Tech Talk

Month: May 2017

Pest of the month: Bean spider mite (Tetranychus ludeni)

Category name: Mites

Importance: Minor – sometimes important

Similar to: Two-spotted mite

Description: Egg: Minute, globular, almost transparent, can have reddish tinge. Immatures: Similar to two-spotted mite. Adult: Uniformly dark red, distinguishing it from two-spotted mite which is yellowish-green with two dark spots. In cooler climates the red overwintering phase of two-spotted mite is a lighter red than that of bean spider mite. More

Eucalyptus rust, Guava rust

Pest of the month: Eucalyptus rust, Guava rust (Puccinia psidii)

Category name: Fungi

Importance: Emergency disease, however currently found only in Eastern Australia.

Symptoms: The fungus attacks young tissues of new leaves, fruits, flowers, shoots and succulent twigs. The disease can cause deformation of leaves, heavy defoliation of branches, dieback, stunted growth and even death. More

Webinars are being held to help with the identification of the major pest mite groups likely to be encountered in a production nursery; and the steps to take once virus-like symptoms are identified to confirm if a virus is present.

The presenters will be Andrew Manners and John Duff, from the Queensland Department of Agriculture and Fisheries (DAF), who collectively have over 45 years of experience in pest and disease management. More

Infected Azalea leaves

Pest of the month: Sudden oak death (Phytophthora ramorum)

Category name: Fungi

Importance: Emergency disease

Symptoms: In oak trees, the earliest symptoms are the appearance of a bleeding canker, burgundy-red to tar-black thick sap, oozing on the bark surface. The disease is typically found from the root crown (the area where the trunk fans out to the roots) to a height of 2 meters. Symptoms on secondary hosts include leaf spots, leaf blight, stem and twig cankers, and shoot tip and branch die-back. Infections on Rhododendron cause brown lesions on leaves and young stems. On Viburnum, the infection usually occurs at the stem base causing the plants to collapse.

Transmission: The organism can be spread in soil and water. It can survive in moist conditions for at least one month. In USA it has been recovered from soil carried on hikers shoes. The fungi can reproduce rapidly on leaf surfaces, allowing rapid build-up of Phytophthora spores, which serve as a source of infection. More

Pest of the month: Alternaria leaf spot (Alternaria spp.)

Category name: Fungi

Importance: Major on susceptible hosts.

Symptoms:  Vary according to host, but often appear initially as small water-soaked flecks on lower leaves, enlarging into circular or irregularly-lobed lesions. Lesions typically become brown-black, and may or may not display concentric rings (the darker bands contain spores of the fungus). Lesions are sometimes surrounded by a chlorotic halo. Older leaf spots may become papery or brittle, leading to tearing and/or the development of ‘shot-hole’ symptoms. In some cases, spots coalesce to cover large areas, resulting in blighting of foliage. Alternaria spp. may also cause a range of other diseases including crown, stem and fruit rots. More