THE PREFERENCES AND DISTRIBUTION OF SUGARCANE SCALE INSECT Aulacaspis tegalensis (HEMIPTERA: DIASPIDIDAE) ON DIFFERENT CLONES OF SUGARCANE

This research was conducted in the field of Gunung Madu Plantations Co., Gunung Batin, Lampung Tengah, in the period of April 2015–May 2016. The experiment was arranged in a randomized completely block design with six sugarcane clones as treatments (GMP 1, GMP 2, RGM 99.370, RGM 97.8837, GMP 3, and GMP 4) and four blocks, every block was separated by the street. The abundance of sugarcane scale insects was observed in 15-day intervals from the plant ages of 4 to 12 months. The results showed that sugarcane clone affected the abundance of sugarcane scale insects. After a lag phase of six months (fifth observation), the sugarcane scale insects started being found on all six sugarcane clones in the field. The abundance of the scale insects then increased and peaked at 10.5 months. The sugarcane scale insects attacked all six clones of sugarcane. Clone GMP 1 was the most preferred with an average scale abundance at 814.4 individuals/stem while the least preferred clone was GMP 4 with average of 179 individuals/stem.

EVALUASI LAPANG TERHADAP DAMPAK APLIKASI INSEKTISIDA ISOPROCARB PADA SERANGGA PREDATOR DAN HAMA KUTU PERISAI AULACASPIS TEGALENSIS Zhnt. (HOMOPTERA: DIASPIDIDAE) DI PERTANAMAN TEBU

Field evaluation of isoprocarb insecticide-application-effects on predacious insects and scale pest Aulacaspis tegalensis Zhnt. (Homoptera: Diaspididae) in sugarcane plantations. The sugarcane scale, Aulacaspis tegalensis Zehntner, is a new serious pest of sugarcane in Lampung Province. Over the years, most control practices against A. tegalensis rely on the use of chemical insecticide. A field study was conducted to assess the impact of isoprocarb (carbamate-insecticide) on sugarcane scale pests and their natural predators in sugarcane plantation. The results indicated that the application of isoprocarb (at recommended concentration = 1.25 mg/L) in sugarcane field failed to cause a significant reduction on scale pest populations. In contrast, the numbers of predacious insects was significantly reduced in isoprocarb-treated-field plots. The predacious insects in association with scale pests in sugarcane fields were predominantly coccinellids. Four species of primary predacious coccinellids attacking scale pests were: Chilocorus melanophthalmus, Chilocorus sp., Scymnus sp, and Telsimia sp. This field study indicated that the predacious species were more susceptible to isoprocarb than their prey.

PERKEMBANGAN POPULASI KUTU PERISAI AULACASPIS TEGALENSIS ZEHNTNER (HOMOPTERA: DIASPIDIDAE) DAN PENGARUH TINGKAT SERANGANNYA TERHADAP PENURUNAN HASIL TEBU DI PT GUNUNG MADU PLANTATIONS, LAMPUNG TENGAH

Population development of a scale insect Aulacaspis tegalensis Zehntner (Homoptera: Diaspididae) and effect of its infestation on sugarcane yield loss in PT Gunung Madu Plantations, Central Lampung. Sugarcane scale insect, Aulacaspis tegalensis, is a new major pest of sugarcane in PT Gunung Madu Plantations (GMP). A survey was conducted at the experimental station of the Research and Development Division of PT GMP to investigate the population growth of the pest and effects of their infestation on sugarcane production. The first study indicated that the population of the pest started to grow when the host plants were at the age of 8 months and reached a peak (300 individuals/stem) on mature sugarcane plants (11 month old). A low population of the pest at younger sugarcane plants might be due to the fact that during their first seven months of growth, sugarcane plants had no stem or even if they had, the leaf sheaths were still closedly intact to the stem, while the scale insects could live and survive optimally at the internodes under the leaf sheaths. The second study showed that the first pest outbreak occurred in 2000 which covered 162.27 ha of sugarcane fields. In the year of 2001, the infested area increased significantly (up to 1157.93 ha). In addition, the effect of the scale insect infestation caused an enormous yield loss. The losses could be expressed as the reductions in: stem weight, pol (polarisation, sucrose content), brix (total soluble solids), and sugar contents.

Studies on the biology and taxonomy of some Chilocorus spp. (Coleoptera: Coccinellidae) preying on Aulacaspis spp. (Hemiptera: Diaspididae) in East Africa, with the description of a new species

Field studies of predators on Aulacaspis tegalensis (Zhnt.) and laboratory breeding experiments, supplemented by taxonomic studies, showed that Chilocorus discoideus Crotch and C. bilineata Korsch. are junior synonyms of C. schioedtei Muls. and that two other forms, originally described as ‘aberrations’, may also belong to this species. Similarly, C. erythrocephalus Muls. and C. solitus Weise are junior synonyms of C. distigma (Klug). C. rufoplagiatus sp. n., allied to C. distigma, is described from the shores of Lake Victoria, and the Oriental species C. nigritus (F.) is recorded from the African mainland for the first time. C. distigma is found in the savanna and steppe areas of Africa and C. schioedtei in the forest and adjoining zones. Comparative studies suggest that, although C. schioedtei has a higher fecundity, it is not displaced by C. distigma as, unlike the latter, it is unable to breed under hot dry conditions. Comparison of host records for these two species show that C. distigma is not restricted to feeding on Diaspididae, as is C. schioedtei, but that otherwise the range of hosts and associated plants is similar for both species. The potential of these species and C. nigritus for use in biological control is discussed and it is suggested that C. schioedtei is only suitable for trial in tropical areas without a dry season, but that C. distigma and C. nigritus may be useful under a wider range of conditions.

Dispersal of the sugar-cane scale Aulacaspis tegalensis (Zhnt.) (Hem., Diaspididae) by air currents

By means of sticky traps and a suction trap, it was demonstrated on a plot of sugar-cane at Kawanda Research Station, Uganda, that large numbers of crawlers of Aulacaspis tegalensis (Zhnt.) become airborne (up to 10/m3). The numbers increase with wind speed up to about 2·0 m/s and then remain constant, but are depressed by increasing humidity. In laboratory experiments, crawler survival was reduced by high temperatures (30°C) and low humidities (30% r.h.), but some individuals should survive the extreme conditions sometimes experienced if airborne from morning until evening. On hatching, crawlers move upwards and towards the light, but downwards in the dark; movement is inhibited by high humidity. These behaviour responses indicate hat the presence of crawlers in the air is not accidental but a dispersal mechanism. At Arusha Chini, an isolated sugar estate in Tanzania, sticky-trap catches downwind of a windbreak confirmed that airborne dispersal of crawlers is a major source of infestation. It is shown that air currents could have carried crawlers to Arusha Chini from a source on the Kenya coast, 260 km to the east.

The biology of Physcus seminotus Silv. and P. subflavus Annecke & Insley (Aphelinidae), parasites of the sugar-cane scale insect Aulacaspis tegalensis (Zhnt.) (Diaspididae)

Physcus seminotus Silv. (properly P. sp. nr. seminotus Silv.) and P. subflavus Annecke & Insley (Aphelinidae) are parasites of the sugar-cane scale insect Aulacaspis tegalensis (Zhnt.) (Diaspididae) in East Africa and they have been purposely introduced into Mauritius where A. tegalensis is an important pest. P. seminotus has brachypterous, flightless females and P. subflavus winged females but their biology is essentially similar. The parasites are arrhenotokous and fertilised and unfertilised eggs are deposited in different sites concomitant with development of female and male larvae on different primary hosts. Female larvae develop endoparasitically in A. tegalensis from fertilised eggs deposited in the host's body cavity. Male larvae develop ectoparasitically on immature Hymenoptera in A. tegalensis from unfertilised eggs deposited in the air-filled cavity of the latter's integumentary remnant. The males of the two Physcus spp. are therefore hyperparasitic and they frequently develop on the immature stages, both male and female, of their own kind (autoparasitism). Unfertilised eggs are laid by virgin females and also by mated females, the latter being able to deposit fertilised and unfertilised eggs at will, depending on the egg site encountered. Sexual dimorphism occurs at all stages, including the deposited egg. The preovipositional adult is the preferred stage of A. tegalensis for deposition of fertilised eggs and development of females is most rapid in such hosts. Development in young hosts is arrested until the hosts have grown to virtually their full size. The host of a male is apparently a matter of chance in so far as evelopment will occur on larval and pupal Hymenoptera of various species found in the empty, inflated, brittle integument of parasitised A. tegalensis. Only one individual, whether male or female, develops per host. Oviposition behaviour of mated females is such that superparasitism is largely avoided but it is liable to occur frequently when virgin females oviposit. Adult females will feed on the body fluids of A. tegalensis that are released by insertion of the ovipositor and also on sugary fluids. They live a month or more, ovipositing continually at a gradually decreasing rate, and laying usually 50–100 eggs.

Studies on the biology, ecology and economic importance of the sugar-cane scale insect, Aulacaspis tegalensis (Zhnt.) (Diaspididae), in Mauritius

Aulacaspis tegalensis (Zhnt.) (Diaspididae) infests the stems, and to a lesser extent the leaves, of sugar-cane. It is indigenous to Malaya and the islands of S.E. Asia, and has been introduced to the Mascarene Islands and East Africa. Its biology and economic importance were studied in Mauritius. Development and construction of the scale in both sexes are described. The life cycle takes 3–9 weeks, the female laying 700–800 eggs over 10 weeks in summer and 14 in winter. Feeding in the stem is in the parenchyma; the path of the stylet is intracellular and vascular bundles are avoided. Stem surfaces are essential for population increase. The leaf sheaths which invest stems tightly or loosely according to their age, have a decisive role among factors that influence intensity and pattern of stem infestation. Field infestations may be severe in dry coastal areas. Populations increase in March-May, and decline in July-November. The determining factors are seasonal weather, crop growth, harvesting and natural enemies. Dispersal, by the eggs and crawlers, is passive. Adelencyrtus miyarai Tachikawa (Encyrtidae) is constantly associated with Aulacaspis tegalensis and is heavily hyperparasitised by Tetrastichus sp. (Eulophidae). The most frequent predators are Lindorus lophanthae (Blaisd.) (Coccinellidae), Cybocephalus mollis Endrödy-Younga (Nitidulidae) and mites. Predators are important only in the regulation of large A. tegalensis populations. Reductions in the sucrose content of the cane juice are directly proportional to the numbers of scales present on each interaode; growth of canes is not obviously affected, but grown canes may die before harvest. Reduced germination and growth may result from use of infested propagative material. Practicable control measures comprise use of clean or hot-water-treated propagative material, field hygiene and block harvesting, removal of dry leaves to expose the stems, and varying the date of harvest.