DNA degradation in Haplaxius crudus (Hemiptera: Cixiidae) and Diaphorina citri (Hemiptera: Liviidae) on yellow sticky traps in Florida

Abstract

Lethal bronzing (LB) and huanglongbing (HLB) are harmful plant diseases causing significant economic losses in Florida agriculture. Both diseases are caused by bacteria that are transmitted by Hemipteran insect vectors. Accurate detection of pathogens within insect vectors can help provide a better understanding of disease epidemiology. Monitoring of the vector of LB is done primarily using sticky traps within palm canopies. However, it is unknown how long pathogen and vector DNA remain intact under field conditions. If significant DNA degradation takes place over the course of days or weeks, there is a possibility of false negatives occurring when detecting pathogens from these surveys. This study determined how long Haplaxius crudus Van Duzee (Hemiptera: Cixiidae) and LB DNA could remain detectable on sticky traps under field conditions in Florida in winter and summer, using PCR and qPCR. Additionally, this study compared the DNA degradation of Diaphorina citri Kuwayama (Hemiptera: Liviidae) and Candidatus Liberibacter asiaticus (CLas), the causal agent of HLB. The results showed that DNA concentration and amplification rate declined as time on sticky traps increased. Degradation varied between different target genes. The amplification rate of insect genes from sticky trap samples suggests that sticky traps should be changed weekly in summer, and every 2 wk in winter for accurate H. crudus detection. Traps should be changed every 4 days for phytoplasma detection. Traps can be changed monthly for accurate D. citri and CLas detection. Based on these results, standard monitoring protocols can be implemented to more accurately detect vectors and pathogens.