rials may be toxic to the predators and interfere with 

 biocontrol (see Table 1). Under favorable conditions, 

 A fallacis reduced TSM populations from outbreak 

 levels (> 5 per leaf and reaching 19 per leaf) to below 



1 mite per leaf within a 2 week period during the first 



2 years of study. Results from 1988 and 1989 sug- 

 gested that the presence of the predatory mites were 

 as beneficial as miticide applications, and that in- 

 digenous populations of predators were almost as 

 effective as released populations. These results were 

 gathered from 16 cooperating growers each year. 



Scouting mites. TSM are very small (1/50"), 

 insect-like creatures that feed on strawberry foliage. 

 Under heavy infestations, TSM feeding destroys 

 leaf chlorophyll and causes leaves to appear bronze 



Sampling Path 

 for Mites, Plant Bug 

 Nymphs, and Clipper 



Sample at 5 to 10 

 locations per field 



Tamijhed 



Plant Bug 



Tiap* 



7 



Figure 1 . Insect and mite sampling pattern in a straw- 

 berry field. 



in color. Yield reductions may occur from repeated 

 heavy infestations. TSM are found on the underside 

 of leaves, are barely visible to the naked eye, and are 

 especially active during hot, dry months. TSM 

 generally form colonies and may be most noticeable 

 by the webbing that they produce in the vicinity of 

 the colonies. These colonies are usually localized in 

 "hot-spots" in the field rather than being evenly dis- 

 tributed throughout the field. Therefore, when 

 looking for mites, the grower must look over the 

 whole field, checking first for bronzing and then 

 looking for mites with a hand lens. TSM and insects 

 are sampled using the V-pattern walk in the field, 

 with 5 to 10 sample locations (see Figure 1). Approxi- 

 mately 5 leaves should be sampled at each locations. 

 (Normally, we place a 2-square foot marker at each 

 sample location and sample inside it for TSM and 

 other pest problems.) Predators should be noted as 

 well. Unfortunately, there is no strict threshold. We 

 recommend predator release (cost is $10.00 per acre) 

 when populations are building from week to week, 

 and the number of mites per leaf reaches 5 in a 50 leaf 

 sample. It is still not clear whether this action 

 threshold is appropriate. 



Tarnished Plant Bug IPM 



Tarnished plant bug (TPB), Lygus lineolaris, is 

 a major pest of strawberry, whose feeding on flowers 

 and immature fruit results in misshapen, seedy, and 

 unmarketable fruit. Losses due to TPB damage can 

 reach levels of 60 to 70% of the crop (Schaefers, 

 1980). Initially, we had hoped to be able to monitor 

 plant bug using a sticky visual trap (white square). 

 Unfortunately, we could not establish an action 

 threshold, though we caught many adult tarnished 

 plant bugs. However, a threshold has been estab- 

 lished for TPB nymphs and nymphs seem to be 

 causing at least as much damage as the adults. 

 Between the two techniques, treatments for TPB can 

 be made more precise. 



Scouting for TPB. TPB is a small (1/4") bronze- 

 colored insect with a triangular marking on its back. 

 The immature stage, or nymph, is smaller and bright 

 green, resembling an aphid, but much more active. 

 Both adults and nymphs feed on the developing 

 flowers and fruit, sucking out plant juices with 

 straw-like mouth parts. This feeding results in 

 deformed fruit; typically "cat-faced" berries, also 

 called "nubbins" or button berries. Such fruit are 

 generally unmarketable. 



To determine when adult TPB are active and 

 moving into the field, place white sticky traps 

 around the edge of the field (see Figure 1). Nymphs 



Fruit Notes, Spring, 1991 



