Here’s an update on some of the topics discussed by the Penn State Extension Vegetable, Small Fruit and Mushroom team during our May 16 conference call.
Allium leafminer presence. Overwintered adults are nearing the end of their spring flight, with symptoms of damage from ALM expected to become more evident on susceptible crops (onion, garlic, leek, chives). The Pa. Dept. of Agriculture added Cumberland, Lycoming, and Snyder counties to the confirmed ALM detection list. Extension educators across the state are continuing to watch for this pest in their regions. For more info, see: http://extension.psu.edu/plants/vegetable-fruit/news/2017/allium-leafminer-spring-update-april-17-2017
Freeze and frost injury. Growers in many parts of the state needed frost protect their berry crops given the earliness of the start of their growth combined with low temperatures on May 8 and 9. Damage was reported where no overhead irrigation was used, malfunctions occurred, or temperatures were simply too low for control measure to be sufficient, with strawberries and blackberries being the crops mainly affected. Damage to black raspberries, a crop where bloom normally occurs only long after the possibility of frost damage passes, was also reported, as well as cabbage being nipped.
Issues on high tunnel vegetables. Chlorosis (yellowing) of high tunnel cucumber leaves and abortion of young fruit was reported. Yellowing on cucurbits can be caused by potassium and zinc deficiencies, but also by angular leafspot (a bacterial disease that can be seed transmitted) so it is important to correctly identify the cause. Young fruit abortion can be caused by heat stress, pollination issues, and boron toxicity if boron was applied. Cases of Botrytis (gray mold), bacterial canker, and stem pith necrosis on high tunnel tomatoes have recently occurred. Bacterial canker can be easily transmitted from plant-to-plant during suckering and pruning operations, so sanitation during these operations in important. Two-spotted spider mites and thrips are also present.
Weeds in strawberries. This is a problem every spring. Fields where growers didn’t use straw to mulch the plants are the most problematic. Here is a link to an article from 2014 that addresses some of the more common spring weeds in strawberries and ways to manage them: http://extension.psu.edu/plants/tree-fruit/news/2014/spring-weeds-in-strawberries
Thrips on greenhouse tomatoes and cucumbers. Thrips can vector viruses, so management measures should be taken. A nice article with lots of photos and thrips management recommendations for greenhouse tomatoes appears here: http://www.e-gro.org/pdf/E107.pdf Note that other “greenhouse pests” – aphids, whiteflies, and spider mites are also present now in various greenhouse and high tunnel crops and should be managed before populations get out-of-hand.
Sweet corn monitoring traps for corn earworm, European corn borer, and fall armyworm will be deployed across the state on cooperating farms in early June. Results will be accessible from the PestWatch homepage at http://www.pestwatch.psu.edu/ . An interactive map for sweet corn can be found at http://www.pestwatch.psu.edu/sweetcorn/tool/index.html . Previous year’s results can be accessed by pulling down an earlier year and using the scrollbar at the bottom of the screen to advance through the year. The map will be updated as results become available for 2017. Thanks to the Pennsylvania Vegetable Growers Association for covering the costs associated with producing the traps.
Other sporadic issues reported include herbicide phytotoxicity in various crops and for an assortment of reasons, cabbage maggot on broccoli, and black vine weevil on strawberries.