The introduced purple scale parasite,Aphytis lepidosaphesCompere, and a method of integrating chemical with biological control

Abstract

be touched by the very maximum dosages." Also, Essig (1909) states: "The purple scale is considered the most serious of all our scale pests, as it is the most difficult to exterminate.... As yet, no natural parasite or predaceous insect has been found which will begin to cope with it." Lepidosaphes beckii is recorded as infesting a variety of plants in many of the locales where it occurs; however, it is rarely found on plants other than citrus in California. Purple scale thrives in areas having moderate temperatures combined with relatively high humidities, and has only been a problem in the more coastal citrus areas in southern California. The area of greatest economic importance is Orange County. The distribution of purple scale in Orange, Los Angeles, Santa Barbara, San Diego, and Ventura counties of California, as given by Quayle (1912), remains essentially the same today, except that eradication measures have kept it virtually nonexistent in Ventura County. Inasmuch as it existed near Pomona, in eastern Los Angeles County, at least fifty years ago, it seems quite likely that spread would have occurred long ago through contiguous citrus plantings into the interior areas of San Bernardino and Riverside counties if the scale were capable of existing in these latter climatic areas. It has also failed to spread from the Santa Ana Canyon citrus plantings into the nearby interior citrus district of Corona. Based on this, similar field observations elsewhere, and on biological information from the laboratory, it appears that due to climatic limitations the purple scale has reached the maximum distribution it can attain outdoors in southern California. Biology, description of stages, and other information relating to the purple scale are well covered by Quayle (1912, 1938) and Ebeling (1959). Past experience indicated that an incipient infestation of purple scale under favorable California coastal conditions was usually first apparent on the inside or center of the tree, attacking the leaves, branches, and fruit, but that eventual spreading over the entire tree might occur, resulting in severe infestation and extensive killing, even of large limbs, unless insecticides were regularly applied. In established tree infestations, in addition to the usually, heavily infested center portion, the majority of the scale was generally found on the leaves, branches, and fruit on the north or northeast quadrants of the trees, apparently not surviving as well on the south and west portions of the trees most exposed to the sun. In addition, trees shaded by windbreaks would frequently be found to be more heavily infested than those receiving more sun. According to DeBach (1953), " ...,purple scale appears to be the key problem standing in the way of progress toward general biological control of orange-tree pests in coastal areas of southern California." Previous studies by the authors of several years' duration in untreated groves indicated that satisfactory biological control of most orange-tree pests other than purple scale might ...

Competitive displacement between ecological homologues

“…Larvae of the Aphytis species studied tend to be gregarious, that is, more than one individual may develop per host. It has been shown that Aphytis lepidosaphes Compere usually lays 2 or more eggs per host and that 2 or more adult parasites usually emerge per host (DeBach and Landi, 1961). This commonly occurs also with A. melinus in the field.…”

Biological control of the San Jose scaleQuadraspidiotus perniciosus(Comstock) (Homoptera: Diaspididae) in southern California

“…Host-feeding, however, has been found to be the greatest cause of "unexplained" mortality in the black scale, S aisse tia oleae (Bern. ), the California red scale, Aonidiella a'urantii (Maskell), the purple scale, Lepidosaphes beckii (Newman}, andothers (De-Bach, 1943, 1969;DeBach and Landi, 1961). Tests were then devised to evaluate the host-feeding behavior of A. aonidiae.…”

“…Host-feeding or mutilation in the genus Aphytis has been recognized as important in the regulation of host population densities (DeBach and Landi, 1961;DeBach, 1969;Quednau, 1964). Quednau (1964) stated that "for an assessment of the utility of an Aphytis species for the biological control of scale pests, not only its fecundity is a factor, but also its controlling influence on the scales by host mutilation activities."…”

Notes on natural enemies attackingLepidosaphes species [Homoptera: Diaspididae] associated withCitrus in Costa Rica

“…However, autonomous entry (ecesis) occurred in many other places. In the Caribbean area, it has been collected in Puerto Rico, Jamaica, Guadaloupe and El Salvador (DeBaeh, 1971 ;DeBaeh & Landi, 1961 ;Rosen & DeBaeh, 1978, 1979. This is the 1 st time that A. lepidosaphes is reported in Costa Rica, but probably it is distributed in all Central American countries.…”

“…The 1 St recorded success in biological control of L. beckii occurred in California, where A. lepidosaphes was introduced from China in 1948 and produced a substantial control (DeBaeh & Landi, 1961). Later, the wasp was carried from California to several countries around the world, but not to Costa Rica.…”