Fig 1.
Blueberry leaves infected with Monilinia vaccinii-corymbosi (Mvc) exhibit fungal conidia in a sugary matrix on the surface of blighted tissue, called mummy berry shoot ‘strikes’ (A and B). Honey bee foraging on a blueberry flower (C).
Table 1.
Concentrations of volatile compounds quantified from Vaccinium corymbosum flowers, healthy leaves, and leaves infected with Monilinia vaccinii-corymbosi (Mvc).
Fig 2.
Number of contacts (approaches that led to contacting each respective tissue) and approaches by Diptera (flies), Hymenoptera (bees) and other insects to blueberry flowers, healthy leaves, and leaves infected with Monilinia vaccinii-corymbosi (Mvc) in three Michigan blueberry plantings in 2008 (a) and 2009 (b) as observed in video-recordings. The difference between flower vs. Mvc-infected leaf contacts for Hymenoptera (Bees) vs. Diptera (Flies) was significant in both years (2008: Pearson χ2 = 60.5, P < 0.001; 2009: Pearson χ2 = 392.7, P < 0.001).
Fig 3.
Summary of nested PCR detection of Monilinia vaccinii-corymbosi (Mvc) on insect bodies collected during 2009 (May 18th–June 4th) in three Michigan blueberry plantings.
Data are summarized by insect orders sampled (a) and family for Hymenoptera and Diptera (b). The number of insects sampled for PCR detection totaled 159. A higher percentage of Hymenoptera tested positive for Mvc compared to Diptera (56% vs. 31%, respectively; Pearson χ2 = 5.7, P = 0.017).
Fig 4.
Host floral scent mimicry by Monilinia vaccinii-corymbosi (Mvc) shoot strikes.
Non-metric multidimensional scaling (NMDS) plot of volatile profiles from Vaccinium corymbosum flowers (red points), uninfected leaves (black), and leaves infected with Mvc (green). Total area occupied by each sample type as represented in 2-dimensional space is shaded in gray. Stress = 0.134. VOC profiles differed significantly among the three tissues sampled (pMANOVA F2,28 = 8.1, P = 0.009), with healthy leaves differing from flowers (F1,19 = 9.8, P = 0.009) and infected leaves (F1,18 = 9.3, P = 0.010), while flowers vs. infected leaves were marginally, but not significantly different (F1,18 = 3.0, P = 0.083).
Fig 5.
Attraction of Diptera (a) and Hymenoptera (b) to individual volatiles and synthetic blends of compounds from blueberry flowers and Monilinia vaccinii-corymbosi (Mvc) shoot strikes. Data are from five blueberry plantings in each of three states (Massachusetts, Michigan and New Jersey; n = 15 plantings total). Diptera did not respond to the volatile treatments (F7,112 = 0.4, P = 0.9), however, the abundance of Hymenoptera was affected by the treatments (F7,112 = 4.2, P < 0.001). Different letters correspond to treatments that are significantly different via Tukey’s post-hoc contrasts (α = 0.05). Means ± SE shown.