Insect Pest - Flies

IPM Threshold Guide for Agronomic Field Crops

The unusually warm winter and early spring we have had up to now has allowed large populations of seed and root maggots to invade our vegetable fields. Some farms have been hit particularly hard in their onion, bean, pea or radish crops this season by maggots. These maggots include seedcorn maggot Delia platura (SCM), onion maggot Delia antiqua (OM) and cabbage maggot Delia radicum (CM). All three species overwinter in the soil as a maggot inside a brown pupal case (fig. 1). In March and April small, grayish-brown flies (fig. 2) emerge, which are usually SCM or CM, OM flies usually peak 2-3 weeks later. Adult flies are most active from 10 a.m. – 2 p.m. and are inactive at night, in strong winds or when temperatures are below 50o F or above 80o F. Adults live 2-4 weeks and females lay hundreds of eggs.

Spinach and beet leafminers have been around in low numbers for the past few weeks, which is a couple of weeks ahead of schedule but have increased rapidly in the last 5-6 days. These leaf miners are found in beets, swiss chard and spinach but I usually find them more in swiss chard than spinach. Both of these leafminers are a type of blotch leafminer, creating irregularly shaped mines. These flies attack crops and weeds in the plant family Chenopodiaceae, which includes chard, beets, and spinach and the weed lamb’s quarters. Both fly species are very similar, but the spinach leafminer may also feed on Solanaceous crops such as peppers.

A list of resources for Grape Pest and Weed Management

A variety of information on commercial strawberry production including organic production, pest and weed management, frost and freeze prevention, and more.

In high tunnels and in the field, I have seen spinach or beet leaf miner Pegomya hyoscyami and P. betae respectively in swiss chard and spinach. These leafminers are a type of blotch leafminer, creating irregularly shaped mines (fig.1). Adults are small flies about 1/3 inch in length and gray to brown. Larvae are whitish and cone-shaped. Flies of both species overwinter as pupae in the soil.

If you grow leeks or onions or other Allium species, you should already be checking for the tell-tale marks left by Allium leaf miner. Allium leaf miner Phytomyza gymnostoma tell-tale marks consist of many linear small white dots (made by the female’s ovipositor) that appear in the middle towards the end of leaf blades (fig. 1) of their preferred hosts of leeks, onions, garlic and other Allium species. Spring crops are usually not as hard hit as fall crops especially when looking at leeks, but this pest has been steadily increasing its geographical range each year and its damage potential. If you had some infestation last year you will especially want to be looking for the signs of this pest.

With the majority of freezing night time lows behind us, strawberry growers should begin scouting for pests during bloom. Earliglow is already in bloom on the Lower Eastern Shore and other cultivars will soon follow with the warm weather forecasted for 4/12-4/16. Be on the watch for spring pests during bloom including thrips, tar-nished plant bug, leafrollers, aphids, leafhoppers which begin attack plants during flowering in Maryland. Author: Haley Sater; Title: Spring Pest Scouting in Strawberries

Spinach and beet leafminers have been around in low numbers for the past few weeks but have increased rapidly in the last 5-6 days. These leaf miners are found in beets, swiss chard and spinach but I usually find them more in swiss chard than spinach.

In high tunnels and in the field, I have seen spinach and beet leaf miners Pegomya hyoscyami and P. betae respectively in swiss chard and spinach. These leafminers are a type of blotch leafminer, creating irregularly shaped mines. These flies attack crops and weeds in the plant family Chenopodiaceae, which includes chard, beets, and spinach and the weed lamb’s quarters. These fly species are very similar, but the spinach leafminer may also feed on Solanaceous crops such as peppers.