Effect of Horticultural Mineral Oil on Huanglongbing Transmission by Diaphorina citri Kuwayama (Hemiptera: Psyllidae) Population in a Commercial Citrus Orchard in Sarawak, Malaysia, Northern Borneo

Abstract

Diaphorina citri Kuwayama transmits a destructive citrus disease caused by a fastidious bacterium ‘Candidatus Liberibacter asiaticus’ (CLas) designated as Huanglongbing (HLB) which posed a risk of detrimental threat to the Malaysian citrus industry. All D. citri life stages show a lumped habit on young flushes and its population fluctuations was closely related to accessibility of young flushes. The study aimed to investigate if the appearance of young flush shoots on citrus influences ACP population fluctuation and if horticultural mineral oil (HMO) could reduce spread of HLB transmission by ACP in a commercial healthy orchard. Field research was carried out from 1 April 2011 to 1 December 2014 in a 2-year-old 1 ha citrus farm that consisted of 200 PCR-certified disease-free grafted non-bearing honey tangerine (Citrus reticulata L.) in southwestern Sarawak, Malaysia. The experiment had two treatments namely control (unsprayed) and nC24 HMO with four replications arranged in a simple randomized block design. ACP eggs, nymphs, and adults per flush shoot was assessed and HLB incidence was monitored for visual inspection of the citrus trees for the current existence of usual signs of characteristic symptoms of HLB such as yellowing shoots, leaf mottling, and corky or enlarged veins on leaves. HLB-specific primer was employed in 16S rDNA polymerase chain reaction to detect the CLas gene in diseased trees. Increase in abundance of D. citri is mainly affected by the citrus flushing cycles and their life stages are completed on these flush shoots. Relative degree of aggregation index for D. citri adults increased during periods of cyclic production of new flush. HMO-treated plots produced a significantly lower percentage up to 11.43% of diseased trees against 42.20% in untreated control plots. HMO is effective against D. citri and recommended to be incorporated in the IPM program to prevent infection and reduce the spread of HLB.

High Altitudes Limit The Incidence of Huanglongbing snd Its Vector, Diaphorina Citri, in Citrus Orchards

“…Thus, C. heterogena may transmit the pathogen; however, the low incidence of the pathogen in mature orchards in Tsirang above 1200 m ASL in our study suggests negligible rates of transmission by this psyllid, if transmission does occur. Mineral oils provide an environmentally-friendly alternative to hard pesticides [61,62,63,64] and should be evaluated for suppression of populations of C. heterogena and other citrus psyllids. In addition, powdery mildew caused by Oidium citri [65] occurs on mandarin in most citrus-growing areas of Bhutan and was also found at the medium and high-altitude sites in Central Java; control of this disease is needed.…”

Decoding Huanglongbing: Understanding the Origins, Impacts, and Remedies for Citrus Greening

“…The results demonstrate that the tree topology of D. citri mtCOI sequences, which were collected from different locations in Indian states, exhibited a clear separation into four distinct clades. Leong et al (2020), conducted a study to analyze the transmission of HLB disease, which is transmitted by D. citri, in connection to its spatial arrangement and flight behavior in reaction to flush cycles in a flourishing area. The results indicate that the Rebel brown-yellow traps were more effective than others in capturing adult D. citri.…”

Detection of citrus vein phloem degeneration disease (Candidatus Liberibacter asiaticum) in orange cv. Selayar, Citrus reticulata L.

“…Especially in Selayar Regency, the citrus cv. Selayar continues to grow and is widely cultivated in Bontomatene District (860 ha, production 11,234.62 tons), Bontomanai District (750 Ha, production 5,250.50 tons), and Bontosikuyu District (1,034 ha, production 3,381.80 tons) [2]. Over time, the development of Selayar oranges began to face a number of obstacles.…”