Natural occurrence of Diadiplosis megalamellae (Barnes) in mealybugs on roses in Kenya

Abstract

Over the last decade there has been an increasing adoption of Integrated Pest Management on rose farms in Kenya. As a consequence, there has been a rise in secondary pests on rose plants, including in particular the citrus mealybug Planococcus citri (Risso). On cut flowerrose farms in Kenya, the presence of the predatory midge Diadiplosis megalamellae (Barnes) (Diptera: Cecidomyiidae) was observed. Therefore, a survey was carried out to quantify the occurrence of D. megalamellae and the association with mealybug infestations in commercial cut flower rose crops in Kenya. Four farms in four different regions of Kenya and eight rose varieties were surveyed. The midge D. megalamellae was present on farms located in Naivasha, Nairobi and Thika, but was absent in Nanyuki region. The midge D. megalamellae was found mainly in P. citri mealybug colonies and, although in much lower numbers, in the long tailed mealybug Pseudococcus longispinus (Targioni Tozzetti) colonies. The number of mealybugs was positively correlated with the number of number of D. megalamellae larvae suggesting increased multiplication of the D. megalamellae when the pest is present in larger numbers. The number of mealybugs increased with an increase in altitude at which a rose farm was located but there were no D. megalamellae present at the high altitude farm. The reasons for differences in mealybug population between farms is discussed along with further work needed, however, as an indigenous Kenyan predator, this midge offers potential for mealybug biocontrol on rose farms in Kenya.

Compatibility between the predators Cryptolaemus montrouzieri (Coleoptera: Coccinellidae) and Chrysoperla externa (Neuroptera: Chrysopidae) in the control of Planococcus citri (Hemiptera: Pseudococcidae) associated with rose crop

“…is not yet registered as a primary pest of the crop, this species has become a constant problem in the cultivation of roses in a protected environment (Messelink, 2014;Anouk et al, 2019;Mishra et al, 2021). In Brazil, large populations of P. citri have occurred in rose crops in the states of Minas Gerais and Ceará, requiring control measures to be taken (UFLA, personal communication).…”