Biocontrol Potential of a Commercially Available Predator Rhyzobius lophanthae Blaisdell (Coleoptera: Coccinellidae) Against Diaphorina citri Kuwayama (Hemiptera: Liviidae)

Abstract

Diaphorina citri Kuwayama is a key pest of citrus and insect vector of Huanglongbing (HLB), also known as citrus greening disease, causing significant losses in Florida and other regions. The naturally occurring effective ladybeetle predators and their impact on D. citri reduced from years of insecticide use against this pest and are not available commercially. Additionally, most species are large-sized, while most eggs and neonates of D. citri are in hard-to-reach locations such as unopened leaves, which makes access difficult for them. We evaluated a commercially available small-sized predatory ladybeetle Rhyzobius lophanthae Blaisdell against D. citri immatures. A single adult consumed an average of 24.9 eggs and 8.7 first and second instar nymphs of D. citri within 24 h. Beetles exhibited Type II functional response against nymphs with an attack rate of 0.92 h^-1 and a handling time of 0.08 h. Their consumption rate increased with nymphal density up to twenty per shoot. In the field test, beetles lived 10 days longer when confined with new shoots infested with D. citri immatures in a voile fabric sleeve cage in citrus trees every two days, versus seven days. In an open field release of R. lophanthae in a citrus orchard, these ladybeetles were found foraging in sentinel and neighboring trees infested with D. citri. The consumption rate of R. lophanthae on D. citri immatures and its survival in Florida orchards suggest its potential for biological control and Integrated Pest Management.

Keywords: Asian citrus psyllid; Huanglongbing (HLB); biological control; natural enemies; pest management.

Figure 1

Mortality of Diaphorina citri eggs (%) (±SE) in the presence and absence of Rhyzobius lophanthae adults over a 24 h period in laboratory conditions.

Figure 2

Mortality of Diaphorina citri nymphs (%) (±SE) in the presence and absence of Rhyzobius lophanthae adults over a 24 h period in laboratory conditions.

Figure 3

The number of Diaphorina citri nymphs consumed by Rhyzobius lophanthae adults within 24 h. The curve represents the best-fitting functional response model (flexible type II functional response); 95% bootstrapped confidence intervals.

Figure 4

The mortality percentage (±SE) of Diaphorina citri immatures under 1, 3, and 5 Rhyzobius lophanthae adults per infested shoot. Different letters on the columns indicate a significant difference between treatments (GLM with binomial distribution followed by post hoc Tukey test, p  <  0.05).

Figure 5

The proportion of Rhyzobius lophanthae adults that survived in the field when supplied with D. citri every two and seven days. There was a significant difference in the survival curves of the two treatments (p < 0.0001).