Asian citrus psyllids and shade: Survival of Diaphorina citri on Murraya exotica foliage exposed to different levels of light

Authors: KELVIN, RUIZ - University Of Puerto Rico; Jenkins, David; Goenaga, Ricardo

Submitted to: Entomological Society of America Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 6/6/2015
Publication Date: 11/15/2015
Citation: Kelvin, R., Jenkins, D.A., Goenaga, R.J. 2015. Asian citrus psyllids and shade: Survival of Diaphorina citri on Murraya exotica foliage exposed to different levels of light. Entomological Society of America Annual Meeting. Abstract.

Interpretive Summary: Anecdotal evidence indicates that Asian citrus psyllid, vector of the causative agent of citrus greening, is less abundant in shady environments. We wanted to test whether foliage exposed to lower levels of light were less suitable for adult Asian citrus psyllids. Using shade cloths of different densities to vary light levels, we exposed host plants (Murraya exotica) to different levels of photosynthetically active radiation, ranging from full sun to 3% of the photosynthetically active radiation of full sun. Plants were maintained under these conditions for two months. Asian citrus psyllids were reared on foliage from plants exposed to different light levels and their longevity was monitored. 50% of the psyllids reared on foliage exposed to full sunlight for one month lived at least 25 days whereas 50% of the psyllids reared on foliage exposed to the lowest levels of light for one month had died by 19 days. Similarly, 50% of the psyllids reared on foliage exposed to full sunlight for two months lived at least 27 days whereas 50% of the psyllids reared on foliage exposed to the lowest levels of light for two months had died by 15 days. These results indicate that plants grown under lower light levels are less suitable for adult Asian citrus psyllid survival. This response could be attributed to glucose, sucrose and starch contents of leaves being reduced by shade. Adequate sources of carbohydrates may be essential for completing insect’s life cycle.

Technical Abstract: Using shade cloths of different densities, potted individuals of Murraya exotica (Rutaceae) were exposed to levels of photosynthetic radiation (PAR) varying from 48 µmol photons per meter2 per second to 1562 µmol photons per meter2 per second (average of three readings taken at noon during conditions of full sun). Diaphorina citri adults colonizing the plants under the different conditions were counted and recorded. Foliage from plants exposed to the treatments for one month and two months were returned to the lab and used in leaf-excise bioassays to determine if Diaphorina citri lived longer on foliage exposed to higher levels of PAR. Excised individual leaves were placed in a 2 ml centrifuge tube with water to keep the leaf hydrated. The excised leaf was then placed in a 50 ml centrifuge tube with a single 3-5 day post-emergent adult Diaphorina citri. Each treatment (level of light) was replicated 10 times and adults were monitored daily for mortality. Kaplan-Meier survival analysis indicated that there were significant differences in longevity between psyllids reared on leaves exposed to full sun and psyllids reared on leaves exposed to reduced solar radiation. Fifty percent of the psyllids reared on foliage exposed to full sunlight for one month lived at least 25 days whereas 50% of the psyllids reared on foliage exposed to the lowest levels of light for one month had died by 19 days. Similarly, 50% of the psyllids reared on foliage exposed to full sunlight for two months lived at least 27 days whereas 50% of the psyllids reared on foliage exposed to the lowest levels of light for two months had died by 15 days. These results indicate that plants grown under lower light levels are less suitable for adult Asian citrus psyllid survival. This response could be attributed to glucose, sucrose and starch contents of leaves being reduced by shade. Adequate sources of carbohydrates may be essential for completing insect’s life cycle.