Apple sawfly Hoplocampa testudinea (Hym., Tenthredinidae) and its parasitoid Lathrolestes ensator in Dutch apple orchards (Hym., Ichneumonidae, Ctenopelmatinae)

Abstract

Changes in population densities of the apple sawfly Hoplocampa testudinea (Klug) and its parasitoid Lathrolestes ensator (Brauns) were monitored in 15 apple orchards for a period of up to 4 years. The parasitoid species was found in all orchards except one, and was more numerous in plantings on sandier soils. Post‐bloom insecticide applications against other pests, and carbaryl for fruit thinning, often decimated both host and parasitoid in integrated pest management orchards. In organic orchards, where synthetic pesticides are banned, and Quassia is the only remedy against sawfly, the pest is more problematic. The low levels of parasitism in all organic orchards, except one, were possibly due to the application of wettable sulphur during the parasitoid flight period. The sawfly usually recovers more quickly than its parasitoid when chemical control is discontinued, because propagation of L. ensator is limited in various ways. The parasitoid is time limited, because suitable second instar host larvae are rarely available for more than a week on a single apple variety. Moreover, parasitism levels stay moderate because the parasitoid females do not avoid superparasitism. Finally, relatively more sawflies than parasitoids emerge after 10 months underground, because the incidence of prolonged diapause is more elevated in L. ensator than in the sawfly. It is suggested that both the high incidence of prolonged diapause and the inability to avoid superparasitism are useful in reducing the risk of local extinction. Elevated sawfly attack in a single early apple variety would reduce exploitation of suitable host larvae in other nearby varieties, in as far as the parasitoid is not able to distinguish fruitlets with accessible second instar host larvae from those with inaccessible older larvae. Although the former are available for a limited time, the latter may keep the parasitoids from moving to the less abundant second instar larvae in late(r) varieties. Reduction of elevated host density in such an early variety by a properly timed application of a short‐lived pesticide, such as Quassia, increases parasitism levels proportionally, and is expected to promote parasitoid movement to host larvae in other varieties nearby.

Kaolin particle films suppress many apple pests, disrupt natural enemies and promote woolly apple aphid

“…The kaolin treatments reduced the apple sawfly infestation by 74% on cv. J. Grieve which, like other early flowering cultivars (Alford 1984; Zijp and Blommers 2002), is susceptible to apple sawfly. Simultaneously, the parasitism level of L. ensator , a common and specific parasitoid of apple sawfly larvae in the Netherlands (Cross et al.…”

Evaluation of temperature sum models and timing of Quassia amara (Simaroubaceae) wood-chip extract to control apple sawfly (Hoplocampa testudinea Klug) in Sweden

“…A quantitative study of Q. amara persistence in the field is lacking. However, the extract has been estimated to be active only over a short period of 4–6 days (Wijnen et al 1994 ; Zijp and Blommers 2002a ). It is, therefore, of primary importance to apply the extract during egg hatch, i.e., earlier than larval penetration McIndoo and Sievers 1917 ; Kienzle et al 2002 ).…”

“…2012). The short persistence of Q. amara extract avoids a negative effect on the later emerging apple sawfly parasitoid Lathrolestes ensator (Zijp and Blommers 2002a, b ). The extract is sprayed after flowering to eradicate neonate larvae of the sawfly.…”

Control of Hoplocampa testudinea using the extract from Quassia amara in organic apple growing

“…The extract was prepared shortly before its application (2-4 days). Quassia wood chips (100 g) were boiled in 2 l of water for one hour following the procedure described by Dodia et al (2008) and Zijp, Blommers (2002). During boiling, chips slowly dropped to the bottom and finally they settled there.…”

“…The possible method acceptable in organic growing is spraying on the basis of natural bitter compounds quassin and neoquassin (Wijnen et al 1994;Zijp, Blommers 2002). These substances belong among oxygenated triterpenes and are contained in the wood of plants of the Simaroubaceae family (Guo et al 2005).…”