A Review of the Association of Ants with Mealybug Wilt Disease of Pineapple

The literature concerning the association between ants and the mealybugs causing pineapple wilt disease is surveyed. A great deal of data on this subject has been published in the relatively obscure technical papers and reports of the defunct Pineapple Research Institute of Hawaii. This review article is an attempt to bring this information to a broader audience and examine it in the context of related research reported in mainstream publications to create a meaningful synthesis. Two species of mealybugs, Dysmicoccus brevipes (Cockerell) and D. neobrevipes Beardsley, are associated with wilt disease of pineapple under field conditions. A third species, Pseudococcus longispinus (Targioni-Tozzetti) induces wilt symptoms in laboratory experiments, but not under field conditions. The symptoms of wilt disease and the geographic distribution of the pineapple mealybug complex are described. The history of the discovery of the disease, the disease etiology, the association of mealybugs with wilt, and the mutualism between ants and mealybugs on pineapple are discussed in detail. At least 28 different species of ants tend mealybugs on pineapples. Pheidole and Solenopsis are the ant genera most commonly associated with pineapple mealybugs throughout the world. The ants and natural enemies associated with mealybugs on pineapple are reviewed as part of a discussion of the role of ants in promoting mealybug infestations. Finally, management techniques for wilt, including ant and mealybug control, are reviewed. Introduction Mealybug wilt disease (also called pineapple wilt or quick wilt) is the leading cause of economic loss in pineapple. Unless the disease is managed, it is not possible to grow pineapple commercially in Hawaii and most other parts of the world (Carter 1934, 1940; Hughes and Samita 1998; Illingworth 1931; Petty and Tustin 1993; Rohrbach and Apt 1986; Rohrbach et al. 1988; Singh and Sastry 1974). The disease is apparently caused by a closterovirus spread through mealybug feeding (Sether and Hu 2002a,b). Three species of mealybugs are associated with mealybug wilt disease of pineapple, though the mealybugs can live on a variety of host plants (Carter 1933a, 1967). These mealybugs have a symbiotic relationship with ants (Phillips 1934, Su 1979). This literature review is a critical look at the interdisciplinary effort to elucidate the nature of the relationship between pineapples, wilt disease, mealybugs, and ants. What Is Mealybug Wilt Disease of Pineapple? Mealybug wilt disease of pineapple is characterized by a loss of turgidity in the leaves. It was first described in Hawaii by Larson (1910). In the 1920s, entire pineapple fields were destroyed by mealybug wilt (Illingworth 1931). By 1930, mealybug wilt had put the Ha-