Strawberry Pests 



Pest control in strawberries includes efforts in all 

 three pest groups: insects, diseases, and weeds. Key insect 

 pests, those which cause economic injury and concern to 

 the grower, include tarnished plant bugs {Lyf^ts Uncolaris), 

 strawberry bud weevils (clipper) {Anlhonoinus sigiwtiis), 

 and two-spotted spider mites {Tetranychus iirticac) (12). 

 Other insect pests exist but arc of lesser concern togrowers. 



Important plant disease organisms include bacte- 

 ria, viruses, and fungi, with fungi being the most prevalent. 

 Fungal pathogens fall into four categories: berry rots, leaf 

 diseases, crown rots, and root rots. The two key diseases 

 of concern are a berry rot, grey mold {Botrs'tis cincrca), and 

 a root rot, black root rot {Rhizoctonia fragaria) (12). Red 

 stele (Phylophthora fragaria) is also a problem in the 

 Northeast but generally is managed successfully through 

 the use of resistant cultivars and soil fumigation. 



Keystrawbcrryweeds vary widely throughout the 

 state but grasses and other perennial weeds are of most 

 concern. These weed problems include dandelion {Ta- 

 raxacum officinale), goldenrod (Solidago canadensis), 

 orchard grass {Dactylis gloinerata), quackgrass {Agropyron 

 repcns), and yellow wood sorrel (Oxalis siricta) (12). Heavy 

 weed infestations will affect yield, plant vigor, and bed 

 longevity. 



Key Insect Pests 



Tarnished plant bug causes misshapen berries 

 with the typical "cat-facing" or apical seediness. It is 

 ubiquitous and can cause severe losses of yield if not 

 controlled. The damage is caused by the feeding of adults 

 or nymphs on the newly developing fruit. Feeding prevents 

 individual achenes from developing, thus causing the de- 

 formity. The later in the development of the berry that 

 feeding occurs, the less significant the injury. However, 

 under heavy infestations, 30 to 50% crop reductions have 

 been reported (10). Current practices include 1 to 3 sprays 

 in the early season with malathion or thiodan. 



Tarnished plant bugs overwinter as adults and lay 

 eggs in early May. Eggs hatch at approximately the same 

 time as the strawberries are approaching 10% bloom. The 

 nymphs cause the majority of the damage and must be the 

 target of a management plan. Sampling for these nymphs 

 may be done by shaking 25 flower trusses from a 2-foot 

 section of row individually over a dish at a number of 

 locations. The current threshold number usingthis method 

 is 1 nymph per 25 flower trusses (10). We were unable to 

 evaluate this method satisfactorily in 1987, because the 



IPM program began at the end of the flowering period. A 

 second monitoring method that we tried was the use of 

 sticky traps to catch the adult tarnished plant bugs, as has 

 been shown in apple orchards (4). This procedure was not 

 satisfactory, because it was difficult to correlate trap 

 catches and damage and to set threshold levels. The use of 

 models for egg hatch and nymphal development according 

 to thermal accumulation has been studied in Quebec (1) 

 and may prove useful in combination with sticky traps for 

 determining first incidence of tarnished plant bug activity. 

 The Massachusetts Strawberry IPM Program will be using 

 the Hower truss/nymph method this year to make spray 

 recommendations based on threshold numbers. The ob- 

 jective is not only to reduce the number of sprays but also 

 to improve the liming of sprays and to fine-tune the rates 

 and materials used against tarnished plant bug. 



Strawbcrrvbud weevil causes a reduction of yield 

 by laying eggs in the newly exposed buds and girdling the 

 pedicel of these buds, which then will not develop. This 

 pest, otherwise known as the clipper because of the nature 

 of the injury, is not as common in Ma.ssachusetts as is the 

 tarnished plant bug, but when it occurs, it can cause severe 

 losses; up to 90% damage has been reported in some states 

 (11). Current practices include 1 to 3 pre-bloom sprays per 

 season of guthion, parathion, or lorsban. 



The strawberry bud weevil overwinters as an adult 

 in hedge-rows or woods and is active when temperatures 

 are above 60°F and buds are available. Sampling for this 

 pest is performed by counting the number of clipped buds 

 per 2 feet of row. Unfortunately, this procedure counts the 

 damage after the fact but is the only satisfactory method 

 available. The threshold number that we are currently 

 using is 1.2 clipped buds per 2 feet of row (11). Samples 

 should be taken from near the field borders, hedge-rows, 

 and woods since these arc areas where we expect to find the 

 clipper first, and we want to halt the invasion of it into the 

 field. When the threshold level is reached, we recommend 

 spraying with guthion at labeled rates. As with the tar- 

 nished plant bug, the objective not only is to reduce the 

 number of sprays but to improve effectiveness by improv- 

 ing the timing. Experiments are planned to aid in the 

 development of a trap or lure similar to that used for the 

 boll weevil, so that we can monitor populations before 

 damage occurs. 



Two-spotted spider miles affect the yield of straw- 

 berries indirectly by sapping the vigor of the plants. These 

 tiny arthropods live on the underside of leaves and feed on 

 plant juices. Under heavy infestation (over 100 mites per 

 leafiet) two-spotted mites can have significant impacts on 

 yields and on the longevity of a bed (9). Many growers do 

 not spray for two-spotted mites because their heaviest 



