Insect Enemies op Greenhouse and Ornamental Plants 9 



will be found satisfactory, provided the spraying takes place shortly 

 after the over-wintering eggs have hatched and is directed against 

 the under-sides of the leaves. 



The Boxwood Leaf Miner 



Monarthropalpus buxi Liab. 12 (Fig. 10 to 17) 



This insect, known as the European boxwood leaf miner, occurs 

 on all varieties of boxwoods in nurseries and private estates in 

 widely separated parts of New Jersey. It was evidently introduced 

 from France or Holland within the past few years, especially from 

 the latter country, as thousands of boxwoods are imported into New 

 Jersey every year from Holland, while only a few come from France. 

 It has, however, been noted by inspectors examining boxwoods from 

 both of these countries. 



The first sign of injury likely to be noticed by most persons 

 is a small yellowish or light green spot on the upper leaf surface. 

 Directly under this on the lower surface is quite a pronounced, 

 irregular, oval blister, caused by the young maggot enlarging its 

 mine. Later in the season, the injury is more pronounced and 

 there will be a slight elevation of the upper surface, with a yellow- 

 ish or brownish discoloration. In severe infestations, the entire 

 leaf is taken up by irregular, oval swellings which are largest on the 

 under surface. Badly infested plants during the spring present 

 the superficial appearance of having been winter-killed, the discolor- 

 ed and disfigured leaves finally dropping off. Closer examination 

 however, will reveal the larvae or pupae within their galls. Box- 

 woods have strictly an ornamental value and a plant having un- 

 sightly bare branches with new leaves developing at the tips is 

 valueless for such a purpose. Specimen plants which have been 

 trimmed for years in some particular shape are sometimes ruined 

 by the insects infesting an entire side or top. 



In New Jersey, the adult midges appear about the latter part 

 of May and the eggs are then deposited in the young developing 

 leaves. These eggs are tiny, oval and translucent, wide in the 

 middle and tapering uniformly toward each rounded end, each 

 being about 1/120 inch long and twice as long as broad. After 

 hatching, which requires from 2 to 3 weeks, the yellowish white 

 maggots mine the leaves all summer, making small oval pockets 

 which sometimes run together on one side of a midrib, if many 

 larva? are present. 



The winter is passed in these pockets, the larvae transforming 

 to light orange-colored pupae in the spring. So as to facilitate the 

 emergence of the adult, the pupa issues partly through the thin 

 lower surface of the leaf. An infested leaf may contain as many 

 as twelve and possibly more larvae. The full-grown larva and pupa 

 qre about 1/8 inch in length and the adults are slender midges with 



12 From Weiss, H. B., 1916. Monarthropalus buxi in New Jersey. In 

 Psyche, v. 23, p. 154-156. 



