1a. Objectives (from AD-416):
Increasing the understanding of the zebra chip potato disease vector biology, vector-pathogen interaction, and the epidemiology of the disease.
1b. Approach (from AD-416):
Assess the role of the potato psyllid in zebra chip potato disease by: 1) conducting insect transmission studies under laboratory conditions to determine liberibacter acquisition and inoculation access time required for the potato psyllid to effectively transmit the bacterium and induce zebra chip, 2) determining the impact of zebra chip on different plant growth stages under controlled field cage conditions, 3) determining density of potato psyllid required for this insect pest to effectively cause zebra chip, 4) assessing environmental conditions that may influence ZC symptom expression, including temperature, relative humidity, and light intensity, and 5) screening potato breeding material for zebra chip. Documents Reimbursable with Texas A&M (SCRI). Log 44012.
3. Progress Report:
The work summarized in this progress report relates to objectives number 1 and 3 in the Project Plan for 018-00D: 1. Develop new knowledge of behavior, genetics, physiology, and ecology of wireworms, aphids, secondary potato pests, and their natural enemies, that provides opportunities for new and improved biorational control of potato insect pests. 3. Develop economical, sustainable, and ecologically sound methods for control of aphids, wireworms, and secondary pests of potatoes; and objective 2 in the Project Plan for 020-00D: 2. Develop bio-intensive methods to manage insect vectors of zebra chip and purple top diseases. Zebra chip, a devastating disease of potato in U.S., Mexico, Central America, and New Zealand, is associated with a new species of the bacterium Liberibacter, transmitted to potato by the potato psyllid. Knowledge of the pathogen transmission biology by the potato psyllid and the epidemiology of zebra chip is essential to improving management of the disease. A series of laboratory and field transmission experiments determined the time that elapses from initial acquisition of the bacterium by the psyllid to the ability of the insect to transmit it to potato plants, time referred to as “latent or incubation period”. It was determined that the incubation period for the bacterium in the psyllid vector is about two weeks. Also, it was determined that Liberibacter was transmitted in a persistent and circulative manner. In addition, it was discovered that hot temperatures significantly reduced the ability of the potato psyllid to effectively inoculate potato plants with Liberibacter. Information from this research will help potato growers timely target the potato psyllid for control before this insect vector is capable of transmitting the zebra chip pathogen to potato crops and depending on environmental conditions.