David asks: While sitting in the dentist’s chair, David asked me how to control snails and slugs and avoid exposure to rat lungworm disease. In that position it was hard to respond fully, so I will do so here.
David asks: While sitting in the dentist’s chair, David asked me how to control snails and slugs and avoid exposure to rat lungworm disease. In that position it was hard to respond fully, so I will do so here.
Tropical Gardener answer: Rat lungworm disease has been in Hawaii for more than 50 years. Although recent cases have gotten a lot of press, the disease is actually rare. Though publicizing information about rat lungworm can raise unnecessary alarm, it is important to increase awareness of the disease among citizens, as well as medical personnel.
Several easy steps on the part of farmers, gardeners and consumers, can greatly reduce the possibility of new cases of the disease and hopefully lower fears and convince people that it is safe to eat locally grown vegetables.
Rat lungworm is a disease that is caused in rats by the nematode Angiostrongylus cantonensis.
The semi slug Parmarion cf. martensi, is an intermediate host and the primary carrier of the nematode in Hawaii. Other fresh water slugs, snails and mollusks can carry the disease-causing nematode, as well.
Since slugs, snails and rodents are present in many of our gardens and farms, controlling these potential carriers of rat lungworm is paramount in prevention. Biological controls, including the introduction of ducks that eat mollusks can be helpful. Some research has been done on increasing a microbial fungus that is toxic to A. cantonensis in the soil. Find the report at https://www.sciencedirect.com/science/article/pii/S0001706X13001253. Several other simple, safe and nontoxic practices are also effective.
Waterproof rat traps placed in papaya or banana groves where rats may be present can lower the rodent population significantly. To see if snails are present in areas around your vegetables, place a tuna or cat food can with beer out overnight. If they are in the area, they will come for a drink and drown. You’ll find them in the can in the morning. If they are present, you can try several other techniques without wasting a lot of beer. Copper strips or wires (or even a row of shinny pennies) along the edge of raised beds can keep snails and slugs out. Applying Sluggo, an organic slug and snail bait, will kill mollusks when used according to the directions. When using any rodenticides and molluscicides, always read and follow the product label.
In addition to reducing the population of rats, slugs and snails in gardens, close inspection and washing of any vegetables that might harbor slugs or snails will reduce the chances of contact with the disease-causing organism.
Leafy green vegetables are sometimes the source for acquiring rat lungworm disease. There is no need to avoid them, especially when they have been grown by a grower with good vector control practices and you have inspected them carefully and washed them well. Young snails and slugs can be very tiny and hard to detect without careful inspection, so vigilance is necessary. Mollusk trails left on vegetables may indicate their presence and should be removed.
Cooking for at least five minutes will kill the organism, but if you are eating the vegetables raw, be sure to inspect and wash carefully. Several washing experiments have shown no greater efficacy in adding bleach, vinegar or salt to water as opposed to just water.
People concerned about possible exposure to A.canonesis may want to consider increasing their consumption of ginger and/or ginger alcoholic extracts. The larvicidal activities of ginger (Zingiber officinale) against A.cantonensis are being seriously researched.
Other important information about controlling rat lungworm disease can be found online at https://manoa.hawaii.edu/ctahr/farmfoodsafety/rat-lungworm and https://health.hawaii.gov/docd/files/2017/03/rodent-control-foldout-brochure.pdf.
Email plant questions to konamg@ctahr.hawaii.edu for answers by Certified Master Gardeners. Some questions will be chosen for inclusion in this column.
Farmer Direct Markets
Wednesday: “Sunset Farmers Market,” 2 p.m. to sunset at the HPM parking lot.
Wednesday and Friday: “Hooulu Farmers Market,” 9 a.m. to 2 p.m. at Sheraton Kona Resort &Spa at Keauhou Bay
Friday: “Pure Kona Market,” 9 a.m. to 5 p.m. at Amy Greenwell Garden in Captain Cook
Saturday: “Keauhou Farmers Market,” 8 a.m. to noon at Keauhou Shopping Center
“Kamuela Farmer’s Market,” 7 a.m. to noon at Pukalani Stables
Sunday: “Pure Kona Green Market,” 9 a.m. to 2 p.m. at Amy Greenwell Garden in Captain Cook
Tuesday through Saturday: “U-Pick greens and produce,” 10a.m. to 4p.m. Tropical Edibles Nursery, Captain Cook.
Plant Advice Lines
Anytime: konamg@ctahr.hawaii.edu
Tuesdays and Thursdays: 9 a.m. to noon at UH-CES in Kainaliu, 322-4892
Mondays, Tuesdays and Fridays: 9 a.m. to noon at UH-CES at Komohana in Hilo:981-5199 or himga@hawaii.edu