Pest Status of the Coconut Bug Pseudotheraptus wayi Brow n (Hemiptera: Coreidae) on Avocados in South Africa * a • • O O O O O O O O O O O T. VAN DER MEULE N O a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a Institute for Tropical Pest Status of the Coconut La situation du ravageur La situación de and Subtropical Crops Bug Pseudotheraptus wayi Pseudotheraptus wayi Pseudotheraptus way i Private Bag X11208 Brown (Hemiptera : Brown (Hemiptera : Brown : Nelspruit 1200 (Hemiptera South Afric a Coreidae) on Avocados Coreidae), la punaise Coreidae), el chinche in South Africa . du cocotier, sur les avocats del cocotero, sobre la A .S . SCHOEMAN en Afrique du Sud . producción del aguacate Department of Entomology en Africa del Sur . University of Pretori a Pretoria 0002 ABSTRACT RÉSUM É RESUMEN South Afric a Avocado (cv . Fuerte) crop loss La baisse de production de La caída de la producció n caused by the coconut bu g lavocat provoquée par en el aguacate provocada (Pseudotheraptus wayi) wa s Pseudotheraptus wayi, un por Pseudotheraptus wayi, studied over a 2-year period in ravageur du cocotier, a fait la chinche del cocotero, fu e 3 areas . Three orchards (1 0 lobjet dune étude pendant objeto de un estudio durant e Part of a M .Sc . thesi s trees / orchard) were monitored deux ans dans trois régions dos años en tres regione s by the senior author to b e weekly to assess fruit drop and dAfrique du Sud. Trois vergers , de Africa del Sur . submitted to the University harvest loss . None of these avec un échantillon de Tres huertos con una muestra of Pretoria, Pretoria 000 2 orchards had been spraye d 10 arbres par verger, ont ét é de 10 árboles cada uno, fueron South Africa with insecticides. Damage surveillés une fois par semain e observados una vez por ranged from 1 .7% on aborte d pour permettre lévaluation semana, lo cual permitió fruit to 76 .2% on ripe fruit, wit h de la chute des fruits et de la evaluar la caída de fruto s means of 6 .6% damage on perte de récolte . Ces vergers y la pérdida de la cosecha . aborted fruit and 15 .9% on nont subi aucun traitement Estos huertos no tuviero n harvested fruit . insecticide . Les dégâts varient ningún tratamiento insecticida . de 1,7 % sur les fruits avortés Los daños variaron de 1,7 % à 76,2 % sur les fruits mûrs , en los frutos abortados a 76,2 % les moyennes atteignant 6,6 % en los frutos maduros . pour les fruits avortés et 15,9 % Los promedios fueron 6,6 % pour les fruits récoltés . para los frutos abortados y 15,9 % para los frutos cosechados . Fruits, vol . 49, n°1, p .71-75 asaaaaaaaaaaasa asaaaaaaaaaaaaa aaaaaaasaaaasa a KEYWORDS MOTS CLÉ S PALABRAS CLAVE Persea americana, Persea americana, avocat, Persea americana , avocados, South Africa, Afrique du Sud, ravageurs aguacate, Sudafrica , pests of plants, damage , des plantes, dégât, plagas de plantas, daños , experiments . expérimentation . experimentos . Fruits, vol . 49, n°1 a 71 from the fruit with their piercing-suckin g . introductio n mouth parts (VAN DER MEULEN, 1992) . To our knowledge, there are no other The coconut bug, Pseudotheraptus wayi reports of P . wayi-incluced damage to Brown (Hemiptera : Coreidae), a coconu t avocado in other parts of the world, but pest in East Africa (MARIAU, 1969), was according to WAITE (1990) a biologically first reported in 1977 in South Africa o n and visually similar species, Amblypelta mangoes and guavas (DE VILLIERS and spp., causes quite severe fruit drop i n WOLMARANS, 1980) . It is now known t o Australia. attack macadamia (DE VILLIERS, 1986) , avocado (DE VILLIERS and VAN DEN BERG , Producers often confuse damage cause d 1984) and mango (VAN DER MEULEN, 1990) . by the coconut bug (Photo 1) with hai l VAN DER MEULEN (1992) reporte d damage, and sometimes even with frui t observing up to 52 .4% damage in an fly damage . However, hail damage is untreated guava orchard . normally only superficial, whereas th e coconut bug produces a hard interna l According to LEVER (1969), the biology of knob just underneath the surface . This the coconut bug (Figure 1) on coconut s knob can be up to 10 mm in diamete r is as follows: on average the female lays when damage is inflicted at a youn g 74 eggs during its life cycle . First-insta r nymphs have not been observed feedin g stage and normally comes off when th e peel is removed . The fruit can also be on coconut palms, but they can caus e severe tissue damage once they are about malformed (Photo 2) when infestation by half-grown . Adults of both sexes fl y adult coconut bugs occurs at an earl y readily when disturbed . Each individual is stage of fruit development, but interna l fruit rot is seldom observed responsible for approximately 200 punc- . Coconut bu g tures during the course of its life . The damage may be distinguished from tha t insect always lives in the crown of th e caused by fruit flies, which form star-lik e palm and nymphs are only found on o r lesions (Photo 2) on the outside of the near the spadix . They are rarely observed peel. In South Africa, there are n o during the day to avoid direct sunshin e available insecticides to control coconut and heavy rain . They feed in the lat e bugs on avocados (VERMEULEN et al., afternoon and early morning, and ar e 1992) . most active on cloudy but not heavil y The aim of the present study wa s overcast days. Population densities vary twofold : to determine whether th e markedly between trees, but are alway s coconut bug causes fruit drop, and to low, with a per-tree average of onl y assess the economic impact of the about one specimen . coconut bug as an avocado pest in Damage to avocado is caused by bot h Eastern Transvaal (South Africa) . adults and nymphs as they extract sa p . material s and methods Three avocado (cv . Fuerte) orchards in three different areas, were assessed in th e study. The sites were: Westfalia (23 .05 S , 30 .07 E), Burgershall (25 .05 S, 31 .05 E) and Excelsior (25 .02 S, 31 .18 E). The trees were between 10 and 15 years old. Ten trees were chosen at random at each sit e and monitored during the study . Figure 1 Firstly, adult coconut bugs were put i n The adult coconut bug gauze cages along with bunches of Pseudotheraptus wayi. young avocado fruit (10-20 mm in length) 72 • Fruits, vol . 49, n° 1 • e e to determine whether they could induc e fruit drop, and to observe how th e lesions develop into damage marks . Two coconut bugs were placed in each cag e with ± 5 fruits, with 5 replicates hung only in the orchard at Excelsior . After feeding, the bugs were removed and th e lesions assessed . Secondly, a trial was conducted to determine what percentage of aborted fruit dropped as a result of coconut bu g damage per se, and what percentage of damage to non-aborted fruit was inflicte d by the coconut bug . This trial was conducted over a 2-year period (1989- 1991). To facilitate collection of aborted fruit, and to standardize sample sizes , pieces of shadow cloth (2 m x 1 m) were stretched between wooden poles 1 m avocados damaged by coconut hugs ar e Photo 1 above ground under the trees, and all given in Table 1 . Percentages of damag e Typical coconut bug damage , fruit that dropped on these traps durin g due to coconut bug are given as a mean often referred to as pencil the first 2 months after fruit set were per orchard per season . damage . collected on a weekly basis. The fruit were then assessed for coconut bu g On harvested fruit, the mean damage du e damage, except for fruit which droppe d to coconut bugs ranged from 1 .7% a t directly after fruit set when they were to o Burgershall in the 1989/90 season to small (5 mm diameter and smaller) . A 76.2% at Excelsior in the same season . sample of 50 ripe fruits per tree were Losses of up to 98% on individual tree s harvested at random at the end of each were recorded on the latter farm . On season . These fruit were examined t o aborted fruit, damage ranged from 3 .8% determine the effects of coconut bug to 9.4% over the 2-year period . With the infestation . exception of Excelsior, the mean damag e for all orchards was 5 .3%, which is close to the generally accepted threshol d Photo 2 Malformed fruit (far right) level of 5% (EDWARDS and HEATH, 1964) . due to coconut bug damage. •••• results However, the damage levels obtained a t The two fruits on the left were Excelsior are not uncommon and, and discussion punctured by fruit flies . Most of the coconut bugs placed in gauze cages began attacking the young avocad o fruit almost immediately . Within a fe w hours, watermark lesions, visible as slightly darker patches than the rest of the peel, appeared on the surface of the fruit. Within 2 days, these marks had become indented dark patches of about 10 mm diameter. Within 7 days, 80% of these fruits had dropped and all wer e aborted after 14 days .