Exegesis:

ho men therismos polus ‘the crop is plentiful/abundant,’ first part of a saying in proverbial form. Its meaning depends on the meaning and connotation of therismos.

therismos ‘process of harvesting,’ or its result, ‘harvest,’ ‘crop,’ preferably the latter. Here it is best understood as a metaphor for the bringing in of those who are destined to enter the kingdom of God. The mission of the seventy is part of this bringing in.

hoi de ergatai oligoi ‘but the workers are few.’

ergatēs ‘worker,’ ‘labourer,’ a general word which refers here to the work of reaping.

deēthēte oun tou kuriou tou therismou ‘pray therefore to the master of the crop.’ ho kurios tou therismou ‘the master of the crop’ is the owner of the crop on the fields who is responsible for the harvesting (cf. An American Translation, New English Bible).

hopōs ergatas ekbalē eis ton therismon autou ‘that he send out workers into his crop,’ scil. in order to reap it for him. For ekballō meaning ‘to send out’ without the connotation of force.

Translation:

Harvest, or, ‘crop,’ ‘what is to be reaped/gathered-in,’ ‘food ripe in the garden’ (Neo-Melanesian); sometimes the term refers to the manner of harvesting, e.g. ‘stuff to be cut’ (Ekari), ‘what is plucked’ (Tzeltal), or to the specific crop that is locally most important, e.g. ‘rice-crop (lit. what-is-treated-with-a-small-knife)’ (Javanese).

Labourers, or, ‘harvesters,’ ‘rice-reapers’ (Javanese), ‘cutters’ (Ekari).

Pray to, or a term without such religious connotation, ‘beseech,’ ‘beg’ (cf. on 5.12).

Lord of the harvest, preferably, ‘the owner of the harvest’; or, ‘the other of the field’ (Melpa, a rendering with religious connotation, the phrase being used also of the spirits to whom sacrifices are offered before the beginning of the harvest).

To send out labourers into his harvest, or, ‘to send harvesters/workers to harvest his field/seeds’ (cf. Shona 1966, Kituba), “send out labourers to reap it for him” (The Four Gospels – a New Translation), ‘to order people to cut-together-his-rice’ (Tae’ 1933). In Zarma ‘the harvest’ is idiomatically rendered as, ‘to kill the field.’

Quoted with permission from Reiling, J. and Swellengrebel, J.L. A Handbook on the Gospel of Luke. (UBS Handbook Series). New York: UBS, 1971. For this and other handbooks for translators see here . Make sure to also consult the Handbook on the Gospel of Mark for parallel or similar verses.