Development of an integrated pest management system for vine mealybug, Planococcus ficus (Signoret), in vineyards in the Western Cape Province, South Africa

[摘要] ENGLISH ABSTRACT:A survey was conducted in the Western Cape Province during the 1999/2000and 2000/2001 seasons on mealybugs occurring in vineyards. P/anococcusficus (Signoret) was the dominant mealybug in vineyards during this time.During this study P. ficus was recorded for the first time on roots ofgrapevines, which has far reaching implications for the control of thisimportant vine leafroll virus vector as control actions were focused on aboveground control. Other mealybugs presently recorded in local vineyardsincluded Pseudococcus /ongispinus (Targioni) and Ferrisia ma/vastra(McDaniel). Pseudococcus viburni (Maskell) and Ps. so/ani Ferris were foundon weeds in vineyards. Natural enemies of P. ficus recorded most frequentlywere species of Nephus predatory beetles, and the parasitaidsCoccidoxenoides peregrinus (Timberlake), Anagyrus sp. and Leptomastixdacty/opii (Howard).Developmental studies on P. ficus and C. peregrinus indicated that theintrinsic rate of increase (rm) was similar, peaking at 25°C (rm = 0.169 for P.ficus; rm = 0.149 for C. peregrinus). The net replacement rate (Ra) was higherfor P. ficus than for C. peregrinus at all five temperatures tested. The Ra forP. ficus reached a maximum at 21°C (308.87) and C. peregrinus at 25°C forC. peregrinus (69.94). The lower and upper thresholds for development of P.ficus were estimated at 16.59 and 35.61°C respectively. The lower thresholdfor development of C. peregrinus was 8.85°C. These parameters indicatedthat both insects were well adapted to temperatures in the Western CapeProvince. The lower minimum threshold temperature of C. peregrinus inrelation to that of P. ficus suggests that C. peregrinus should be more activeduring winter and early spring than P. ficus.A central systematic presence-absence sampling system was developed forP. ficus. Monitoring three different plant parts on the vine indicated that newgrowth areas on vines adjacent to the main stem could serve as an earlywarning system for pending P. ficus bunch infestations. Intervention shouldbe planned when 2 % of the stems are infested with P. ficus when using thissystem.Seasonal population studies of P. ficus and its natural enemies showed thatstem infestation by P. ficus reached peak levels during January in Robertsonand Stellenbosch and during February in the Hex River Valley. Vinemealybugs colonised new growth early in the season, followed by the leavesand eventually the bunches towards the end of the season. High steminfestations early in the season resulted in high bunch infestation levels atharvest. A density dependent relationship was evident between P. ficuspopulations and parasitoid populations, suggesting that the parasitoids playeda mayor role in the biological control of P. ficus populations. Biological controlwas however only achieved towards the end of the season when damage tothe crop had already occurred.Mass releases of C. peregrinus on P. ficus populations were done in order toaugment biological control as an alternative to chemical control. Between fiveand six releases of 20 000 C. peregrinus per release were done at monthlyintervals in three grapegrowing areas. Mass released C. peregrinuscontrolled P. ficus adequately in the Hex River Valley. Control of P. ficususing this approach was no worse than using chemical control in Robertsonand Stellenbosch. C. peregrinus is commercially available and can thereforebe used as an alternative to chemical control by producers.Degree day estimation was used to predict development of P. ficuspopulations. This information was used as an input in a P. ficus pestmanagement model. Data acquired from P. ficus and ant monitoring wereused as components to construct a decision chart. This chart can be used byproducers to optimise the control of P. ficus populations using either chemicalcontrol or mass releases of C. peregrinus.

[发布机构] Stellenbosch University