Evaluation of Emergence Traps for Monitoring Blueberry Gall Midge (Diptera: Cecidomyiidae) Adults and Within Field Distribution of Midge Infestation

Abstract

The blueberry gall midge, Dasineura oxycoccana (Johnson) (Diptera: Cecidomyiidae), is a key pest of rabbiteye blueberry, Vaccinium virgatum Aiton, in the southeastern United States, but it has not been studied extensively and little is known about its ecology and management. Studies were conducted to develop an improved method for monitoring D. oxycoccana adults and to determine the within-field distribution of infestation. Four emergence traps were evaluated in an organic rabbiteye blueberry planting for their effectiveness in capturing D. oxycoccana adults early in the season. These traps included a jar trap, wheat blossom midge trap, petri dish trap, and bucket trap. The petri dish and bucket traps captured the highest numbers of adults in 2007 and 2008, respectively. Both traps had a clear plastic panel coated with adhesive. Adult midges emerging from the soil beneath the traps were caught in the adhesive as they flew up toward the light. Emergence traps are useful for detecting the presence of adults early in the season before larval infestation is apparent in the flower buds. To determine the pattern of midge infestation, flower buds were collected weekly from January to March in 2006 from rabbiteye blueberry plants located in a plot at the southwest border of an existing blueberry planting. There were no differences found in the number of larvae collected from various distances within blueberry rows. However, when flower buds were collected from an isolated rabbiteye plot in 2007 and 2008, D. oxycoccana infestation was not uniform. In both years, the southern border row had a significantly higher number of midge larvae per bud compared with the other rows.

An equal sex ratio followed by differential sex mortality causes overestimation of females in gall midges: no evidence for sex ratio regulation

“…Although the occurrence of female-biased sex ratio has been repeatedly observed in various species of gall midges (Matuszewski 1982;McClay 1996;Dorchin and Freidberg 2004;Rajamani et al 2004;Shahu et al 2004;Smith et al 2004;Ogah et al 2010), some studies, focusing on the precise sex ratio at the time of emergence, have revealed an equal or almost equal number of male and female progenies in the populations (Baxendale and Teetes 1981;Mo and Liu 2007;Roubos and Liburd 2010). This means that the estimated sex ratio in natural populations is not directly applicable to the time of reproduction or even the time of adult emergence.…”

“…According to previous studies, the sex ratio of gall midges tends to be almost 1:1 when it is calculated just at the time of adult emergence using methods that prevent emerging individuals from dispersal (Baxendale and Teetes 1981;Smith et al 2004;Mo and Liu 2007;Roubos and Liburd 2010); however, by direct sampling from natural populations, a female-biased sex ratio is usually estimated (Havelka and Zemek 1999;Dorchin and Freidberg 2004;Rajamani et al 2004;Smith et al 2004;Dorchin et al 2007). This contradiction between various studies shows that some secondary factors are involved in sex ratio biases from the primary sex ratio (1:1) after the appearance of adult gall midges in nature.…”

Distribution and Phenology ofDasineura oxycoccana(Diptera: Cecidomyiidae) in Michigan Blueberries

“…Peaks of emergence and infestation occurred through July and August. In Florida, where blueberry gall midge is an economically important pest of rabbiteye blueberry, initial catches can occur as early as 14 January, with peak adult emergence on 21 March (Roubos and Liburd 2010a). There, the growing and harvest season are much earlier than in Michigan.…”

“…In 2010 and 2011, emergence traps similar to those tested by Roubos and Liburd (2010a) were deployed within the same four Þelds in which the yellow sticky traps were placed. In 2010, from 9 April to 23 August, 12 emergence traps were retrieved and replaced once per week at each farm, and the number of blueberry gall midge adults trapped in the petri dish was counted.…”

“…Although time consuming, bud and shoot tip dissections were found to be the most effective for conÞrming the presence of larval infestation (Sarzynski and Liburd 2003). Emergence traps were later tested to determine the early emergence of the adult ßies (Roubos and Liburd 2010a). Presence and phenology of the midge were also determined in Oregon and Washington northern highbush blueberries using shoot tip dissections and observations for damage (Yang 2005, Tanigoshi et al 2010.…”