A little sleuthing can deduce the “whodunit” in our rose gardens

Those who have seen or read our fair share of murder mysteries know that the answer to “whodunit” lies in the skills of espionage, deduction and assumption. Tracking down evidence and dividing potential culprits is key to finding the culprit, not only in our favorite Agatha Christie novels and movies but also in our gardens.

Is this fault the offender the culprit or just an ordinary bystander? Or could it be that a benevolent member of the Nature Garden Task Force comes to watch over our yard and help us wipe out the enemies of our garden?

The Hunt for the Villain: Wide Blows

Although some insects feed only at certain stages of their life cycle, all of them eat and feed.

Herbivores They feed on plants.

omnivores and plants Such as praying mantis, grasshoppers, and earwigs feed on other insects, but also feed on “greens”.

scavengers They feed on dead plants or dead animals.

Bird wings and larvae feed on insects and other moths and are our garden friends.

(Rita Berwich)

Predatory and parasitic insects Such as wings, dragonflies, killer bugs, pirate bugs, girl bugs, lady beetles, servid flies and their larvae feed on other insects and moths. This group of insects (and spiders and birds) are our friends in our gardens.

Dragonfly rests on a branch near the water.

Dragonfly water tempts our gardens. They are our garden friends and feed on insects and other moths.

(Rita Berwich)

Sarvid flies on a pink flower.

Sarvid flies and their larvae feed on insects and moths, and they become friends in our gardens.

(Rita Berwich)

Gardeners can exclude the last two groups from our list of culprits and focus our attention on herbivores and a few carnivores.

harassing the offender

Check the plant. Sometimes we can catch a red-handed pest. In this case, after the end of our detective work, we can immediately switch to manual “removal” methods. If we notice the damage but can’t see the insect, we can speculate either that the insect pests have moved, that we are dealing with nocturnal feeders, or that the pests are too small to be seen with the naked eye.

Check the type of plant damage until you reach zero in ‘whodunit’. Insects have mouthparts that are designed to either chew or pierce and suck. Holes in buds, blossoms, leaves, jagged, coiled, or tented leaves are clues that you are dealing with a chewing insect. wrinkled deformed leaves; soft belt on the underside of dry and dusty foliage; burnt or solitary appearance of buds and flowers; Twisted serpentine trails or spots within the leaves indicate that your garden enemy is a sucking pest.

Note which part of the plant is under attack. Insects are specific in their eating habits and have preferences for roots, leaves, reeds, stems, buds, inflorescences, or stamens.

Season can be a guide. Some pests are year-round problems, but the season in which the pest is most active can provide clues to “unity.”

An assortment of the usual suspects

spring pests

Green aphids on the plant.

aphids It penetrates into plant tissues and absorbs plant sap, which leads to deformed growth. You will see them on new leaves, stems, and buds.

(Rita Berwich)

aphids It is the first pest in the spring. They arrive in large numbers and distort new spring growth by puncturing and sucking out the leaves, stems, and new, tender shoots. They reproduce quickly but their numbers drop dramatically during the year as there are many predators. This soft pest is easily crushed with our fingers and blown away with jets of water.

The hobelia beetle appears on a white flower.

Hobelia beetles chew holes in the petals and damage the stamens of the white, off-white rose flowers.

(Rita Berwich)

Hobelia beetles They chew holes in the petals and damage the stamens of the white, light-colored roses. Pick them up by hand and drop them into a bucket of soapy water or crush them underfoot. Fortunately, they only have one generation per year and are only a problem from March to the end of May.

Whole rose beetle: Chewed flowers and foliage with serrated or jagged edges are clues that whole brown rose beetles that feed at night may be at work. Drop it in a bucket of soapy water.

Slug rose on the underside of the leaf.

Pink slugs are hard to see because they feed on the underside of the leaf. These are the pests responsible for the skeletal lacy rose leaves.

(Rose Berwich)

Coarse rose ingot: These are the pests responsible for the skeletal lacy rose leaves. To reduce this pest, it is necessary to catch it as soon as it first appears in May, and then continue to monitor it for the rest of the year. They are saw larvae and look (but are not) green larvae. They are hard to see because they feed on the underside of the leaf. Crush them or remove infected leaves.

Bud worms dig single holes in the buds and consume the developing petals, preventing the rose from opening properly.

Bud worms dig single holes in the buds and consume the developing petals, preventing the rose from opening properly.

(Rita Berwich)

caterpillars: It is easy to spot holes in buds, damaged flowers and chewed and skeletal leaves, but caterpillars are difficult to find, and many are night-feeding. Black droppings are advice to look nearby for actively feeding larvae. A folded sheet, two sheets of paper “silk” together or a sheet rolled and tied with silk can be evidence of larvae masking. Bud worms and small worms dig single holes in the buds and consume the developing petals, preventing the rose from opening properly. Cut and discard damaged shoots, which may still harbor caterpillars.

paper hoppers: Mottled or yellowing leaves may be a sign that the bleached green leafhoppers may suck the underside of the pink foliage with their piercing mouthparts.

thrips They discolor and damage the blossoms as they suck the sap from the petals. They appear as small, fast-moving black dots within the light or light-colored buds and flowers of roses. A bud bent at an acute angle is often the first sign of thrips damage. Frequent mowing and getting rid of spent blooms and yellow leaves can help reduce thrips and leaf bouncy. Sticky traps are popular with some organic gardeners, but know that these traps can “stick” their benefits.

summer pests

spiders They are spiders, not insects. Their sucking-feeding results in spotted leaves and a soft strip on the underside of the foliage, and sometimes rapid defoliation, especially in hot, dry weather. When caught early, spider mites can be controlled by powerful jets of water directed to the underside of leaves, repeated three to four times a week. Mite infestations often occur after the use of a broad spectrum insecticide such as Sevin.

Grasshoppers chew pests that feed day and night and do a lot of damage to the leaves and flowers.

Grasshoppers chew pests that feed day and night and do a lot of damage to the leaves and flowers.

(Rita Berwich)

Grasshoppers: I thought locusts and katydids were a summer and fall pest, but I started seeing them in my garden also in the spring. Chewing pests, they feed day and night and do a lot of damage to the leaves and flowers. The damage to these hard-to-catching and highly mobile pests can be difficult to determine as they are not often found at crime scenes.

Bronze buds and distorted leaves are evidence of hot pepper thrips.

We can’t see pepper thrips with the naked eye, but the bronzed buds and distorted, burnt leaves and flowers are their clear signature.

(Rita Berwich)

Pepper thrips: We can’t see pepper thrips with the naked eye, but it’s the biggest problem in our rose gardens. By the time we see the first damage, they already have a steady life cycle going on in the garden. Hot pepper larvae and adults extract sap from new, tender growth buds with pierced and sucking mouthparts. The first sign of damage is a slight red-green marbling on the back of the new foliage and a slight wrinkling or puckering on the new foliage. This is followed by dirty brown streaks on the back of new leaves, brown or bronze buds, a hot pepper thrips imprint, and discolored and burnt flowers. Cut and bundle damaged growth. This pest does not have enough enemies in the garden, although small pirates, larvae of the lacquerfly and cervids are predators. Some rosaries spray new foliage on roses prophylactically in the hot months. Captain Jack’s Deadbug Brew with the active ingredient Spinosad is an organic pesticide that targets hot pepper thrips and will not harm beetles, greengroves, minute pirate insects and predatory mites. However, spraying should be done in the evening as it is toxic to bees exposed to treatment for 3 hours after application.

Fig beetles (green fruit beetles): The iridescent green metallic fig beetles arrive with raucous sounds and actively feed on peaches, figs, apples, and roses from late June through early fall. Fortunately, there is only one generation of these beetles each year. Drop it in a bucket of soapy water or crush it underfoot.

Scale They are sap-sucking insects with piercing mouthparts that feed on rose canes and prefer the warmer months. Some types of scales form a hard shell and some are thin-bodied. Females breed under the shell cover and nymphs (reptiles) emerge in spring and summer from their covers and attach to the stick to feed. Get rid of limescale by scrubbing with an old toothbrush or a cloth dampened with rubbing alcohol. Severely infested canes should be cut.

innocent until proven guilty

Your garden will be visited by many, many types of insects and very few of these visitors will harm your roses. Learn about the dozens of pests found in San Diego’s rose gardens and you can assume the rest are innocent…unless they’re proven guilty, of course!

Perwich is a member of the San Diego Rose Society, and is a Rosarian consultant and master gardener with UC Cooperative Extension.

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