Contributions to the knowledge of almond pests in East Mediterranean countries

Abstract

The lecanine scale, Didesmococcus unifasciatus (Arch.) was recently found in two widely‐separated orchards in Lebanon. Its biology was studied locally. The scale is bisexual and univoltine. Young adults of both sexes appear and mate during the last week of April. Fertilized females double their size between the end of April when copulation occurs and the oviposition period in mid‐June. A female lays between 1500 and 2400 eggs in three to five days under its scale, and egg hatching occurs some four to five days later. The scale passes through three larval instars. Winter is passed in the second larval instar. D. uni‐fasciatus does not seem to have a true diapause period in Lebanon. This scale has a large number of natural enemies that keep it under control. Where contact insecticides are regularly used, a great reduction in populations of its natural enemies occurs, and infestation by this scale results in the death of almond trees within a period of three to five years after the start of an infestation. Zusammenfassung Zur Kenntnis der Mandelschädlinge des Mittelmeergebietes. II. Didesmococcus unifasciatus (Arch.) Ein starkes Auftreten von D. unifasciatus in 2 Obstanlagen des Libanon wurde näher untersucht. Die Schildlaus ist bisexuell und univoltin. Die jungen Adulten beider Ge‐schlechter erschienen und kopulierten Ende April. Nach der Befruchtung bis zur Eiablage Mitte Juni verdoppelten die Weibchen ihre Größe. Ein Weibchen legte zwischen 1500–2400 Eier innerhalb von 3–5 Tagen unter seinem Schild ab. 4–5 Tage spärer schlüpften die Lar‐ven, die in ihrer Entwicklung 3 Stadien durchlaufen. Das 2. Stadium überwintert. D. uni‐fasciatus scheint im Libanon keine echte Diapause durchzumachen. Die Schildlaus hat eine große Zahl Feinde. Wo Kontaktinsektizide regelmäßig im Obstbau verwendet werden, sind die Populationen der natürlichen Feinde stark reduziert, was zur Vermehrung der Schildlaus führt. Bei starkem Befall kann der Baum nach 3–5 Jahren zum Absterben gebracht werden.

Almond seed wasp (Hymenoptera: Eurytomidae) sex pheromone: effect of trap type, trap position, blend ratio and time of the day on male attraction

“…Previous studies successfully monitored E. amygdali adult emergence by the use of cages containing previously infested almonds (Mentzelos & Atjemis, 1970;Katsoyannos et al, 1992). In those studies, it was confirmed that males appear first; and, in some cases, there is a considerable interval between the peaks of emergence of males and females (Talhouk, 1977;Katsoyannos et al, 1992). Hence, insecticidal applications that are based on the emergence of the first adults may not be effective for a satisfactory level of control of E. amygdali.…”

“…The almond seed wasp, Eurytoma amygdali Enderlein (Hymenoptera: Eurytomidae), is a key pest of almonds in a number of European countries and in the Middle East (Avidov & Harpaz, 1969;Mentzelos & Atjemis, 1970;Plaut, 1971Plaut, , 1972Talhouk, 1977;Arambourg et al, 1983;Zerova & Fursov, 1991). E. amygdali has one generation per year and the larvae overwinter inside the infested almonds that remain mummified on the trees.…”

“…Control measures for this pest are based on cultural practices, such as collection and destruction of the infested almonds, and on chemical applications against the young larvae. The effectiveness of the insecticide treatments depends heavily on the time of insecticide application; newly hatched larvae bore inside the nucleus and feed on the fruit embryo where they are protected from insecticides (Mentzelos & Atjemis, 1970;Plaut, 1972;Talhouk, 1977).…”

Pest categorisation of Didesmococcus unifasciatus

“…Together with male pupal elongation female scales acquire a convex spheroidal shape, initially 2.0 and 2.5 mm in diameter and 1.9 mm height. In general, individuals destined to become females settle on the borders of a colony while males occupy the centre (Talhouk, 1975).…”

“…As oviposition starts the body shrinks with the extrusion of eggs, which is completed in 3-5 days, besides, the female stops egesting honeydew and the ants, particularly attracted by the copious honeydew egested by the young female adults, disappear. When oviposition is completed, the dorsum of the insect loses its shiny aspect, becomes dull brown and the horizontal red band disappears (Talhouk, 1975).…”