GROWTH HABIT FACTOR

Press, Volume CVI, Issue 31071, 28 May 1966, Page 10

GROWTH HABIT FACTOR

i By

A. D LOWE

The apparent preference of the stem-weevil for certain grasses was discussed by Dr. R. ?■ Pottinger, of Lincoln College, at the Entomological Society conference in New Plymouth. Plots of single plants of several varieties of grasses planted at the college farm had been examined for percentage ingestation of tillers by the grub of this weevil and had yielded counts as follows: Perennial, 54 per cent infested; long rotation, 45; Italian, 77; short rotation. 83; browntop, 77; meadow fescue, 63; timothy, 58; cocksfoot 52.

Counts showed that numbers of eggs laid by female weevils appeared uniform over all varieties, as did the number of larvae surviving. Dr. Pottinger asked wherein then did the varietal differences frequently observed lie? The growth habit of the varieties, he said, ap-

peared to be the main source of a variation in response to attack.

The economic damage attributable to this pest was important in that it could, and frequently did. wipe out voting seedlings, leading to re-sowing and losses in grazing days even months. Tolerance of the pest appeared to be due to the ability of some varieties to send up fresh tiller growth in summer, thus diluting the effect of the primary infesta tion. The effect was well illustrated in the non recovery of some of the ryegrasses, or by comparing, say. meadow fescue with cocksfoot. Fescue suffered heavily in the first attack and usually failed to recover because of an inability to rapidly develop fresh tiller buds. Cocksfoot, in contrast, could make fresh tillers and good regrowth in readiness for winter conditions.

All popular pasture plant, were subject to attack those that could re-tiller in summer or even in autumn would persist while others were eliminated. Drought in places like Canterbury accen tuated the effect of attack by this insect.