Impact on US Citrus Production
The long term goal of the CitrusGreening Solutions project is to provide a therapeutic delivery system to growers to prevent CLas infection of the plant and/or prevent development of HLB in already infected citrus.
- First identified in the US in Florida in August 2005
- Estimated that approximately 80% of Florida citrus trees are infected, and some groves no longer productive
- Associated with a phloem limited bacterium, Liberibacter asiaticus (CLas), vectored by the Asian Citrus Psyllid (widespread in Florida and Texas, increasing and beyond eradication in California and Arizona)
- Within a few years of infection, many citrus trees become weak, have poor quality fruit, with lots of fruit drop, and trees may die or become useless
- Estimated average crop reduction of 40% compared to healthy trees (Singerman, 2015) - many Florida growers going out of business
Infected citrus fruit and leaves (Credit: Bove 2006)
Trend in Florida Citrus Production
Data from USDA
Four years of HLB progression in same Hamlin Sweet Orange tree. Note thinner canopy, lighter leaf and fruit color and presence of many green fruit on tree in 2015.
This represents fairly successful management using extensive foliar nutrition and aggressive psyllid control, and likely is around the 40% cropping reduction of typical HLB-infected sweet orange in Florida. Photo courtesy of Hardee, DeSoto
Abandoned unproductive groves from HLB infection are widespread (33,000 acres+ and 43,000 trees removed)
Florida response to HLB
- Initially very rapid disease development, from first find of a diseased tree up to 39% of trees in a grove in 10 months
- At first most growers scouted and removed infected trees but rapid spread made few willing to remove producing trees
- Most try to control psyllids and maintain infected trees through foliar nutrition programs (now approximately $2000/acre cost for production up from approximately $800/acre before HLB was in Florida)
- Production and fruit quality are declining. What can be done to maintain yield and quality in infected trees?
- A major concern is that production will drop below critical volume to maintain juice industry and infrastructure
Fruit quality, flavor and preharvest drop
Fruit quality affects of HLB have been assessed:
- Highly symptomatic are worst
- Non-symptomatic fruit are slightly different from healthy but acceptable
- Preharvest fruit drop is much greater in HLB-infected trees, even with nutrient enhancement
HLB-infected tree in decline on the left. HLB-infected tree that is cropping well but with lots of preharvest drop on the right. Photo courtesy of Steve Rogers
Overview of US Citrus Production
If we combine juice and fresh, then citrus is #1 fruit consumed in the US. 50x106 cartons of fresh fruit are exported every year.
Total value of US citrus industry is approximately $9 billion
- 75% production is sweet orange
- 11% grapefruit
Florida produces 66% of the total US Citrus production
- 85% oranges (96% juiced)
- 12% grapefruit (58% juiced)