Entomology

SUGARCANE WHITEFLY, ALEUROLOBUS BARODENSIS MASKELL, AND ITS PARASITES IN THAILAND

K. Charernsom and W. Suasa-ard

National Biological Control Research Centre (NBCRC), Barigkok, Thailand

Key words: Sugarcane whitefly, Aleurolobus barodensis Maskell; nymphal

parasites

ABSTRACT

The study on the sugarcane whitefly, Aleurolobus barodensisMaskeII (Homoptera: Aley- rodidae) was conducted at the NBCRC Field laboratory at Kampaengsaen, Nakhon Pathom, and supplemented with investigations under field conditions at Suphanburi, Thailand. The investigations included various aspects on biology, ecology and popula- tion dynamics of the sugarcane whitefly and its associated parasites. This investigation revealed that Encarsia ochaiviggiani and Azotus bimaculatus were the most important nymphal parasites of sugarcane whitefly in Thailand.

INTRODUCTION

The sugarcane whitefly, Aleurolobus barodensis Maskell (Homoptera: Aleyrodidae) is one of the key pests of sugarcane, Saccharum officinarum, in many countries such as India, Indonesia, Philippines, Thailand, Fiji and Ceylon. A barodensis (Siddique and Senena7) causes economic damagq in many sugarcane growing areas in Thailand. Out- breaks usually occur in August to December, causing losses of quality and quantity of sugar, and in heavy infestations, death of the plant. The purpose of this study was to inv~stigate the biological attributes, including the con- struction and analysis of the life taljle of A barodensis; to study the population dynam- ics of A barodensis and its associated parasites; and to assess the important parasites which act as biological control agents of A barodensis in Thailand.

1 MATERIALS AND METHODS

Stock culture of sugarcane whitefly

Nymphs and resting nymphs of A barodensis on sugarcane leaves were collected from the field and kept in fine screen insect rearing cages, measuring 60 x 60 x 90 cm. The young shoots of sugarcane planted in clay pots were provided for oviposition of emerged adults. Plants with newly laid eggs were removed to a new cage measuring 60 x 60 x 90 cm, and new plants were substituted. Shoots of sugarcane with second instar nymphs were removed to a green house, adequate moisture being provided. The nymphs were reared up to the resting nymph stage and then transferred to an oviposition cage. Sugar- cane was planted every week in clay pots to provide food for the nymphs. In this way it was possible to maintain a stock culture of A barodensis for various studies such as biological attributes, life table study and other laboratory investigations.

Biological study of A barodensis

Newly laid eggs of A barodensis on the leaves of sugarcane shoots from stock culture were marked'and moved to a new cage, and daily observations were made. Newly hatched nymphs were transferred to new leaves of shoots of sugarcane planted in clay pots. The nymphs were reared singly on sugarcane leaves. The base of each sugarcane

K. CHARERNSOM AND W. SUASA-ARD

leaf was surrounded by moist cotton wool to prevent the first nymph moving to another leaf. The nymphs were reared on the same leaf until resting stage. The life history data

1 of A barodensis was recorded throughout the developmental period. A pair of emerged adults of A barodensis were kept in the oviposition cage with young

1 shoots of sugarcane. The number of eggs laid, the number of eggs per batch, the ovipo- sition site, and the adult life span and other biological data were recorded.

I Life table study of A barodensis

The life table study of A barodensiswas carried out using 160 newly laid eggs on leaves of sugarcane shoots from stock culture. Young shoots of sugarcane planted in clay plots with eggs were kept in an insect rearing cage, measuring 60 x 60 x 90 cm, with ade- quate moisture. The newly hatched nymphs were transferred to another leaf of a healthy plant for development until the adults emerged. The adults were reared in oviposition cages and young shoots of sugarcane planted in clay pots were provided for oviposi- tion. The young shoots of sugarcane were changed daily. Data on the number of adults surviving and eggs laid were recorded daily until emerged adults died. These recorded data were used for the construction and analysis of the biological life table using tech- niques given by Birch', Harcourt2, Laughlin3, Morris and Miller5 and Nspompeth6.

I I Survey and evaluation of parasites

Field survey and evaluation of parasites of A baredensis were done by collecting and examining all stages of sugarcane whitefly. The nymphs and pupae were brought to the laboratory for further examination. Daily observation was done for the emergence of parasites. The adult parasites thus obtained were kept for further identification, the more important parasites were reared and used for further biological study and evalua-

I I tion of their effectiveness.

I Ill Population study of A barodensis

The population study was carried out at Ampher Samchuk, Suphanburi. The sugarcane was planted in rows with 25 x 100 cm spacing. The area used for the study was about one hectare. The fourth leaf from the top of stalks was selected as the sampling unit, and 100 samples were taken at two-weekly intervals from the time of the emergence of sugarcane and during the following two years. The number of nymphs and adults of sugarcane whitefly per leaf and the number of parasi- tized nymphs were recorded and evaluated. The data thus collected were used for the analysis of various population parameters and the assessment of natural enemies. The data from these field experiments was analyzed according to the techniques of Morris4, Napompeth6, and Southwoods.

RESULTS

I I Biological studies of Aleurolobus barodensis

I A barodensis is a small insect, the average size of female adults being 2.1 + 0.13 mm, and of male adults 1.65 + 0.07 mm in length from the head to abdomen. Wings are white, the head, abdomen and legs are pale brown and the eyes are red. The female adult lays eggs in single rows on both sides of leaf blades, but mostly on the upper side. The average number of eggs per row was observed to be 15.15 ?Z 3.61, ranging from 12-20. The average number of eggs laid per female ranged from 40-150. Individu-

4 al eggs were triangle shaped with a stalk at one end, and light yellow when newly laid, changing to dark before hatching. The average dimensions of eggs were 0.12 +

i

f NTOMOLOGY

9.01 mm in width and 0.19 + 0.01 mm in length. , The newly hatched nymphs were pale yellow in colour, with red eyes, and the average dimensions of newly hatched nymphs were 9.15 k 0.01 mm in width and 0.29 t 0.01 mm in Iqngtli, F~rst instar nymphs were pale yellow In colour. Nymphs molted four times before reaching the resting stage. The second to fourth instar nymphs were dark in colour but different in size and the amount of wax on the body. The average dimensions of the first lnstar nymphs were 0.15 -t. 0.01 mm in width and 0.29 + 0.01 mm in length. The second instar nymphs measured 0.26 -1: 0.01 mm in width and 0.52 + 0.04 mm in length. Third instar nymphs measured 0.47 t 0.06 mm in width and 0.98 k $0.12 m p in )qngfh,,qnd f&rth instqrs 0.83 k 0.15 mm in width and 0.85 + 0.28 mm in length. The r??t,ing stage ny,mph!rn&aiured 0.88 + 0.15 mm in width and 1.9 + 0.33 mm in

7, 5.77 + 113 and 5.39 k 1.36 The tlme f r ~ m the f~rst to the lust ilnstar averaged 17.11 %+ 1.46 dqys, The rest~ng nymph stpge lasted 14.08 + 1 16, days. A$ults_lived foy 2,85 d 0,67 days. The total life cycle of ,$ barodensr,~ was 41,65 t (2.39 days 2 l J 3 1 , I

Stage of 11131 L ' developmeht ' 1 ' l f l

I Adult: 2.85k0.67 1 2 - 4 1

calculated from the table were the net reproductive rate of increase (R,) = 22.8649, the capacity for increase (r,) = 0.1116, the finite rate of increase (A) = 1.2930 and the short generation time (T,) = 28.0398 days. They indicate that a population of A barodensiscould multiply 22.8649 times in each generation, or it could multiply 1.2930 times every three days.

K. CHARERNSOM AND W. SUASA-ARD

Table 2 - Bielogical life table, age-specific fecundity t reproductive rate (R,) of Aleurolobus bsrsde er laboratory co 3 -~r 2.2OC and 76-4 2 7.3% RH). = i j ,

i \

i/ lX = The probability of an individual being alive at the beginning of the age- , - > , interval

I n 1 l i # 7' mx =Thea"umbkr of female eggs or\offspri I

I t I Survey and evaluation of parasites I

bield surveys for parasites of A barodensis revka~ed three species of hymend$tera, En: 'carsia ochai;Azofc)s b,~c~culatus and Anagyrus 8accharicola. They are all nym'phal para, 'sites. It was evident that E ocha, played the moit dominant role in the natu'ral confro] 'of A barodensis. About 83.6 percent o f parasitized hymphs of A barodensrs w&r"e'baras~- itized by E ochai. I

i I

Population study I

h he populationsof,A bqrodensis in 1986 and 1987,, In plant cane and ratoon at Suphan- buri'are shown in Fig 1. It wa;apparent that the populatyon of'^ bahdensiswas higher In 1987 thdn In 1986, and a little h~gher in ratoon than In plant cane. The population was low during the young shoot stage of sugarcane and high during the final six mont,hs of sugarcane growth in both years. It was evident that,whitefly preferr,ed tosattack the leaves of mature sugarcane. Assessment and evaluation of E ocha~ as an ~mportant biological control agent was car- ried out at Suphanbur~ in 1987, by uslng the numbers of parasitized nymphs as the criter~on for evaluation. The relat~onship between the total numbers of nymphs of A barodensis and those of nymphs parasitized by E ochai is shown In Fig 2. It was apparent that parasitl- zation increased as the total number of nymphs increased. The percent parasitization by E ochai throughout the year was about 22.2. ,

AJO+D.IO~DI Japun .Alp!do~ Ald!+lnw pino3 s!suapojoq v jo uo!+olndod ay+ +oy+ paloaAaJ alqa+ aj!l 1o3!6010!q ay+ jo Apn+s a y l .u~+s!yod puo o!pul u! auo~o6ns jo s+sad +ua+~od -w! oslo am h l j a + ! y ~ puo sJaJoq y+ow ,ouauaS pua anbipp!~ o+ 6u!p~omv .puol!oyl u! auo~~o6ns jo s+sad +uo+~odw! ay+ 40 auo s! 's!suapojoq snqolojnalv 'Al ja+!y~ auo3~a6ns

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'puol!or(l '!Jnquoqdns 4 0 4/9861 6u!~np auo9 uoo+w puo DUO, (uold uo s!suapo~oq SnqoloJnalv )o A+!suap uo!+olndod -1 a~n6!9

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K. CHARERNSOM AND W. SUASA-ARD

conditions, the mortality of A barodensis was high in the early stages of development but its fecundity was also high. The mortality could be quite different under field condi- tions because of the existence of various regulatory factors in the sugarcane agroecosystem. The analysis of the population of A barodensis showed that it was high during the last six months of growth of the crop, indicating that the pest prefers to attack mature cane. The assessment and evaluation of parasites revealed that E ochai plays an important role in regulating the population of sugarcane whitefly.

CONCLUSIONS

Aleurolobus barodensis is an important pest of sugarcane in Thailand. It lays its eggs on the leaf blade of sugarcane, after hatching nymphs have fed on the leaves. The nym- phal period was found to be 17.11 + 1.46 days, and the total life cycle from egg to adult was 41.65 + 2.39 days. The analysis of biological life tables of A barodensis revealed that the net reproductive rate of increase (R,) was 22.8649, the capacity for increase (r,) 0.1116; the short generation time (T,) 28.0398 days; and the finite rate of increase (A) 1.2930. From field surveys and the evaluation of parasites of A barodensis, three species of hymenoptera were found. Among these Encarsia ochai played the most important role in the natural control of sugarcane whitefly. The percent parasitization by E ochai was 22.2 for the entire year. The results obtained from this investigation could be very useful in augmenting biologi- cal control of sugarcane whitefly.

REFERENCES

1. Birch, LC (1948). The intrinsic rate of natural increase of an insect population. J Anim Ecol 17: 15-26.

2. Harcourt, DG (1969). The development and use of life tables in the study of natural insect populations. Ann Rev Entornol 14: 175-196.

3. Laughlin, R (1965). Capacity for increase: a useful population statistic. J Anim Ecol 34: 77-91.

4. Morris, RF (1960). Sampling insect populations. Ann Rev Entomol 5: 243-264. 5. Morris, RF and Miller, CA (1954). The development of life tables for the spruce bud-

worm. Can J Zoo! 32: 283-301. 6. Napompeth, B (1973). Ecology and population dynamics of the corn planthopper,

Peregrinus rnaidis (Ashmead) (Homoptera: Delphacidae), in Hawaii. PhD Disserta- tion, Univ Hawaii.

7. Siddique, ZA and Senena, AP (1960). Studies on the control of sugarcane whitefly and the effect of its infestation on juice. Ind J Entornol 22(1): 99-103.

8. Southwood, TRE (1969). Population studies of insects attacking sugarcane, pp 427-459. In JR Williams, JR Metcalfe, RW Mungomery and R Mathes (eds), Pests of Sugarcane. Elsevier, Amsterdam.

ENTOMOLOGY 41 L'ALEURQDE DE LA CANNE A SUCRE, ALEUROLOBUS

BARBDENSIS MASKELL ET SES PARASITES EN THAlLANDE

K. Charernsom y W. S. Ard

National Biological Control Research Centre (NBCRC), Bangkok, Thailand I Pdlabras claves: mosca blanca de la caAa de azbcar, Aleurolobus

barodensis Maskel I, par6sitos ninfales.

Mots-cles: L'aleurode de la canne a sucre, Aleurolobus barodensis Maskell, parasites du state nymphal.

Des etudes sur I'aleurode de la canne a sucre, Aleurolobus barodensis Maskell (Homop- tere: Alleyrodidas) furent menees ou Field Laboratoty du CNRCB 6 Kampaengsaen, Nak- han Patham, et cornpli?ti.es par des etudds ?;i champ b Suphanburi, Thailande. Ces etudes portaient sur les divers aspects biologiques, ecologiques ainsi que sur la dyna- mique des populations de I'aleurode et de ses parasites. Les resultats revdent que En- carsla achai Viggiani et Azotus birnaculatus sont les parasites les plus importants du I

stade nymphal de I'aleurode (de la canne a sucre) en Tah~lande.

LA MOSCA BLANCA DE LA C A ~ A DE AZUCAR, ALEUROLOBUS BARBDENSIS MASKELL Y SUS PARASITOS EN TAlLANDlA

K. Charernsom y W. S. Ard

National Biological Control Research Centre (NBCRC), Bangkok, Thailand

Palabras claves: mosca blanca de la caAa de azbcar, Aleurolobus

barodensis Maskel I, par6sitos ninfales.

RESUMEN I El estudio de la mosca blanca de la curia de azircar, Aleurolobus barodensis Maskell (Homoptera: Aleyrodidae) fue conducido en el campo experimental de Kampaengsaen, Nakhon Pathom, y complementado con investigaciones bajo condiciones de campo en Suphanburi, Tailandia. La investigaci6n incluy6 varios aspectos de la biologia ecologia y dinamica poblacional de la mosca blanca de la curia de aztjcar y sus parasitos aso- ciados. Esta investigacibn pone de manifiesto que Encarsia ochaiviggiani y Azotus bi- rnaculatusfueron 10s mas importantes parasitos simples de la mosca blanca de la catia