Postharvest Biology and Technology of Fruits, Vegetables, and Flowers

406 POSTHARVEST BIOLOGY & TECHNOLOGY OF FRUITS, VEGETABLES, & FLOWERS
Lentaza-Rizos and Balokas (2001) measured the residue concentration of potatoes
treated with CIPC. Residue levels in tubers decrease by 20% after 1 month of storage,
and 40% after 65 days of storage. Their studies showed washing in water for minute removes
88% and peeling removes 91–98% of total residue (Tsumura-Hasegawa et al., 1992;
Lentaza-Rizos and Balokas, 2001). Internal sprouting is reported occasionally in commercial
lots treated with CIPC. This is attributed to the unequal distribution of CIPC in the
commercial storage.
19.5.6 Maleic hydrazide
Maleic hydrazide is applied as foliar chemical in potato, onion, and tobacco to inhibit
sprouting (Gichohi and Pritchard, 1995). Maleic hydrazide is applied to the growing potato
crop, and is translocated to the developing tubers where it arrests cell division, but does not
limit cell expansion. Early application during tuber development can be problematic, and
will limit tuber size and yield. Best results were obtained when the chemical was applied
around 2 weeks before vine killing. Ideal daytime temperatures at the time of application
is less than 85 ◦ F. Irrigation or rainfall within 24 h of application may reduce effectiveness
(Weiss et al., 1980). Caldiz (2001) showed sprout inhibition with maleic hydrazide was
possible for 8 months with no loss of weight and tubers could produce good-quality french
fries. Maleic hydrazide delays the initial sprouting date, but there is no reduction in yield
when used on seed potatoes (Caldiz, 2001). Disorders associated with maleic hydrazide are
bud end cracking and elephant hide on tubers due to uneven application. Maleic hydrazide
is applied only once in a season, and plants should not be under stress conditions when it is
applied.
19.5.7 1,4-DMN
Ethyl substituted naphthalenes are naturally occurring in potato tubers and contribute to
flavor in baked potatoes (Buttery et al., 1970; Coleman et al., 1981). These compounds
showed sprout-suppressant activity on a short-term basis approximately for 30 days. Different
isomers of dimethylnaphthalene (DMN) and diisopropylnaphthalene (DIPN) were
tested and compared for their sprout-suppressant activity by Lewis et al. (1997). Lewis et al.
(1997) found that DIPN was more efficient than DMN in sprout suppression. Mode of action
of these compounds for sprout suppression is by regulating phytohormones (Kleinkopf
et al., 2003). The short-term nature of the sprout-suppressant activity of 1,4-DMN allows
for a potential use in the seed industry. Diisopropylnaphthalene is also applied as an aerosol
for treating potatoes in storage. The active ingredient in 1,4-Sight TM and 1,4-Ship TM is
1,4-dimethylnaphthalene, and Amplify TM is 2,6-diisopropylnaphthalene. 1,4-DMN is marketed
specifically to control sprouting of seed during storage and transit. Beveridge et al.
(1981a) was the first to suggest that 1,4-DMN has an effect on tuber size distribution in a
crop growing from treated seed potatoes and showed its concentration dependence. DMN
is applied after the wound healing (curing) process and natural tuber dormancy ends and
before sprouting occurs. This product is custom applied and highly toxic to fish. Care must
be taken in disposing of water that is used in the storage bins treated with DMN.
The different mode of action of DMN is exploited by the potato storage industry by
alternating with the popular sprout suppressant, CIPC, for long-term storage needs. The