L.), on trees growing in cultivated plots than on trees in uncultivated plots. They were unable, however, to demonstrate striking differences in the percentages of parasitized scales or fungi-affected scales and concluded that tree stimulation, a result of cultivation, was the important factor in the development of larger scale infestations.The present study was conducted to obtain preliminary cultivation data on the major injurious insects and mites attacking Florida citrus and to correlate, if possible, any differences recorded with changes in the rates of parasitism or predation. EXPERIMENTAL PROCEDURE The Florida Entomologist Vol. 44, No. 2 z ? m O e> 4C

<p><strong>Mine-damaged leaves by </strong><strong><em>Phyllocnistis citrella</em></strong><em> </em><strong>Stainton provide refuge for phytoseiids on grapefruit in Florida and Texas*</strong></p>

“…Iphiseiodes quadripilis and T. peregrinus are generalist predators (Muma, 1961) and the former shows preference for grapefruit over orange as a substrate (Villanueva & Childers, 2006). Stigmaeids were found throughout the duration of this study in Florida, where their patchy distribution and variable numbers were similar to what was reported by Muma & Selhime (1971) for the stigmaeid Agistemus floridanus Gonzalez in Florida.…”

New Phytoseiid mites of the FrenchWest Indies, with description of a new species, and new records (Acari: Mesostigmata)

“…Muma (1969) reported that T. peregrinus was able to reproduce and develop on Panonychus citri (McGregor) but did perform better on eggs and crawlers of chaff scale, Parlatoria pergandii Comstock, and six-spotted spider mite, Eotetranychus sexmaculatus (Riley). This phytoseiid was also reported to feed on Phyllocoptruta oleivora (Ashmead), providing some degree of rust mite suppression on lime (Peña, 1992).…”

Influence of ground cover management on diversity and density of phytoseiid mites (Acari: Phytoseiidae) in Guadeloupean citrus orchards

“…However, few studies have been carried out on the occurrence of phytoseiid mites on ground cover in citrus orchards. Muma (1961) observed higher numbers of phytoseiid mites in citrus orchards with cover crops than without. Gravena et al (1993) showed that the presence of Ageratum conyzoides L. (Asteraceae), a common wild plant in Guadeloupe, and Eupatorium pauciflorum Humboldt, Bonpland and Kunth (Asteraceae) in citrus orchards in Brazil led to an increase of phytoseiid mite densities, compared to a bare ground management.…”