Interaction of Rotylenchulus reniformis and Meloidogyne javanica with mealybug wilt of pineapple, in microplots

Abstract

Mealybug wilt of pineapple (MWP) is a disease complex whose etiology seems to involve the mealybug Dysmicoccus brevipes and pineapple mealybug wilt-associated virus-1, −2 and/or −3. MWP, the reniform and the root-knot nematodes (RN, RKN) are major problems of pineapple crop worldwide. Although these nematodes are often found in MWP-affected plantations, so far, no study has investigated possible interactions among these pests causing symptoms and affecting the development of pineapple plants. Pineapple plantlets free of diseases and pests (Vitoria cultivar) were inoculated with i) RN; ii) RKN; iii) viruliferous mealybugs; iv) RN and viruliferous mealybugs; and v) RKN and viruliferous mealybugs. Uninoculated plants served as controls. After inoculation, the plants were transplanted into microplots, where shoot symptoms and growth were assessed at 9 and 16 months after inoculation. RN, RKN and MWP induced distinct shoot symptoms, which appeared much worse in co-inoculated plants, including the collapse and death of nearly half of the experimental plants at 16 months. RKN, RN and MWP, alone or in combination, reduced the fresh weight of the root system up to 88 % and shoot weight up to 68 %. The interaction among these pests was additive. The results of this experiment emphasize the need for further studies conducted in commercial plantations to understand the interactions among RKN, RN and MWP, and their relative importance, since these are often misdiagnosed and consequently poorly managed.