Pests of one plant family spread more easily through a solid block of it
As recorded: A specialist pest or pathogen finds and builds on a continuous single-family host patch more readily than one broken by non-host families.
A good hunch A person has checked it against its sources. If you skip this, it still grows, just less well. The planner suggests it.
How it works
Resource concentration. A specialist locates and holds its host more efficiently at higher host density and continuity, so an unbroken run of one family across adjacent beds is an easier target than the same family separated by a non-host (associational resistance).
What to do about it
Where one family fills adjacent beds in a single season, breaking the run with a non-host family between them lengthens the distance the specialist must travel to the next host. The app discloses this and never docks a score. A continuous single-family block can be the right call anyway (a wind-pollinated crop like corn sets better massed), so the app names the trade-off and leaves the choice to the gardener.
How much it matters: No garden-yield figure is stated or estimated. The resource-concentration effect is real for SPECIALIST herbivores and inconsistent for generalists, which is why it only advises.
The evidence
Evidence: checked against 2 sources in the research-based literature.
The 2 sources
… the resource concentration hypothesis, which states that herbivores are more likely to find and remain on hosts that are growing in dense or nearly pure stands; that the most specialized species frequently attain higher relative densities in simple environments.
… strong, direct support for the hypothesis that host plants are harder to find and easier to lose in vegetationally diverse habitats than in monocultures.
Plants it applies to
- Arugula
- Butternut
- Cabbage
- Cucumber
- Eggplant
- Horseradish
- Luffa
- Melon
- Mustard greens
- Pepper
- Potato
- Radish
- Rutabaga
- Summer squash
- Sweet alyssum
- Tomatillo
- Tomato
- Turnip
- Watermelon
- Winter squash
Read next
How this rule has changed
Every change is dated, newest first. The full record, with each reason, is in the data download.
- Wording made clearer
- Wording made clearer
- Wording made clearer
- A person read the sources and confirmed it
- Added to the rules
Cite this page
Milpa Gardens. "Pests of one plant family spread more easily through a solid block of it." Evidence grade: A good hunch. https://milpa.garden/rules/specialist-pest-pathogen-finds-builds-continuous-family/
A garden planner built on graded evidence. Every claim states its evidence grade and links its sources on the page. Cite it with the grade, and add the date you read it.
Report a problem with this claim
How we grade evidence
- Well established
- The rule names its mechanism and is settled, by sources a person has read and checked or by plain arithmetic and geometry.
- Promising
- The mechanism is named and the literature backs it. A few questions are still open.
- A good hunch
- Plausible by its mechanism, but field studies are thin, so treat it as a lean.
- Contested
- The evidence points both ways, or no study has tested it, so the planner does not enforce it.
- Refuted
- The claim did not survive its sources. It is kept so the folklore can be answered.