Plum
Curculio,
Conotrachelus
nenuphar (Herbst) in BlueberryBiology: 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). Guthion and Imidan are very effective.
Additional Reading:
