Ministry’s policy on cyst nematodes

Press, Volume CXV, Issue 33775, 22 February 1975, Page 7

Ministry’s policy on cyst nematodes

The policy of the Ministry of Agriculture on the potato cyst nematode, which has been found in Christchurch, is explained in a new pamphlet issued by the Ministry.

It says that the policy recognises the threat of the nematode to the potato growing industry and to garden produce exports generally.

“Our objective is to prevent the spread of the nematode and to eventually eradicate it. To achieve this we have a three-step programme: survey, quarantine and control.

“Surveys of potato-grow-ing areas are being undertaken by experienced field staff. Pre-harvest root forking has proved a reliable sampling technique, making use of a team approach at the optimum growth stage for cyst identification. Soil samples are also collected from suspect areas.

“As soon as a suspect sample is confirmed by laboratory diagnosis the grower is notified and all the land he occupies is placed in quarantine under the Plants Act 1970. STRICT QUARANTINE “Strict quarantine procuedures are necessary to prevent the spread of the soil-bome cysts. The land is declared to be an inf gated area under ‘The Potatory st Nematode Regulations. .-3974’ and the following restrictions are required: “Implements, machinery, footwear, containers and anything likely to spead contaminated soil must be cleaned before leaving infested land. “Approval must be obtained before lifting the affected crop. “The potatoes may be marketed but only to an approved outlet. Potatoes from infested land (where the nematode is present) are cleaned prior to sale. Potatoes from any other ‘high risk’ land farmed in association with the infested land, and within a radius of 80 kilometres, must be sold on the local market and only for domestic consumption.

“Control and eventual eradication is based on the following approach: “On infested land, double fumigation with a nematicide is required and this destroys close to 100 per cent of the cysts. “The growing of alternative crops to those of the potato family will result in the natural death of the few remaining cysts. Current research will establish the time that cyst-enclosed eggs can survive, but for the foreseeable future nonhost crops must be grown.

“The nematode population builds up slowly on contaminated land. Therefore on declared ‘high risk’ areas it will require several seasori’s repeat fork sampling before any consideration can be given to declaring the land nematode-free. MOST DAMAGING

The Ministry pamphlet says that the potato cyst nematode is one of the most damaging of the potato and tomato plant family.

“Damage is caused by the tiny worm-like females boring into the roots to feed on the plant juices. Poor growth of plants in one or more spots in a potato paddock is usually the first sign of an infestation. These intial infestations may go undetected for many years, because there is no visible damage to either the aboveground part of the plant, or the tubers.

RAPID BUILD-UP “However, nematode populations can build up rapidly where land is in regular potato production. Cultivation spreads the soil-borne cysts and poor overall growth results throughout the paddock. Heavy infestations cause wilting (particularly at midday during dry weather), stunted growth and reduced yields. “The life cycle of the nematode has three stages — egg, larva, and adult. The eggs are enclosed in protective, flask-shaped cysts — which are dead swollen bodies of the female. The cysts are smaller than a pin head, and each of them contains about 300 eggs.

FEEDING STAGE “The eggs remain dormant in soil until stimulated to 'hatch by a chemical released from the roots of host plants. The larva then migrate to the roots and enter them. This feeding stage ceases when the eggs begin to develop in the fertilised female. She breaks through the root surface and swells with the maturing eggs to form the characteristic white cyst that can be identified by a close examination of the roots. i fully the

brown cysts drop off the l plant and contaminate the I soil. The ability of the eggs; to remain dormant for many! years in the absence of hostj plants is a characteristic i that makes the pest a I serious problem.” INFESTATION A Ministry statement i issued in Wellington on Monday said that so far the j nematode had been con-! firmed on 40 hectares in Christchurch and a further I 40 hectares were under sus-i picion. After successfully isolat-I ing and gaining control of! the disease in Pukekohe, I plant health authorities were [ disappointed to find such well established infestations in the Christchurch district, I said Mr L. G. Morrison, [ • Deputy Director (plant [ health) with the Ministry of; Agriculture. “Our direct concern is the overseas market. A number: of countries .will not take : potatoes from nematode infested areas. Other countries are concerned with cyst introduction and may prohibit the importation of any root vegetables from infected I areas. This includes onions i for which we have a very| good export market at i present.” According to Mr J. D. Currie, the Ministry’s chief advisory officer, (plant health), it is most unlike that there is any relationship between the Pukekohe outbreak and that in Christchurch.