Field experiments compared pesticidal and plant growth effects of soil solarization, alone and in combination, with overall applications of several nematicides. Nematodes, including Meloidogyne incognita J2, that were targeted for control were significantly reduced (P < 0.05) by solarization, 1,3-dichloropropene (44 and 132 liter/ha), ethoprop (13.5 kg/ha), metham sodium (64 liter/ha), formaldehyde (111 liter/ha), and by solarization-nematicide combinations. Control of Pythium ultimum also was obtained by all of the treatments; however, none of the chemicals or combinations of chemicals and solarization controlled nematodes or P. ultimum significantly better than solarization alone. Numbers of cotton (Gossypium hirsutum cv. Acala SJ-2) seed-applied Trichoderma viride and Bacillus subtilis which colonized the plant rhizosphere were not affected. Yield of carrot and survival of cotton seedlings was sometimes increased by solarization and (or) chemical treatments. No significant phytotoxicity from soil treatments was found on cotton or carrot.

Reproduct ion of Pratylenchus vulnus Allen and Jensen on rose was repor ted faster at 32.2 C than at 23.9 and 15.6 C (6). Reproduct ion on alfalfa tissue was faster at 25 C than at 20 and 30 C (3), while on 'Lovell ' peach and bush bean, reproduct ion was faster at 28.3 C than at 24.4, 20.6, 16.7, and 12.8 C (1). Populat ions of P. vulnus and other species of root-lesion nematodes are often raised on carrot disks (4,5), but the o p t i m u m tempera ture for reproduct ion on carrot disks has not been determined. Therefore , the following tests were performed to determine the o p t i m u m temperature for reproduct ion on carrot disks and to examine the effect of t empera ture on the nematodes ' motili ty. Specimens of P. vulnus were collected,

In greenhouse tests using potted grape plants three nematicides, aldicarb 10 G at 4.5 ai/ha, phenamiphos 15 G at 22 kg ai/ha, and oxamyl liquid at 4.5 kg ai/ha, were tested against Xiphinema index on 'Thompson Seedless' grape. Different timings for chemical treatments and X. index inoculations were used to determine some of the aspects of the mode of action. When nematodes and nematicides were applied simultaneously, nematodes were reduced from the initial 500 to the averages 5, 1, and 4, respectively, for aldicarb, phenamiphos, and oxamyl. Similar counts (respectively, 3, 1, and 2) were obtained when the nematicides were added first and the nematodes 14 d later. Nematode counts were 83, 112, and 1,346 when nematicides were applied first, and 14 days later plants were washed free of soil, repotted in untreated soil, and then inoculated. In untreated controls the population increased to an average of 2,703. Plant growth was inversely related to the level of nematode population resulting from the treatment.

Soil fumigation trials using either methyl bromide, 1, 3-dichloropropene, or carbon disulfide were evaluated for control of the nematode vector (Xiphinema index)-fanleaf virus complex in California vineyards. Methyl bromide and 1,3-dichloropropene failed to eradicate either nematodes or fanleaf virus from the soil but both reduced numbers of nematodes and incidence of disease to levels that were judged acceptable. Carbon disulfide neither reduced nematodes nor disease incidence to levels that were judged acceptable. Vine yields at one site treated with 1,3-dichloropropene remained productive for a period of 10 years at a rate high enough to justify treatment even though nematodes and fanleaf virus were slowly spreadng within the replanted vineyard. Wet soils and soils with high clay content prevented successful control of nematode and virus by any material. (Mention of a trademark or proprietary product does not guarantee a warranty of the product by the U.S. Department of Agriculture and does not imply approval of it to the exclusion of other products that also may be suitable.)

Pratylenchus vulnus is involved in a desease of Rosa noisettiana 'Manetti' rose rootstock characterized by darkening of roots, death of feeder roots, and stunting of entire plants. The disease is more severe when plants are grown in silt loam soil than when they are grown in sandy loam soil. The nematodes reproduce best in silt loam soil at 20 C. Meloidogyne hapla did not affect the growh of Manetti. Rosa sp. 'Dr. Huey', Manetti, and R. odorata rose rootstocks were found to be goos hosts for P. vulnus whereas R. multiflora was less suitable. M. hapla reproduced well on R. odorata, Dr. Huey, and R. multiflora, but not on Manetti.

A solid‐state bromide electrode was used in direct potentiometric determination of inorganic bromide in soil and plant extracts. The extraction procedure gave over 94% bromide recovery from soil samples. Results were similar to those obtained with X‐ray diffraction method for bromide determination in carnation plants.

Measurement of dibromochloropropane (DBCP) by gas chromatography showed that an injection of DBCP at a depth of 20 cm resulted in higher concentrations and deeper penetration in sandy clay loam and silt loam than when it was applied in water. Application of the same amount to the soil surface in 15 cm of water showed DBCP is trapped near the surface in these soils. Persistence is longer in these two soils and in loamy sand after injection. The most rapid penetration after application in water occurred in loamy sand where the rate and depth of penetration were greater than those measured after injection.

AbstractMethyl bromide was applied with and without polyethylene covers at rates of 337, 449, 673 and 898 kg/ha to replant vineyard soils to control plant parasitic nematodes. Distribution of the gas in the soil atmosphere at different depths was measured by gas chromatography. Higher doses, low soil moisture and deeper placement of methyl bromide resulted in more rapid soil penetration and higher concentrations of the gas at the deeper soil levels. Placement of methyl bromide in the soil at 0.76‐0.81 m without polyethylene cover resulted in gas distribution at concentrations sufficient for nematode kill as deep as 2.44 m.

Applications of 1,2-dibromo-3-chloropropane (DBCP) were made to mini-field plots of Yolo sandy loam by means of injection, flooding and sprinkler irrigation. Soil samples were removed at various depths and time intervals, processed to extract the chemical and the amount present determined by gas chromatography and correlated to the degree of kill of Meloidogyne incognita. Deepest penetration in soil occurred by injection. Application of water to injected plots moved the chemical deeper into the soil than no irrigation. In flood applications most of the chemical was retrained near the soil surface with only small quantities reaching a depths of 15 cm. Application by sprinkler resulted in shallow penetration. Excellent correlation between depths of chemical penetration and nematode kills were obtained.

Laboratory experiments were conducted by applying 1,2-dibromo-3-chloropropane (DBCP) to sealed vials of soil infested with Meloidogyne javanica. A minimum initial concentration of 0.25 mug of DBCP/g of oven-dry soil killed all nematodes within 35 days. A concentration of 1.0 mug/g killed all nematodes within 28 days. The rate of degradation of this chemical was determined by treatment of steamed and nonsteamed dry soil in open and sealed vials. Extraction of tile chemical, followed by quantification by gas chromatography, showed approximately 100% of the amount applied recovered after 14 days in sealed vials without soil. With soil present, approximately 10% of the amount of chemical applied was recovered.

Tomato has been utilized for many years in the rotation with sugarbeet to control the sugarbee t nematode, Heterodera schachtii. Although tomato was assumed to be a nonhost for H. schachtii, Raski (5) reported a few f e m a l e s and cys t s on roo t s o f two yellow-fruited cultivars, and Golden and Shafer (2) reported white females and cysts on the r e d f r u i t e d cu l t iva r , Pearson XL. Since resistance-breaking biotypes of Heterodera rostochiensis were reported after cropping continuously to resistant potato varieties (1,3, 4), similar investigations appeared desirable for the sugarbeet nematode. Our studies were undertaken to determine whether a strain or biotype of H. schachtii would develop on tomato to such an extent as to cause damage or at least maintain the nematode populations making tomato an unsuitable crop to rotate with sugarbeet.