Meloidogyne hapla Root-knot nematode Damage.  Because of the world-wide distribution of the root-knot nematodes and the damage they are known to cause,  these nematodes must be ranked as important disease producers.  Biology.   Meloidogyne hapla is a sedentary endoparasite and only second-stage juveniles (the infective stage) and adult males (which may be rare) are present in soil. The female is usually pear-shaped, with a fragile white cuticle, and may be up to 2 mm in diameter.  Ecology.  Meloidogyne hapla is distributed worldwide,  commonly in cooler environments.  Symptoms.  Small distinct galls on roots; poor growth; shortened lifespan of the vine; reduced yield.  Damage to other crops.  Yield losses recorded of 36% on alfalfa in midwest (U.S.), 70% on peanuts in southeast (U.S.), 50% on carrots in northeast (U.S.), 20% on sugarbeets in Poland, 46% on potatoes in Canada, 64% on onions in Canada. Control.  Cultural control (using clean root-stock) and chemical control are effective. Links and References.  Grape nematode- Root-knot.  Oregon State University.