BIOLOGICAL CONTROL OF INVASIVE PESTS OF ORCHARD AND VEGETABLE CROPS IN THE SUBTROPICAL SOUTH

Over the life of the project, progress was made on all 5 objectives, under NP 304, Crop Production & Quarantine. We characterized chemical composition of aroma of lemon and lime trees, host plants of ACP and commonly grown in southern CA neighborhoods. Aroma analyses was used to develop potential scent attractants for helping detect ACP in urban areas. After 1 yr of testing, lemon formulation was most promising as an attractant, but further testing is needed. A 2-yr study characterized composition of predatory insect and spider fauna in residential citrus trees and its potential for reducing ACP populations in south TX. ACP populations were low both years at all locations; 99+% of ACP observed were adults; however, in both years drought inhibited growth necessary for ACP reproduction. Uniformly, spiders dominated predator fauna, at >90% of predators collected. Variation in spider communities existed but most common species were found at all locations. Lab studies found that ACP adults are not acceptable prey for the more common spiders from these field samples; 10 species of spider from 6 families almost uniformly attacked but immediately released psyllids. Only Apollophanes punctipes (Philodromidae) consistently attacked and fed on adult ACP. Under dry conditions, it is unlikely that these predators will cause significant ACP mortality. In greenhouse trials adult ACP transferred Isaria fumosorosea (Ifr) spores from dispensers to nymphs developing on potted orange jasmine plants. Ifr mycelia grew on infected nymph cadavers and as a saprophyte on molted skins, honeydew, and waxy excrement, resulting in fungal coverage of entire nymph clusters. Adult ACP visited 98% of sentinel nymph clusters over 5 days. Thus infected ACP can be expected to visit nymph clusters and spread the disease. A dose-response study was conducted to determine level of infection achieved in sentinel nymph clusters when exposed to sporulating adult cadavers; 50-83% of psyllids became infected. Additional cadavers had little impact on infection level. Conidiospores released from single cadavers are highly contagious and can infect multiple nymph clusters. Initial field tests were conducted in Mexican lime trees at a trailer park community near Weslaco. In control clusters, we found few dead individuals and no Ifr-infected individuals. In clusters exposed to dusted adults, a mean of 39% of individuals were infected. Zebra Chip (ZC) disease of potatoes has spread to potato- production areas of TX, KS, NE, NM, and CA, and most recently was found in ID, OR, and WA, and in New Zealand. Causal agent is Candidatus Liberibacter solanacearum, related to citrus greening. Economic losses have been high, leading to intensive pest management programs to minimize disease impact. The potato psyllid vectors the disease to potatoes. A 4- yr, multistate, multi-institutional field survey program was initiated to learn more about seasonal phenology and variability of the psyllid and its associated pathogen. Field data on intensity and variability of disease pressure was used to develop an IPM program, implemented as a best management practice for growers.