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  • Author or Editor: Warren C. Micke x
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A replicated rootstock trial for almond was established in 1986 in the central San Joaquin Valley, a major almond growing area for this most widely planted tree crop in California. `Nonpareil', the major cultivar in California, was used for this trial with `Fritz' grown as the pollenizing cultivar. Two standard rootstocks for almond, `Nemaguard' and `Lovell' peach, were compared to two newer peach-almond hybrid rootstocks, `Bright's' and `Hansen'. After eight years both hybrid rootstocks produced significantly larger trees than the peach rootstocks, based on trunk cross-sectional area. Trees on hybrid rootstocks frequently produced greater yields than those on peach rootstocks; although, differences were not always significant. However, there were generally no significant differences in production per trunk cross-sectional area (yield efficiency). Thus, increased production by trees on hybrid rootstock was the result of larger tree size and not an inherent increase in productive efficiency of the tree itself. Since trees on hybrid rootstock should be planted further apart than those on peach, production per hectare should not be significantly increased, at least under good growing conditions as represented in this trial.

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`Gala', the third most widely planted apple cultivar in California, requires early and precise thinning to produce good fruit size. Thus, chemical thinning would be ideally suited for this cultivar. However, the normally prolonged bloom for apples in California makes timing of chemical thinning applications difficult. In 1995 and 1996 trials, several chemical thinning treatments provided significantly reduced fruit set on `Gala' compared to the untreated control. Three treatments showed promise for commercial use: 1) carbaryl, two applications at petal fall and again at 10-15 mm diameter of the king fruit; 2) carbaryl plus NAD at petal fall; and 3) carbaryl plus 6-benzyladenine and GA4+7 (Accel®), two applications at petal fall and at ≈10 mm diameter of the king fruit. These treatments generally gave reduced fruit set per 100 flower clusters, fruit set per fruiting cluster and/or numbers of fruit removed by follow-up hand-thinning. None of these treatments showed evidence of phytotoxicity, and some increased fruit size over the untreated control.

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Abstract

The original ‘Brooks’ cherry (Prunus avium L.) seedling was evaluated at the Wolfskill Ranch of the University of California, Davis from 1970 to 1985. Clones of the original seedling have been evaluated for fruit quality in Contra Costa County since 1978 and in Fresno County at the University's Kearney Agricultural Center since 1981. ‘Brooks’ registered its most outstanding performance at the Kearney Field Station.

Open Access

A rootstock comparison trial for almond was planted in sandy soil near Atwater, Calif., in Feb.1989. The study consisted of five replications of five trees each for six rootstocks, each with two cultivars. The rootstocks were `Nemaguard' peach, `Nemared' peach, `Hansen 536' peach × almond hybrid, `'Bright's hybrid' (peach × almond), `Halford' peach seedling, and `Lovell' peach seedling. Two cultivars, `Nonpareil' and `Carmel', were used with each rootstock. The accumulated kernel production from `Nonpareil' through the 1998 harvest was highest for trees on `Hansen 536', second highest for those on `Nemaguard', and third highest for trees on `Bright's Hybrid'. The accumulated kernel production from `Carmel' was greatest for trees on `Bright's Hybrid' and second highest for those on `Hansen 536'. The hybrids have produced the largest trees, as indicated by trunk circumference, for both `Nonpareil' and `Carmel'. The greater production of trees on the hybrid rootstocks over those on the peach seedling rootstocks was probably a result of their greater size and not that the trees on the hybrid rootstocks were inherently higher-yielding.

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Under California conditions `Granny Smith' apple does not “self-thin” sufficiently to promote good return bloom nor to provide fruit size desired for the fresh market. Preliminary studies conducted during 1985-87 indicated that 1-naphthyl N-methylcarbamate (carbaryl), 1-naphthaleneacetic Acid (NAA), and 1-naphthaleneacetamide (NAD) could be useful for thinning `Granny Smith'. Detailed studies conducted in 1988 and 89 using dilute handgun applications demonstrated that all 3 materials provided reasonable thinning as shown by fruit set counts. NAA and NAD tended to slow fruit growth as compared to carbaryl. Carbaryl tended to uniformly thin clusters while NAA and NAD were more likely to remove all the fruit from some clusters and few fruit from others, especially in 1988. Compared to the control, all materials applied in 1988 improved return bloom in 1989 with carbaryl having a slightly greater effect than NAA and NAD. As a result of these studies carbaryl at 1.7 to 2.2 kg (active ingredient) per ha as a dilute application is being suggested for grower trials in California.

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Under California conditions `Granny Smith' apple does not “self-thin” sufficiently to promote good return bloom nor to provide fruit size desired for the fresh market. Preliminary studies conducted during 1985-87 indicated that 1-naphthyl N-methylcarbamate (carbaryl), 1-naphthaleneacetic Acid (NAA), and 1-naphthaleneacetamide (NAD) could be useful for thinning `Granny Smith'. Detailed studies conducted in 1988 and 89 using dilute handgun applications demonstrated that all 3 materials provided reasonable thinning as shown by fruit set counts. NAA and NAD tended to slow fruit growth as compared to carbaryl. Carbaryl tended to uniformly thin clusters while NAA and NAD were more likely to remove all the fruit from some clusters and few fruit from others, especially in 1988. Compared to the control, all materials applied in 1988 improved return bloom in 1989 with carbaryl having a slightly greater effect than NAA and NAD. As a result of these studies carbaryl at 1.7 to 2.2 kg (active ingredient) per ha as a dilute application is being suggested for grower trials in California.

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