Water Spinach, Kang Kung - Pests
Tarnished plant bug adults (Lygus rugulipennis) feed on the succulent tissue
where new leaves are developing in the leaf internodes. They pierce the tissue
and inject a toxin into cells, which causes death of cell tissues, prevents the
new leaves from developing, or causes distortion of the emerging leaf as it
unfolds. A blackened, dead area at the growing tip is evidence of their feeding.
Tarnished plant bugs also cause holes in the leaves which enlarge with the leaf,
often in a somewhat symmetrical pattern on the two halves of the leaf. Damage to
the growing tip stops the elongation of the plants and stimulates more branching
below. Since the markets prefer a longer-stemmed plant, this effect reduces
marketability and delays harvest. Holes in the leaves also reduce the
marketability of the greens.
Management of tarnished plant bug should begin with reducing favorable habitat
surrounding the production area, including eliminating fallow, weedy areas. Use
of row covers can exclude tarnished plant bugs. Insecticide registrations on
this crop are limited since it is a noxious weed. Insecticides used should
include only materials that have a broad label for all leafy green crops, such
as neem.
Other leaf-feeding insects include the golden tortoise beetle (Metriona bicolor)
which may be seen as adults which can change from shiny gold-colored to dull
rust colored, or the larvae, which have the habit of piling frass on their
backs. The spotted cucumber beetle (Diabrotica undecimpunctata howardi) may also
be present. Both of these beetles cause chewing injury to leaves, but rarely
reach numbers high enough to cause significant damage. Where natural enemies are
excluded or with excessively high nitrogen levels, outbreaks of green peach
aphid (Mysus persicae) can occur. High numbers of aphids cause leaves to curl.
Insecticidal soap used at weekly intervals can reduce infestations. Normally,
beneficial insects keep aphid populations below damaging levels.
Because water spinach is not nationally recognized as a legal food crop there
are no pesticides specifically labeled for it. It is important not to use
pesticides that are not labeled for the crop.
Two critical reasons for this are:
- It is illegal
- There is a risk that illegal or toxic residues will remain on the crop
and harm those who eat it.
However, it would be legal to use pesticides that are labeled for the entire
leafy vegetable crop group. The specific target pest does not have to be listed
on the label but the leafy greens crop group must be on the label. Pay special
attention to label restrictions regarding the days to harvest interval. In
Massachusetts, there are general use insecticide products with the following
active ingredients that are labeled for use on leafy vegetables; spinosad, neem,
Beauvaria bassiana, and permethrin (dilute products with 0.25% active
ingredient; please note that some permethrin products are restricted or do not
have the leafy green crop group on the label).
Water spinach requires rapid and careful post-harvest handling to maintain
quality. Once harvested, shoot tips and leaves easily wilt. Cool in 50°F as soon
as possible after harvest, and maintain high relative humidity with good
ventilation. Produce should be used soon after harvest to minimize quality loss. |
