Plum Curculio, Conotrachelus nenuphar (Herbst) in Blueberry

I. Introduction: The plum curculio (PC) was described under the apple section, but injury and monitoring are somewhat different with blueberry.

Biology: Usually thought of as apple, peach and plum pest but also on blueberry, huckleberry, grape, persimmon and cherry (Milholland & Meyer 1984). One of the most potentially damaging pests during the petal fall period. Life cycle covered in apple section. Adults become active when average daily temperatures near 10-15oC (50-60oF) for 3-4 2 or more consecutive days and high temperatures are 24oC (75oF) for 2 or more consecutive days (Milholland & Meyer 1984). Often active when early varieties beginning to bloom (Marucci 1966). Female oviposits in fruit, leaving crescent-shaped scar. Larvae develop in fruit, over about a 2-week period. Infested berries turn blue prematurely, often dropping to ground before uninfested berries turn blue. A few late-maturing larvae may reach market (Marucci 1966). Most of the adults produced enter diapause, but a few mate and produce a second generation (Mampe & Neunzig 1967). Reissig et al. (1998) reported that injury progressed faster and ended earlier in smaller apple trees than larger trees, probably because of differences in tree architecture; this may relate also to a relatively small host plant as blueberry.

A note on plum curculio strains. There are two strains of plum curculio. The northern strain has an obligatory chilling requirement. Therefore there is a single generation per season. The southern strain lacks this chilling requirement and can develop two generations seasonally. A rough map showing the distribution of the northern (single-brooded) and southern (double-brooded) strains was developed by Chapman (1938).  There are genetic differences among geographic strains of PC (Zhang et al. 2008).  Furthermore, there are Wolbachia symbionts in PC, also with geographical differences in their genetics (Zhang et al. 2010).  These differences in Wobachia infections likely result in observed differences to mate within and among PC strains (Zhang and Pfeiffer 2008).

Monitoring: Shake branches over a sheet. Examine fruit for fresh injury, especially on borders adjacent to woodlands.

Control: Two applications of a contact insecticide usually necessary (Milholland & Meyer 1984); first when adults begin to return to field; second timed to end of migration period, when max. temps. reach 32oC (90oF) (Milholland & Meyer 1984). Imidan is very effective.

Additional Reading:

Amiss, A. A. and J. W. Snow. 1985. Conotrachelus nenuphar. p. 227-235. In: P. Singh and R. F. Morse (eds). Handbook of Insect Rearing. Vol. 1. Elsevier NY. 488 p.
Mampe, C. D. and H. H. Neunzig.  1967.  The biology, parasitism, and population sampling of the plum curculio on blueberry in North Carolina.  J. Econ. Entomol. 60: 807-812.Reissig, W. H., J .P. Nyrop & R. Straub.  1998. Oviposition model for timing insecticide sprays against plum curculio (Coleoptera: Curculionidae) in New York State.  Environ. Entomol. 27: 1053-1061.
Zhang, X., S. Luckhart, J. Tu and D. G. Pfeiffer.  2010.  Analysis of Wolbachia strains associated with Conotrachelus nenuphar (Coleoptera: Curculionidae) in the eastern United States.  Environ. Entomol. 39: 396-405.
Zhang, X., J. Tu, S. Luckhart and D. G. Pfeiffer.  2008.  Genetic diversity of plum curculio, Conotrachelus nenuphar (Herbst) (Coleoptera: Curculionidae) among geographical populations in the eastern United States.  Ann. Entomol. Soc. Am. 101: 824-832.
Zhang, X., and D. G. Pfeiffer.  2008.  Evaluation of reproductive compatibility of interstrain matings among plum curculio populations in the eastern United StatesEnviron. Entomol. 37: 1208-1213.

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Maintained by: Douglas G. Pfeiffer

Department of Entomology
Virginia Tech