Alan D Clift

The effect of tibia morphology on vector competency of mushroom sciarid flies

Mushroom sciarid flies Lycoriella ingenua (Dufour) and Bradysia ocellaris (Comstock) are major pests of cultivated mushrooms, Agaricus bisporus (Lange) Imbach. The economic threshold of these pests is very low because they vector pathogens across mushroom beds, e.g. Verticillium fungicola which causes ‘dry bubble’ disease. Under controlled conditions, B. ocellaris transported more V. fungicola spores than L. ingenua from infected to sterile culture plates. Similar results were obtained when L. ingenua and B. ocellaris were collected from a growing room infected with V. fungicola then introduced onto sterile culture plates for 90 min. The external morphology of B. ocellaris and L. ingenua was examined using scanning electron microscopy. The micrographs showed clusters of V. fungicola spores attached to the inner side of a comb‐like row of bristles on the fore tibia of B. ocellaris whereas L. ingenua does not possess an equivalent structure on the fore tibia. These morphological differences are the most probable explanation for the greater competence of B. ocellaris as a vector of V. fungicola compared with L. ingenua.

Effect of compost and casing treatments of insecticides against the sciarid Bradysia ocellaris (Diptera: Sciaridae) and on the total yield of cultivated mushrooms, Agaricus bisporus

BACKGROUND Bradysia ocellaris (Comstock) is one of the major pests of cultivated mushrooms, Agaricus bisporus (Lange) Imbach. The feeding of sciarid fly larvae causes damage to the cultivation substrates, compost and casing. A comparative study of insecticidal treatments incorporated into compost and casing against B. ocellaris was conducted during 2003-2004. Treatments with an organophosphate, diazinon, a pyrazole, fipronil, and an insect growth regulator (IGR), triflumuron, were incorporated into casing. Another IGR, cyromazine, was incorporated into compost. Insecticidal incorporation into compost and casing has been associated with reductions in mushroom yield. Therefore, the effect of these insecticidal treatments on the overall yield was evaluated. RESULTS A combined treatment, incorporation of cyromazine at 10 mg kg(-1) into compost and of triflumuron at 20 mg kg(-1) into casing, provided 100% control against B. ocellaris. There was no apparent reduction in yield as a result of incorporation of the tested chemicals into either compost or casing. CONCLUSION The results obtained from this study suggest that incorporation of insecticides into both compost and casing is required to control a moderate to high pressure of insect pests. There were no significant yield reductions as a result of the incorporation of pesticides in the Australian mushroom-growing system.

Host–parasite interaction between cultivated mushroom, Agaricus bisporus hybrid strain Sylvan A15, and the mycoparasite Verticillium fungicola, a causal agent of dry bubble disease

Verticillium fungicola is one of the most economically significant pathogens of the cultivated mushroom Agaricus bisporus throughout the world. A. bisporus basidiomes are reported to be more susceptible to infection by V. Fungicola than the vegetative mycelium. V. Fungicola spores were also reported to be dependent on A. bisporus mycelium. Transmission and scanning electron microscopy were used to investigate the host-pathogen interactions at the mycelial and sporophore stages of A. bisporus. The transmission electron micrographs showed that the V. Fungicola mycelium grows very close to the A. bisporus mycelium. There were no specialised penetration structures or any evidence of direct penetration of the pathogen in the host tissue. The scanning electron micrograph of the necrotic tissue of the diseased mushroom shows clusters of phialoconidia and hyphae of the pathogen in large numbers.

Adoption of Exotic Plants by an Endemic Australian Weevil, Orthorhinus cylindrirostris (Coleoptera: Curculionidae)

ABSTRACT The elephant weevil Orthorhinus cylindrirostris (F.) (Coleoptera: Curculionidae) is endemic to Australia and has colonized several exotic crops including citrus, blueberries, and grapevines. Wecompared the life history of this pest on two native and two exotic host plants: hickory wattle Acacia falcata Willdenow, rough-barked apple Angophora floribunda (Smith) Sweet, lemon Citrus limon (L.) Burman, and blueberry Vaccinium corymbosum (L.). Blueberry was attacked more often (22 of the 24 plants) than lemon, rough-barked apple, and hickory wattle (6–8 plants of each species attacked of the 24). Adult emergence followed a similar pattern across hosts but emergence was low overall (58 adults from 176 eggs). Only blueberry had more than one weevil emerge from a single plant. Development from oviposition to adult emergence can take up to 2 yr, particularly on blueberry. Adult life span and weight varied between individuals although no effect of host plant was detected. Similar plant chemistry is unlikely to have triggered host range expansion by this species because the exotic host plants are from different families (Rutaceae, Vitaceae, and Ericaceae) to the native host plants (Myrtaceae, Mimosaceae, and Fabaceae). O. cylindrirostris colonized citrus trees over a century ago, yet it appears to have no preference for lemon over native host plants. In contrast, O. cylindrirostris has developed a preference for blueberry, the higher quality host plant, only a few decades after colonization.

Blueberry Cultivars Differ in Susceptibility to the Elephant Weevil, Orthorhinus cylindrirostris (Coleoptera: Curculionidae)

Abstract The accumulated damage from elephant weevil larvae, Orthorhinus cylindrirostris (F.) (Coleoptera: Curculionidae), reduces blueberry yield and shortens the productive lifespan of blueberry plants by several years. Selective breeding to develop pest-resistant blueberry cultivars is a possible control option, but the relationship between O. cylindrirostris populations, plant damage, and blueberry yield has not been described. A field survey of 17 blueberry cultivars was conducted on a commercial farm to measure O. cylindrirostris populations (emergence holes and adult numbers) and yield from plants of different ages (2–12 yr). Blueberry plants accumulated damage over time, that is, older plants tended to have more O. cylindrirostris emergence holes than younger plants. All cultivars received some level of O. cylindrirostris attack but this did not always lead to yield losses. Newer cultivars that have been in production since 2000 were less susceptible to O. cylindrirostris than older cultivars. Removal of highly susceptible cultivars from commercial blueberry farms may reduce O. cylindrirostris populations. There is potential for selective breeding to increase plant resistance to O. cylindrirostris if the specific resistance mechanisms can be identified in blueberry.