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Garden pest insects and how to get rid of them

Invasive pest Bagrada hilaris known as a stink bug
Invasive pest Bagrada hilaris known as a stink bug

It looks like this might be a bad year for pest insects in our gardens.

One reader asked if there was any way to control for the sudden onset of grasshoppers eating up her organic garden.

Grasshoppers lay their eggs in late summer and fall to overwinter in the soil in undisturbed grassy or weedy areas. In spring, the grasshopper nymphs hatch and move into food source areas. Removing weeds and grasses and cultivating the soil to a depth of two inches to expose egg mass pods that can be destroyed before they hatch will keep down the population. Grasshopper populations rise when several successive years of warm, wet springs provide ample forage. During major outbreaks, grasshopper hordes will feed on almost any green plant. As the forage plants die back in our summer heat, grasshopper populations will drop.

FBEE 2020 ELINOR TEAGUE circle
Elinor Teague

It’s easier to kill grasshopper nymphs than the adults. And it’s better to kill them before the primary invasion into your garden. Baits containing the protozoan Nosema locustae are available but work on only a few species, few of which breed in California. Row covers can provide some protection, but really hungry grasshoppers will chew through the covers to get to the food.

Nonorganic grasshopper controls include carbaryl baits that are less toxic to bees than highly toxic sprays. Place chemical baits around the perimeter of your garden soon to attract the more vulnerable grasshopper nymphs.

Another reader sent a photo of an insect for identification and reported huge numbers of the bug in her garden. It’s a bagrada bug – a stink bug – and it’s a fairly recent invader in the Central Valley and a real pest. Adult bagrada bugs are black with orange markings, shield-shaped and about 1/4-inch long and wide. The UC IPM website, http://ipm.ucanr.edu, has good photos of the bug. An adult female can lay up to 150 eggs over a two- to three-week period. Populations usually peak in summer when the fruit and vegetable crops that bagrada bugs feed on ripen, but the first hatch comes with the first warm weather.

Host plants for bagrada bugs are in the mustard family-broccoli, cabbages, cauliflower – and most especially, sweet alyssum that’s found in many home gardens. Remove all leftover winter crops in the mustard family and sweet alyssum if there is a large population in your garden. Screens and row covers can prevent the bugs from reaching crops.

▪ Note: The 2018 Master Gardener Spring Garden Tour will take place 9 a.m. to 5 p.m. Saturday, rain or shine. Five gorgeous private gardens in Fresno and Clovis are featured this year as well as the Master Gardeners’ demonstration garden, the Garden of the Sun, 1750 N. Winery Ave. in Fresno. The plant sale at the Garden of the Sun is a great first stop on the tour. Come early – the plants sell out quickly.

Master Gardener docents will be on hand at every garden to answer your garden questions. Bring photos of your garden problems and be prepared to take photos of the tour gardens for inspiration and ideas.

Tickets are $35 the day of the tour and can be purchased at each of the gardens. Check out the Master Gardener website for more details: www.ucanr.edu/sites/mgfresno.

Elinor Teague: etgrow@comcast.net

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