The usual dimension of the plastic houses is 25m × ... - Agriculture Cultivation Pest and Disease Management vegetable_production_under_protective_structures

The usual dimension of the plastic houses is 25m × 6.5m. Each house has a semicircular top covered with clear

plastic treated with an ultraviolet (UV) light protectant. In the center of the semicircular top, a 30 cm portion along

the entire length is left free of the plastic cover, but closed with nylon net. This facilitates ventilation and reduces

the buildup of heat inside. The ventilation facility is made rainproof by erecting a transparent plastic shade over

the top. The side walls are covered with nylon netting. At the front side, a 60-mesh netting double door is

installed (AVRDC, 2007).

There are two types of a temporary plastic house, which is used for a single growing season: a single-bed type

with an arched roof and a double-bed type with an A-shaped roof covered with UV-protectant polyethylene film.

The width is 2.4m for the single-bed shelter and 4.8m for the double-bed shelter. The height at the center of both

types is 2.4 m (Palada et al., 2003). The sides are covered with nylon netting to exclude insect pests and prevent

rain from blowing in. The growth and yield of cucumber, sweet pepper, and small-headed cabbage were

significantly improved when grown under rain shelters during the hot-wet season in Vietnam. In addition, these

structures significantly reduced the incidence of fungal and viral diseases (Hanh, 2003).

About the author

Low net tunnels

Growers who cannot afford the high initial construction costs of nethouses or plastic houses can grow vegetables

under temporary net tunnels. The net tunnels are constructed with U-shaped iron or aluminum bars, which are

covered with nylon netting over each bed (Talekar et al., 2003). Leafy vegetables such as Brassica rapa var

chinensis, B. oleracea var. alboglabra, B. rapa var.

parachinensis, and B. juncea grown under tunnels were less

damaged by heavy rain and insect pests. This resulted in a

reduced number of insecticide applications, better produce

quality, and higher marketable yield. Amaranthus yield has

tripled under net tunnels in Vietnam. Insect populations on

cauliflower under net tunnels were greatly reduced, by 80%

in Cambodia; marketable yields were 1.5 to 2.0 times

greater under net tunnels than in the open field (Palada and

Ali, 2007). Growing head cabbage under net tunnels in the

Solomon Islands reduced insect incidence by 38-72%, and

resulted in significantly higher economic returns (Neave et

al., 2011).

Low-cost, temporary net tunnels. – R. Srinivasan

Ramasamy Srinivasan is an

Entomologist and Head of

Entomology Group at AVRDC

– The World Vegetable Center.

He has ten years research and

development experience in

tropical vegetable entomology,

with special interests in insect-

plant interactions, chemical

ecology of insect pests,

biological control, and insect

growth regulators.

Email:

srini.ramasamy@worldveg.org

This Technical Innovation

Brief is published by:

SP-IPM Secretariat

SP-IPM@cgiar.org

www.spipm.cgiar.org

Conclusion

Vegetable production under protective structures reduces yield losses from insect pests, diseases, and heavy

rains, and results in higher productivity and returns per unit area. Protective structures enable growers to

produce vegetables successfully during the off-season, which enhances the availability of fresh produce at times

when vegetables are usually in short supply. Because vegetable prices are higher during the off-season, growers

also enjoy higher returns per unit area.