Distribution of the Psylhd Vectors of Citrus Greening Disease, with Notes on the Biology and Bionomics of Diaphorina Citri.·
Total Page：16
File Type：pdf, Size：1020Kb
8 FAO PLANT PROTECTION BULLETIN Distribution of the PsylHd Vectors of Citrus Greening Disease, with Notes on the Biology and Bionomics of Diaphorina citri.· H.D. .Catling, Malkerns Research Station, Malkerns, Swaziland In 1968, the author, under the auspices of The two main vectors responsible for green FAD, assisted the Philippine Bureau of Plant ing disease are Trioza erytreae (Del G.) and Industry in initiating research on the Oriental Diaphorina citri (Kuw.). insect vector of citrus greening disease. Sur veys vI/ere carried out in the Philippines on Distribution of Trioza erytreae the distribution of the vector, and observa tions on symptoms in declining citrus groves In 1965, McClean and Oberholzer (22) prov were made during short visits to Hong Kong, ed that greening in South Africa is transmitted Thailand, India and Nepal. by the psyllid T. er.vtreae. This vector is restricted to Africa south of the Sahara (see Figure 1), and has also been recorded in Mad Greening diseases agascar (3), Mauritius (26), Reunion (4, 26) and Saint Helena (15). It is suspected to occur In the last three decades a number of closely in Angola,l and has been observed by the author related citrus virus diseases have appeared in in Rhodesia, and in Swaziland (10). most regions of the world where citrus is grown. A number of workers now believe that the greening disease of South Africa, leaf mottling Distribution of Diaphorina citri of the Philippines, and much of the citrus It has been shown conclusively that the dieback in India are caused by one and the psyllid D. citri, is the main vector of greening same virus. It is also becoming increasingly disease in Asia and the Far East. In 1965 clear that the stubborn disease of America, Tirtawidjaja et al. (34) demonstrated that the vein-phloem degeneration of Indonesia, yellow vein-phloem degeneration disease of Indonesia shoot of China (Mainland), and likubin of is transmitted by D. citri. Salibe and Cortez China (Taiwan) are very similar to greening. (28) published preliminary evidence that D. Results described in this paper tend to support citri is the vector of Philippine leaf mottling this view. and this was later confirmed by Celina et al. Excellent descriptions of the symptomology (14) and Martinez and Wallace (21). In India. of greening, leaf mottling and stubborn disease Capoor et al. (6) have shown convincingly may be found in recent papers (5, 21, 23, 28). that D. citri is an efficient vector of greening. In the field, however, particularly in Asia and Figure I and Table 1 show that D. citri is the Far East, recognition of the disease from widely distributed in the Orient and is present symptoms alone is often difficult. Very sim in Brazil. The vector occurs in the Ryukyu ilar leaf symptoms may be caused by a wide archipelago (24) but as far as can be ascer~ variety of factors varying from nutritional tained it has not been recorded in Japan. disorders to the presence of other diseases such Greening-like diseases have been reported from as root rots and gummosis, and even other 11 out of the 15 countries where this vector virus diseases such as tristeza and exocortis. is known to occur on citrus. Furthermore, Hence, tissue graft and insect transmission studies are often necessary before a reliable 1 Eastop. V.F. 1969. Personal communication (spec diagnosis can be made. imens in the British Museum). PLANT PROTECTION BULLETIN 9 ~~~~~~~~~~~~~~~~----,~,.,'-- -T. ~ytreae ~-- D.citri Figure I. Distribution of Trioza erytreae and Diaphorina cUn. (From Map No. 234, Commonwealth Institute of Entomology) the disease is suspected in Malaysia and Hong D. citri was collected by the author in the Kong and there is a strong possibility that it Philippines, China (Taiwan), Hong Kong, Thai is present in Burma and Pakistan - especially land and Nepal, and he has since received in West Pakistan bordering the Indian Punjab. specimens from Brazil and Reunion. Both D. citri and T. erytreae occur in Reunion and TABLE 1. - DISTRIBUTION OF D. citri AND THE PRESENCE Mauritius. OF GREENI;\IG-L1KE DISEASES OF CITRUS Country Greening-like diseases Surveys for D. citri and greening in the Philippines Burma (16) Surveys were carried out by two methods, Ceylon (35) Greening (26) depending mainly on the size of the grove China (Taiwan) (19) Likubin (5, 31) selected. In most large groves, 50 to 200 India (16, 19) Greening (17) flushes were examined for eggs and young Indonesia (16, 19) Decline (32), vein-phloem stages of the insect with a hand lens either degeneration (34) Asia in situ or after removal from the trees (sur East and West Pak- istan 1 (19) veys). In small or backyard groves, or where Hong Kong (30) Probable greening (8) trees were semidormant, a rapid search was Malaysia (16) Possible greening 2 made, lasting 10 to 20 minutes or until the Nepal l Greening (9) vector was discovered (spot checks). The rate Philippines (16, 19) Greening (leaf mottling) of discovery was taken as a measure of (21, 28) prevalence. Mauritius 1 (26) Greening (26) Greening was identified mainly by leaf and { Reunion (4) Greening (4, 26) fruit symptoms. In addition, a small number Stubborn (5), probable { Brazill (20) greening (27) of fruit and bark samples were taken from diseased trees for indexing by the fluorescent 1969. Personal communication (spec- test of Schwarz (29). ~~r~~;~:~t~!r!~~'~Ulll). - 2 Chiarappa. L. 1968. Per- The results are summarized in Table 2. 10 FAa PLANT PROTECTION BULLETIN TABLE 2. - SURVEYS AND SPOT CHECKS FOR D. citri IN CITRUS GROVES IN THE PHILIPPINES DURING JULY AND AUGUST 1968 Surveys Spot cllccks Region Province 'I-:N~mber I Number 1 Number I Percentage Number of groves of groves Iof flushes of flushes of spot Number surveyed infested examined infested checks infested Batangas I" 11 11 1 100 I 35.9 I 7 6 Southern Cavite Tagalog 2~ 2~ 2~ 2;:~ I Laguna I Quezon i Albay 5 4 350 I 42.6 7 7 Bicol Camerines Norte 4 o 230 0.0 5 o Camerines Sur 4 3 250 8.4 11 8 Sorsogon 1 I 50 36.0 I 1 Mindoro Oriental 4 o 600 0.0 3 o Cotabato 4 2 400 20.8 4 2 Mindanao Davao de Sur 2 1 150 10.0 5 1 Davao Oriental 3 1 250 27.6 3 1 Northern Benguet o 100 0.0 3 o Luzon La Union 2 1 Southern Tagalog. With one exception, D. in the season for a valid comparison of fruit citri was fairly abundant in all groves searched symptoms, but it would appear that they are in this region. Centered in Batangas prov not reliable in mandarins. No definite marker ince, this is the oldest and formerly the most substance was found in two fruit samples from important citrus-growing area in the Philip diseased Ladu mandarins, but a bark sample pines. Since the rampant spread of the dis from the same trees was clearly positive for ease in the late 1950s, however, more than greening. Greening symptoms were also ob a million trees have died and the 1968 crop served in several neglected Valencia trees in was estimated at about one tenth of that Batangas, three fruit samples showing low harvested in 1960. Since much of the prop concentrations of marker substance and a agative material used in other citrus areas single bark sample again being clearly positive, originated from Batangas, the disease has Bicol and Mindoro. Table 2 shows that the probably been inadvertently introduced into vector was common in the Bicol region, with most of the recognized citrus areas of the the exception of Camarines Norte, but was Philippines. not found in seven groves in Mindoro Orien Disease symptoms were found in every grove, tal. It is possible, however, that further search most trees showing severe decline, with the would reveal its presence in these areas. Scat exception of the Rosario/Padre Garcia area, tered leaf symptoms were observed in both where trees continue to bear and grow well. regions but in only three groves could this Apart from the absence of vein-yellowing, be associated with greening. In one grove there was a striking resemblance between leaf in Mindoro there was evidence that the dis symptoms and general tree appearance of man ease had been introduced with propagative darins in Batangas (mainly Ladu and Szin material from Batangas. kom varieties), with greening-affected sweet Mindanao and northern Luzon. The vector orange trees in South Africa. It was too early was present in most groves examined in Min- PLANT PROTECTION BULLETIN 11 danao and in one in northern Luzon. Very to trees examined in the Philippines. As in few symptoms were observed in either region. South Africa and the Philippines, lemons and The vector is thus widely distributed in the limes at Pokhara were only slightly affected Philippines and the potential exists for green by the disease and were still growing and ing to spread to most of the citrus-growing bearing well. The vector is also reported to areas. Fortunately, diseased groves outside of be present in the eastern terai (belt of marshy the severely affected Batangas areas appear to jungle between the foothills and the plains) be relatively few and are isolated. from where leaf symptoms have been noted. There is evidence that greening-infected ma terial has been introduced into Nepal from Surveys in other countries Uttar Pradesh, India. Hong Kong. D. citri was found in one of the three groves visited in 1968. During Notes on the biology of D. citri another visit in 1969 fairly conclusive greening symptoms were observed in sweet orange, From the literature, it appears that there mandarins and pomelos.